RISC-V: Add kexec/kdump support

Add RISC-V to the list of supported kexec architecturs, we need to add the definition early-on so that later patches can use it.

EM_RISCV is 243 as per ELF psABI specification here:
https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md

Signed-off-by Nick Kossifidis <[email protected]>

---
 include/uapi/linux/kexec.h | 1 +
 1 file changed, 1 insertion(+)

include/uapi/linux/kexec.h +0 -0

index 05669c87a..778dc191c 100644

This patch adds support for kexec on RISC-V. On SMP systems it depends on HOTPLUG_CPU in order to be able to bring up all harts after kexec. It also needs a recent OpenSBI version that supports the HSM extension. I tested it on riscv64 QEMU on both an smp and a non-smp system.

v5:
* For now depend on MMU, further changes needed for NOMMU support
* Make sure stvec is aligned
* Cleanup some unneeded fences
* Verify control code's buffer size
* Compile kexec_relocate.S with medany and norelax

v4:
* No functional changes, just re-based

v3:
* Use the new smp_shutdown_nonboot_cpus() call.
* Move riscv_kexec_relocate to .rodata

v2:
* Pass needed parameters as arguments to riscv_kexec_relocate instead of using global variables.
* Use kimage_arch to hold the fdt address of the included fdt.
* Use SYM_* macros on kexec_relocate.S.
* Compatibility with STRICT_KERNEL_RWX.
* Compatibility with HOTPLUG_CPU for SMP
* Small cleanups

Signed-off-by Nick Kossifidis <[email protected]>

---
  arch/riscv/Kconfig                 |  15 +++
  arch/riscv/include/asm/kexec.h     |  47 ++++++++
  arch/riscv/kernel/Makefile         |   5 +
  arch/riscv/kernel/kexec_relocate.S | 156 ++++++++++++++++++++++++
  arch/riscv/kernel/machine_kexec.c  | 186 +++++++++++++++++++++++++++++
  5 files changed, 409 insertions(+)

create mode 100644 arch/riscv/include/asm/kexec.h create mode 100644 arch/riscv/kernel/kexec_relocate.S create mode 100644 arch/riscv/kernel/machine_kexec.c

arch/riscv/Kconfig +15 -0

index 8ea60a0a1..3716262ef 100644
@@ -389,6 +389,21 @@ config RISCV_SBI_V01
  	help
  	  This config allows kernel to use SBI v0.1 APIs. This will be
  	  deprecated in future once legacy M-mode software are no longer in use.
+
+config KEXEC
+	bool "Kexec system call"
+	select KEXEC_CORE
+	select HOTPLUG_CPU if SMP
+	depends on MMU
+	help
+	  kexec is a system call that implements the ability to shutdown your
+	  current kernel, and to start another kernel. It is like a reboot
+	  but it is independent of the system firmware. And like a reboot
+	  you can start any kernel with it, not just Linux.
+
+	  The name comes from the similarity to the exec system call.
+
+
  endmenu
 
  menu "Boot options"

arch/riscv/include/asm/kexec.h new file +10 -0

new file mode 100644
index 000000000..efc69feb4
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2019 FORTH-ICS/CARV
+ *  Nick Kossifidis <[email protected]>
+ */
+
+#ifndef _RISCV_KEXEC_H
+#define _RISCV_KEXEC_H
+
+/* Maximum physical address we can use pages from */

arch/riscv/include/asm/kexec.h new file +27 -0

+
+#define KEXEC_ARCH KEXEC_ARCH_RISCV
+
+static inline void
+crash_setup_regs(struct pt_regs *newregs,
+		 struct pt_regs *oldregs)
+{
+	/* Dummy implementation for now */
+}
+
+
+#define ARCH_HAS_KIMAGE_ARCH
+
+struct kimage_arch {
+	unsigned long fdt_addr;
+};
+
+const extern unsigned char riscv_kexec_relocate[];
+const extern unsigned int riscv_kexec_relocate_size;
+
+typedef void (*riscv_kexec_do_relocate)(unsigned long first_ind_entry,
+					unsigned long jump_addr,
+					unsigned long fdt_addr,
+					unsigned long hartid,
+					unsigned long va_pa_off);
+
+#endif

arch/riscv/kernel/Makefile +4 -0

index 3dc0abde9..c2594018c 100644
@@ -9,6 +9,10 @@ CFLAGS_REMOVE_patch.o	= $(CC_FLAGS_FTRACE)
  CFLAGS_REMOVE_sbi.o	= $(CC_FLAGS_FTRACE)
  endif
 
+ifdef CONFIG_KEXEC
+AFLAGS_kexec_relocate.o := -mcmodel=medany -mno-relax
+endif
+
  extra-y += head.o
  extra-y += vmlinux.lds
 

arch/riscv/kernel/Makefile +0 -0

  obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o
 

arch/riscv/kernel/kexec_relocate.S new file +23 -0

new file mode 100644
index 000000000..616c20771
@@ -0,0 +1,156 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2019 FORTH-ICS/CARV
+ *  Nick Kossifidis <[email protected]>
+ */
+
+#include <asm/asm.h>	/* For RISCV_* and REG_* macros */
+#include <asm/page.h>	/* For PAGE_SHIFT */
+#include <linux/linkage.h> /* For SYM_* macros */
+
+.section ".rodata"
+SYM_CODE_START(riscv_kexec_relocate)
+
+	/*
+	 * s0: Pointer to the current entry
+	 * s1: (const) Phys address to jump to after relocation
+	 * s2: (const) Phys address of the FDT image
+	 * s3: (const) The hartid of the current hart
+	 * s4: Pointer to the destination address for the relocation
+	 * s5: (const) Number of words per page
+	 * s6: (const) 1, used for subtraction
+	 * s7: (const) va_pa_offset, used when switching MMU off
+	 * s8: (const) Physical address of the main loop

arch/riscv/kernel/kexec_relocate.S new file +123 -0

+	li	s6, 1
+	mv	s7, a4
+	mv	s8, zero
+	mv	s9, zero
+	mv	s10, zero
+	mv	s11, zero
+
+	/* Disable / cleanup interrupts */
+	csrw	sie, zero
+	csrw	sip, zero
+
+	/*
+	 * When we switch SATP.MODE to "Bare" we'll only
+	 * play with physical addresses. However the first time
+	 * we try to jump somewhere, the offset on the jump
+	 * will be relative to pc which will still be on VA. To
+	 * deal with this we set stvec to the physical address at
+	 * the start of the loop below so that we jump there in
+	 * any case.
+	 */
+	la	s8, 1f
+	sub	s8, s8, s7
+	csrw	stvec, s8
+
+	/* Process entries in a loop */
+.align 2
+1:
+	addi	s10, s10, 1
+	REG_L	t0, 0(s0)		/* t0 = *image->entry */
+	addi	s0, s0, RISCV_SZPTR	/* image->entry++ */
+
+	/* IND_DESTINATION entry ? -> save destination address */
+	andi	t1, t0, 0x1
+	beqz	t1, 2f
+	andi	s4, t0, ~0x1
+	j	1b
+
+2:
+	/* IND_INDIRECTION entry ? -> update next entry ptr (PA) */
+	andi	t1, t0, 0x2
+	beqz	t1, 2f
+	andi	s0, t0, ~0x2
+	addi	s9, s9, 1
+	csrw	sptbr, zero
+	jalr	zero, s8, 0
+
+2:
+	/* IND_DONE entry ? -> jump to done label */
+	andi	t1, t0, 0x4
+	beqz	t1, 2f
+	j	4f
+
+2:
+	/*
+	 * IND_SOURCE entry ? -> copy page word by word to the
+	 * destination address we got from IND_DESTINATION
+	 */
+	andi	t1, t0, 0x8
+	beqz	t1, 1b		/* Unknown entry type, ignore it */
+	andi	t0, t0, ~0x8
+	mv	t3, s5		/* i = num words per page */
+3:	/* copy loop */
+	REG_L	t1, (t0)	/* t1 = *src_ptr */
+	REG_S	t1, (s4)	/* *dst_ptr = *src_ptr */
+	addi	t0, t0, RISCV_SZPTR /* stc_ptr++ */
+	addi	s4, s4, RISCV_SZPTR /* dst_ptr++ */
+	sub	t3, t3, s6	/* i-- */
+	addi	s11, s11, 1	/* c++ */
+	beqz	t3, 1b		/* copy done ? */
+	j	3b
+
+4:
+	/* Pass the arguments to the next kernel  / Cleanup*/
+	mv	a0, s3
+	mv	a1, s2
+	mv	a2, s1
+
+	/* Cleanup */
+	mv	a3, zero
+	mv	a4, zero
+	mv	a5, zero
+	mv	a6, zero
+	mv	a7, zero
+
+	mv	s0, zero
+	mv	s1, zero
+	mv	s2, zero
+	mv	s3, zero
+	mv	s4, zero
+	mv	s5, zero
+	mv	s6, zero
+	mv	s7, zero
+	mv	s8, zero
+	mv	s9, zero
+	mv	s10, zero
+	mv	s11, zero
+
+	mv	t0, zero
+	mv	t1, zero
+	mv	t2, zero
+	mv	t3, zero
+	mv	t4, zero
+	mv	t5, zero
+	mv	t6, zero
+	csrw	sepc, zero
+	csrw	scause, zero
+	csrw	sscratch, zero
+
+	/*
+	 * Make sure the relocated code is visible
+	 * and jump to the new kernel
+	 */
+	fence.i
+
+	jalr	zero, a2, 0
+
+SYM_CODE_END(riscv_kexec_relocate)
+riscv_kexec_relocate_end:
+
+	.section ".rodata"
+SYM_DATA(riscv_kexec_relocate_size,
+	.long riscv_kexec_relocate_end - riscv_kexec_relocate)
+

