Unifying LKL into UML

This patch introduces the nommu operation with UML code so that host interface can be shrineked for broader environments support.

The nommu mode is implemneted as SUBARCH of arch/um, which places at arch/um/nommu. This SUBARCH defines mode-specific code of memory management as well as thread implementation, along with the uapi headers to be exported to users.

The headers we introduce in this patch are simple wrappers to the asm-generic headers or stubs for things we don't support, such as ptrace, DMA, signals, ELF handling and low level processor operations.

nommu mode shares most of arch/um code (irq, thread_info, process scheduling) but implements its own facilities, which are memory management (nommu), thread primitives (struct arch_thread), system call interface, and console.

The outlook of updated directory structure is as follows:

arch/um

   |-- configs         (untouched)
   |-- drivers         unuse stdio_console.c for !MMU
   |-- include
   |   |-- asm         updated with !CONFIG_MMU
   |   |-- linux       (untouched)
   |   `-- shareda     updated with new functions
   |       `-- skas    (untouched)
   |   `-- uapi        added for upai header installation
   |-- kernel          updated to integrate with !MMU
   |   `-- skas        (untouched, don't use for !MMU)
   |-- nommu           SUBARCH dir (internally =um/nommu)
   |   |-- include
   |   |   |-- asm     headers for subarch specific info
   |   |   `-- uapi    headers for user-visible APIs
   |   `-- um
   |       `-- shared  headers for subarch specific info

`-- scripts added a script for header installation

---
 arch/um/nommu/Makefile                        |   1 +
 arch/um/nommu/Makefile.um                     |  18 +++
 arch/um/nommu/include/asm/Kbuild              |   6 +
 arch/um/nommu/include/asm/archparam.h         |   1 +
 arch/um/nommu/include/asm/atomic.h            |  11 ++
 arch/um/nommu/include/asm/atomic64.h          | 114 ++++++++++++++++++
 arch/um/nommu/include/asm/bitsperlong.h       |  12 ++
 arch/um/nommu/include/asm/byteorder.h         |   7 ++
 arch/um/nommu/include/asm/cpu.h               |  13 ++
 arch/um/nommu/include/asm/elf.h               |  15 +++
 arch/um/nommu/include/asm/mm_context.h        |   8 ++
 arch/um/nommu/include/asm/processor.h         |  46 +++++++
 arch/um/nommu/include/asm/ptrace.h            |  21 ++++
 arch/um/nommu/include/asm/sched.h             |  23 ++++
 arch/um/nommu/include/asm/segment.h           |   9 ++
 arch/um/nommu/include/uapi/asm/Kbuild         |   4 +
 arch/um/nommu/include/uapi/asm/bitsperlong.h  |  11 ++
 arch/um/nommu/include/uapi/asm/byteorder.h    |  11 ++
 arch/um/nommu/include/uapi/asm/sigcontext.h   |  12 ++
 arch/um/nommu/um/delay.c                      |  31 +++++
 arch/um/nommu/um/shared/sysdep/archsetjmp.h   |  13 ++
 arch/um/nommu/um/shared/sysdep/faultinfo.h    |   8 ++
 .../nommu/um/shared/sysdep/kernel-offsets.h   |  12 ++
 arch/um/nommu/um/shared/sysdep/mcontext.h     |   9 ++
 arch/um/nommu/um/shared/sysdep/ptrace.h       |  42 +++++++
 arch/um/nommu/um/shared/sysdep/ptrace_user.h  |   7 ++
 arch/um/nommu/um/unimplemented.c              |  70 +++++++++++
 arch/um/nommu/um/user_constants.h             |  13 ++
 28 files changed, 548 insertions(+)
 create mode 100644 arch/um/nommu/Makefile
 create mode 100644 arch/um/nommu/Makefile.um
 create mode 100644 arch/um/nommu/include/asm/Kbuild
 create mode 100644 arch/um/nommu/include/asm/archparam.h
 create mode 100644 arch/um/nommu/include/asm/atomic.h
 create mode 100644 arch/um/nommu/include/asm/atomic64.h
 create mode 100644 arch/um/nommu/include/asm/bitsperlong.h
 create mode 100644 arch/um/nommu/include/asm/byteorder.h
 create mode 100644 arch/um/nommu/include/asm/cpu.h
 create mode 100644 arch/um/nommu/include/asm/elf.h
 create mode 100644 arch/um/nommu/include/asm/mm_context.h
 create mode 100644 arch/um/nommu/include/asm/processor.h
 create mode 100644 arch/um/nommu/include/asm/ptrace.h
 create mode 100644 arch/um/nommu/include/asm/sched.h
 create mode 100644 arch/um/nommu/include/asm/segment.h
 create mode 100644 arch/um/nommu/include/uapi/asm/Kbuild
 create mode 100644 arch/um/nommu/include/uapi/asm/bitsperlong.h
 create mode 100644 arch/um/nommu/include/uapi/asm/byteorder.h
 create mode 100644 arch/um/nommu/include/uapi/asm/sigcontext.h
 create mode 100644 arch/um/nommu/um/delay.c
 create mode 100644 arch/um/nommu/um/shared/sysdep/archsetjmp.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/faultinfo.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/kernel-offsets.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/mcontext.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/ptrace.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/ptrace_user.h
 create mode 100644 arch/um/nommu/um/unimplemented.c
 create mode 100644 arch/um/nommu/um/user_constants.h

new file mode 100644
index 000000000000..792d6005489e
@@ -0,0 +1 @@
+#

new file mode 100644
index 000000000000..6cb0e9494d05
@@ -0,0 +1,18 @@
+KBUILD_CFLAGS += -fno-builtin -fPIC
+ELF_FORMAT=$(shell $(LD) -r -print-output-format)
+
+ifeq ($(shell uname -s), Linux)
+NPROC=$(shell nproc)
+else # e.g., FreeBSD
+NPROC=$(shell sysctl -n hw.ncpu)
+endif
+
+um_headers_install: $(objtree)/$(HOST_DIR)/include/generated/uapi/asm/syscall_defs.h headers
+	$(Q)$(srctree)/$(ARCH_DIR)/scripts/headers_install.py \
+		$(subst -j,-j$(NPROC),$(findstring -j,$(MAKEFLAGS))) \
+		$(INSTALL_PATH)/include
+
+$(objtree)/$(HOST_DIR)/include/generated/uapi/asm/syscall_defs.h: vmlinux
+	$(Q)$(OBJCOPY) -j .syscall_defs -O binary --set-section-flags .syscall_defs=alloc $< $@
+	$(Q) export tmpfile=$(shell mktemp); \
+	sed 's/\x0//g' $@ > $$tmpfile; mv $$tmpfile $@ ; rm -f $$tmpfile

new file mode 100644
index 000000000000..2532e1a0a0d1
@@ -0,0 +1,6 @@
+generic-y += cmpxchg.h
+generic-y += local64.h
+generic-y += seccomp.h
+generic-y += string.h
+generic-y += syscall.h
+generic-y += user.h

new file mode 100644
index 000000000000..ea32a7d3cf1b
@@ -0,0 +1 @@
+/* SPDX-License-Identifier: GPL-2.0 */

new file mode 100644
index 000000000000..63e2e16bda92
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_ATOMIC_H
+#define __UM_NOMMU_ATOMIC_H
+
+#include <asm-generic/atomic.h>
+
+#ifndef CONFIG_GENERIC_ATOMIC64
+#include "atomic64.h"
+#endif /* !CONFIG_GENERIC_ATOMIC64 */
+
+#endif

new file mode 100644
index 000000000000..a150cee41e75
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_BITSPERLONG_H
+#define __UM_NOMMU_BITSPERLONG_H
+
+#include <uapi/asm/bitsperlong.h>
+
+#define BITS_PER_LONG __BITS_PER_LONG
+
+#define BITS_PER_LONG_LONG 64
+
+#endif
+

new file mode 100644
index 000000000000..920a5fd26cad
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_BYTEORDER_H
+#define __UM_NOMMU_BYTEORDER_H
+
+#include <uapi/asm/byteorder.h>
+
+#endif

new file mode 100644
index 000000000000..c101c078ef21
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_CPU_H
+#define __UM_NOMMU_CPU_H
+
+int lkl_cpu_get(void);
+void lkl_cpu_put(void);
+int lkl_cpu_try_run_irq(int irq);
+int lkl_cpu_init(void);
+void lkl_cpu_wait_shutdown(void);
+void lkl_cpu_change_owner(lkl_thread_t owner);
+void lkl_cpu_set_irqs_pending(void);
+
+#endif

new file mode 100644
index 000000000000..edcf63edeed1
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_ELF_H
+#define __UM_NOMMU_ELF_H
+
+#define elf_check_arch(x) 0
+
+#ifdef CONFIG_64BIT
+#define ELF_CLASS ELFCLASS64
+#else
+#define ELF_CLASS ELFCLASS32
+#endif
+
+#define elf_gregset_t long
+#define elf_fpregset_t double
+#endif

new file mode 100644
index 000000000000..a2e53984aabd
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_MM_CONTEXT_H
+#define __UM_NOMMU_MM_CONTEXT_H
+
+struct uml_arch_mm_context {
+};
+
+#endif

new file mode 100644
index 000000000000..b214410e9825
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_PTRACE_H
+#define __UM_NOMMU_PTRACE_H
+
+#include <linux/errno.h>
+
+static int reg_dummy __attribute__((unused));
+
+#define PT_REGS_ORIG_SYSCALL(r) (reg_dummy)
+#define PT_REGS_SYSCALL_RET(r) (reg_dummy)
+#define PT_REGS_SET_SYSCALL_RETURN(r, res) (reg_dummy = (res))
+#define REGS_SP(r) (reg_dummy)
+
+#define user_mode(regs) 0
+#define kernel_mode(regs) 1
+#define profile_pc(regs) 0
+#define user_stack_pointer(regs) 0
+
+extern void new_thread_handler(void);
+
+#endif

new file mode 100644
index 000000000000..a4496f482633
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_SCHED_H
+#define __UM_NOMMU_SCHED_H
+
+#include <linux/sched.h>
+#include <uapi/asm/host_ops.h>
+
+static inline void thread_sched_jb(void)
+{
+	if (test_ti_thread_flag(current_thread_info(), TIF_HOST_THREAD)) {
+		set_ti_thread_flag(current_thread_info(), TIF_SCHED_JB);
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		lkl_ops->jmp_buf_set(&current_thread_info()->task->thread.arch.sched_jb,
+				     schedule);
+	} else {
+		lkl_bug("%s can be used only for host task", __func__);
+	}
+}
+
+void switch_to_host_task(struct task_struct *);
+int host_task_stub(void *unused);
+
+#endif

new file mode 100644
index 000000000000..5608da95cb60
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_SEGMENT_H
+#define __UM_NOMMU_SEGMENT_H
+
+typedef struct {
+	unsigned long seg;
+} mm_segment_t;
+
+#endif /* _ASM_LKL_SEGMENT_H */

new file mode 100644
index 000000000000..4f79e5c4846d
@@ -0,0 +1,4 @@
+# UAPI Header export list
+
+# no generated-y since we need special user headers handling
+# see arch/um/script/headers_install.py

new file mode 100644
index 000000000000..852566ac2e52
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __UM_NOMMU_UAPI_BITSPERLONG_H
+#define __UM_NOMMU_UAPI_BITSPERLONG_H
+
+#ifdef CONFIG_64BIT
+#define __BITS_PER_LONG 64
+#else
+#define __BITS_PER_LONG 32
+#endif
+
+#endif

new file mode 100644
index 000000000000..e7ad11a751cf
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __UM_NOMMU_UAPI_BYTEORDER_H
+#define __UM_NOMMU_UAPI_BYTEORDER_H
+
+#if defined(CONFIG_BIG_ENDIAN)
+#include <linux/byteorder/big_endian.h>
+#else
+#include <linux/byteorder/little_endian.h>
+#endif
+
+#endif

new file mode 100644
index 000000000000..b934ae7f5550
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __UM_NOMMU_UAPI_SIGCONTEXT_H
+#define __UM_NOMMU_UAPI_SIGCONTEXT_H
+
+#include <asm/ptrace-generic.h>
+
+struct sigcontext {
+	struct pt_regs regs;
+	unsigned long oldmask;
+};
+
+#endif

new file mode 100644
index 000000000000..58a366d9b5f0
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/jiffies.h>
+#include <linux/delay.h>
+#include <os.h>
+
+void __ndelay(unsigned long nsecs)
+{
+	long long start = os_nsecs();
+
+	while (os_nsecs() < start + nsecs)
+		;
+}
+
+void __udelay(unsigned long usecs)
+{
+	__ndelay(usecs * NSEC_PER_USEC);
+}
+
+void __const_udelay(unsigned long xloops)
+{
+	__udelay(xloops / 0x10c7ul);
+}
+
+void __delay(unsigned long loops)
+{
+	__ndelay(loops / 5);
+}
+
+void calibrate_delay(void)
+{
+}

new file mode 100644
index 000000000000..4a5c10d7521b
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARCH_UM_SETJMP_H
+#define __ARCH_UM_SETJMP_H
+
+struct __jmp_buf {
+	unsigned long __dummy;
+};
+#define JB_IP __dummy
+#define JB_SP __dummy
+
+typedef struct __jmp_buf jmp_buf[1];
+
+#endif /* __ARCH_UM_SETJMP_H */

new file mode 100644
index 000000000000..49210742212d
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARCH_UM_FAULTINFO_H
+#define __ARCH_UM_FAULTINFO_H
+
+struct faultinfo {
+};
+
+#endif /* __ARCH_UM_FAULTINFO_H */

new file mode 100644
index 000000000000..a004bffb7b8d
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/stddef.h>
+#include <linux/sched.h>
+#include <linux/elf.h>
+#include <linux/crypto.h>
+#include <linux/kbuild.h>
+#include <asm/mman.h>
+
+void foo(void)
+{
+#include <common-offsets.h>
+}

new file mode 100644
index 000000000000..b734012a74da
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARCH_UM_MCONTEXT_H
+#define __ARCH_UM_MCONTEXT_H
+
+extern void get_regs_from_mc(struct uml_pt_regs *regs, mcontext_t *mc);
+
+#define GET_FAULTINFO_FROM_MC(fi, mc) (fi = fi)
+
+#endif /* __ARCH_UM_MCONTEXT_H */

new file mode 100644
index 000000000000..86d5cb20fb9f
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARCH_UM_PTRACE_USER_H
+#define __ARCH_UM_PTRACE_USER_H
+
+#define FP_SIZE 1
+
+#endif

new file mode 100644
index 000000000000..2245d3d24120
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_USER_CONSTANTS_H
+#define __UM_NOMMU_USER_CONSTANTS_H
+
+/* XXX: put dummy values */
+#define UM_FRAME_SIZE 4
+#define HOST_FP_SIZE 1
+#define HOST_IP 1
+#define HOST_SP 2
+#define HOST_BP 3
+#define UM_NR_CPUS 1
+
+#endif

2.21.0 (Apple Git-122.2)

This patch introduces the host operations that define the interface between the LKL and the host. These operations must be provided either by a host library or by the application itself.

---
 arch/um/include/asm/host_ops.h            |  9 ++++++++
 arch/um/nommu/include/uapi/asm/host_ops.h | 25 +++++++++++++++++++++++
 2 files changed, 34 insertions(+)
 create mode 100644 arch/um/include/asm/host_ops.h
 create mode 100644 arch/um/nommu/include/uapi/asm/host_ops.h

new file mode 100644
index 000000000000..f52423cc4ced
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_LKL_HOST_OPS_H
+#define _ASM_LKL_HOST_OPS_H
+
+#include <uapi/asm/host_ops.h>
+
+extern struct lkl_host_operations *lkl_ops;
+
+#endif

new file mode 100644
index 000000000000..d3dad11b459e
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __UM_NOMMU_UAPI_HOST_OPS_H
+#define __UM_NOMMU_UAPI_HOST_OPS_H
+
+/* Defined in {posix,nt}-host.c */
+struct lkl_mutex;
+struct lkl_sem;
+typedef unsigned long lkl_thread_t;
+struct lkl_jmp_buf {
+	unsigned long buf[128];
+};
+
+/**
+ * lkl_host_operations - host operations used by the Linux kernel
+ *
+ * These operations must be provided by a host library or by the application
+ * itself.
+ *
+ */
+struct lkl_host_operations {
+};
+
+void lkl_bug(const char *fmt, ...);
+
+#endif

2.21.0 (Apple Git-122.2)

nommu mode follows the way !CONFIG_MMU architecture of other linux archs. Ther is not much work left to do other than initializing the boot allocator and providing the page and page table definitions.