arch/riscv/kernel/machine_kexec.c new file +127 -0

new file mode 100644
index 000000000..2ce6c3daf
@@ -0,0 +1,186 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 FORTH-ICS/CARV
+ *  Nick Kossifidis <[email protected]>
+ */
+
+#include <linux/kexec.h>
+#include <asm/kexec.h>		/* For riscv_kexec_* symbol defines */
+#include <linux/smp.h>		/* For smp_send_stop () */
+#include <asm/cacheflush.h>	/* For local_flush_icache_all() */
+#include <asm/barrier.h>	/* For smp_wmb() */
+#include <asm/page.h>		/* For PAGE_MASK */
+#include <linux/libfdt.h>	/* For fdt_check_header() */
+#include <asm/set_memory.h>	/* For set_memory_x() */
+#include <linux/compiler.h>	/* For unreachable() */
+#include <linux/cpu.h>		/* For cpu_down() */
+
+/**
+ * kexec_image_info - Print received image details
+ */
+static void
+kexec_image_info(const struct kimage *image)
+{
+	unsigned long i;
+ * harts and possibly devices etc) for a kexec reboot.
+ */
+void machine_shutdown(void)
+
+	pr_debug("Kexec image info:\n");
+	pr_debug("\ttype:        %d\n", image->type);
+	pr_debug("\tstart:       %lx\n", image->start);
+	pr_debug("\thead:        %lx\n", image->head);
+	pr_debug("\tnr_segments: %lu\n", image->nr_segments);
+
+	for (i = 0; i < image->nr_segments; i++) {
+		pr_debug("\t    segment[%lu]: %016lx - %016lx", i,
+			image->segment[i].mem,
+			image->segment[i].mem + image->segment[i].memsz);
+		pr_debug("\t\t0x%lx bytes, %lu pages\n",
+			(unsigned long) image->segment[i].memsz,
+			(unsigned long) image->segment[i].memsz /  PAGE_SIZE);
+	}
+}
+
+/**
+ * machine_kexec_prepare - Initialize kexec
+ *
+ * This function is called from do_kexec_load, when the user has
+ * provided us with an image to be loaded. Its goal is to validate
+ * the image and prepare the control code buffer as needed.
+ * Note that kimage_alloc_init has already been called and the
+ * control buffer has already been allocated.
+ */
+int
+machine_kexec_prepare(struct kimage *image)
+{
+	struct kimage_arch *internal = &image->arch;
+	struct fdt_header fdt = {0};
+	void *control_code_buffer = NULL;
+	unsigned int control_code_buffer_sz = 0;
+	int i = 0;
+
+	kexec_image_info(image);
+
+	if (image->type == KEXEC_TYPE_CRASH) {
+		pr_warn("Loading a crash kernel is unsupported for now.\n");
+		return -EINVAL;
+	}
+
+	/* Find the Flattened Device Tree and save its physical address */
+	for (i = 0; i < image->nr_segments; i++) {
+		if (image->segment[i].memsz <= sizeof(fdt))
+			continue;
+
+		if (copy_from_user(&fdt, image->segment[i].buf, sizeof(fdt)))
+			continue;
+
+		if (fdt_check_header(&fdt))
+			continue;
+
+		internal->fdt_addr = (unsigned long) image->segment[i].mem;
+		break;
+	}
+
+	if (!internal->fdt_addr) {
+		pr_err("Device tree not included in the provided image\n");
+		return -EINVAL;
+	}
+
+	/* Copy the assembler code for relocation to the control page */
+	control_code_buffer = page_address(image->control_code_page);
+	control_code_buffer_sz = page_size(image->control_code_page);
+	if (unlikely(riscv_kexec_relocate_size > control_code_buffer_sz)) {
+		pr_err("Relocation code doesn't fit within a control page\n");
+		return -EINVAL;
+	}
+	memcpy(control_code_buffer, riscv_kexec_relocate,
+		riscv_kexec_relocate_size);
+
+	/* Mark the control page executable */
+	set_memory_x((unsigned long) control_code_buffer, 1);
+
+	return 0;
+}
+
+
+/**
+ * machine_kexec_cleanup - Cleanup any leftovers from
+ *			   machine_kexec_prepare
+ *
+ * This function is called by kimage_free to handle any arch-specific
+ * allocations done on machine_kexec_prepare. Since we didn't do any
+ * allocations there, this is just an empty function. Note that the
+ * control buffer is freed by kimage_free.
+ */
+void
+machine_kexec_cleanup(struct kimage *image)
+{
+}
+
+
+/*
+ * machine_shutdown - Prepare for a kexec reboot
+ *
+ * This function is called by kernel_kexec just before machine_kexec
+ * below. Its goal is to prepare the rest of the system (the other
+ * harts and possibly devices etc) for a kexec reboot.

arch/riscv/kernel/machine_kexec.c new file +42 -0

+	smp_shutdown_nonboot_cpus(smp_processor_id());
+#endif
+}
+
+/**
+ * machine_crash_shutdown - Prepare to kexec after a kernel crash
+ *
+ * This function is called by crash_kexec just before machine_kexec
+ * below and its goal is similar to machine_shutdown, but in case of
+ * a kernel crash. Since we don't handle such cases yet, this function
+ * is empty.
+ */
+void
+machine_crash_shutdown(struct pt_regs *regs)
+{
+}
+
+/**
+ * machine_kexec - Jump to the loaded kimage
+ *
+ * This function is called by kernel_kexec which is called by the
+ * reboot system call when the reboot cmd is LINUX_REBOOT_CMD_KEXEC,
+ * or by crash_kernel which is called by the kernel's arch-specific
+ * trap handler in case of a kernel panic. It's the final stage of
+ * the kexec process where the pre-loaded kimage is ready to be
+ * executed. We assume at this point that all other harts are
+ * suspended and this hart will be the new boot hart.
+ */
+void __noreturn
+machine_kexec(struct kimage *image)
+{
+	struct kimage_arch *internal = &image->arch;
+	unsigned long jump_addr = (unsigned long) image->start;
+	unsigned long first_ind_entry = (unsigned long) &image->head;
+	unsigned long this_hart_id = raw_smp_processor_id();
+	unsigned long fdt_addr = internal->fdt_addr;
+	void *control_code_buffer = page_address(image->control_code_page);
+	riscv_kexec_do_relocate do_relocate = control_code_buffer;
+
+	pr_notice("Will call new kernel at %08lx from hart id %lx\n",
+		  jump_addr, this_hart_id);
+	pr_notice("FDT image at %08lx\n", fdt_addr);

Le 4/5/21 à 4:57 AM, Nick Kossifidis a écrit :

arch/riscv/include/asm/kexec.h line 20

Quoted 3 lines

arch/riscv/include/asm/kexec.h new file +3 -0

+
+/* Reserve a page for the control code buffer */
+#define KEXEC_CONTROL_PAGE_SIZE 4096

PAGE_SIZE instead ?

Quoted 1 line

+obj-${CONFIG_KEXEC} += kexec_relocate.o machine_kexec.o

Other obj-$() use parenthesis.

arch/riscv/kernel/kexec_relocate.S line 33

Quoted 1 line

arch/riscv/kernel/kexec_relocate.S new file +1 -0

+	li	s5, ((1 << PAGE_SHIFT) / RISCV_SZPTR)

1 << PAGE_SHIFT = PAGE_SIZE

Quoted 1 line

+#if defined(CONFIG_HOTPLUG_CPU) && (CONFIG_SMP)

Shouldn't it be defined(CONFIG_SMP) ?