The backstore memory is allocated via a host operation and the memory size to be used is specified when the kernel is started, in the lkl_start_kernel call.

---
 arch/um/include/asm/mmu.h                 |  3 +
 arch/um/include/asm/mmu_context.h         |  8 +++
 arch/um/include/asm/page.h                | 15 ++++
 arch/um/include/asm/pgtable.h             | 27 +++++++
 arch/um/include/asm/uaccess.h             |  6 ++
 arch/um/nommu/include/uapi/asm/host_ops.h |  5 ++
 arch/um/nommu/um/bootmem.c                | 86 +++++++++++++++++++++++
 7 files changed, 150 insertions(+)
 create mode 100644 arch/um/nommu/um/bootmem.c

index 5b072aba5b65..c06d6cb67dd7 100644
@@ -13,6 +13,9 @@ typedef struct mm_context {
 	struct mm_id id;
 	struct uml_arch_mm_context arch;
 	struct page *stub_pages[2];
+#ifndef CONFIG_MMU
+	unsigned long		end_brk;
+#endif
 } mm_context_t;
 
 extern void __switch_mm(struct mm_id * mm_idp);

index b4deb1bfbb68..92cc838bb477 100644
@@ -6,6 +6,7 @@
 #ifndef __UM_MMU_CONTEXT_H
 #define __UM_MMU_CONTEXT_H
 
+#ifdef CONFIG_MMU
 #include <linux/sched.h>
 #include <linux/mm_types.h>
 

@@ -74,4 +75,11 @@ extern int init_new_context(struct task_struct *task, struct mm_struct *mm);
 
 extern void destroy_context(struct mm_struct *mm);
 
+#else
+#include <asm-generic/mmu_context.h>
+
+extern void force_flush_all(void);
+
+#endif /* CONFIG_MMU */
+
 #endif

index 95af12e82a32..c9d5e487ac6b 100644
@@ -7,6 +7,8 @@
 #ifndef __UM_PAGE_H
 #define __UM_PAGE_H
 
+#ifdef CONFIG_MMU
+
 #include <linux/const.h>
 
 /* PAGE_SHIFT determines the page size */

@@ -120,4 +122,17 @@ extern unsigned long uml_physmem;
 #define __HAVE_ARCH_GATE_AREA 1
 #endif
 
+#else  /* CONFIG_MMU */
+#define CONFIG_KERNEL_RAM_BASE_ADDRESS memory_start
+#include <asm-generic/page.h>
+
+#define __va_space (8*1024*1024)
+
+#ifndef __ASSEMBLY__
+#include <mem.h>
+void free_mem(void);
+#endif
+
+#endif /* !CONFIG_MMU  */
+
 #endif	/* __UM_PAGE_H */

index b5ddf5d98bd5..5c19f6a58ef7 100644
@@ -21,6 +21,8 @@
 #define _PAGE_PROTNONE	0x010	/* if the user mapped it with PROT_NONE;
 				   pte_present gives true */
 
+#ifdef CONFIG_MMU
+
 #ifdef CONFIG_3_LEVEL_PGTABLES
 #include <asm/pgtable-3level.h>
 #else

@@ -362,4 +364,29 @@ do {						\
 	__flush_tlb_one((vaddr));		\
 } while (0)
 
+#else  /* CONFIG_MMU */
+
+#include <asm-generic/pgtable-nopud.h>
+#include <asm-generic/pgtable.h>
+
+#define swapper_pg_dir		((pgd_t *)0)
+#define PAGE_KERNEL             __pgprot(0)
+#define PGDIR_SHIFT		21
+#define PGDIR_SIZE		(1UL << PGDIR_SHIFT)
+#define PGDIR_MASK		(~(PGDIR_SIZE-1))
+
+#define VMALLOC_START 0
+
+/*
+ * ZERO_PAGE is a global shared page that is always zero: used
+ * for zero-mapped memory areas etc..
+ */
+extern unsigned long *empty_zero_page;
+#define ZERO_PAGE(vaddr)	(virt_to_page(empty_zero_page))
+
+extern unsigned long end_iomem;
+
+#endif /* !CONFIG_MMU */
+
+
 #endif

index fe66d659acad..95db8f06d295 100644
@@ -21,6 +21,7 @@
 #define __addr_range_nowrap(addr, size) \
 	((unsigned long) (addr) <= ((unsigned long) (addr) + (size)))
 
+#ifdef CONFIG_MMU
 extern unsigned long raw_copy_from_user(void *to, const void __user *from, unsigned long n);
 extern unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n);
 extern long __strncpy_from_user(char *dst, const char __user *src, long count);

@@ -46,4 +47,9 @@ static inline int __access_ok(unsigned long addr, unsigned long size)
 		uaccess_kernel());
 }
 
+#else
+#include <asm-generic/uaccess.h>
+#endif /* CONFIG_MMU */
+
+
 #endif

index d3dad11b459e..5253c3f8de0e 100644
@@ -16,8 +16,13 @@ struct lkl_jmp_buf {
  * These operations must be provided by a host library or by the application
  * itself.
  *
+ * @mem_alloc - allocate memory
+ * @mem_free - free memory
+ *
  */
 struct lkl_host_operations {
+	void *(*mem_alloc)(unsigned long mem);
+	void (*mem_free)(void *mem);
 };
 
 void lkl_bug(const char *fmt, ...);

2.21.0 (Apple Git-122.2)

nommu mode does not support user processes but it must support kernel threads as part as the normal kernel work-flow. It uses host operations to create and terminate host threads that are going to run the kernel threads. It also uses semaphores to synchronize those threads and to allow the Linux kernel scheduler to control how the kernel threads run.

Each kernel thread runs in a host threads and has a host semaphore associated with it - the thread's scheduling semaphore. The semaphore counter is initialized to 0. The first thing a kernel thread does after getting spawned, before running any kernel code, is to perform a down operation to block the thread.

The kernel controls host threads scheduling by performing up and down operations on the scheduling semaphore. In __switch_context an up operation on the next thread is performed to wake up a blocked thread, and a down operation is performed on the prev thread to block it.

A thread is terminated by marking it in free_thread_info and performing an up operation on the scheduling semaphore at which point the marked thread will terminate itself.

UML common part (process.c) is extended to call idle functions of SUBARCH as well as kernel thread detection with a flag information of TIF_HOST_THREAD.

---
 arch/um/include/asm/thread_info.h         |  24 ++
 arch/um/kernel/process.c                  |   8 +-
 arch/um/nommu/include/uapi/asm/host_ops.h |  54 +++++
 arch/um/nommu/um/cpu.c                    | 236 ++++++++++++++++++++
 arch/um/nommu/um/threads.c                | 258 ++++++++++++++++++++++
 5 files changed, 579 insertions(+), 1 deletion(-)
 create mode 100644 arch/um/nommu/um/cpu.c
 create mode 100644 arch/um/nommu/um/threads.c

index 4c19ce4c49f1..433584f6b9d0 100644
@@ -40,6 +40,7 @@ struct thread_info {
 	.real_thread = NULL,			\
 }
 
+#ifdef CONFIG_MMU
 /* how to get the thread information struct from C */
 static inline struct thread_info *current_thread_info(void)
 {

@@ -52,6 +53,27 @@ static inline struct thread_info *current_thread_info(void)
 	return ti;
 }
 
+#else
+
+#define __HAVE_THREAD_FUNCTIONS
+#define task_thread_info(task)	((struct thread_info *)(task)->stack)
+#define task_stack_page(task)	((task)->stack)
+#define end_of_stack(p) (&task_thread_info(p)->aux_fp_regs[FP_SIZE-1])
+
+void threads_init(void);
+void threads_cleanup(void);
+
+unsigned long *alloc_thread_stack_node(struct task_struct *p, int node);
+void setup_thread_stack(struct task_struct *p, struct task_struct *org);
+void free_thread_stack(struct task_struct *tsk);
+
+extern struct thread_info *_current_thread_info;
+static inline struct thread_info *current_thread_info(void)
+{
+	return _current_thread_info;
+}
+#endif /* CONFIG_MMU */
+
 #endif
 
 #define TIF_SYSCALL_TRACE	0	/* syscall trace active */

@@ -63,6 +85,8 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_RESTORE_SIGMASK	7
 #define TIF_NOTIFY_RESUME	8
 #define TIF_SECCOMP		9	/* secure computing */
+#define TIF_SCHED_JB		10
+#define TIF_HOST_THREAD		11
 
 #define _TIF_SYSCALL_TRACE	(1 << TIF_SYSCALL_TRACE)
 #define _TIF_SIGPENDING		(1 << TIF_SIGPENDING)

index e5238a42ea17..0dafded5947e 100644
@@ -157,7 +157,8 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
 		unsigned long arg, struct task_struct * p, unsigned long tls)
 {
 	void (*handler)(void);
-	int kthread = current->flags & PF_KTHREAD;
+	int kthread = current->flags & PF_KTHREAD ||
+		test_ti_thread_flag(current_thread_info(), TIF_HOST_THREAD);
 	int ret = 0;
 
 	p->thread = (struct thread_struct) INIT_THREAD;

@@ -214,10 +215,15 @@ static void um_idle_sleep(void)
 	}
 }
 
+void __weak subarch_cpu_idle(void)
+{
+}
+
 void arch_cpu_idle(void)
 {
 	cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
 	um_idle_sleep();
+	subarch_cpu_idle();
 	local_irq_enable();
 }
 

2.21.0 (Apple Git-122.2)

The application API is based on the kernel system call interface in order to offer a stable API to applications. Note that we can't offer the full Linux system call interface due to the limitations of nommu mode such as lack of virtual memory, signal, user processes, etc.

The host is using dedicated kernel thread, which is switched upon the entry of lkl_syscall so that numbers of context switches can be reduced for the faster performance.

To expose the API definitions to applications, this commit uses syscall_wrapper to define arch-specific information of syscall, and this is used to generate syscall_defs.h for lkl so that it can be used as a template of the list of syscall available for LKL apps.

To avoid collisions between the Linux API and the LKL API (e.g. struct stat, MKNOD, etc.) we use a python script to modify the user headers and to prefix all of the global symbols (structures, typedefs, defines) with LKL, lkl, _LKL, _lkl, __LKL or __lkl.

---
 arch/um/include/uapi/asm/Kbuild             |   2 +
 arch/um/nommu/include/asm/syscall_wrapper.h |  57 ++++
 arch/um/nommu/include/asm/syscalls.h        |  15 +
 arch/um/nommu/include/uapi/asm/host_ops.h   |  14 +
 arch/um/nommu/include/uapi/asm/syscalls.h   | 287 ++++++++++++++++++++
 arch/um/nommu/include/uapi/asm/unistd.h     |  15 +
 arch/um/nommu/um/syscalls.c                 | 199 ++++++++++++++
 arch/um/scripts/headers_install.py          | 197 ++++++++++++++
 8 files changed, 786 insertions(+)
 create mode 100644 arch/um/include/uapi/asm/Kbuild
 create mode 100644 arch/um/nommu/include/asm/syscall_wrapper.h
 create mode 100644 arch/um/nommu/include/asm/syscalls.h
 create mode 100644 arch/um/nommu/include/uapi/asm/syscalls.h
 create mode 100644 arch/um/nommu/include/uapi/asm/unistd.h
 create mode 100644 arch/um/nommu/um/syscalls.c
 create mode 100755 arch/um/scripts/headers_install.py

new file mode 100644
index 000000000000..a983c7f049bc
@@ -0,0 +1,2 @@
+# no generated-y since we need special user headers handling
+# see arch/um/script/headers_install.py

new file mode 100644
index 000000000000..6061d9415dad
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+int syscalls_init(void);
+void syscalls_cleanup(void);
+long lkl_syscall(long no, long *params);
+void wakeup_idle_host_task(void);
+
+#define sys_mmap sys_ni_syscall
+#define sys_rt_sigreturn sys_ni_syscall
+#define sys_arch_prctl sys_ni_syscall
+#define sys_iopl sys_ni_syscall
+#define sys_ioperm sys_ni_syscall
+#define sys_clone sys_ni_syscall
+
+int run_syscalls(void);

index 720385fccbdf..6ee9489fc47e 100644
@@ -38,6 +38,15 @@ struct lkl_jmp_buf {
  * @gettid - returns the host thread id of the caller, which need not
  * be the same as the handle returned by thread_create
  *
+ * @tls_alloc - allocate a thread local storage key; returns 0 if successful; if
+ * destructor is not NULL it will be called when a thread terminates with its
+ * argument set to the current thread local storage value
+ * @tls_free - frees a thread local storage key; returns 0 if successful
+ * @tls_set - associate data to the thread local storage key; returns 0 if
+ * successful
+ * @tls_get - return data associated with the thread local storage key or NULL
+ * on error
+ *
  * @jmp_buf_set - runs the give function and setups a jump back point by saving
  * the context in the jump buffer; jmp_buf_longjmp can be called from the give
  * function or any callee in that function to return back to the jump back

@@ -72,6 +81,11 @@ struct lkl_host_operations {
 	int (*thread_equal)(lkl_thread_t a, lkl_thread_t b);
 	long (*gettid)(void);
 
+	struct lkl_tls_key *(*tls_alloc)(void (*destructor)(void *));
+	void (*tls_free)(struct lkl_tls_key *key);
+	int (*tls_set)(struct lkl_tls_key *key, void *data);
+	void *(*tls_get)(struct lkl_tls_key *key);
+
 	void (*jmp_buf_set)(struct lkl_jmp_buf *jmpb, void (*f)(void));
 	void (*jmp_buf_longjmp)(struct lkl_jmp_buf *jmpb, int val);
 

new file mode 100644
index 000000000000..1762ebb829f5
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __UM_NOMMU_UAPI_UNISTD_H
+#define __UM_NOMMU_UAPI_UNISTD_H
+
+#define __ARCH_WANT_NEW_STAT
+#include <asm/bitsperlong.h>
+
+#if __BITS_PER_LONG == 64
+#define __ARCH_WANT_SYS_NEWFSTATAT
+#endif
+
+#include <asm-generic/unistd.h>
+
+
+#endif

2.21.0 (Apple Git-122.2)

This commit also disables stdio-console of UM if !CONFIG_MMU to avoid conflicts between multiple consoles.

---
 arch/um/drivers/Makefile                  |  8 ++++-
 arch/um/nommu/include/uapi/asm/host_ops.h |  3 ++
 arch/um/nommu/um/console.c                | 42 +++++++++++++++++++++++
 3 files changed, 52 insertions(+), 1 deletion(-)
 create mode 100644 arch/um/nommu/um/console.c

index ae96c83e312d..694da4aa550d 100644
@@ -37,7 +37,13 @@ $(obj)/vde.o: $(obj)/vde_kern.o $(obj)/vde_user.o
 # When the above is fixed, don't forget to add this too!
 #targets += $(obj)/pcap.o
 
-obj-y := stdio_console.o fd.o chan_kern.o chan_user.o line.o
+ifdef CONFIG_MMU
+obj-y := stdio_console.o
+else
+obj-y :=
+endif
+obj-y += fd.o chan_kern.o chan_user.o line.o
+
 obj-$(CONFIG_SSL) += ssl.o
 obj-$(CONFIG_STDERR_CONSOLE) += stderr_console.o
 

index 6ee9489fc47e..133877c857a1 100644
@@ -15,6 +15,7 @@ struct lkl_jmp_buf {
  *
  * These operations must be provided by a host library or by the application
  * itself.
+ * @print - optional operation that receives console messages
  *
  * @sem_alloc - allocate a host semaphore an initialize it to count
  * @sem_free - free a host semaphore

@@ -63,6 +64,8 @@ struct lkl_jmp_buf {
  *
  */
 struct lkl_host_operations {
+	void (*print)(const char *str, int len);
+
 	struct lkl_sem *(*sem_alloc)(int count);
 	void (*sem_free)(struct lkl_sem *sem);
 	void (*sem_up)(struct lkl_sem *sem);

2.21.0 (Apple Git-122.2)

Add the lkl_start_kernel and lkl_sys_halt APIs that start and respectively stops the Linux kernel.

lkl_start_kernel creates a separate threads that will run the initial and idle kernel thread. It waits for the kernel to complete initialization before returning, to avoid races with system calls issues by the host application.

During the setup phase, we create "/init" in initial ramfs root filesystem to avoid mounting the "real" rootfs since ramfs is good enough for now.

lkl_sys_halt will shutdown the kernel, terminate all threads and free all host resources used by the kernel before returning.

---
 arch/um/nommu/include/uapi/asm/host_ops.h |  14 ++
 arch/um/nommu/um/setup.c                  | 161 ++++++++++++++++++++++
 tools/um/uml/process.c                    |   2 +
 3 files changed, 177 insertions(+)
 create mode 100644 arch/um/nommu/um/setup.c

index 133877c857a1..0811494c080c 100644
@@ -16,6 +16,7 @@ struct lkl_jmp_buf {
  * These operations must be provided by a host library or by the application
  * itself.
  * @print - optional operation that receives console messages
+ * @panic - called during a kernel panic
  *
  * @sem_alloc - allocate a host semaphore an initialize it to count
  * @sem_free - free a host semaphore

@@ -65,6 +66,7 @@ struct lkl_jmp_buf {
  */
 struct lkl_host_operations {
 	void (*print)(const char *str, int len);
+	void (*panic)(void);
 
 	struct lkl_sem *(*sem_alloc)(int count);
 	void (*sem_free)(struct lkl_sem *sem);

@@ -96,6 +98,18 @@ struct lkl_host_operations {
 	void (*mem_free)(void *mem);
 };
 
+/**
+ * lkl_start_kernel - registers the host operations and starts the kernel
+ *
+ * The function returns only after the kernel is shutdown with lkl_sys_halt.
+ *
+ * @lkl_ops - pointer to host operations
+ * @cmd_line - format for command line string that is going to be used to
+ * generate the Linux kernel command line
+ */
+int lkl_start_kernel(struct lkl_host_operations *ops,
+		     const char *fmt, ...);
+
 void lkl_bug(const char *fmt, ...);
 
 #endif

index e52dd37ddadc..c39d914e80ac 100644
@@ -114,6 +114,8 @@ void os_kill_process(int pid, int reap_child)
 
 void os_kill_ptraced_process(int pid, int reap_child)
 {
+	if (pid == 0)
+		return;
 	kill(pid, SIGKILL);
 	ptrace(PTRACE_KILL, pid);
 	ptrace(PTRACE_CONT, pid);

2.21.0 (Apple Git-122.2)

In order to cooperate with UML's irq infrastructure and nommu threads based on host threads, irq handlers shall synchronize the our scheduler which is controlled by struct lkl_cpu. To do that, the irq infra notifies its entry of handlers by obtaining cpu access of thread scheduler (lkl_cpu_try_run_irq) and its release (lkl_cpu_put).

In additon to that, in order to stick the signal handler's thread to the one of the idle thread, several required configurations of (thread's) signal mask are added: otherwise handlers running on arbitrary thread cannot obtain cpu access and immediately fall into pending interrupt which may slow down the delivery of signals.

---
 arch/um/include/shared/os.h     |  1 +
 arch/um/kernel/irq.c            | 13 +++++++++++++
 arch/um/kernel/time.c           |  2 ++
 arch/um/nommu/include/asm/cpu.h |  3 +++
 arch/um/nommu/um/cpu.c          | 17 ++++++++++++++---
 arch/um/nommu/um/setup.c        |  5 +++++
 arch/um/nommu/um/threads.c      |  3 +++
 tools/um/uml/signal.c           | 12 ++++++++++--
 8 files changed, 51 insertions(+), 5 deletions(-)

index f467d28fc0b4..0da3ce22e16f 100644
@@ -241,6 +241,7 @@ extern int set_signals(int enable);
 extern int set_signals_trace(int enable);
 extern int os_is_signal_stack(void);
 extern void deliver_alarm(void);
+extern void set_pending_signals(int sig);
 
 /* util.c */
 extern void stack_protections(unsigned long address);

index 3577118bb4a5..4ce7f5fef7f8 100644
@@ -19,6 +19,7 @@
 #include <kern_util.h>
 #include <os.h>
 #include <irq_user.h>
+#include <asm/cpu.h>
 
 
 extern void free_irqs(void);

@@ -541,6 +542,11 @@ unsigned long to_irq_stack(unsigned long *mask_out)
 	unsigned long mask, old;
 	int nested;
 
+#ifndef CONFIG_MMU
+	if (!nommu_irq_enter(ffs(*mask_out) - 1))
+		return 1;
+#endif
+
 	mask = xchg(&pending_mask, *mask_out);
 	if (mask != 0) {
 		/*

@@ -557,6 +563,10 @@ unsigned long to_irq_stack(unsigned long *mask_out)
 			old |= mask;
 			mask = xchg(&pending_mask, old);
 		} while (mask != old);
+
+#ifndef CONFIG_MMU
+		nommu_irq_exit();
+#endif
 		return 1;
 	}
 

@@ -594,6 +604,9 @@ unsigned long from_irq_stack(int nested)
 	*to = *ti;
 
 	mask = xchg(&pending_mask, 0);
+#ifndef CONFIG_MMU
+	nommu_irq_exit();
+#endif
 	return mask & ~1;
 }
 

index 25eaa6a0c658..9e141fe8fe27 100644
@@ -597,11 +597,13 @@ static struct clock_event_device timer_clockevent = {
 
 static irqreturn_t um_timer(int irq, void *dev)
 {
+#ifdef CONFIG_MMU
 	if (get_current()->mm != NULL)
 	{
         /* userspace - relay signal, results in correct userspace timers */
 		os_alarm_process(get_current()->mm->context.id.u.pid);
 	}
+#endif
 
 	(*timer_clockevent.event_handler)(&timer_clockevent);
 

index c101c078ef21..c52a78c77bea 100644
@@ -10,4 +10,7 @@ void lkl_cpu_wait_shutdown(void);
 void lkl_cpu_change_owner(lkl_thread_t owner);
 void lkl_cpu_set_irqs_pending(void);
 
+void nommu_irq_exit(void);
+int nommu_irq_enter(int sig);
+
 #endif

index 9986a3f8c5dd..75d8bdc1847e 100644
@@ -8,15 +8,16 @@
 #include <asm/sched.h>
 #include <asm/syscalls.h>
 #include <init.h>
+#include <os.h>
 
 void run_irqs(void)
 {
-	panic("unimplemented %s", __func__);
+	unblock_signals();
 }
 
-int set_irq_pending(int irq)
+void set_irq_pending(int sig)
 {
-	panic("unimplemented %s", __func__);
+	set_pending_signals(sig);
 }
 
 /*

@@ -174,6 +175,16 @@ int lkl_cpu_try_run_irq(int irq)
 	return ret;
 }
 
+int nommu_irq_enter(int sig)
+{
+	return lkl_cpu_try_run_irq(sig);
+}
+
+void nommu_irq_exit(void)
+{
+	return lkl_cpu_put();
+}
+
 static void lkl_cpu_shutdown(void)
 {
 	__sync_fetch_and_add(&cpu.shutdown_gate, MAX_THREADS);

index 25aa003792d4..f74baea50bd3 100644
@@ -36,6 +36,8 @@ static void __init *lkl_run_kernel(void *arg)
 
 	panic_blink = lkl_panic_blink;
 
+	/* signal should be received at this thread (main and idle threads) */
+	init_new_thread_signals();
 	threads_init();
 	lkl_cpu_get();
 	start_kernel();

@@ -58,6 +60,9 @@ int __init lkl_start_kernel(struct lkl_host_operations *ops,
 	if (ret)
 		goto out_free_init_sem;
 
+	change_sig(SIGALRM, 0);
+	change_sig(SIGIO, 0);
+
 	ret = lkl_ops->thread_create(lkl_run_kernel, NULL);
 	if (!ret) {
 		ret = -ENOMEM;

index 3e70eccc191a..df96057100fd 100644
@@ -151,6 +151,9 @@ static void *thread_bootstrap(void *_tba)
 	int (*f)(void *) = tba->f;
 	void *arg = tba->arg;
 
+	change_sig(SIGALRM, 0);
+	change_sig(SIGIO, 0);
+
 	lkl_ops->sem_down(ti->task->thread.arch.sched_sem);
 	kfree(tba);
 	if (ti->task->thread.prev_sched)

index b58bc68cbe64..2b5c98de21cd 100644
@@ -218,8 +218,8 @@ void set_handler(int sig)
 
 	sigemptyset(&sig_mask);
 	sigaddset(&sig_mask, sig);
-	if (sigprocmask(SIG_UNBLOCK, &sig_mask, NULL) < 0)
-		panic("sigprocmask failed - errno = %d\n", errno);
+	if (pthread_sigmask(SIG_UNBLOCK, &sig_mask, NULL) < 0)
+		panic("pthread_sigmask failed - errno = %d\n", errno);
 }
 
 int change_sig(int signal, int on)

@@ -355,3 +355,11 @@ int os_is_signal_stack(void)
 
 	return ss.ss_flags & SS_ONSTACK;
 }
+
+void set_pending_signals(int sig)
+{
+	if (sig == SIGIO)
+		signals_pending |= SIGIO_MASK;
+	else if (sig == SIGALRM)
+		signals_pending |= SIGALRM_MASK;
+}

2.21.0 (Apple Git-122.2)

Basic Makefiles for building library of nommu mode. Add a new architecture specific target for installing the resulting library files and headers.

To make nommu binaries build, UML introduced an additional option, UMMODE variable, to switch the output file of build: kernel (default), or library (nommu). Those modes are not able to be ON at the same time.

To build on library mode, users do the following:

make defconfig ARCH=um UMMODE=library
make ARCH=um UMMODE=library

---
 arch/um/Kconfig           | 17 ++++++++++++++---
 arch/um/Makefile          | 10 +++++++++-
 arch/um/kernel/Makefile   | 12 ++++++++----
 arch/um/nommu/um/Kconfig  | 37 +++++++++++++++++++++++++++++++++++++
 arch/um/nommu/um/Makefile |  4 ++++
 5 files changed, 72 insertions(+), 8 deletions(-)
 create mode 100644 arch/um/nommu/um/Kconfig
 create mode 100644 arch/um/nommu/um/Makefile

index a0a9fd3ab96c..300fcc90cff3 100644
@@ -22,9 +22,20 @@ config UML
 	select TTY # Needed for line.c
 	select MODULE_REL_CRCS if MODVERSIONS
 
+config UMMODE_LIB
+	bool "UML mode: library mode"
+	default y if "$(UMMODE)" = "library"
+	help
+	 This mode switches a mode to build a library of UML (Linux
+	 Kernel Library/LKL).  This switch is exclusive to "kernel mode"
+	 of UML, which is traditional mode of UML.
+
+	 For more detail about LKL, see
+	 <file:Documentation/virt/uml/lkl.txt>.
+
 config MMU
 	bool
-	default y
+	default y if !UMMODE_LIB
 
 config NO_IOMEM
 	def_bool y

@@ -45,12 +56,12 @@ config LOCKDEP_SUPPORT
 
 config STACKTRACE_SUPPORT
 	bool
-	default y
+	default y if MMU
 	select STACKTRACE
 
 config GENERIC_CALIBRATE_DELAY
 	bool
-	default y
+	default y if MMU
 
 config HZ
 	int

index af0cf64c1428..7e640e65a80e 100644
@@ -17,6 +17,10 @@ else
         KBUILD_DEFCONFIG := $(SUBARCH)_defconfig
 endif
 
+ifeq ($(UMMODE),library)
+  SUBARCH := um/nommu
+endif
+
 ARCH_DIR := arch/um
 OS := $(shell uname -s)
 # We require bash because the vmlinux link and loader script cpp use bash

@@ -102,9 +106,13 @@ all: linux.o
 
 linux.o: vmlinux
 	@echo '  LINK $@'
-	$(Q)$(OBJCOPY) -R .eh_frame $< $@
+	$(Q)$(OBJCOPY) -R .eh_frame -L sem_init -L sem_post -L sem_wait -L sem_destroy $< $@
 
+ifeq ($(UMMODE),library)
+install: linux.o um_headers_install
+else
 install: linux.o
+endif
 	@echo "  INSTALL $(INSTALL_PATH)/lib/$<"
 	@mkdir -p $(INSTALL_PATH)/lib/
 	@cp $< $(INSTALL_PATH)/lib/

index 5aa882011e04..bdc4108bc52e 100644
@@ -14,10 +14,14 @@ CPPFLAGS_vmlinux.lds := -DSTART=$(LDS_START)		\
 			$(LDS_EXTRA)
 extra-y := vmlinux.lds
 
-obj-y = config.o exec.o exitcode.o irq.o ksyms.o mem.o \
-	physmem.o process.o ptrace.o reboot.o sigio.o \
-	signal.o syscall.o sysrq.o time.o tlb.o trap.o \
-	um_arch.o umid.o maccess.o kmsg_dump.o skas/
+obj-y = config.o exitcode.o irq.o ksyms.o \
+	process.o reboot.o sigio.o \
+	signal.o syscall.o time.o \
+	um_arch.o umid.o maccess.o kmsg_dump.o
+
+ifdef CONFIG_MMU
+obj-y += exec.o mem.o physmem.o ptrace.o sysrq.o tlb.o trap.o skas/
+endif
 
 obj-$(CONFIG_BLK_DEV_INITRD) += initrd.o
 obj-$(CONFIG_GPROF)	+= gprof_syms.o

new file mode 100644
index 000000000000..20b3eaccb6f0
@@ -0,0 +1,37 @@
+config UML_NOMMU
+	def_bool y
+	depends on !SMP && !MMU
+	select UACCESS_MEMCPY
+	select ARCH_THREAD_STACK_ALLOCATOR
+	select ARCH_HAS_SYSCALL_WRAPPER
+
+config 64BIT
+	bool
+	default y
+
+config GENERIC_CSUM
+	def_bool y
+
+config GENERIC_ATOMIC64
+	bool
+	default y if !64BIT
+
+config SECCOMP
+	bool
+	default n
+
+config GENERIC_HWEIGHT
+	def_bool y
+
+config GENERIC_CALIBRATE_DELAY
+	bool
+	default n
+
+config STACKTRACE_SUPPORT
+	bool
+	default n
+
+# XXX: need this to work well with tap13.py
+config PRINTK_TIME
+	bool
+	default y

new file mode 100644
index 000000000000..b580e0fe97b5
@@ -0,0 +1,4 @@
+include/generated/user_constants.h: $(srctree)/arch/um/nommu/um/user_constants.h
+	$(Q)cp -f $^ $@
+
+obj-y = bootmem.o console.o cpu.o delay.o setup.o syscalls.o threads.o unimplemented.o

2.21.0 (Apple Git-122.2)

This patch adds the skeleton for the host library.

The host library is implementing the host operations needed by nommu mode and is split into host dependent (depends on a specific host, e.g. POSIX hosts) and host independent parts (will work on all supported hosts).