This patch adds support for kexec on RISC-V. On SMP systems it depends on HOTPLUG_CPU in order to be able to bring up all harts after kexec. It also needs a recent OpenSBI version that supports the HSM extension. I tested it on riscv64 QEMU on both an smp and a non-smp system.

v5:
* For now depend on MMU, further changes needed for NOMMU support
* Make sure stvec is aligned
* Cleanup some unneeded fences
* Verify control code's buffer size
* Compile kexec_relocate.S with medany and norelax

v4:
* No functional changes, just re-based

v3:
* Use the new smp_shutdown_nonboot_cpus() call.
* Move riscv_kexec_relocate to .rodata

v2:
* Pass needed parameters as arguments to riscv_kexec_relocate instead of using global variables.
* Use kimage_arch to hold the fdt address of the included fdt.
* Use SYM_* macros on kexec_relocate.S.
* Compatibility with STRICT_KERNEL_RWX.
* Compatibility with HOTPLUG_CPU for SMP
* Small cleanups

Signed-off-by Nick Kossifidis <[email protected]>

---
 arch/riscv/Kconfig                 |  15 +++
 arch/riscv/include/asm/kexec.h     |  47 ++++++++
 arch/riscv/kernel/Makefile         |   5 +
 arch/riscv/kernel/kexec_relocate.S | 156 ++++++++++++++++++++++++
 arch/riscv/kernel/machine_kexec.c  | 186 +++++++++++++++++++++++++++++
 5 files changed, 409 insertions(+)
 create mode 100644 arch/riscv/include/asm/kexec.h
 create mode 100644 arch/riscv/kernel/kexec_relocate.S
 create mode 100644 arch/riscv/kernel/machine_kexec.c

arch/riscv/Kconfig +15 -0

index 8ea60a0a1..3716262ef 100644
@@ -389,6 +389,21 @@ config RISCV_SBI_V01
 	help
 	  This config allows kernel to use SBI v0.1 APIs. This will be
 	  deprecated in future once legacy M-mode software are no longer in use.
+
+config KEXEC
+	bool "Kexec system call"
+	select KEXEC_CORE
+	select HOTPLUG_CPU if SMP
+	depends on MMU
+	help
+	  kexec is a system call that implements the ability to shutdown your
+	  current kernel, and to start another kernel. It is like a reboot
+	  but it is independent of the system firmware. And like a reboot
+	  you can start any kernel with it, not just Linux.
+
+	  The name comes from the similarity to the exec system call.
+
+
 endmenu
 
 menu "Boot options"

arch/riscv/include/asm/kexec.h new file +47 -0

new file mode 100644
index 000000000..efc69feb4
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2019 FORTH-ICS/CARV
+ *  Nick Kossifidis <[email protected]>
+ */
+
+#ifndef _RISCV_KEXEC_H
+#define _RISCV_KEXEC_H
+
+/* Maximum physical address we can use pages from */
+#define KEXEC_SOURCE_MEMORY_LIMIT (-1UL)
+
+/* Maximum address we can reach in physical address mode */
+#define KEXEC_DESTINATION_MEMORY_LIMIT (-1UL)
+
+/* Maximum address we can use for the control code buffer */
+#define KEXEC_CONTROL_MEMORY_LIMIT (-1UL)
+
+/* Reserve a page for the control code buffer */
+#define KEXEC_CONTROL_PAGE_SIZE 4096
+
+#define KEXEC_ARCH KEXEC_ARCH_RISCV
+
+static inline void
+crash_setup_regs(struct pt_regs *newregs,
+		 struct pt_regs *oldregs)
+{
+	/* Dummy implementation for now */
+}
+
+
+#define ARCH_HAS_KIMAGE_ARCH
+
+struct kimage_arch {
+	unsigned long fdt_addr;
+};
+
+const extern unsigned char riscv_kexec_relocate[];
+const extern unsigned int riscv_kexec_relocate_size;
+
+typedef void (*riscv_kexec_do_relocate)(unsigned long first_ind_entry,
+					unsigned long jump_addr,
+					unsigned long fdt_addr,
+					unsigned long hartid,
+					unsigned long va_pa_off);
+
+#endif

arch/riscv/kernel/Makefile +5 -0

index 3dc0abde9..c2594018c 100644
@@ -9,6 +9,10 @@ CFLAGS_REMOVE_patch.o	= $(CC_FLAGS_FTRACE)
 CFLAGS_REMOVE_sbi.o	= $(CC_FLAGS_FTRACE)
 endif
 
+ifdef CONFIG_KEXEC
+AFLAGS_kexec_relocate.o := -mcmodel=medany -mno-relax
+endif
+
 extra-y += head.o
 extra-y += vmlinux.lds
 

@@ -54,6 +58,7 @@ obj-$(CONFIG_SMP) += cpu_ops_sbi.o
 endif
 obj-$(CONFIG_HOTPLUG_CPU)	+= cpu-hotplug.o
 obj-$(CONFIG_KGDB)		+= kgdb.o
+obj-${CONFIG_KEXEC}		+= kexec_relocate.o machine_kexec.o
 
 obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o
 

arch/riscv/kernel/kexec_relocate.S new file +156 -0

new file mode 100644
index 000000000..616c20771
@@ -0,0 +1,156 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2019 FORTH-ICS/CARV
+ *  Nick Kossifidis <[email protected]>
+ */
+
+#include <asm/asm.h>	/* For RISCV_* and REG_* macros */
+#include <asm/page.h>	/* For PAGE_SHIFT */
+#include <linux/linkage.h> /* For SYM_* macros */
+
+.section ".rodata"
+SYM_CODE_START(riscv_kexec_relocate)
+
+	/*
+	 * s0: Pointer to the current entry
+	 * s1: (const) Phys address to jump to after relocation
+	 * s2: (const) Phys address of the FDT image
+	 * s3: (const) The hartid of the current hart
+	 * s4: Pointer to the destination address for the relocation
+	 * s5: (const) Number of words per page
+	 * s6: (const) 1, used for subtraction
+	 * s7: (const) va_pa_offset, used when switching MMU off
+	 * s8: (const) Physical address of the main loop
+	 * s9: (debug) indirection page counter
+	 * s10: (debug) entry counter
+	 * s11: (debug) copied words counter
+	 */
+	mv	s0, a0
+	mv	s1, a1
+	mv	s2, a2
+	mv	s3, a3
+	mv	s4, zero
+	li	s5, ((1 << PAGE_SHIFT) / RISCV_SZPTR)
+	li	s6, 1
+	mv	s7, a4
+	mv	s8, zero
+	mv	s9, zero
+	mv	s10, zero
+	mv	s11, zero
+
+	/* Disable / cleanup interrupts */
+	csrw	sie, zero
+	csrw	sip, zero
+
+	/*
+	 * When we switch SATP.MODE to "Bare" we'll only
+	 * play with physical addresses. However the first time
+	 * we try to jump somewhere, the offset on the jump
+	 * will be relative to pc which will still be on VA. To
+	 * deal with this we set stvec to the physical address at
+	 * the start of the loop below so that we jump there in
+	 * any case.
+	 */
+	la	s8, 1f
+	sub	s8, s8, s7
+	csrw	stvec, s8
+
+	/* Process entries in a loop */
+.align 2
+1:
+	addi	s10, s10, 1
+	REG_L	t0, 0(s0)		/* t0 = *image->entry */
+	addi	s0, s0, RISCV_SZPTR	/* image->entry++ */
+
+	/* IND_DESTINATION entry ? -> save destination address */
+	andi	t1, t0, 0x1
+	beqz	t1, 2f
+	andi	s4, t0, ~0x1
+	j	1b
+
+2:
+	/* IND_INDIRECTION entry ? -> update next entry ptr (PA) */
+	andi	t1, t0, 0x2
+	beqz	t1, 2f
+	andi	s0, t0, ~0x2
+	addi	s9, s9, 1
+	csrw	sptbr, zero
+	jalr	zero, s8, 0
+
+2:
+	/* IND_DONE entry ? -> jump to done label */
+	andi	t1, t0, 0x4
+	beqz	t1, 2f
+	j	4f
+
+2:
+	/*
+	 * IND_SOURCE entry ? -> copy page word by word to the
+	 * destination address we got from IND_DESTINATION
+	 */
+	andi	t1, t0, 0x8
+	beqz	t1, 1b		/* Unknown entry type, ignore it */
+	andi	t0, t0, ~0x8
+	mv	t3, s5		/* i = num words per page */
+3:	/* copy loop */
+	REG_L	t1, (t0)	/* t1 = *src_ptr */
+	REG_S	t1, (s4)	/* *dst_ptr = *src_ptr */
+	addi	t0, t0, RISCV_SZPTR /* stc_ptr++ */
+	addi	s4, s4, RISCV_SZPTR /* dst_ptr++ */
+	sub	t3, t3, s6	/* i-- */
+	addi	s11, s11, 1	/* c++ */
+	beqz	t3, 1b		/* copy done ? */
+	j	3b
+
+4:
+	/* Pass the arguments to the next kernel  / Cleanup*/
+	mv	a0, s3
+	mv	a1, s2
+	mv	a2, s1
+
+	/* Cleanup */
+	mv	a3, zero
+	mv	a4, zero
+	mv	a5, zero
+	mv	a6, zero
+	mv	a7, zero
+
+	mv	s0, zero
+	mv	s1, zero
+	mv	s2, zero
+	mv	s3, zero
+	mv	s4, zero
+	mv	s5, zero
+	mv	s6, zero
+	mv	s7, zero
+	mv	s8, zero
+	mv	s9, zero
+	mv	s10, zero
+	mv	s11, zero
+
+	mv	t0, zero
+	mv	t1, zero
+	mv	t2, zero
+	mv	t3, zero
+	mv	t4, zero
+	mv	t5, zero
+	mv	t6, zero
+	csrw	sepc, zero
+	csrw	scause, zero
+	csrw	sscratch, zero
+
+	/*
+	 * Make sure the relocated code is visible
+	 * and jump to the new kernel
+	 */
+	fence.i
+
+	jalr	zero, a2, 0
+
+SYM_CODE_END(riscv_kexec_relocate)
+riscv_kexec_relocate_end:
+
+	.section ".rodata"
+SYM_DATA(riscv_kexec_relocate_size,
+	.long riscv_kexec_relocate_end - riscv_kexec_relocate)
+