---
 tools/um/Makefile                  |   7 +-
 tools/um/Targets                   |   3 +-
 tools/um/include/lkl.h             | 151 +++++++++++++++++++++++++++++
 tools/um/include/lkl_host.h        |  26 +++++
 tools/um/uml/Build                 |  15 ++-
 tools/um/uml/nommu/Build           |   1 +
 tools/um/uml/nommu/registers.c     |  21 ++++
 tools/um/uml/nommu/unimplemented.c |  21 ++++
 8 files changed, 238 insertions(+), 7 deletions(-)
 create mode 100644 tools/um/include/lkl.h
 create mode 100644 tools/um/include/lkl_host.h
 create mode 100644 tools/um/uml/nommu/Build
 create mode 100644 tools/um/uml/nommu/registers.c
 create mode 100644 tools/um/uml/nommu/unimplemented.c

index 552ed5f1edae..a93e060b1f89 100644
@@ -5,6 +5,7 @@
 MAKEFLAGS += -r --no-print-directory
 
 KCONFIG?=defconfig
+UMMODE?=kernel
 
 ifneq ($(silent),1)
   ifneq ($(V),1)

@@ -47,8 +48,9 @@ all: $(TARGETS)
 
 # rule to build linux.o
 $(OUTPUT)lib/linux.o:
-	$(Q)CFLAGS= $(MAKE) -C ../.. ARCH=um $(KOPT) $(KCONFIG)
-	$(Q)CFLAGS= $(MAKE) -C ../.. ARCH=um $(KOPT) install INSTALL_PATH=$(OUTPUT)
+	$(Q)CFLAGS= $(MAKE) -C ../.. ARCH=um UMMODE=$(UMMODE) $(KOPT) $(KCONFIG)
+	$(Q)CFLAGS= $(MAKE) -C ../.. ARCH=um UMMODE=$(UMMODE) $(KOPT) install \
+	INSTALL_PATH=$(OUTPUT)
 
 $(OUTPUT)liblinux.a: $(OUTPUT)lib/linux.o $(OUTPUT)uml/liblinux-in.o $(OUTPUT)lib/liblinux-in.o
 	$(QUIET_AR)$(AR) -rc $@ $^

@@ -67,6 +69,7 @@ $(OUTPUT)%-in.o: $(OUTPUT)lib/linux.o FORCE
 clean:
 	$(call QUIET_CLEAN, objects)find $(OUTPUT) -name '*.o' -delete -o -name '\.*.cmd'\
 	 -delete -o -name '\.*.d' -delete
+	$(call QUIET_CLEAN, headers)$(RM) -r $(OUTPUT)/include/lkl/
 	$(call QUIET_CLEAN, liblinux.a)$(RM) $(OUTPUT)/liblinux.a
 	$(call QUIET_CLEAN, $(TARGETS))$(RM) $(TARGETS)
 

index a4711f1ef422..4e1f0f4d81a3 100644
@@ -1,4 +1,5 @@
 progs-y += uml/linux
-LDLIBS_linux-y := -lrt -lpthread -lutil
+
+LDLIBS := -lrt -lpthread -lutil
 LDFLAGS_linux-y := -no-pie -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc
 LDFLAGS_linux-$(UML_STATIC) += -static

new file mode 100644
index 000000000000..85e80eb4ad0d
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LKL_HOST_H
+#define _LKL_HOST_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <lkl/asm/host_ops.h>
+#include <lkl.h>
+
+extern struct lkl_host_operations lkl_host_ops;
+
+/**
+ * lkl_printf - print a message via the host print operation
+ *
+ * @fmt: printf like format string
+ */
+int lkl_printf(const char *fmt, ...);
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

index 435a9670d3ff..191c6479ad72 100644
@@ -8,11 +8,19 @@ KCOV_INSTRUMENT                := n
 
 include $(objtree)/include/config/auto.conf
 
-liblinux-y += execvp.o file.o helper.o irq.o main.o mem.o process.o \
-	registers.o sigio.o signal.o start_up.o time.o tty.o \
-	umid.o user_syms.o util.o drivers/ skas/
+liblinux-y += execvp.o file.o helper.o irq.o mem.o process.o \
+	registers.o sigio.o signal.o time.o tty.o \
+	umid.o user_syms.o util.o drivers/
 
+ifdef CONFIG_MMU
+liblinux-y += main.o start_up.o skas/
+HEADER_ARCH 	:= x86
 liblinux-y += x86/
+else
+HEADER_ARCH 	:= um/nommu
+liblinux-y += nommu/
+endif
+
 
 liblinux-$(CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA) += elf_aux.o
 

@@ -23,7 +31,6 @@ CFLAGS := -g -O2
 
 # from arch/um/Makefile
 ARCH_DIR := arch/um
-HEADER_ARCH 	:= x86
 HOST_DIR := arch/$(HEADER_ARCH)
 ifdef CONFIG_64BIT
   KBUILD_CFLAGS += -mcmodel=large

new file mode 100644
index 000000000000..98fd6b86a085
@@ -0,0 +1 @@
+liblinux-y = registers.o unimplemented.o

new file mode 100644
index 000000000000..11573a204720
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+
+struct uml_pt_regs;
+
+int get_fp_registers(int pid, unsigned long *regs)
+{
+	return 0;
+}
+
+int save_i387_registers(int pid, unsigned long *fp_regs)
+{
+	return 0;
+}
+
+void arch_init_registers(int pid)
+{
+}
+
+void get_regs_from_mc(struct uml_pt_regs *regs, void *mc)
+{
+}

new file mode 100644
index 000000000000..9da3e5c8bafb
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <generated/user_constants.h>
+
+struct uml_pt_regs;
+
+/* os-Linux/skas/process.c */
+int userspace_pid[UM_NR_CPUS];
+void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
+{}
+
+
+/* x86/os-Linux/task_size.c */
+unsigned long os_get_top_address(void)
+{
+	return 0;
+}
+
+/* start-up.c */
+void os_early_checks(void)
+{
+}

2.21.0 (Apple Git-122.2)

Add basic utility functions for getting a string from a kernel error code and a fprintf like function that uses the host print operation. The latter is useful for informing the user about errors that occur in the host library.

---
 tools/um/lib/Build     |   4 +
 tools/um/lib/jmp_buf.c |  14 +++
 tools/um/lib/jmp_buf.h |   8 ++
 tools/um/lib/utils.c   | 210 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 236 insertions(+)
 create mode 100644 tools/um/lib/Build
 create mode 100644 tools/um/lib/jmp_buf.c
 create mode 100644 tools/um/lib/jmp_buf.h
 create mode 100644 tools/um/lib/utils.c

new file mode 100644
index 000000000000..fc967af4104a
@@ -0,0 +1,4 @@
+include $(objtree)/include/config/auto.conf
+
+liblinux-$(CONFIG_UMMODE_LIB) += utils.o
+liblinux-$(CONFIG_UMMODE_LIB) += jmp_buf.o

new file mode 100644
index 000000000000..f6bdd7e4bd83
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <setjmp.h>
+#include <lkl_host.h>
+
+void jmp_buf_set(struct lkl_jmp_buf *jmpb, void (*f)(void))
+{
+	if (!setjmp(*((jmp_buf *)jmpb->buf)))
+		f();
+}
+
+void jmp_buf_longjmp(struct lkl_jmp_buf *jmpb, int val)
+{
+	longjmp(*((jmp_buf *)jmpb->buf), val);
+}

new file mode 100644
index 000000000000..8782cbaaf51f
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LKL_LIB_JMP_BUF_H
+#define _LKL_LIB_JMP_BUF_H
+
+void jmp_buf_set(struct lkl_jmp_buf *jmpb, void (*f)(void));
+void jmp_buf_longjmp(struct lkl_jmp_buf *jmpb, int val);
+
+#endif

2.21.0 (Apple Git-122.2)

This commit implements LKL host operations for POSIX hosts. The operations are implemented to be portable in various POSIX OSs.

---
 tools/um/lib/Build        |   2 +
 tools/um/lib/posix-host.c | 292 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 294 insertions(+)
 create mode 100644 tools/um/lib/posix-host.c

index fc967af4104a..dddff26a3b4e 100644
@@ -1,4 +1,6 @@
 include $(objtree)/include/config/auto.conf
+CFLAGS_posix-host.o += -D_FILE_OFFSET_BITS=64
 
 liblinux-$(CONFIG_UMMODE_LIB) += utils.o
+liblinux-$(CONFIG_UMMODE_LIB) += posix-host.o
 liblinux-$(CONFIG_UMMODE_LIB) += jmp_buf.o

2.21.0 (Apple Git-122.2)

Add a simple LKL test application (boot) that starts the kernel and performs simple tests that minimally exercise the LKL API.

---
 tools/um/Makefile       |   5 +-
 tools/um/Targets        |   6 +
 tools/um/tests/Build    |   1 +
 tools/um/tests/boot.c   | 393 ++++++++++++++++++++++++++++++++++++++++
 tools/um/tests/boot.sh  |   9 +
 tools/um/tests/run.py   | 172 ++++++++++++++++++
 tools/um/tests/tap13.py | 209 +++++++++++++++++++++
 tools/um/tests/test.c   | 126 +++++++++++++
 tools/um/tests/test.h   |  72 ++++++++
 tools/um/tests/test.sh  | 181 ++++++++++++++++++
 10 files changed, 1173 insertions(+), 1 deletion(-)
 create mode 100644 tools/um/tests/Build
 create mode 100644 tools/um/tests/boot.c
 create mode 100755 tools/um/tests/boot.sh
 create mode 100755 tools/um/tests/run.py
 create mode 100644 tools/um/tests/tap13.py
 create mode 100644 tools/um/tests/test.c
 create mode 100644 tools/um/tests/test.h
 create mode 100644 tools/um/tests/test.sh

index a93e060b1f89..20de2e4c162f 100644
@@ -73,7 +73,10 @@ clean:
 	$(call QUIET_CLEAN, liblinux.a)$(RM) $(OUTPUT)/liblinux.a
 	$(call QUIET_CLEAN, $(TARGETS))$(RM) $(TARGETS)
 
+run-tests:
+	./tests/run.py $(tests)
+
 FORCE: ;
-.PHONY: all clean FORCE
+.PHONY: all clean FORCE run-tests
 .IGNORE: clean
 .NOTPARALLEL : lib/linux.o

index 4e1f0f4d81a3..2bb90381843c 100644
@@ -1,4 +1,10 @@
+ifeq ($(UMMODE),library)
+progs-y += tests/boot
+else
 progs-y += uml/linux
+endif
+
+LDFLAGS_boot-y := -pie
 
 LDLIBS := -lrt -lpthread -lutil
 LDFLAGS_linux-y := -no-pie -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc

new file mode 100644
index 000000000000..26a607f90dc8
@@ -0,0 +1 @@
+boot-y += boot.o test.o

new file mode 100755
index 000000000000..d985c04b0ac1
@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: GPL-2.0
+
+script_dir=$(cd $(dirname ${BASH_SOURCE:-$0}); pwd)
+source $script_dir/test.sh
+
+lkl_test_plan 1 "boot"
+lkl_test_run 1
+lkl_test_exec $script_dir/boot

2.21.0 (Apple Git-122.2)

This commit adds block device support for nommu mode, and also added several host utilities to run a simple test program (tools/um/test/disk.c) successfully.

---
 arch/um/include/asm/xor.h                 |   3 +-
 arch/um/include/shared/as-layout.h        |   1 +
 arch/um/kernel/um_arch.c                  |   5 +
 arch/um/nommu/include/uapi/asm/host_ops.h |   7 +
 arch/um/nommu/include/uapi/asm/unistd.h   |   2 +
 arch/um/nommu/um/Kconfig                  |   8 +
 arch/um/nommu/um/setup.c                  |  12 +
 tools/um/Targets                          |   2 +
 tools/um/include/lkl.h                    | 206 ++++++++++
 tools/um/include/lkl_host.h               |   1 +
 tools/um/lib/Build                        |   1 +
 tools/um/lib/fs.c                         | 461 ++++++++++++++++++++++
 tools/um/lib/posix-host.c                 |   1 +
 tools/um/lib/utils.c                      |   3 +
 tools/um/tests/Build                      |   1 +
 tools/um/tests/cla.c                      | 159 ++++++++
 tools/um/tests/cla.h                      |  33 ++
 tools/um/tests/disk.c                     | 168 ++++++++
 tools/um/tests/disk.sh                    |  70 ++++
 tools/um/tests/run.py                     |   2 +
 20 files changed, 1145 insertions(+), 1 deletion(-)
 create mode 100644 tools/um/lib/fs.c
 create mode 100644 tools/um/tests/cla.c
 create mode 100644 tools/um/tests/cla.h
 create mode 100644 tools/um/tests/disk.c
 create mode 100755 tools/um/tests/disk.sh

index 36b33d62a35d..a5ea458a1ae9 100644
@@ -4,4 +4,5 @@
 
 /* pick an arbitrary one - measuring isn't possible with inf-cpu */
 #define XOR_SELECT_TEMPLATE(x)	\
-	(time_travel_mode == TT_MODE_INFCPU ? &xor_block_8regs : NULL)
+	(time_travel_mode == TT_MODE_INFCPU || (!IS_ENABLED(CONFIG_MMU)) ? \
+	 &xor_block_8regs : NULL)

index 5f286ef2721b..4423437a5ace 100644
@@ -57,6 +57,7 @@ extern unsigned long host_task_size;
 
 extern int linux_main(int argc, char **argv);
 extern void uml_finishsetup(void);
+extern void uml_set_args(char *args);
 
 struct siginfo;
 extern void (*sig_info[])(int, struct siginfo *si, struct uml_pt_regs *);

index 78d6042fd2e6..ed0149821518 100644
@@ -42,6 +42,11 @@ static void __init add_arg(char *arg)
 	strcat(command_line, arg);
 }
 
+void __init uml_set_args(char *args)
+{
+	strcat(command_line, args);
+}
+
 /*
  * These fields are initialized at boot time and not changed.
  * XXX This structure is used only in the non-SMP case.  Maybe this

index 0811494c080c..1b2507502969 100644
@@ -15,6 +15,11 @@ struct lkl_jmp_buf {
  *
  * These operations must be provided by a host library or by the application
  * itself.
+ *
+ * @um_devices - string containg the list of UML devices in command line
+ * format. This string is appended to the kernel command line and
+ * is provided here for convenience to be implemented by the host library.
+ *
  * @print - optional operation that receives console messages
  * @panic - called during a kernel panic
  *

@@ -65,6 +70,8 @@ struct lkl_jmp_buf {
  *
  */
 struct lkl_host_operations {
+	const char *um_devices;
+
 	void (*print)(const char *str, int len);
 	void (*panic)(void);
 

index 1762ebb829f5..320762099a62 100644
@@ -3,6 +3,8 @@
 #define __UM_NOMMU_UAPI_UNISTD_H
 
 #define __ARCH_WANT_NEW_STAT
+#define __ARCH_WANT_SET_GET_RLIMIT
+
 #include <asm/bitsperlong.h>
 
 #if __BITS_PER_LONG == 64

index 20b3eaccb6f0..c6a3f472fe75 100644
@@ -4,6 +4,10 @@ config UML_NOMMU
 	select UACCESS_MEMCPY
 	select ARCH_THREAD_STACK_ALLOCATOR
 	select ARCH_HAS_SYSCALL_WRAPPER
+	select VFAT_FS
+	select NLS_CODEPAGE_437
+	select NLS_ISO8859_1
+	select BTRFS_FS
 
 config 64BIT
 	bool

@@ -35,3 +39,7 @@ config STACKTRACE_SUPPORT
 config PRINTK_TIME
 	bool
 	default y
+
+config RAID6_PQ_BENCHMARK
+	bool
+	default n

index f74baea50bd3..6b49bf7a99fb 100644
@@ -45,13 +45,25 @@ static void __init *lkl_run_kernel(void *arg)
 	return NULL;
 }
 
+static char _cmd_line[COMMAND_LINE_SIZE];
 int __init lkl_start_kernel(struct lkl_host_operations *ops,
 			    const char *fmt, ...)
 {
+	va_list ap;
 	int ret;
 
 	lkl_ops = ops;
 
+	va_start(ap, fmt);
+	ret = vsnprintf(_cmd_line, COMMAND_LINE_SIZE, fmt, ap);
+	va_end(ap);
+
+	if (ops->um_devices)
+		strscpy(_cmd_line + ret, ops->um_devices,
+			COMMAND_LINE_SIZE - ret);
+
+	uml_set_args(_cmd_line);
+
 	init_sem = lkl_ops->sem_alloc(0);
 	if (!init_sem)
 		return -ENOMEM;

index 2bb90381843c..f5f8ec4b9dbb 100644
@@ -1,10 +1,12 @@
 ifeq ($(UMMODE),library)
 progs-y += tests/boot
+progs-y += tests/disk
 else
 progs-y += uml/linux
 endif
 
 LDFLAGS_boot-y := -pie
+LDFLAGS_disk-y := -pie
 
 LDLIBS := -lrt -lpthread -lutil
 LDFLAGS_linux-y := -no-pie -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc

index 85e80eb4ad0d..12dd95616e43 100644
@@ -10,6 +10,7 @@ extern "C" {
 #include <lkl.h>
 
 extern struct lkl_host_operations lkl_host_ops;
+extern char lkl_um_devs[4096];
 