arch/riscv/kernel/machine_kexec.c new file +186 -0

new file mode 100644
index 000000000..2ce6c3daf
@@ -0,0 +1,186 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 FORTH-ICS/CARV
+ *  Nick Kossifidis <[email protected]>
+ */
+
+#include <linux/kexec.h>
+#include <asm/kexec.h>		/* For riscv_kexec_* symbol defines */
+#include <linux/smp.h>		/* For smp_send_stop () */
+#include <asm/cacheflush.h>	/* For local_flush_icache_all() */
+#include <asm/barrier.h>	/* For smp_wmb() */
+#include <asm/page.h>		/* For PAGE_MASK */
+#include <linux/libfdt.h>	/* For fdt_check_header() */
+#include <asm/set_memory.h>	/* For set_memory_x() */
+#include <linux/compiler.h>	/* For unreachable() */
+#include <linux/cpu.h>		/* For cpu_down() */
+
+/**
+ * kexec_image_info - Print received image details
+ */
+static void
+kexec_image_info(const struct kimage *image)
+{
+	unsigned long i;
+
+	pr_debug("Kexec image info:\n");
+	pr_debug("\ttype:        %d\n", image->type);
+	pr_debug("\tstart:       %lx\n", image->start);
+	pr_debug("\thead:        %lx\n", image->head);
+	pr_debug("\tnr_segments: %lu\n", image->nr_segments);
+
+	for (i = 0; i < image->nr_segments; i++) {
+		pr_debug("\t    segment[%lu]: %016lx - %016lx", i,
+			image->segment[i].mem,
+			image->segment[i].mem + image->segment[i].memsz);
+		pr_debug("\t\t0x%lx bytes, %lu pages\n",
+			(unsigned long) image->segment[i].memsz,
+			(unsigned long) image->segment[i].memsz /  PAGE_SIZE);
+	}
+}
+
+/**
+ * machine_kexec_prepare - Initialize kexec
+ *
+ * This function is called from do_kexec_load, when the user has
+ * provided us with an image to be loaded. Its goal is to validate
+ * the image and prepare the control code buffer as needed.
+ * Note that kimage_alloc_init has already been called and the
+ * control buffer has already been allocated.
+ */
+int
+machine_kexec_prepare(struct kimage *image)
+{
+	struct kimage_arch *internal = &image->arch;
+	struct fdt_header fdt = {0};
+	void *control_code_buffer = NULL;
+	unsigned int control_code_buffer_sz = 0;
+	int i = 0;
+
+	kexec_image_info(image);
+
+	if (image->type == KEXEC_TYPE_CRASH) {
+		pr_warn("Loading a crash kernel is unsupported for now.\n");
+		return -EINVAL;
+	}
+
+	/* Find the Flattened Device Tree and save its physical address */
+	for (i = 0; i < image->nr_segments; i++) {
+		if (image->segment[i].memsz <= sizeof(fdt))
+			continue;
+
+		if (copy_from_user(&fdt, image->segment[i].buf, sizeof(fdt)))
+			continue;
+
+		if (fdt_check_header(&fdt))
+			continue;
+
+		internal->fdt_addr = (unsigned long) image->segment[i].mem;
+		break;
+	}
+
+	if (!internal->fdt_addr) {
+		pr_err("Device tree not included in the provided image\n");
+		return -EINVAL;
+	}
+
+	/* Copy the assembler code for relocation to the control page */
+	control_code_buffer = page_address(image->control_code_page);
+	control_code_buffer_sz = page_size(image->control_code_page);
+	if (unlikely(riscv_kexec_relocate_size > control_code_buffer_sz)) {
+		pr_err("Relocation code doesn't fit within a control page\n");
+		return -EINVAL;
+	}
+	memcpy(control_code_buffer, riscv_kexec_relocate,
+		riscv_kexec_relocate_size);
+
+	/* Mark the control page executable */
+	set_memory_x((unsigned long) control_code_buffer, 1);
+
+	return 0;
+}
+
+
+/**
+ * machine_kexec_cleanup - Cleanup any leftovers from
+ *			   machine_kexec_prepare
+ *
+ * This function is called by kimage_free to handle any arch-specific
+ * allocations done on machine_kexec_prepare. Since we didn't do any
+ * allocations there, this is just an empty function. Note that the
+ * control buffer is freed by kimage_free.
+ */
+void
+machine_kexec_cleanup(struct kimage *image)
+{
+}
+
+
+/*
+ * machine_shutdown - Prepare for a kexec reboot
+ *
+ * This function is called by kernel_kexec just before machine_kexec
+ * below. Its goal is to prepare the rest of the system (the other
+ * harts and possibly devices etc) for a kexec reboot.
+ */
+void machine_shutdown(void)
+{
+	/*
+	 * No more interrupts on this hart
+	 * until we are back up.
+	 */
+	local_irq_disable();
+
+#if defined(CONFIG_HOTPLUG_CPU) && (CONFIG_SMP)
+	smp_shutdown_nonboot_cpus(smp_processor_id());
+#endif
+}
+
+/**
+ * machine_crash_shutdown - Prepare to kexec after a kernel crash
+ *
+ * This function is called by crash_kexec just before machine_kexec
+ * below and its goal is similar to machine_shutdown, but in case of
+ * a kernel crash. Since we don't handle such cases yet, this function
+ * is empty.
+ */
+void
+machine_crash_shutdown(struct pt_regs *regs)
+{
+}
+
+/**
+ * machine_kexec - Jump to the loaded kimage
+ *
+ * This function is called by kernel_kexec which is called by the
+ * reboot system call when the reboot cmd is LINUX_REBOOT_CMD_KEXEC,
+ * or by crash_kernel which is called by the kernel's arch-specific
+ * trap handler in case of a kernel panic. It's the final stage of
+ * the kexec process where the pre-loaded kimage is ready to be
+ * executed. We assume at this point that all other harts are
+ * suspended and this hart will be the new boot hart.
+ */
+void __noreturn
+machine_kexec(struct kimage *image)
+{
+	struct kimage_arch *internal = &image->arch;
+	unsigned long jump_addr = (unsigned long) image->start;
+	unsigned long first_ind_entry = (unsigned long) &image->head;
+	unsigned long this_hart_id = raw_smp_processor_id();
+	unsigned long fdt_addr = internal->fdt_addr;
+	void *control_code_buffer = page_address(image->control_code_page);
+	riscv_kexec_do_relocate do_relocate = control_code_buffer;
+
+	pr_notice("Will call new kernel at %08lx from hart id %lx\n",
+		  jump_addr, this_hart_id);
+	pr_notice("FDT image at %08lx\n", fdt_addr);
+
+	/* Make sure the relocation code is visible to the hart */
+	local_flush_icache_all();
+
+	/* Jump to the relocation code */
+	pr_notice("Bye...\n");
+	do_relocate(first_ind_entry, jump_addr, fdt_addr,
+		    this_hart_id, va_pa_offset);
+	unreachable();
+}

* Kernel region is always present and we know where it is, no need to look for it inside the loop, just ignore it like the rest of the reserved regions within system's memory.

* Don't call memblock_free inside the loop, if called it'll split the region of pre-allocated resources in two parts, messing things up, just re-use the previous pre-allocated resource and free any unused resources after both loops finish.

* memblock_alloc may add a region when called, so increase the number of pre-allocated regions by one to be on the safe side (reported and patched by Geert Uytterhoeven)

Signed-off-by Geert Uytterhoeven <[email protected]>

Signed-off-by Nick Kossifidis <[email protected]>

arch/riscv/kernel/setup.c +1 -13

@@ -129,53 +139,42 @@ static void __init init_resources(void)
        struct resource *res = NULL;
        struct resource *mem_res = NULL;
        size_t mem_res_sz = 0;
-       int ret = 0, i = 0;
-
-       code_res.start = __pa_symbol(_text);
-       code_res.end = __pa_symbol(_etext) - 1;
-       code_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
-
-       rodata_res.start = __pa_symbol(__start_rodata);
-       rodata_res.end = __pa_symbol(__end_rodata) - 1;
-       rodata_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
-
-       data_res.start = __pa_symbol(_data);
-       data_res.end = __pa_symbol(_edata) - 1;
-       data_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+       int num_resources = 0, res_idx = 0;

Hi Nick,

Thanks for your patch!

Quoted 9 lines · Nick Kossifidis

* Kernel region is always present and we know where it is, no need to look for it inside the loop, just ignore it like the rest of the reserved regions within system's memory.

* Don't call memblock_free inside the loop, if called it'll split the region of pre-allocated resources in two parts, messing things up, just re-use the previous pre-allocated resource and free any unused resources after both loops finish.

Quoted 5 lines

* memblock_alloc may add a region when called, so increase the number of pre-allocated regions by one to be on the safe side (reported and patched by Geert Uytterhoeven)

Signed-off-by Geert Uytterhoeven <[email protected]>

Where does this SoB come from?

Quoted 34 lines

Signed-off-by Nick Kossifidis <[email protected]>

arch/riscv/kernel/setup.c +3 -16

@@ -129,53 +139,42 @@ static void __init init_resources(void)
        struct resource *res = NULL;
        struct resource *mem_res = NULL;
        size_t mem_res_sz = 0;
-       int ret = 0, i = 0;
-
-       code_res.start = __pa_symbol(_text);
-       code_res.end = __pa_symbol(_etext) - 1;
-       code_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
-
-       rodata_res.start = __pa_symbol(__start_rodata);
-       rodata_res.end = __pa_symbol(__end_rodata) - 1;
-       rodata_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
-
-       data_res.start = __pa_symbol(_data);
-       data_res.end = __pa_symbol(_edata) - 1;
-       data_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+       int num_resources = 0, res_idx = 0;
+       int ret = 0;
 
-       bss_res.start = __pa_symbol(__bss_start);
-       bss_res.end = __pa_symbol(__bss_stop) - 1;
-       bss_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+       /* + 1 as memblock_alloc() might increase 

memblock.reserved.cnt */
+ num_resources = memblock.memory.cnt + memblock.reserved.cnt +
1;
+ res_idx = num_resources - 1;

Quoted 2 lines

- mem_res_sz = (memblock.memory.cnt + memblock.reserved.cnt) *
sizeof(*mem_res);

Oh, you incorporated my commit ce989f1472ae350e ("RISC-V: Fix out-of-bounds accesses in init_resources()") (from v5.12-rc4) into your patch. Why? This means your patch does not apply against upstream.

Hello Geert,
Στις 2021-04-06 10:19, Geert Uytterhoeven έγραψε:

Quoted 53 lines

Quoted 9 lines · Nick Kossifidis

* Kernel region is always present and we know where it is, no need to look for it inside the loop, just ignore it like the rest of the reserved regions within system's memory.

* Don't call memblock_free inside the loop, if called it'll split the region of pre-allocated resources in two parts, messing things up, just re-use the previous pre-allocated resource and free any unused resources after both loops finish.

Quoted 5 lines

* memblock_alloc may add a region when called, so increase the number of pre-allocated regions by one to be on the safe side (reported and patched by Geert Uytterhoeven)

Signed-off-by Geert Uytterhoeven <[email protected]>

Where does this SoB come from?

Quoted 34 lines

Signed-off-by Nick Kossifidis <[email protected]>

arch/riscv/kernel/setup.c +3 -16

@@ -129,53 +139,42 @@ static void __init init_resources(void)
        struct resource *res = NULL;
        struct resource *mem_res = NULL;
        size_t mem_res_sz = 0;
-       int ret = 0, i = 0;
-
-       code_res.start = __pa_symbol(_text);
-       code_res.end = __pa_symbol(_etext) - 1;
-       code_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
-
-       rodata_res.start = __pa_symbol(__start_rodata);
-       rodata_res.end = __pa_symbol(__end_rodata) - 1;
-       rodata_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
-
-       data_res.start = __pa_symbol(_data);
-       data_res.end = __pa_symbol(_edata) - 1;
-       data_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+       int num_resources = 0, res_idx = 0;
+       int ret = 0;
 
-       bss_res.start = __pa_symbol(__bss_start);
-       bss_res.end = __pa_symbol(__bss_stop) - 1;
-       bss_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+       /* + 1 as memblock_alloc() might increase

memblock.reserved.cnt */
+ num_resources = memblock.memory.cnt + memblock.reserved.cnt +
1;
+ res_idx = num_resources - 1;

Quoted 8 lines

Quoted 2 lines

- mem_res_sz = (memblock.memory.cnt + memblock.reserved.cnt) *
sizeof(*mem_res);

Oh, you incorporated my commit ce989f1472ae350e ("RISC-V: Fix out-of-bounds
accesses in init_resources()") (from v5.12-rc4) into your patch. Why? This means your patch does not apply against upstream.

Sorry if this looks awkward, I'm under the impression that new features go on for-next instead of fixes and your patch hasn't been merged on for-next yet. I thought it would be cleaner to have one patch to merge for init_resources instead of two, and simpler for people to test the series. I can rebase this on top of fixes if that works better for you or Palmer.

Hi Nick,

Quoted 64 lines · Nick Kossifidis

Hello Geert,
Στις 2021-04-06 10:19, Geert Uytterhoeven έγραψε:

Quoted 53 lines

Quoted 9 lines · Nick Kossifidis

* Kernel region is always present and we know where it is, no need to look for it inside the loop, just ignore it like the rest of the reserved regions within system's memory.

* Don't call memblock_free inside the loop, if called it'll split the region of pre-allocated resources in two parts, messing things up, just re-use the previous pre-allocated resource and free any unused resources after both loops finish.

Quoted 5 lines

* memblock_alloc may add a region when called, so increase the number of pre-allocated regions by one to be on the safe side (reported and patched by Geert Uytterhoeven)

Signed-off-by Geert Uytterhoeven <[email protected]>

Where does this SoB come from?

Quoted 34 lines

Signed-off-by Nick Kossifidis <[email protected]>

arch/riscv/kernel/setup.c +3 -16

@@ -129,53 +139,42 @@ static void __init init_resources(void)
        struct resource *res = NULL;
        struct resource *mem_res = NULL;
        size_t mem_res_sz = 0;
-       int ret = 0, i = 0;
-
-       code_res.start = __pa_symbol(_text);
-       code_res.end = __pa_symbol(_etext) - 1;
-       code_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
-
-       rodata_res.start = __pa_symbol(__start_rodata);
-       rodata_res.end = __pa_symbol(__end_rodata) - 1;
-       rodata_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
-
-       data_res.start = __pa_symbol(_data);
-       data_res.end = __pa_symbol(_edata) - 1;
-       data_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+       int num_resources = 0, res_idx = 0;
+       int ret = 0;
 
-       bss_res.start = __pa_symbol(__bss_start);
-       bss_res.end = __pa_symbol(__bss_stop) - 1;
-       bss_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+       /* + 1 as memblock_alloc() might increase

memblock.reserved.cnt */
+ num_resources = memblock.memory.cnt + memblock.reserved.cnt +
1;
+ res_idx = num_resources - 1;

Quoted 8 lines

Quoted 2 lines

- mem_res_sz = (memblock.memory.cnt + memblock.reserved.cnt) *
sizeof(*mem_res);

Oh, you incorporated my commit ce989f1472ae350e ("RISC-V: Fix out-of-bounds
accesses in init_resources()") (from v5.12-rc4) into your patch. Why? This means your patch does not apply against upstream.