 /**
  * lkl_printf - print a message via the host print operation

index dddff26a3b4e..29491b40746c 100644
@@ -4,3 +4,4 @@ CFLAGS_posix-host.o += -D_FILE_OFFSET_BITS=64
 liblinux-$(CONFIG_UMMODE_LIB) += utils.o
 liblinux-$(CONFIG_UMMODE_LIB) += posix-host.o
 liblinux-$(CONFIG_UMMODE_LIB) += jmp_buf.o
+liblinux-$(CONFIG_UMMODE_LIB) += fs.o

index b6b5b2902254..8fd88031bf2b 100644
@@ -263,6 +263,7 @@ static void *tls_get(struct lkl_tls_key *key)
 }
 
 struct lkl_host_operations lkl_host_ops = {
+	.um_devices = lkl_um_devs,
 	.panic = panic,
 	.print = print,
 	.mem_alloc = (void *)malloc,

index 4930479a8a35..ac65cd744a14 100644
@@ -4,6 +4,9 @@
 #include <string.h>
 #include <lkl_host.h>
 
+/* XXX: find a better place */
+char lkl_um_devs[4096];
+
 static const char * const lkl_err_strings[] = {
 	"Success",
 	"Operation not permitted",

index 26a607f90dc8..b62919cadc50 100644
@@ -1 +1,2 @@
 boot-y += boot.o test.o
+disk-y += disk.o test.o cla.o

new file mode 100644
index 000000000000..3d879233681f
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _LKL_TEST_CLA_H
+#define _LKL_TEST_CLA_H
+
+enum cl_arg_type {
+	CL_ARG_USER = 0,
+	CL_ARG_BOOL,
+	CL_ARG_INT,
+	CL_ARG_STR,
+	CL_ARG_STR_SET,
+	CL_ARG_IPV4,
+	CL_ARG_END,
+};
+
+struct cl_arg;
+
+typedef int (*cl_arg_parser_t)(struct cl_arg *arg, const char *value);
+
+struct cl_arg {
+	const char *long_name;
+	char short_name;
+	const char *help;
+	int has_arg;
+	enum cl_arg_type type;
+	void *store;
+	void *set;
+	cl_arg_parser_t parser;
+};
+
+int cla_parse_args(int argc, const char **argv, struct cl_arg *args);
+
+
+#endif /* _LKL_TEST_CLA_H */

index c96ede90b6ad..97d6dedc217c 100755
@@ -50,6 +50,8 @@ mydir=os.path.dirname(os.path.realpath(__file__))
 
 tests = [
     'boot.sh',
+    'disk.sh -t ext4',
+    'disk.sh -t vfat',
 ]
 
 parser = argparse.ArgumentParser(description='LKL test runner')

2.21.0 (Apple Git-122.2)

This is another spin of the unification of LKL into UML. Based on the discussion of v4 patchset, we have tried to address issue raised and rewrote the patchset from scratch. The summary is listed in the changelog below.

Although there are still bugs in the patchset, we'd like to ask your opinions on the design we changed.

The milestone section is also updated: this patchset is for the milestone 1, though the common init API is still not implemented yet.

Changes in rfc v6:
- rebase with the current linus tree

Changes in rfc v5:
- rewrite whole patchset from scratch
- move arch-dependent code of arch/um and arch/x86/um to tools/um
- mainly code under os-Linux/ involved
- introduce 2-stage build (kernel, and host-dependent parts)
- clean up vmlinux.lds.S
- put LKL-specific implementations as a SUBARCH under arch/um/nommu
- introduce !CONFIG_MMU in arch/um
- use struct arch_thread and arch_switch_to() for subarch-specific thread implementation
- integrate with the IRQ infrastructure of UML
- tested with block device drivers (ubd) for the proof

Changes in rfc v4: (https://lwn.net/Articles/816276/)
- Rebase on the current uml/master branch
- Fix IRQ handling (bug fix)
- drop a patch for CONFIG_GENERIC_ATOMIC64 (comment by Peter Zijlstra)
- implement vector net driver for UMMODE_LIB (comment by Anton)
- clean up uapi headers to avoid duplicates
- clean up IRQ handling code (comment by Anton)
- fix error handling in test code (comments by David Disseldorp)

Changes in rfc v3:
- use UML drivers (net, block) from LKL programs
- drop virtio device implementations
- drop mingw32 (Windows) host
- drop android (arm/aarch64) host
- drop FreeBSD (x86_64) host
- drop LD_PRELOAD (hijack) support
- update milestone

rfc v2:
- use UMMODE instead of SUBARCH to switch UML or LKL
- tools/lkl directory is still there. I confirmed we can move under arch/um (e.g., arch/um/lkl/hosts). I will move it IF this is preferable.
- drop several patches involved non-uml directory
- drop several patches which are not required
- refine commit logs
- document updated

LKL (Linux Kernel Library) is aiming to allow reusing the Linux kernel code as extensively as possible with minimal effort and reduced maintenance overhead.

Examples of how LKL can be used are: creating userspace applications (running on Linux and other operating systems) that can read or write Linux filesystems or can use the Linux networking stack, creating kernel drivers for other operating systems that can read Linux filesystems, bootloaders support for reading/writing Linux filesystems, etc.

With LKL, the kernel code is compiled into an object file that can be directly linked by applications. The API offered by LKL is based on the Linux system call interface.

LKL is originally implemented as an architecture port in arch/lkl, but this series of commits tries to integrate this into arch/um as one of the mode of UML. This was discussed during RFC email of LKL (*1).

The latest LKL version can be found at https://github.com/lkl/linux

Milestone
=========
This patches is a first step toward upstreaming *library mode* of Linux kernel, but we think we need to have several steps toward our goal, describing in the below.

Milestone 1: LKL lib on top of UML
* Kernel - Host build split
- Build UML as a relocatable object using the UML's kernel linker script.
- Move the ptrace and other well isolated os code out of arch/um to tools/um
- Use standard host toolchain to create a static library stripped of the ptrace code. Use standard host toolchain to build the main UML executable.
- Add library init API that creates the UML kernel process and starts UML.
* System calls APIs
- Add new system call interface based on UML's irq facility.
- Use the LKL scripts to export the required headers to create system calls APIs that use the UML system calls infrastructure.
- Keep the underlying host and driver operations (threads, irqs, etc.) as they are now in UML.
* Boot test
- Port the LKL boot test to verify that we are able to programatically issue system calls.

Milestone 2: add virtio disk support
* Export asm/io.h operations to host/os. Create IO access operations and redirect them to weak os_ variants that use the current UML implementation.
* Add the LKL IO access layer including generic virtio handling and the virtio block device code.
* Port LKL disk test and disk apps (lklfuse, fs2tar, cptofs)

Milestone 3: new arch ports
* Abstract the system call / IRQ mode the move the implementation to host
* Abstract the thread model and move the implementation to host
* Add LKL thread model and LKL ports

Building LKL the host library and LKL applications
==================================================

% cd tools/um
% make

will build LKL as a object file, it will install it in tools/um/lib together with the headers files in tools/um/include then will build the host library, tests and a few of application examples:

* tests/boot - a simple applications that uses LKL and exercises the basic LKL APIs

% make run-tests

should run the above tests/boot and tests/net-test and report errors if there are any.

Supported hosts
===============

Currently LKL supports Linux userspace applications. New hosts can be added relatively easy if the host supports gcc and GNU ld. Previous versions of LKL supported Windows kernel and Haiku kernel hosts, and we also have WIP patches with rump-hypercall interface, used in UEFI, as well as macOS userspace (part of POSIX).

There is also musl-libc port for LKL, which might be interested in for some folks.

Further readings about LKL
=========================

- Discussion in github LKL issue
https://github.com/lkl/linux/issues/304

- LKL (an article)
https://www.researchgate.net/profile/Nicolae_Tapus2/publication/224164682_LKL_The_Linux_kernel_library/links/02bfe50fd921ab4f7c000000.pdf

*1 RFC email to LKML (back in 2015)
https://www.mail-archive.com/[email protected]/msg1012277.html

Please review the following changes for suitability for inclusion. If you have any objections or suggestions for improvement, please respond to the patches. If you agree with the changes, please provide your Acked-by.

The following changes since commit 805c6d3c19210c90c109107d189744e960eae025:

Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs (2020-09-22 15:08:41 -0700)

are available in the Git repository at:

git://github.com/thehajime/linux b7b911105ecec6fd84f59e56d3a2c1789002bcbd
https://github.com/thehajime/linux/tree/uml-lkl-5.9rc6-v6

Hajime Tazaki (18):
um: move arch/um/os-Linux dir to tools/um/uml
um: move arch/x86/um/os-Linux to tools/um/uml/
scritps: um: suppress warnings if SRCARCH=um
um: extend arch_switch_to for alternate SUBARCH
um: add nommu mode for UML library mode
um: nommu: host interface
um: nommu: memory handling
um: nommu: kernel thread support
um: nommu: system call interface and application API
um: nommu: basic console support
um: nommu: initialization and cleanup
um: nommu: integrate with irq infrastructure of UML
um: nommu: plug in the build system
um: host: add nommu build for ARCH=um
um: host: add utilities functions
um: host: posix host operations
um: host: add test programs
um: nommu: add block device support of UML

Octavian Purdila (3):
um: split build in kernel and host parts
um: add os init and exit calls
um: host: implement os_initcalls and os_exitcalls