Quoted 6 lines

Sorry if this looks awkward, I'm under the impression that new features go on for-next instead of fixes and your patch hasn't been merged on for-next yet. I thought it would be cleaner to have one patch to merge for init_resources instead of two, and simpler for people to test the series. I can rebase this on top of fixes if that works better for you or Palmer.

Ideally the fixes branch is part of the next branch. That also helps to avoid other people having to fix conflicts when merging both.

* Kernel region is always present and we know where it is, no need to look for it inside the loop, just ignore it like the rest of the reserved regions within system's memory.

* Don't call memblock_free inside the loop, if called it'll split the region of pre-allocated resources in two parts, messing things up, just re-use the previous pre-allocated resource and free any unused resources after both loops finish.

* memblock_alloc may add a region when called, so increase the number of pre-allocated regions by one to be on the safe side (reported and patched by Geert Uytterhoeven)

Signed-off-by Geert Uytterhoeven <[email protected]>

Signed-off-by Nick Kossifidis <[email protected]>

---
 arch/riscv/kernel/setup.c | 90 ++++++++++++++++++++-------------------
 1 file changed, 46 insertions(+), 44 deletions(-)

arch/riscv/kernel/setup.c +46 -44

index e85bacff1..030554bab 100644
@@ -60,6 +60,7 @@ static DEFINE_PER_CPU(struct cpu, cpu_devices);
  * also add "System RAM" regions for compatibility with other
  * archs, and the rest of the known regions for completeness.
  */
+static struct resource kimage_res = { .name = "Kernel image", };
 static struct resource code_res = { .name = "Kernel code", };
 static struct resource data_res = { .name = "Kernel data", };
 static struct resource rodata_res = { .name = "Kernel rodata", };

@@ -80,45 +81,54 @@ static int __init add_resource(struct resource *parent,
 	return 1;
 }
 
-static int __init add_kernel_resources(struct resource *res)
+static int __init add_kernel_resources(void)
 {
 	int ret = 0;
 
 	/*
 	 * The memory region of the kernel image is continuous and
-	 * was reserved on setup_bootmem, find it here and register
-	 * it as a resource, then register the various segments of
-	 * the image as child nodes
+	 * was reserved on setup_bootmem, register it here as a
+	 * resource, with the various segments of the image as
+	 * child nodes.
 	 */
-	if (!(res->start <= code_res.start && res->end >= data_res.end))
-		return 0;
 
-	res->name = "Kernel image";
-	res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+	code_res.start = __pa_symbol(_text);
+	code_res.end = __pa_symbol(_etext) - 1;
+	code_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 
-	/*
-	 * We removed a part of this region on setup_bootmem so
-	 * we need to expand the resource for the bss to fit in.
-	 */
-	res->end = bss_res.end;
+	rodata_res.start = __pa_symbol(__start_rodata);
+	rodata_res.end = __pa_symbol(__end_rodata) - 1;
+	rodata_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 
-	ret = add_resource(&iomem_resource, res);
+	data_res.start = __pa_symbol(_data);
+	data_res.end = __pa_symbol(_edata) - 1;
+	data_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+
+	bss_res.start = __pa_symbol(__bss_start);
+	bss_res.end = __pa_symbol(__bss_stop) - 1;
+	bss_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+
+	kimage_res.start = code_res.start;
+	kimage_res.end = bss_res.end;
+	kimage_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+
+	ret = add_resource(&iomem_resource, &kimage_res);
 	if (ret < 0)
 		return ret;
 
-	ret = add_resource(res, &code_res);
+	ret = add_resource(&kimage_res, &code_res);
 	if (ret < 0)
 		return ret;
 
-	ret = add_resource(res, &rodata_res);
+	ret = add_resource(&kimage_res, &rodata_res);
 	if (ret < 0)
 		return ret;
 
-	ret = add_resource(res, &data_res);
+	ret = add_resource(&kimage_res, &data_res);
 	if (ret < 0)
 		return ret;
 
-	ret = add_resource(res, &bss_res);
+	ret = add_resource(&kimage_res, &bss_res);
 
 	return ret;
 }

@@ -129,53 +139,42 @@ static void __init init_resources(void)
 	struct resource *res = NULL;
 	struct resource *mem_res = NULL;
 	size_t mem_res_sz = 0;
-	int ret = 0, i = 0;
-
-	code_res.start = __pa_symbol(_text);
-	code_res.end = __pa_symbol(_etext) - 1;
-	code_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
-
-	rodata_res.start = __pa_symbol(__start_rodata);
-	rodata_res.end = __pa_symbol(__end_rodata) - 1;
-	rodata_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
-
-	data_res.start = __pa_symbol(_data);
-	data_res.end = __pa_symbol(_edata) - 1;
-	data_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+	int num_resources = 0, res_idx = 0;
+	int ret = 0;
 
-	bss_res.start = __pa_symbol(__bss_start);
-	bss_res.end = __pa_symbol(__bss_stop) - 1;
-	bss_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+	/* + 1 as memblock_alloc() might increase memblock.reserved.cnt */
+	num_resources = memblock.memory.cnt + memblock.reserved.cnt + 1;
+	res_idx = num_resources - 1;
 
-	mem_res_sz = (memblock.memory.cnt + memblock.reserved.cnt) * sizeof(*mem_res);
+	mem_res_sz = num_resources * sizeof(*mem_res);
 	mem_res = memblock_alloc(mem_res_sz, SMP_CACHE_BYTES);
 	if (!mem_res)
 		panic("%s: Failed to allocate %zu bytes\n", __func__, mem_res_sz);
+
 	/*
 	 * Start by adding the reserved regions, if they overlap
 	 * with /memory regions, insert_resource later on will take
 	 * care of it.
 	 */
+	ret = add_kernel_resources();
+	if (ret < 0)
+		goto error;
+
 	for_each_reserved_mem_region(region) {
-		res = &mem_res[i++];
+		res = &mem_res[res_idx--];
 
 		res->name = "Reserved";
 		res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
 		res->start = __pfn_to_phys(memblock_region_reserved_base_pfn(region));
 		res->end = __pfn_to_phys(memblock_region_reserved_end_pfn(region)) - 1;
 
-		ret = add_kernel_resources(res);
-		if (ret < 0)
-			goto error;
-		else if (ret)
-			continue;
-
 		/*
 		 * Ignore any other reserved regions within
 		 * system memory.
 		 */
 		if (memblock_is_memory(res->start)) {
-			memblock_free((phys_addr_t) res, sizeof(struct resource));
+			/* Re-use this pre-allocated resource */
+			res_idx++;
 			continue;
 		}
 

@@ -186,7 +185,7 @@ static void __init init_resources(void)
 
 	/* Add /memory regions to the resource tree */
 	for_each_mem_region(region) {
-		res = &mem_res[i++];
+		res = &mem_res[res_idx--];
 
 		if (unlikely(memblock_is_nomap(region))) {
 			res->name = "Reserved";

@@ -204,6 +203,9 @@ static void __init init_resources(void)
 			goto error;
 	}
 
+	/* Clean-up any unused pre-allocated resources */
+	mem_res_sz = (num_resources - res_idx + 1) * sizeof(*mem_res);
+	memblock_free((phys_addr_t) mem_res, mem_res_sz);
 	return;
 
  error:

This patch adds support for kdump, the kernel will reserve a region for the crash kernel and jump there on panic. In order for userspace tools (kexec-tools) to prepare the crash kernel kexec image, we also need to expose some information on /proc/iomem for the memory regions used by the kernel and for the region reserved for crash kernel. Note that on userspace the device tree is used to determine the system's memory layout so the "System RAM" on /proc/iomem is ignored.

I tested this on riscv64 qemu and works as expected, you may test it by triggering a crash through /proc/sysrq_trigger:

echo c > /proc/sysrq_trigger

v3:
* Move ELF_CORE_COPY_REGS to asm/elf.h instead of uapi/asm/elf.h
* Set stvec when disabling MMU
* Minor cleanups and re-base

v2:
* Properly populate the ioresources tree, so that it can be used later on for implementing strict /dev/mem.
* Minor cleanups and re-base

Signed-off-by Nick Kossifidis <[email protected]>

---
  arch/riscv/include/asm/elf.h        |  6 +++
  arch/riscv/include/asm/kexec.h      | 19 ++++---
  arch/riscv/kernel/Makefile          |  2 +-
  arch/riscv/kernel/crash_save_regs.S | 56 +++++++++++++++++++++
  arch/riscv/kernel/kexec_relocate.S  | 68 ++++++++++++++++++++++++-
  arch/riscv/kernel/machine_kexec.c   | 43 +++++++++-------
  arch/riscv/kernel/setup.c           | 11 ++++-
  arch/riscv/mm/init.c                | 77 +++++++++++++++++++++++++++++
  8 files changed, 255 insertions(+), 27 deletions(-)

create mode 100644 arch/riscv/kernel/crash_save_regs.S

arch/riscv/include/asm/elf.h +6 -0

index 5c725e1df..f4b490cd0 100644
@@ -81,4 +81,10 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm,
  	int uses_interp);
  #endif /* CONFIG_MMU */
 
+#define ELF_CORE_COPY_REGS(dest, regs)			\
+do {							\
+	*(struct user_regs_struct *)&(dest) =		\
+		*(struct user_regs_struct *)regs;	\
+} while (0);
+
  #endif /* _ASM_RISCV_ELF_H */

arch/riscv/include/asm/kexec.h +13 -6

index efc69feb4..4fd583acc 100644
@@ -21,11 +21,16 @@
 
  #define KEXEC_ARCH KEXEC_ARCH_RISCV
 
+extern void riscv_crash_save_regs(struct pt_regs *newregs);
+
  static inline void
  crash_setup_regs(struct pt_regs *newregs,
  		 struct pt_regs *oldregs)
  {
-	/* Dummy implementation for now */
+	if (oldregs)
+		memcpy(newregs, oldregs, sizeof(struct pt_regs));
+	else
+		riscv_crash_save_regs(newregs);
  }
 
 

@@ -38,10 +43,12 @@ struct kimage_arch {
  const extern unsigned char riscv_kexec_relocate[];
  const extern unsigned int riscv_kexec_relocate_size;
 
-typedef void (*riscv_kexec_do_relocate)(unsigned long first_ind_entry,
-					unsigned long jump_addr,
-					unsigned long fdt_addr,
-					unsigned long hartid,
-					unsigned long va_pa_off);
+typedef void (*riscv_kexec_method)(unsigned long first_ind_entry,
+				   unsigned long jump_addr,
+				   unsigned long fdt_addr,
+				   unsigned long hartid,
+				   unsigned long va_pa_off);
+
+extern riscv_kexec_method riscv_kexec_norelocate;
 
  #endif

arch/riscv/kernel/Makefile +1 -1

index c2594018c..07f676ad3 100644
@@ -58,7 +58,7 @@ obj-$(CONFIG_SMP) += cpu_ops_sbi.o
  endif
  obj-$(CONFIG_HOTPLUG_CPU)	+= cpu-hotplug.o
  obj-$(CONFIG_KGDB)		+= kgdb.o
-obj-${CONFIG_KEXEC}		+= kexec_relocate.o machine_kexec.o
+obj-${CONFIG_KEXEC}		+= kexec_relocate.o crash_save_regs.o machine_kexec.o
 
  obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o
 

arch/riscv/kernel/crash_save_regs.S new file +56 -0

new file mode 100644
index 000000000..7832fb763
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020 FORTH-ICS/CARV
+ *  Nick Kossifidis <[email protected]>
+ */
+
+#include <asm/asm.h>    	/* For RISCV_* and REG_* macros */
+#include <asm/csr.h>		/* For CSR_* macros */
+#include <asm/asm-offsets.h>	/* For offsets on pt_regs */
+#include <linux/linkage.h>	/* For SYM_* macros */
+
+.section ".text"
+SYM_CODE_START(riscv_crash_save_regs)
+	REG_S ra,  PT_RA(a0)	/* x1 */
+	REG_S sp,  PT_SP(a0)	/* x2 */
+	REG_S gp,  PT_GP(a0)	/* x3 */
+	REG_S tp,  PT_TP(a0)	/* x4 */
+	REG_S t0,  PT_T0(a0)	/* x5 */
+	REG_S t1,  PT_T1(a0)	/* x6 */
+	REG_S t2,  PT_T2(a0)	/* x7 */
+	REG_S s0,  PT_S0(a0)	/* x8/fp */
+	REG_S s1,  PT_S1(a0)	/* x9 */
+	REG_S a0,  PT_A0(a0)	/* x10 */
+	REG_S a1,  PT_A1(a0)	/* x11 */
+	REG_S a2,  PT_A2(a0)	/* x12 */
+	REG_S a3,  PT_A3(a0)	/* x13 */
+	REG_S a4,  PT_A4(a0)	/* x14 */
+	REG_S a5,  PT_A5(a0)	/* x15 */
+	REG_S a6,  PT_A6(a0)	/* x16 */
+	REG_S a7,  PT_A7(a0)	/* x17 */
+	REG_S s2,  PT_S2(a0)	/* x18 */
+	REG_S s3,  PT_S3(a0)	/* x19 */
+	REG_S s4,  PT_S4(a0)	/* x20 */
+	REG_S s5,  PT_S5(a0)	/* x21 */
+	REG_S s6,  PT_S6(a0)	/* x22 */
+	REG_S s7,  PT_S7(a0)	/* x23 */
+	REG_S s8,  PT_S8(a0)	/* x24 */
+	REG_S s9,  PT_S9(a0)	/* x25 */
+	REG_S s10, PT_S10(a0)	/* x26 */
+	REG_S s11, PT_S11(a0)	/* x27 */
+	REG_S t3,  PT_T3(a0)	/* x28 */
+	REG_S t4,  PT_T4(a0)	/* x29 */
+	REG_S t5,  PT_T5(a0)	/* x30 */
+	REG_S t6,  PT_T6(a0)	/* x31 */
+
+	csrr t1, CSR_STATUS
+	csrr t2, CSR_EPC
+	csrr t3, CSR_TVAL
+	csrr t4, CSR_CAUSE
+
+	REG_S t1, PT_STATUS(a0)
+	REG_S t2, PT_EPC(a0)
+	REG_S t3, PT_BADADDR(a0)
+	REG_S t4, PT_CAUSE(a0)
+	ret
+SYM_CODE_END(riscv_crash_save_regs)

arch/riscv/kernel/kexec_relocate.S +14 -1

index 616c20771..14220f70f 100644
@@ -150,7 +150,73 @@ SYM_CODE_START(riscv_kexec_relocate)
  SYM_CODE_END(riscv_kexec_relocate)
  riscv_kexec_relocate_end:
 
-	.section ".rodata"
+
+/* Used for jumping to crashkernel */
+.section ".text"
+SYM_CODE_START(riscv_kexec_norelocate)
+	/*
+	 * s0: (const) Phys address to jump to
+	 * s1: (const) Phys address of the FDT image
+	 * s2: (const) The hartid of the current hart
+	 * s3: (const) va_pa_offset, used when switching MMU off
+	 */
+	mv	s0, a1
+	mv	s1, a2
+	mv	s2, a3
+	mv	s3, a4

arch/riscv/kernel/kexec_relocate.S +43 -0

+
+.align 2
+1:
+	/* Pass the arguments to the next kernel  / Cleanup*/
+	mv	a0, s2
+	mv	a1, s1
+	mv	a2, s0
+
+	/* Cleanup */
+	mv	a3, zero
+	mv	a4, zero
+	mv	a5, zero
+	mv	a6, zero
+	mv	a7, zero
+
+	mv	s0, zero
+	mv	s1, zero
+	mv	s2, zero
+	mv	s3, zero
+	mv	s4, zero
+	mv	s5, zero
+	mv	s6, zero
+	mv	s7, zero
+	mv	s8, zero
+	mv	s9, zero
+	mv	s10, zero
+	mv	s11, zero
+
+	mv	t0, zero
+	mv	t1, zero
+	mv	t2, zero
+	mv	t3, zero
+	mv	t4, zero
+	mv	t5, zero
+	mv	t6, zero
+	csrw	sepc, zero
+	csrw	scause, zero
+	csrw	sscratch, zero
+
+	jalr	zero, a2, 0
+SYM_CODE_END(riscv_kexec_norelocate)
+
+.section ".rodata"
  SYM_DATA(riscv_kexec_relocate_size,
  	.long riscv_kexec_relocate_end - riscv_kexec_relocate)
 

arch/riscv/kernel/machine_kexec.c +25 -18

index 2ce6c3daf..e0596c0ac 100644
@@ -59,11 +59,6 @@ machine_kexec_prepare(struct kimage *image)
 
  	kexec_image_info(image);
 
-	if (image->type == KEXEC_TYPE_CRASH) {
-		pr_warn("Loading a crash kernel is unsupported for now.\n");
-		return -EINVAL;
-	}
-
  	/* Find the Flattened Device Tree and save its physical address */
  	for (i = 0; i < image->nr_segments; i++) {
  		if (image->segment[i].memsz <= sizeof(fdt))