 arch/um/Kconfig                               |  29 +-
 arch/um/Makefile                              |  25 +-
 arch/um/drivers/Makefile                      |  10 +-
 .../um/{os-Linux => }/drivers/ethertap_kern.c |   0
 arch/um/{os-Linux => }/drivers/tuntap_kern.c  |   0
 arch/um/include/asm/common.lds.S              |  99 ----
 arch/um/include/asm/host_ops.h                |   9 +
 arch/um/include/asm/mmu.h                     |   3 +
 arch/um/include/asm/mmu_context.h             |   8 +
 arch/um/include/asm/page.h                    |  15 +
 arch/um/include/asm/pgtable.h                 |  27 +
 arch/um/include/asm/thread_info.h             |  24 +
 arch/um/include/asm/uaccess.h                 |   6 +
 arch/um/include/asm/xor.h                     |   3 +-
 arch/um/include/shared/as-layout.h            |   1 +
 .../drivers => include/shared}/etap.h         |   0
 arch/um/include/shared/init.h                 |  19 +-
 arch/um/include/shared/os.h                   |   1 +
 .../drivers => include/shared}/tuntap.h       |   0
 arch/um/include/uapi/asm/Kbuild               |   2 +
 arch/um/kernel/Makefile                       |  12 +-
 arch/um/kernel/dyn.lds.S                      | 171 -------
 arch/um/kernel/irq.c                          |  13 +
 arch/um/kernel/process.c                      |  14 +-
 arch/um/kernel/reboot.c                       |   5 +
 arch/um/kernel/time.c                         |   2 +
 arch/um/kernel/um_arch.c                      |  16 +
 arch/um/kernel/uml.lds.S                      | 115 -----
 arch/um/kernel/vmlinux.lds.S                  |  91 +++-
 arch/um/nommu/Makefile                        |   1 +
 arch/um/nommu/Makefile.um                     |  18 +
 arch/um/nommu/include/asm/Kbuild              |   6 +
 arch/um/nommu/include/asm/archparam.h         |   1 +
 arch/um/nommu/include/asm/atomic.h            |  11 +
 arch/um/nommu/include/asm/atomic64.h          | 114 +++++
 arch/um/nommu/include/asm/bitsperlong.h       |  12 +
 arch/um/nommu/include/asm/byteorder.h         |   7 +
 arch/um/nommu/include/asm/cpu.h               |  16 +
 arch/um/nommu/include/asm/elf.h               |  15 +
 arch/um/nommu/include/asm/mm_context.h        |   8 +
 arch/um/nommu/include/asm/processor.h         |  46 ++
 arch/um/nommu/include/asm/ptrace.h            |  21 +
 arch/um/nommu/include/asm/sched.h             |  23 +
 arch/um/nommu/include/asm/segment.h           |   9 +
 arch/um/nommu/include/asm/syscall_wrapper.h   |  57 +++
 arch/um/nommu/include/asm/syscalls.h          |  15 +
 arch/um/nommu/include/uapi/asm/Kbuild         |   4 +
 arch/um/nommu/include/uapi/asm/bitsperlong.h  |  11 +
 arch/um/nommu/include/uapi/asm/byteorder.h    |  11 +
 arch/um/nommu/include/uapi/asm/host_ops.h     | 122 +++++
 arch/um/nommu/include/uapi/asm/sigcontext.h   |  12 +
 arch/um/nommu/include/uapi/asm/syscalls.h     | 287 +++++++++++
 arch/um/nommu/include/uapi/asm/unistd.h       |  17 +
 arch/um/nommu/um/Kconfig                      |  45 ++
 arch/um/nommu/um/Makefile                     |   4 +
 arch/um/nommu/um/bootmem.c                    |  86 ++++
 arch/um/nommu/um/console.c                    |  42 ++
 arch/um/nommu/um/cpu.c                        | 247 ++++++++++
 arch/um/nommu/um/delay.c                      |  31 ++
 arch/um/nommu/um/setup.c                      | 179 +++++++
 arch/um/nommu/um/shared/sysdep/archsetjmp.h   |  13 +
 arch/um/nommu/um/shared/sysdep/faultinfo.h    |   8 +
 .../nommu/um/shared/sysdep/kernel-offsets.h   |  12 +
 arch/um/nommu/um/shared/sysdep/mcontext.h     |   9 +
 arch/um/nommu/um/shared/sysdep/ptrace.h       |  42 ++
 arch/um/nommu/um/shared/sysdep/ptrace_user.h  |   7 +
 arch/um/nommu/um/syscalls.c                   | 199 ++++++++
 arch/um/nommu/um/threads.c                    | 261 ++++++++++
 arch/um/nommu/um/unimplemented.c              |  70 +++
 arch/um/nommu/um/user_constants.h             |  13 +
 arch/um/os-Linux/Makefile                     |  19 -
 arch/um/os-Linux/drivers/Makefile             |  13 -
 arch/um/scripts/headers_install.py            | 197 ++++++++
 arch/x86/um/Makefile                          |   2 +-
 arch/x86/um/os-Linux/Makefile                 |  13 -
 arch/x86/um/ptrace_32.c                       |   2 +-
 arch/x86/um/syscalls_64.c                     |   2 +-
 scripts/headers_install.sh                    |   4 +
 scripts/link-vmlinux.sh                       |  42 +-
 tools/um/Makefile                             |  82 ++++
 tools/um/Targets                              |  13 +
 tools/um/include/lkl.h                        | 357 ++++++++++++++
 tools/um/include/lkl_host.h                   |  27 +
 tools/um/lib/Build                            |   7 +
 tools/um/lib/fs.c                             | 461 ++++++++++++++++++
 tools/um/lib/jmp_buf.c                        |  14 +
 tools/um/lib/jmp_buf.h                        |   8 +
 tools/um/lib/posix-host.c                     | 293 +++++++++++
 tools/um/lib/utils.c                          | 213 ++++++++
 tools/um/tests/Build                          |   2 +
 tools/um/tests/boot.c                         | 393 +++++++++++++++
 tools/um/tests/boot.sh                        |   9 +
 tools/um/tests/cla.c                          | 159 ++++++
 tools/um/tests/cla.h                          |  33 ++
 tools/um/tests/disk.c                         | 168 +++++++
 tools/um/tests/disk.sh                        |  70 +++
 tools/um/tests/run.py                         | 174 +++++++
 tools/um/tests/tap13.py                       | 209 ++++++++
 tools/um/tests/test.c                         | 126 +++++
 tools/um/tests/test.h                         |  72 +++
 tools/um/tests/test.sh                        | 181 +++++++
 tools/um/uml/Build                            |  57 +++
 tools/um/uml/drivers/Build                    |  10 +
 .../um/uml}/drivers/ethertap_user.c           |   0
 .../um/uml}/drivers/tuntap_user.c             |   0
 {arch/um/os-Linux => tools/um/uml}/elf_aux.c  |   0
 {arch/um/os-Linux => tools/um/uml}/execvp.c   |   4 -
 {arch/um/os-Linux => tools/um/uml}/file.c     |   0
 {arch/um/os-Linux => tools/um/uml}/helper.c   |   0
 {arch/um/os-Linux => tools/um/uml}/irq.c      |   0
 {arch/um/os-Linux => tools/um/uml}/main.c     |   0
 {arch/um/os-Linux => tools/um/uml}/mem.c      |   0
 tools/um/uml/nommu/Build                      |   1 +
 tools/um/uml/nommu/registers.c                |  21 +
 tools/um/uml/nommu/unimplemented.c            |  21 +
 {arch/um/os-Linux => tools/um/uml}/process.c  |   2 +
 .../um/os-Linux => tools/um/uml}/registers.c  |   0
 {arch/um/os-Linux => tools/um/uml}/sigio.c    |   0
 {arch/um/os-Linux => tools/um/uml}/signal.c   |  12 +-
 .../skas/Makefile => tools/um/uml/skas/Build  |   6 +-
 {arch/um/os-Linux => tools/um/uml}/skas/mem.c |   0
 .../os-Linux => tools/um/uml}/skas/process.c  |   3 +-
 {arch/um/os-Linux => tools/um/uml}/start_up.c |   0
 {arch/um/os-Linux => tools/um/uml}/time.c     |   0
 {arch/um/os-Linux => tools/um/uml}/tty.c      |   0
 {arch/um/os-Linux => tools/um/uml}/umid.c     |   0
 .../um/os-Linux => tools/um/uml}/user_syms.c  |   1 +
 {arch/um/os-Linux => tools/um/uml}/util.c     |  26 +
 tools/um/uml/x86/Build                        |  11 +
 .../os-Linux => tools/um/uml/x86}/mcontext.c  |   0
 .../um/os-Linux => tools/um/uml/x86}/prctl.c  |   0
 .../os-Linux => tools/um/uml/x86}/registers.c |   0
 .../os-Linux => tools/um/uml/x86}/task_size.c |   0
 .../um/os-Linux => tools/um/uml/x86}/tls.c    |   0
 134 files changed, 5850 insertions(+), 522 deletions(-)
 rename arch/um/{os-Linux => }/drivers/ethertap_kern.c (100%)
 rename arch/um/{os-Linux => }/drivers/tuntap_kern.c (100%)
 delete mode 100644 arch/um/include/asm/common.lds.S
 create mode 100644 arch/um/include/asm/host_ops.h
 rename arch/um/{os-Linux/drivers => include/shared}/etap.h (100%)
 rename arch/um/{os-Linux/drivers => include/shared}/tuntap.h (100%)
 create mode 100644 arch/um/include/uapi/asm/Kbuild
 delete mode 100644 arch/um/kernel/dyn.lds.S
 delete mode 100644 arch/um/kernel/uml.lds.S
 create mode 100644 arch/um/nommu/Makefile
 create mode 100644 arch/um/nommu/Makefile.um
 create mode 100644 arch/um/nommu/include/asm/Kbuild
 create mode 100644 arch/um/nommu/include/asm/archparam.h
 create mode 100644 arch/um/nommu/include/asm/atomic.h
 create mode 100644 arch/um/nommu/include/asm/atomic64.h
 create mode 100644 arch/um/nommu/include/asm/bitsperlong.h
 create mode 100644 arch/um/nommu/include/asm/byteorder.h
 create mode 100644 arch/um/nommu/include/asm/cpu.h
 create mode 100644 arch/um/nommu/include/asm/elf.h
 create mode 100644 arch/um/nommu/include/asm/mm_context.h
 create mode 100644 arch/um/nommu/include/asm/processor.h
 create mode 100644 arch/um/nommu/include/asm/ptrace.h
 create mode 100644 arch/um/nommu/include/asm/sched.h
 create mode 100644 arch/um/nommu/include/asm/segment.h
 create mode 100644 arch/um/nommu/include/asm/syscall_wrapper.h
 create mode 100644 arch/um/nommu/include/asm/syscalls.h
 create mode 100644 arch/um/nommu/include/uapi/asm/Kbuild
 create mode 100644 arch/um/nommu/include/uapi/asm/bitsperlong.h
 create mode 100644 arch/um/nommu/include/uapi/asm/byteorder.h
 create mode 100644 arch/um/nommu/include/uapi/asm/host_ops.h
 create mode 100644 arch/um/nommu/include/uapi/asm/sigcontext.h
 create mode 100644 arch/um/nommu/include/uapi/asm/syscalls.h
 create mode 100644 arch/um/nommu/include/uapi/asm/unistd.h
 create mode 100644 arch/um/nommu/um/Kconfig
 create mode 100644 arch/um/nommu/um/Makefile
 create mode 100644 arch/um/nommu/um/bootmem.c
 create mode 100644 arch/um/nommu/um/console.c
 create mode 100644 arch/um/nommu/um/cpu.c
 create mode 100644 arch/um/nommu/um/delay.c
 create mode 100644 arch/um/nommu/um/setup.c
 create mode 100644 arch/um/nommu/um/shared/sysdep/archsetjmp.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/faultinfo.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/kernel-offsets.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/mcontext.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/ptrace.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/ptrace_user.h
 create mode 100644 arch/um/nommu/um/syscalls.c
 create mode 100644 arch/um/nommu/um/threads.c
 create mode 100644 arch/um/nommu/um/unimplemented.c
 create mode 100644 arch/um/nommu/um/user_constants.h
 delete mode 100644 arch/um/os-Linux/Makefile
 delete mode 100644 arch/um/os-Linux/drivers/Makefile
 create mode 100755 arch/um/scripts/headers_install.py
 delete mode 100644 arch/x86/um/os-Linux/Makefile
 create mode 100644 tools/um/Makefile
 create mode 100644 tools/um/Targets
 create mode 100644 tools/um/include/lkl.h
 create mode 100644 tools/um/include/lkl_host.h
 create mode 100644 tools/um/lib/Build
 create mode 100644 tools/um/lib/fs.c
 create mode 100644 tools/um/lib/jmp_buf.c
 create mode 100644 tools/um/lib/jmp_buf.h
 create mode 100644 tools/um/lib/posix-host.c
 create mode 100644 tools/um/lib/utils.c
 create mode 100644 tools/um/tests/Build
 create mode 100644 tools/um/tests/boot.c
 create mode 100755 tools/um/tests/boot.sh
 create mode 100644 tools/um/tests/cla.c
 create mode 100644 tools/um/tests/cla.h
 create mode 100644 tools/um/tests/disk.c
 create mode 100755 tools/um/tests/disk.sh
 create mode 100755 tools/um/tests/run.py
 create mode 100644 tools/um/tests/tap13.py
 create mode 100644 tools/um/tests/test.c
 create mode 100644 tools/um/tests/test.h
 create mode 100644 tools/um/tests/test.sh
 create mode 100644 tools/um/uml/Build
 create mode 100644 tools/um/uml/drivers/Build
 rename {arch/um/os-Linux => tools/um/uml}/drivers/ethertap_user.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/drivers/tuntap_user.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/elf_aux.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/execvp.c (98%)
 rename {arch/um/os-Linux => tools/um/uml}/file.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/helper.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/irq.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/main.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/mem.c (100%)
 create mode 100644 tools/um/uml/nommu/Build
 create mode 100644 tools/um/uml/nommu/registers.c
 create mode 100644 tools/um/uml/nommu/unimplemented.c
 rename {arch/um/os-Linux => tools/um/uml}/process.c (99%)
 rename {arch/um/os-Linux => tools/um/uml}/registers.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/sigio.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/signal.c (96%)
 rename arch/um/os-Linux/skas/Makefile => tools/um/uml/skas/Build (56%)
 rename {arch/um/os-Linux => tools/um/uml}/skas/mem.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/skas/process.c (99%)
 rename {arch/um/os-Linux => tools/um/uml}/start_up.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/time.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/tty.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/umid.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/user_syms.c (99%)
 rename {arch/um/os-Linux => tools/um/uml}/util.c (89%)
 create mode 100644 tools/um/uml/x86/Build
 rename {arch/x86/um/os-Linux => tools/um/uml/x86}/mcontext.c (100%)
 rename {arch/x86/um/os-Linux => tools/um/uml/x86}/prctl.c (100%)
 rename {arch/x86/um/os-Linux => tools/um/uml/x86}/registers.c (100%)
 rename {arch/x86/um/os-Linux => tools/um/uml/x86}/task_size.c (100%)
 rename {arch/x86/um/os-Linux => tools/um/uml/x86}/tls.c (100%)

2.21.0 (Apple Git-122.2)

From: Octavian Purdila <[email protected]>

This patch splits the UML build in two parts: a kernel part that generates a relocatable object (linux.o) and a host build part that links the relocatable object into an executable.

This allows us to simplify the linker script since we can now remove the host bits (e.g. .rel sections). It also gives us greater flexibility since it will be much easier to support other architectures and OSes if we use the standard linker script.

The host build part has been implemented in tools/um so that we can reuse the available host build infrastructure.

The patch also changes the UML build invocation, if before

 $ make ARCH=um defconfig
 $ make ARCH=um

was generating the executable now this only generates the relocatable object.

To fully build UML use:

 $ make -C tools/um

which will generate tools/lkl/linux as the UML executable. To statically compiled UML use:

 $ make -C tools/lkl UML_STATIC=y

---
 arch/um/Kconfig                  |  12 +--
 arch/um/Makefile                 |  14 ++-
 arch/um/include/asm/common.lds.S |  99 ------------------
 arch/um/kernel/dyn.lds.S         | 171 -------------------------------
 arch/um/kernel/uml.lds.S         | 115 ---------------------
 arch/um/kernel/vmlinux.lds.S     |  91 ++++++++++++++--
 scripts/link-vmlinux.sh          |  42 +++-----
 tools/um/Makefile                |  72 +++++++++++++
 tools/um/Targets                 |   4 +
 tools/um/uml/Build               |   0
 10 files changed, 184 insertions(+), 436 deletions(-)
 delete mode 100644 arch/um/include/asm/common.lds.S
 delete mode 100644 arch/um/kernel/dyn.lds.S
 delete mode 100644 arch/um/kernel/uml.lds.S
 create mode 100644 tools/um/Makefile
 create mode 100644 tools/um/Targets
 create mode 100644 tools/um/uml/Build

index eb51fec75948..e41d31d0d875 100644
@@ -20,6 +20,7 @@ config UML
 	select GENERIC_CLOCKEVENTS
 	select HAVE_GCC_PLUGINS
 	select TTY # Needed for line.c
+	select MODULE_REL_CRCS if MODVERSIONS
 
 config MMU
 	bool

@@ -79,17 +80,6 @@ config STATIC_LINK
 	  NOTE: This option is incompatible with some networking features which
 	  depend on features that require being dynamically loaded (like NSS).
 
-config LD_SCRIPT_STATIC
-	bool
-	default y
-	depends on STATIC_LINK
-
-config LD_SCRIPT_DYN
-	bool
-	default y
-	depends on !LD_SCRIPT_STATIC
-	select MODULE_REL_CRCS if MODVERSIONS
-
 config HOSTFS
 	tristate "Host filesystem"
 	help

index 1cea46ff9bb7..fdfaff4633e8 100644
@@ -95,14 +95,20 @@ KBUILD_CPPFLAGS += -I$(srctree)/$(HOST_DIR)/include \
 KERNEL_DEFINES = $(strip -Derrno=kernel_errno -Dsigprocmask=kernel_sigprocmask \
 			 -Dmktime=kernel_mktime $(ARCH_KERNEL_DEFINES))
 KBUILD_CFLAGS += $(KERNEL_DEFINES)
+LDFLAGS_vmlinux += -r
 
-PHONY += linux
+PHONY += linux.o
 
-all: linux
+all: linux.o
 
-linux: vmlinux
+linux.o: vmlinux
 	@echo '  LINK $@'
-	$(Q)ln -f $< $@
+	$(Q)$(OBJCOPY) -R .eh_frame $< $@
+
+install: linux.o
+	@echo "  INSTALL $(INSTALL_PATH)/lib/$<"
+	@mkdir -p $(INSTALL_PATH)/lib/
+	@cp $< $(INSTALL_PATH)/lib/
 
 define archhelp
   echo '* linux		- Binary kernel image (./linux) - for backward'

new file mode 100644
index 000000000000..a4711f1ef422
@@ -0,0 +1,4 @@
+progs-y += uml/linux
+LDLIBS_linux-y := -lrt -lpthread -lutil
+LDFLAGS_linux-y := -no-pie -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc
+LDFLAGS_linux-$(UML_STATIC) += -static

new file mode 100644
index 000000000000..e69de29bb2d1

2.21.0 (Apple Git-122.2)

This will break packaging in all distributions. We need to figure out an alternative way which is backward compatible with their builds.

Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/

Hmm, I understand the situation.
We may have to put additional steps after generating the relocatable object in arch/um/Makefile.

-- Hajime

Cool.

I will go through the rest of the patches and if I notice something I will comment on specific ones.

Brgds,

Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/

_______________________________________________
linux-um mailing list
[email protected]
http://lists.infradead.org/mailman/listinfo/linux-um

It also fails now.

ERROR: modpost: "memmove" [drivers/net/slip/slhc.ko] undefined!
ERROR: modpost: "memset" [drivers/net/ppp/ppp_generic.ko] undefined!
ERROR: modpost: "memset" [drivers/net/tun.ko] undefined!
ERROR: modpost: "memmove" [drivers/block/loop.ko] undefined!
ERROR: modpost: "memset" [drivers/block/loop.ko] undefined!
ERROR: modpost: "memset" [fs/autofs/autofs4.ko] undefined!
ERROR: modpost: "memset" [fs/isofs/isofs.ko] undefined!
ERROR: modpost: "memset" [fs/binfmt_misc.ko] undefined! make[1]: *** [scripts/Makefile.modpost:111: Module.symvers] Error 1 make[1]: *** Deleting file 'Module.symvers'
make: *** [Makefile:1388: modules] Error 2
make: *** Waiting for unfinished jobs....

Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/

_______________________________________________
linux-um mailing list
[email protected]
http://lists.infradead.org/mailman/listinfo/linux-um

Thanks for the review, I found this is a regression of patch 03/21, 364a2fc126e5 um: move arch/um/os-Linux dir to tools/um/uml

I will try to find a fix.

-- Hajime

From: Octavian Purdila <[email protected]>

These calls are added in preparation for moving some of the code from the kernel to the host build.

---
 arch/um/include/shared/init.h | 14 ++++----------
 arch/um/kernel/reboot.c       |  5 +++++
 arch/um/kernel/um_arch.c      | 11 +++++++++++
 3 files changed, 20 insertions(+), 10 deletions(-)

index c66de434a983..d09308330ca5 100644
@@ -109,19 +109,13 @@ extern struct uml_param __uml_setup_start, __uml_setup_end;
 
 #ifdef __UM_HOST__
 
-#define __define_initcall(level,fn) \
-	static initcall_t __initcall_##fn __used \
-	__attribute__((__section__(".initcall" level ".init"))) = fn
-
-/* Userspace initcalls shouldn't depend on anything in the kernel, so we'll
- * make them run first.
- */
-#define __initcall(fn) __define_initcall("1", fn)
+#undef __uml_exit_call
+#define __uml_exit_call		__used __section(os_exitcalls)
+#define __init_call		__used __section(os_initcalls)
 
+#define __initcall(fn) static initcall_t __initcall_##fn __init_call = fn
 #define __exitcall(fn) static exitcall_t __exitcall_##fn __exit_call = fn
 
-#define __init_call	__used __section(.initcall.init)
-
 #endif
 
 #endif /* _LINUX_UML_INIT_H */

index 48c0610d506e..5420aec411f4 100644
@@ -35,10 +35,15 @@ static void kill_off_processes(void)
 	read_unlock(&tasklist_lock);
 }
 
+void __weak os_exitcalls(void)
+{
+}
+
 void uml_cleanup(void)
 {
 	kmalloc_ok = 0;
 	do_uml_exitcalls();
+	os_exitcalls();
 	kill_off_processes();
 }
 

index 00141e70de56..e2cb76c03b25 100644
@@ -377,3 +377,14 @@ void *text_poke(void *addr, const void *opcode, size_t len)
 void text_poke_sync(void)
 {
 }
+
+int __weak os_initcalls(void)
+{
+	return 0;
+}
+
+int __init run_os_initcalls(void)
+{
+	return os_initcalls();
+}
+early_initcall(run_os_initcalls);

2.21.0 (Apple Git-122.2)

This patch moves underlying OS dependent part under arch/um to tools/um directory so that arch/um code does not need to build host build facilities (e.g., libc).

---
 arch/um/Makefile                              |  3 +-
 arch/um/drivers/Makefile                      |  2 +
 .../um/{os-Linux => }/drivers/ethertap_kern.c |  0
 arch/um/{os-Linux => }/drivers/tuntap_kern.c  |  0
 .../drivers => include/shared}/etap.h         |  0
 arch/um/include/shared/init.h                 |  5 ++
 .../drivers => include/shared}/tuntap.h       |  0
 arch/um/os-Linux/Makefile                     | 19 --------
 arch/um/os-Linux/drivers/Makefile             | 13 -----
 tools/um/Makefile                             |  6 ++-
 tools/um/uml/Build                            | 48 +++++++++++++++++++
 tools/um/uml/drivers/Build                    | 10 ++++
 .../um/uml}/drivers/ethertap_user.c           |  0
 .../um/uml}/drivers/tuntap_user.c             |  0
 {arch/um/os-Linux => tools/um/uml}/elf_aux.c  |  0
 {arch/um/os-Linux => tools/um/uml}/execvp.c   |  4 --
 {arch/um/os-Linux => tools/um/uml}/file.c     |  0
 {arch/um/os-Linux => tools/um/uml}/helper.c   |  0
 {arch/um/os-Linux => tools/um/uml}/irq.c      |  0
 {arch/um/os-Linux => tools/um/uml}/main.c     |  0
 {arch/um/os-Linux => tools/um/uml}/mem.c      |  0
 {arch/um/os-Linux => tools/um/uml}/process.c  |  0
 .../um/os-Linux => tools/um/uml}/registers.c  |  0
 {arch/um/os-Linux => tools/um/uml}/sigio.c    |  0
 {arch/um/os-Linux => tools/um/uml}/signal.c   |  0
 .../skas/Makefile => tools/um/uml/skas/Build  |  6 +--
 {arch/um/os-Linux => tools/um/uml}/skas/mem.c |  0
 .../os-Linux => tools/um/uml}/skas/process.c  |  3 +-
 {arch/um/os-Linux => tools/um/uml}/start_up.c |  0
 {arch/um/os-Linux => tools/um/uml}/time.c     |  0
 {arch/um/os-Linux => tools/um/uml}/tty.c      |  0
 {arch/um/os-Linux => tools/um/uml}/umid.c     |  0
 .../um/os-Linux => tools/um/uml}/user_syms.c  |  1 +
 {arch/um/os-Linux => tools/um/uml}/util.c     |  0
 34 files changed, 74 insertions(+), 46 deletions(-)
 rename arch/um/{os-Linux => }/drivers/ethertap_kern.c (100%)
 rename arch/um/{os-Linux => }/drivers/tuntap_kern.c (100%)
 rename arch/um/{os-Linux/drivers => include/shared}/etap.h (100%)
 rename arch/um/{os-Linux/drivers => include/shared}/tuntap.h (100%)
 delete mode 100644 arch/um/os-Linux/Makefile
 delete mode 100644 arch/um/os-Linux/drivers/Makefile
 create mode 100644 tools/um/uml/drivers/Build
 rename {arch/um/os-Linux => tools/um/uml}/drivers/ethertap_user.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/drivers/tuntap_user.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/elf_aux.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/execvp.c (98%)
 rename {arch/um/os-Linux => tools/um/uml}/file.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/helper.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/irq.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/main.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/mem.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/process.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/registers.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/sigio.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/signal.c (100%)
 rename arch/um/os-Linux/skas/Makefile => tools/um/uml/skas/Build (56%)
 rename {arch/um/os-Linux => tools/um/uml}/skas/mem.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/skas/process.c (99%)
 rename {arch/um/os-Linux => tools/um/uml}/start_up.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/time.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/tty.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/umid.c (100%)
 rename {arch/um/os-Linux => tools/um/uml}/user_syms.c (99%)
 rename {arch/um/os-Linux => tools/um/uml}/util.c (100%)

index fdfaff4633e8..1f958a9280fe 100644
@@ -24,8 +24,7 @@ OS := $(shell uname -s)
 SHELL := /bin/bash
 
 core-y			+= $(ARCH_DIR)/kernel/		\
-			   $(ARCH_DIR)/drivers/		\
-			   $(ARCH_DIR)/os-$(OS)/
+			   $(ARCH_DIR)/drivers/
 
 MODE_INCLUDE	+= -I$(srctree)/$(ARCH_DIR)/include/shared/skas
 

index 2a249f619467..ae96c83e312d 100644
@@ -48,6 +48,8 @@ obj-$(CONFIG_UML_NET_VECTOR) += vector.o
 obj-$(CONFIG_UML_NET_VDE) += vde.o
 obj-$(CONFIG_UML_NET_MCAST) += umcast.o
 obj-$(CONFIG_UML_NET_PCAP) += pcap.o
+obj-$(CONFIG_UML_NET_ETHERTAP) += ethertap_kern.o
+obj-$(CONFIG_UML_NET_TUNTAP) += tuntap_kern.o
 obj-$(CONFIG_UML_NET) += net.o 
 obj-$(CONFIG_MCONSOLE) += mconsole.o
 obj-$(CONFIG_MMAPPER) += mmapper_kern.o 

similarity index 100%
rename from arch/um/os-Linux/drivers/ethertap_kern.c
rename to arch/um/drivers/ethertap_kern.c

similarity index 100%
rename from arch/um/os-Linux/drivers/tuntap_kern.c
rename to arch/um/drivers/tuntap_kern.c

similarity index 100%
rename from arch/um/os-Linux/drivers/etap.h
rename to arch/um/include/shared/etap.h

index d09308330ca5..305789667584 100644
@@ -41,7 +41,12 @@
 typedef int (*initcall_t)(void);
 typedef void (*exitcall_t)(void);
 
+#ifndef __UM_HOST__
 #include <linux/compiler_types.h>
+#else
+#define __used                          __attribute__((__used__))
+#define __section(S)                    __attribute__((__section__(#S)))
+#endif
 
 /* These are for everybody (although not all archs will actually
    discard it in modules) */

similarity index 100%
rename from arch/um/os-Linux/drivers/tuntap.h
rename to arch/um/include/shared/tuntap.h

deleted file mode 100644
index 839915b8c31c..000000000000
@@ -1,19 +0,0 @@
-# SPDX-License-Identifier: GPL-2.0
-# 
-# Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
-#
-
-# Don't instrument UML-specific code
-KCOV_INSTRUMENT                := n
-
-obj-y = execvp.o file.o helper.o irq.o main.o mem.o process.o \
-	registers.o sigio.o signal.o start_up.o time.o tty.o \
-	umid.o user_syms.o util.o drivers/ skas/
-
-obj-$(CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA) += elf_aux.o
-
-USER_OBJS := $(user-objs-y) elf_aux.o execvp.o file.o helper.o irq.o \
-	main.o mem.o process.o registers.o sigio.o signal.o start_up.o time.o \
-	tty.o umid.o util.o
-
-include arch/um/scripts/Makefile.rules

deleted file mode 100644
index d79e75f1b69a..000000000000
@@ -1,13 +0,0 @@
-# SPDX-License-Identifier: GPL-2.0
-# 
-# Copyright (C) 2000, 2002 Jeff Dike ([email protected])
-#
-
-ethertap-objs := ethertap_kern.o ethertap_user.o
-tuntap-objs := tuntap_kern.o tuntap_user.o
-
-obj-y = 
-obj-$(CONFIG_UML_NET_ETHERTAP) += ethertap.o
-obj-$(CONFIG_UML_NET_TUNTAP) += tuntap.o
-
-include arch/um/scripts/Makefile.rules

index a63466ef7ef5..07b9b93ed817 100644
@@ -50,7 +50,7 @@ $(OUTPUT)lib/linux.o:
 	$(Q)CFLAGS= $(MAKE) -C ../.. ARCH=um $(KOPT) $(KCONFIG)
 	$(Q)CFLAGS= $(MAKE) -C ../.. ARCH=um $(KOPT) install INSTALL_PATH=$(OUTPUT)
 
-$(OUTPUT)liblinux.a: $(OUTPUT)lib/linux.o $(OUTPUT)uml/liblinux-in.o
+$(OUTPUT)liblinux.a: $(OUTPUT)lib/linux.o $(OUTPUT)uml/liblinux-in.o $(OUTPUT)lib/liblinux-in.o
 	$(QUIET_AR)$(AR) -rc $@ $^
 
 # rule to link programs

@@ -60,6 +60,10 @@ $(OUTPUT)%: $(OUTPUT)%-in.o $(OUTPUT)liblinux.a
 $(OUTPUT)%-in.o: FORCE
 	$(Q)$(MAKE) -f $(srctree)/tools/build/Makefile.build dir=$(patsubst %/,%,$(dir $*)) obj=$(notdir $*)
 
+# rule to build objects
+$(OUTPUT)%-in.o: $(OUTPUT)lib/linux.o
+	$(Q)$(MAKE) -f $(srctree)/tools/build/Makefile.build dir=$(patsubst %/,%,$(dir $*)) obj=$(notdir $*)
+
 clean:
 	$(call QUIET_CLEAN, objects)find $(OUTPUT) -name '*.o' -delete -o -name '\.*.cmd'\
 	 -delete -o -name '\.*.d' -delete

new file mode 100644
index 000000000000..c7a8eaa97d72
@@ -0,0 +1,10 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (C) 2000, 2002 Jeff Dike ([email protected])
+#
+
+include $(objtree)/include/config/auto.conf
+
+
+liblinux-$(CONFIG_UML_NET_ETHERTAP) += ethertap_user.o
+liblinux-$(CONFIG_UML_NET_TUNTAP) += tuntap_user.o

similarity index 100%
rename from arch/um/os-Linux/drivers/ethertap_user.c
rename to tools/um/uml/drivers/ethertap_user.c

similarity index 100%
rename from arch/um/os-Linux/drivers/tuntap_user.c
rename to tools/um/uml/drivers/tuntap_user.c

similarity index 100%
rename from arch/um/os-Linux/elf_aux.c
rename to tools/um/uml/elf_aux.c

similarity index 98%
rename from arch/um/os-Linux/execvp.c
rename to tools/um/uml/execvp.c
index 84a0777c2a45..c105e0e7b778 100644
@@ -26,12 +26,8 @@
 #include <errno.h>
 #include <limits.h>
 
-#ifndef TEST
-#include <um_malloc.h>
-#else
 #include <stdio.h>
 #define um_kmalloc malloc
-#endif
 #include <os.h>
 
 /* Execute FILE, searching in the `PATH' environment variable if it contains

similarity index 100%
rename from arch/um/os-Linux/file.c
rename to tools/um/uml/file.c

similarity index 100%
rename from arch/um/os-Linux/helper.c
rename to tools/um/uml/helper.c

similarity index 100%
rename from arch/um/os-Linux/irq.c
rename to tools/um/uml/irq.c

similarity index 100%
rename from arch/um/os-Linux/main.c
rename to tools/um/uml/main.c

similarity index 100%
rename from arch/um/os-Linux/mem.c
rename to tools/um/uml/mem.c

similarity index 100%
rename from arch/um/os-Linux/process.c
rename to tools/um/uml/process.c

similarity index 100%
rename from arch/um/os-Linux/registers.c
rename to tools/um/uml/registers.c

similarity index 100%
rename from arch/um/os-Linux/sigio.c
rename to tools/um/uml/sigio.c

similarity index 100%
rename from arch/um/os-Linux/signal.c
rename to tools/um/uml/signal.c

similarity index 56%
rename from arch/um/os-Linux/skas/Makefile
rename to tools/um/uml/skas/Build
index c4566e788815..5fc9d62df863 100644
@@ -3,8 +3,4 @@
 # Copyright (C) 2002 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
 #
 
-obj-y := mem.o process.o
-
-USER_OBJS := $(obj-y)
-
-include arch/um/scripts/Makefile.rules
+liblinux-y += mem.o process.o

similarity index 100%
rename from arch/um/os-Linux/skas/mem.c
rename to tools/um/uml/skas/mem.c

similarity index 99%
rename from arch/um/os-Linux/skas/process.c
rename to tools/um/uml/skas/process.c
index 4fb877b99dde..fca6a08e81bd 100644
@@ -21,7 +21,6 @@
 #include <registers.h>
 #include <skas.h>
 #include <sysdep/stub.h>
-#include <linux/threads.h>
 
 int is_skas_winch(int pid, int fd, void *data)
 {

@@ -248,7 +247,7 @@ static int userspace_tramp(void *stack)
 	return 0;
 }
 
-int userspace_pid[NR_CPUS];
+int userspace_pid[UM_NR_CPUS];
 
 /**
  * start_userspace() - prepare a new userspace process

similarity index 100%
rename from arch/um/os-Linux/start_up.c
rename to tools/um/uml/start_up.c

similarity index 100%
rename from arch/um/os-Linux/time.c
rename to tools/um/uml/time.c

similarity index 100%
rename from arch/um/os-Linux/tty.c
rename to tools/um/uml/tty.c

similarity index 100%
rename from arch/um/os-Linux/umid.c
rename to tools/um/uml/umid.c

similarity index 99%
rename from arch/um/os-Linux/user_syms.c
rename to tools/um/uml/user_syms.c
index 715594fe5719..4047fd7bfdb7 100644
@@ -13,6 +13,7 @@
 #undef strstr
 #undef memcpy
 #undef memset
+#define EXPORT_SYMBOL(x)
 
 extern size_t strlen(const char *);
 extern void *memmove(void *, const void *, size_t);

similarity index 100%
rename from arch/um/os-Linux/util.c
rename to tools/um/uml/util.c

2.21.0 (Apple Git-122.2)

From: Octavian Purdila <[email protected]>

This patch implements the init and exit calls for host code. It uses the automatic __start_<section> and __stop_<section> variables that are defined by gcc / ld when using custom sections.

Note that this patch should be merged with "um: move arch/um/os-Linux dir to tools/um" but for now it is separate to make the review easier.

---
 tools/um/uml/util.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

index ecf2f390fad2..4011b36fee7e 100644
@@ -186,3 +186,29 @@ void os_warn(const char *fmt, ...)
 	vfprintf(stderr, fmt, list);
 	va_end(list);
 }
+
+extern void (*__start_os_exitcalls)(void);
+extern void (*__stop_os_exitcalls)(void);
+
+void os_exitcalls(void)
+{
+	exitcall_t *call;
+
+	call = &__stop_os_exitcalls;
+	while (--call >= &__start_os_exitcalls)
+		(*call)();
+}
+
+extern int (*__start_os_initcalls)(void);
+extern int (*__stop_os_initcalls)(void);
+
+int os_initcalls(void)
+{
+	initcall_t *call;
+
+	call = &__stop_os_initcalls;
+	while (--call >= &__start_os_initcalls)
+		(*call)();
+
+	return 0;
+}

2.21.0 (Apple Git-122.2)

Similar to arch/um/os-Linux code, arch/x86 also contains OS dependent part as well. This patch moves underlying OS dependent part to tools/um directory so that arch/x86 code does not need to build host build facilities (e.g., libc).

---
 arch/x86/um/Makefile                                |  2 +-
 arch/x86/um/os-Linux/Makefile                       | 13 -------------
 tools/um/Makefile                                   |  2 +-
 tools/um/uml/Build                                  |  2 ++
 tools/um/uml/x86/Build                              | 11 +++++++++++
 .../x86/um/os-Linux => tools/um/uml/x86}/mcontext.c |  0
 {arch/x86/um/os-Linux => tools/um/uml/x86}/prctl.c  |  0
 .../um/os-Linux => tools/um/uml/x86}/registers.c    |  0
 .../um/os-Linux => tools/um/uml/x86}/task_size.c    |  0
 {arch/x86/um/os-Linux => tools/um/uml/x86}/tls.c    |  0
 10 files changed, 15 insertions(+), 15 deletions(-)
 delete mode 100644 arch/x86/um/os-Linux/Makefile
 create mode 100644 tools/um/uml/x86/Build
 rename {arch/x86/um/os-Linux => tools/um/uml/x86}/mcontext.c (100%)
 rename {arch/x86/um/os-Linux => tools/um/uml/x86}/prctl.c (100%)
 rename {arch/x86/um/os-Linux => tools/um/uml/x86}/registers.c (100%)
 rename {arch/x86/um/os-Linux => tools/um/uml/x86}/task_size.c (100%)
 rename {arch/x86/um/os-Linux => tools/um/uml/x86}/tls.c (100%)

index 77f70b969d14..25e9846b36a2 100644
@@ -13,7 +13,7 @@ obj-y = bugs_$(BITS).o delay.o fault.o ldt.o \
 	ptrace_$(BITS).o ptrace_user.o setjmp_$(BITS).o signal.o \
 	stub_$(BITS).o stub_segv.o \
 	sys_call_table_$(BITS).o sysrq_$(BITS).o tls_$(BITS).o \
-	mem_$(BITS).o subarch.o os-$(OS)/
+	mem_$(BITS).o subarch.o
 
 ifeq ($(CONFIG_X86_32),y)
 

deleted file mode 100644
index 253bfb8cb702..000000000000
@@ -1,13 +0,0 @@
-#
-# Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
-# Licensed under the GPL
-#
-
-obj-y = registers.o task_size.o mcontext.o
-
-obj-$(CONFIG_X86_32) += tls.o
-obj-$(CONFIG_64BIT) += prctl.o
-
-USER_OBJS := $(obj-y)
-
-include arch/um/scripts/Makefile.rules

index 07b9b93ed817..552ed5f1edae 100644
@@ -61,7 +61,7 @@ $(OUTPUT)%-in.o: FORCE
 	$(Q)$(MAKE) -f $(srctree)/tools/build/Makefile.build dir=$(patsubst %/,%,$(dir $*)) obj=$(notdir $*)
 
 # rule to build objects
-$(OUTPUT)%-in.o: $(OUTPUT)lib/linux.o
+$(OUTPUT)%-in.o: $(OUTPUT)lib/linux.o FORCE
 	$(Q)$(MAKE) -f $(srctree)/tools/build/Makefile.build dir=$(patsubst %/,%,$(dir $*)) obj=$(notdir $*)
 
 clean:

index 8e0607ee8b0a..435a9670d3ff 100644
@@ -12,6 +12,8 @@ liblinux-y += execvp.o file.o helper.o irq.o main.o mem.o process.o \
 	registers.o sigio.o signal.o start_up.o time.o tty.o \
 	umid.o user_syms.o util.o drivers/ skas/
 
+liblinux-y += x86/
+
 liblinux-$(CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA) += elf_aux.o
 
 export O = $(srctree)

new file mode 100644
index 000000000000..16bbc7eb19d1
@@ -0,0 +1,11 @@
+#
+# Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+# Licensed under the GPL
+#
+
+include $(objtree)/include/config/auto.conf
+
+liblinux-y = registers.o task_size.o mcontext.o
+
+liblinux-$(CONFIG_X86_32) += tls.o
+liblinux-$(CONFIG_64BIT) += prctl.o

similarity index 100%
rename from arch/x86/um/os-Linux/mcontext.c
rename to tools/um/uml/x86/mcontext.c

similarity index 100%
rename from arch/x86/um/os-Linux/prctl.c
rename to tools/um/uml/x86/prctl.c

similarity index 100%
rename from arch/x86/um/os-Linux/registers.c
rename to tools/um/uml/x86/registers.c

similarity index 100%
rename from arch/x86/um/os-Linux/task_size.c
rename to tools/um/uml/x86/task_size.c

similarity index 100%
rename from arch/x86/um/os-Linux/tls.c
rename to tools/um/uml/x86/tls.c

2.21.0 (Apple Git-122.2)

This commit fixes numbers of warning messages about leaked CONFIG options. nommu mode of UML requires copies of kernel headers to offer syscall-like API for the library users. Thus, the warnings are to be avoided to function this exposure of API.

---
 scripts/headers_install.sh | 4 ++++
 1 file changed, 4 insertions(+)

index dd554bd436cc..8890a0147012 100755
@@ -93,6 +93,10 @@ include/uapi/linux/pktcdvd.h:CONFIG_CDROM_PKTCDVD_WCACHE
 
 for c in $configs
 do
+	if [ "$SRCARCH" = "um" ] ; then
+		break
+	fi
+
 	leak_error=1
 
 	for ignore in $config_leak_ignores

2.21.0 (Apple Git-122.2)

This commit introduces additional argument of previous task when context switch happens. New SUBARCH can use the new information to switch tasks in a subarch-specific manner.

The patch is particularly required by nommu mode implemented as a SUBARCH of UML.

---
 arch/um/kernel/process.c  | 6 +++---
 arch/x86/um/ptrace_32.c   | 2 +-
 arch/x86/um/syscalls_64.c | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

index 26b5e243d3fc..87a8cfa228ca 100644
@@ -80,7 +80,7 @@ static inline void set_current(struct task_struct *task)
 		{ external_pid(), task });
 }
 
-extern void arch_switch_to(struct task_struct *to);
+extern void arch_switch_to(struct task_struct *from, struct task_struct *to);
 
 void *__switch_to(struct task_struct *from, struct task_struct *to)
 {

@@ -88,7 +88,7 @@ void *__switch_to(struct task_struct *from, struct task_struct *to)
 	set_current(to);
 
 	switch_threads(&from->thread.switch_buf, &to->thread.switch_buf);
-	arch_switch_to(current);
+	arch_switch_to(from, to);
 
 	return current->thread.prev_sched;
 }

@@ -145,7 +145,7 @@ void fork_handler(void)
 	 * arch_switch_to isn't needed. We could want to apply this to
 	 * improve performance. -bb
 	 */
-	arch_switch_to(current);
+	arch_switch_to(NULL, current);
 
 	current->thread.prev_sched = NULL;
 

index 2497bac56066..0f184710d4ca 100644
@@ -11,7 +11,7 @@
 
 extern int arch_switch_tls(struct task_struct *to);
 
-void arch_switch_to(struct task_struct *to)
+void arch_switch_to(struct task_struct *from, struct task_struct *to)
 {
 	int err = arch_switch_tls(to);
 	if (!err)

index 58f51667e2e4..2ef9474d2bd2 100644
@@ -80,7 +80,7 @@ SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
 	return arch_prctl(current, option, (unsigned long __user *) arg2);
 }
 
-void arch_switch_to(struct task_struct *to)
+void arch_switch_to(struct task_struct *from, struct task_struct *to)
 {
 	if ((to->thread.arch.fs == 0) || (to->mm == NULL))
 		return;

2.21.0 (Apple Git-122.2)

This patch introduces the nommu operation with UML code so that host interface can be shrineked for broader environments support.

The nommu mode is implemneted as SUBARCH of arch/um, which places at arch/um/nommu. This SUBARCH defines mode-specific code of memory management as well as thread implementation, along with the uapi headers to be exported to users.

The headers we introduce in this patch are simple wrappers to the asm-generic headers or stubs for things we don't support, such as ptrace, DMA, signals, ELF handling and low level processor operations.

nommu mode shares most of arch/um code (irq, thread_info, process scheduling) but implements its own facilities, which are memory management (nommu), thread primitives (struct arch_thread), system call interface, and console.

The outlook of updated directory structure is as follows:

arch/um

   |-- configs         (untouched)
   |-- drivers         unuse stdio_console.c for !MMU
   |-- include
   |   |-- asm         updated with !CONFIG_MMU
   |   |-- linux       (untouched)
   |   `-- shareda     updated with new functions
   |       `-- skas    (untouched)
   |   `-- uapi        added for upai header installation
   |-- kernel          updated to integrate with !MMU
   |   `-- skas        (untouched, don't use for !MMU)
   |-- nommu           SUBARCH dir (internally =um/nommu)
   |   |-- include
   |   |   |-- asm     headers for subarch specific info
   |   |   `-- uapi    headers for user-visible APIs
   |   `-- um
   |       `-- shared  headers for subarch specific info

`-- scripts added a script for header installation

---
 arch/um/nommu/Makefile                        |   1 +
 arch/um/nommu/Makefile.um                     |  18 +++
 arch/um/nommu/include/asm/Kbuild              |   6 +
 arch/um/nommu/include/asm/archparam.h         |   1 +
 arch/um/nommu/include/asm/atomic.h            |  11 ++
 arch/um/nommu/include/asm/atomic64.h          | 114 ++++++++++++++++++
 arch/um/nommu/include/asm/bitsperlong.h       |  12 ++
 arch/um/nommu/include/asm/byteorder.h         |   7 ++
 arch/um/nommu/include/asm/cpu.h               |  13 ++
 arch/um/nommu/include/asm/elf.h               |  15 +++
 arch/um/nommu/include/asm/mm_context.h        |   8 ++
 arch/um/nommu/include/asm/processor.h         |  46 +++++++
 arch/um/nommu/include/asm/ptrace.h            |  21 ++++
 arch/um/nommu/include/asm/sched.h             |  23 ++++
 arch/um/nommu/include/asm/segment.h           |   9 ++
 arch/um/nommu/include/uapi/asm/Kbuild         |   4 +
 arch/um/nommu/include/uapi/asm/bitsperlong.h  |  11 ++
 arch/um/nommu/include/uapi/asm/byteorder.h    |  11 ++
 arch/um/nommu/include/uapi/asm/sigcontext.h   |  12 ++
 arch/um/nommu/um/delay.c                      |  31 +++++
 arch/um/nommu/um/shared/sysdep/archsetjmp.h   |  13 ++
 arch/um/nommu/um/shared/sysdep/faultinfo.h    |   8 ++
 .../nommu/um/shared/sysdep/kernel-offsets.h   |  12 ++
 arch/um/nommu/um/shared/sysdep/mcontext.h     |   9 ++
 arch/um/nommu/um/shared/sysdep/ptrace.h       |  42 +++++++
 arch/um/nommu/um/shared/sysdep/ptrace_user.h  |   7 ++
 arch/um/nommu/um/unimplemented.c              |  70 +++++++++++
 arch/um/nommu/um/user_constants.h             |  13 ++
 28 files changed, 548 insertions(+)
 create mode 100644 arch/um/nommu/Makefile
 create mode 100644 arch/um/nommu/Makefile.um
 create mode 100644 arch/um/nommu/include/asm/Kbuild
 create mode 100644 arch/um/nommu/include/asm/archparam.h
 create mode 100644 arch/um/nommu/include/asm/atomic.h
 create mode 100644 arch/um/nommu/include/asm/atomic64.h
 create mode 100644 arch/um/nommu/include/asm/bitsperlong.h
 create mode 100644 arch/um/nommu/include/asm/byteorder.h
 create mode 100644 arch/um/nommu/include/asm/cpu.h
 create mode 100644 arch/um/nommu/include/asm/elf.h
 create mode 100644 arch/um/nommu/include/asm/mm_context.h
 create mode 100644 arch/um/nommu/include/asm/processor.h
 create mode 100644 arch/um/nommu/include/asm/ptrace.h
 create mode 100644 arch/um/nommu/include/asm/sched.h
 create mode 100644 arch/um/nommu/include/asm/segment.h
 create mode 100644 arch/um/nommu/include/uapi/asm/Kbuild
 create mode 100644 arch/um/nommu/include/uapi/asm/bitsperlong.h
 create mode 100644 arch/um/nommu/include/uapi/asm/byteorder.h
 create mode 100644 arch/um/nommu/include/uapi/asm/sigcontext.h
 create mode 100644 arch/um/nommu/um/delay.c
 create mode 100644 arch/um/nommu/um/shared/sysdep/archsetjmp.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/faultinfo.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/kernel-offsets.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/mcontext.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/ptrace.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/ptrace_user.h
 create mode 100644 arch/um/nommu/um/unimplemented.c
 create mode 100644 arch/um/nommu/um/user_constants.h

new file mode 100644
index 000000000000..792d6005489e
@@ -0,0 +1 @@
+#

new file mode 100644
index 000000000000..6cb0e9494d05
@@ -0,0 +1,18 @@
+KBUILD_CFLAGS += -fno-builtin -fPIC
+ELF_FORMAT=$(shell $(LD) -r -print-output-format)
+
+ifeq ($(shell uname -s), Linux)
+NPROC=$(shell nproc)
+else # e.g., FreeBSD
+NPROC=$(shell sysctl -n hw.ncpu)
+endif
+
+um_headers_install: $(objtree)/$(HOST_DIR)/include/generated/uapi/asm/syscall_defs.h headers
+	$(Q)$(srctree)/$(ARCH_DIR)/scripts/headers_install.py \
+		$(subst -j,-j$(NPROC),$(findstring -j,$(MAKEFLAGS))) \
+		$(INSTALL_PATH)/include
+
+$(objtree)/$(HOST_DIR)/include/generated/uapi/asm/syscall_defs.h: vmlinux
+	$(Q)$(OBJCOPY) -j .syscall_defs -O binary --set-section-flags .syscall_defs=alloc $< $@
+	$(Q) export tmpfile=$(shell mktemp); \
+	sed 's/\x0//g' $@ > $$tmpfile; mv $$tmpfile $@ ; rm -f $$tmpfile

new file mode 100644
index 000000000000..2532e1a0a0d1
@@ -0,0 +1,6 @@
+generic-y += cmpxchg.h
+generic-y += local64.h
+generic-y += seccomp.h
+generic-y += string.h
+generic-y += syscall.h
+generic-y += user.h

new file mode 100644
index 000000000000..ea32a7d3cf1b
@@ -0,0 +1 @@
+/* SPDX-License-Identifier: GPL-2.0 */

new file mode 100644
index 000000000000..63e2e16bda92
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_ATOMIC_H
+#define __UM_NOMMU_ATOMIC_H
+
+#include <asm-generic/atomic.h>
+
+#ifndef CONFIG_GENERIC_ATOMIC64
+#include "atomic64.h"
+#endif /* !CONFIG_GENERIC_ATOMIC64 */
+
+#endif

new file mode 100644
index 000000000000..a150cee41e75
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_BITSPERLONG_H
+#define __UM_NOMMU_BITSPERLONG_H
+
+#include <uapi/asm/bitsperlong.h>
+
+#define BITS_PER_LONG __BITS_PER_LONG
+
+#define BITS_PER_LONG_LONG 64
+
+#endif
+

new file mode 100644
index 000000000000..920a5fd26cad
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_BYTEORDER_H
+#define __UM_NOMMU_BYTEORDER_H
+
+#include <uapi/asm/byteorder.h>
+
+#endif

new file mode 100644
index 000000000000..c101c078ef21
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_CPU_H
+#define __UM_NOMMU_CPU_H
+
+int lkl_cpu_get(void);
+void lkl_cpu_put(void);
+int lkl_cpu_try_run_irq(int irq);
+int lkl_cpu_init(void);
+void lkl_cpu_wait_shutdown(void);
+void lkl_cpu_change_owner(lkl_thread_t owner);
+void lkl_cpu_set_irqs_pending(void);
+
+#endif

new file mode 100644
index 000000000000..edcf63edeed1
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_ELF_H
+#define __UM_NOMMU_ELF_H
+
+#define elf_check_arch(x) 0
+
+#ifdef CONFIG_64BIT
+#define ELF_CLASS ELFCLASS64
+#else
+#define ELF_CLASS ELFCLASS32
+#endif
+
+#define elf_gregset_t long
+#define elf_fpregset_t double
+#endif

new file mode 100644
index 000000000000..a2e53984aabd
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_MM_CONTEXT_H
+#define __UM_NOMMU_MM_CONTEXT_H
+
+struct uml_arch_mm_context {
+};
+
+#endif

new file mode 100644
index 000000000000..b214410e9825
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_PTRACE_H
+#define __UM_NOMMU_PTRACE_H
+
+#include <linux/errno.h>
+
+static int reg_dummy __attribute__((unused));
+
+#define PT_REGS_ORIG_SYSCALL(r) (reg_dummy)
+#define PT_REGS_SYSCALL_RET(r) (reg_dummy)
+#define PT_REGS_SET_SYSCALL_RETURN(r, res) (reg_dummy = (res))
+#define REGS_SP(r) (reg_dummy)
+
+#define user_mode(regs) 0
+#define kernel_mode(regs) 1
+#define profile_pc(regs) 0
+#define user_stack_pointer(regs) 0
+
+extern void new_thread_handler(void);
+
+#endif