@@ -85,17 +80,21 @@ machine_kexec_prepare(struct kimage *image)
  	}
 
  	/* Copy the assembler code for relocation to the control page */
-	control_code_buffer = page_address(image->control_code_page);
-	control_code_buffer_sz = page_size(image->control_code_page);
-	if (unlikely(riscv_kexec_relocate_size > control_code_buffer_sz)) {
-		pr_err("Relocation code doesn't fit within a control page\n");
-		return -EINVAL;
-	}
-	memcpy(control_code_buffer, riscv_kexec_relocate,
-		riscv_kexec_relocate_size);
+	if (image->type != KEXEC_TYPE_CRASH) {
+		control_code_buffer = page_address(image->control_code_page);
+		control_code_buffer_sz = page_size(image->control_code_page);
 
-	/* Mark the control page executable */
-	set_memory_x((unsigned long) control_code_buffer, 1);
+		if (unlikely(riscv_kexec_relocate_size > control_code_buffer_sz)) {
+			pr_err("Relocation code doesn't fit within a control page\n");
+			return -EINVAL;
+		}
+
+		memcpy(control_code_buffer, riscv_kexec_relocate,
+			riscv_kexec_relocate_size);
+
+		/* Mark the control page executable */
+		set_memory_x((unsigned long) control_code_buffer, 1);
+	}
 
  	return 0;
  }

@@ -147,6 +146,9 @@ void machine_shutdown(void)
  void
  machine_crash_shutdown(struct pt_regs *regs)
  {
+	crash_save_cpu(regs, smp_processor_id());
+	machine_shutdown();
+	pr_info("Starting crashdump kernel...\n");
  }
 
  /**

@@ -169,7 +171,12 @@ machine_kexec(struct kimage *image)
  	unsigned long this_hart_id = raw_smp_processor_id();
  	unsigned long fdt_addr = internal->fdt_addr;
  	void *control_code_buffer = page_address(image->control_code_page);
-	riscv_kexec_do_relocate do_relocate = control_code_buffer;
+	riscv_kexec_method kexec_method = NULL;
+
+	if (image->type != KEXEC_TYPE_CRASH)
+		kexec_method = control_code_buffer;
+	else
+		kexec_method = (riscv_kexec_method) &riscv_kexec_norelocate;
 
  	pr_notice("Will call new kernel at %08lx from hart id %lx\n",
  		  jump_addr, this_hart_id);

@@ -180,7 +187,7 @@ machine_kexec(struct kimage *image)
 
  	/* Jump to the relocation code */
  	pr_notice("Bye...\n");
-	do_relocate(first_ind_entry, jump_addr, fdt_addr,
-		    this_hart_id, va_pa_offset);
+	kexec_method(first_ind_entry, jump_addr, fdt_addr,
+		     this_hart_id, va_pa_offset);
  	unreachable();
  }

arch/riscv/kernel/setup.c +10 -1

index 030554bab..31866dce9 100644
@@ -20,6 +20,7 @@
  #include <linux/swiotlb.h>
  #include <linux/smp.h>
  #include <linux/efi.h>
+#include <linux/crash_dump.h>
 
  #include <asm/cpu_ops.h>
  #include <asm/early_ioremap.h>

@@ -160,6 +161,14 @@ static void __init init_resources(void)
  	if (ret < 0)
  		goto error;
 
+#ifdef CONFIG_KEXEC_CORE
+	if (crashk_res.start != crashk_res.end) {
+		ret = add_resource(&iomem_resource, &crashk_res);
+		if (ret < 0)
+			goto error;
+	}
+#endif
+
  	for_each_reserved_mem_region(region) {
  		res = &mem_res[res_idx--];
 

@@ -252,7 +261,6 @@ void __init setup_arch(char **cmdline_p)
  	efi_init();
  	setup_bootmem();
  	paging_init();
-	init_resources();
  #if IS_ENABLED(CONFIG_BUILTIN_DTB)
  	unflatten_and_copy_device_tree();
  #else

@@ -263,6 +271,7 @@ void __init setup_arch(char **cmdline_p)
  #endif
  	misc_mem_init();
 
+	init_resources();
  	sbi_init();
 
  	if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))

arch/riscv/mm/init.c +28 -0

index 7f5036fbe..e71b35cec 100644
@@ -2,6 +2,8 @@
  /*
   * Copyright (C) 2012 Regents of the University of California
   * Copyright (C) 2019 Western Digital Corporation or its affiliates.
+ * Copyright (C) 2020 FORTH-ICS/CARV
+ *  Nick Kossifidis <[email protected]>
   */
 
  #include <linux/init.h>

@@ -14,6 +16,7 @@
  #include <linux/libfdt.h>
  #include <linux/set_memory.h>
  #include <linux/dma-map-ops.h>
+#include <linux/crash_dump.h>
 
  #include <asm/fixmap.h>
  #include <asm/tlbflush.h>

@@ -586,6 +589,77 @@ void mark_rodata_ro(void)
  }
  #endif
 
+#ifdef CONFIG_KEXEC_CORE
+/*
+ * reserve_crashkernel() - reserves memory for crash kernel
+ *
+ * This function reserves memory area given in "crashkernel=" kernel command
+ * line parameter. The memory reserved is used by dump capture kernel when
+ * primary kernel is crashing.
+ */
+static void __init reserve_crashkernel(void)
+{
+	unsigned long long crash_base = 0;
+	unsigned long long crash_size = 0;
+	unsigned long search_start = memblock_start_of_DRAM();
+	unsigned long search_end = memblock_end_of_DRAM();
+
+	int ret = 0;
+
+	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
+				&crash_size, &crash_base);
+	if (ret || !crash_size)
+		return;
+
+	crash_size = PAGE_ALIGN(crash_size);
+
+	if (crash_base == 0) {

arch/riscv/mm/init.c +12 -0

+		if (crash_base == 0) {
+			pr_warn("crashkernel: couldn't allocate %lldKB\n",
+				crash_size >> 10);
+			return;
+		}
+	} else {
+		/* User specifies base address explicitly. */
+		if (!memblock_is_region_memory(crash_base, crash_size)) {
+			pr_warn("crashkernel: requested region is not memory\n");
+			return;
+		}
+

arch/riscv/mm/init.c +17 -0

+			pr_warn("crashkernel: requested region is misaligned\n");
+			return;
+		}
+	}
+	memblock_reserve(crash_base, crash_size);
+
+	pr_info("crashkernel: reserved 0x%016llx - 0x%016llx (%lld MB)\n",
+		crash_base, crash_base + crash_size, crash_size >> 20);
+
+	crashk_res.start = crash_base;
+	crashk_res.end = crash_base + crash_size - 1;
+}
+#endif /* CONFIG_KEXEC_CORE */
+
  void __init paging_init(void)
  {
  	setup_vm_final();

@@ -598,6 +672,9 @@ void __init misc_mem_init(void)
  	arch_numa_init();
  	sparse_init();
  	zone_sizes_init();
+#ifdef CONFIG_KEXEC_CORE
+	reserve_crashkernel();
+#endif
  	memblock_dump_all();
  }
 

arch/riscv/kernel/kexec_relocate.S SYM_CODE_START(riscv_kexec_relocate) · line 176

Quoted 6 lines

arch/riscv/kernel/kexec_relocate.S +5 -0

+	/* Switch to physical addressing */
+	la	s4, 1f
+	sub	s4, s4, s3
+	csrw	stvec, s4
+	csrw	sptbr, zero

satp is used everywhere instead of sptbr. And maybe you could CSR_**** naming, like you did in riscv_crash_save_regs and like it's done in head.S too.

arch/riscv/mm/init.c void mark_rodata_ro(void) · line 626

Quoted 6 lines

arch/riscv/mm/init.c +6 -0

+		crash_base = memblock_find_in_range(search_start, search_end,
+#ifdef CONFIG_64BIT
+						    crash_size, SZ_2M);
+#else
+						    crash_size, SZ_4M);
+#endif

You can use PMD_SIZE here and get rid of #ifdef.

arch/riscv/mm/init.c void mark_rodata_ro(void) · line 648

Quoted 6 lines

arch/riscv/mm/init.c +6 -0

+
+#ifdef CONFIG_64BIT
+		if (!IS_ALIGNED(crash_base, SZ_2M)) {
+#else
+		if (!IS_ALIGNED(crash_base, SZ_4M)) {
+#endif

Ditto here.

This patch adds support for kdump, the kernel will reserve a region for the crash kernel and jump there on panic. In order for userspace tools (kexec-tools) to prepare the crash kernel kexec image, we also need to expose some information on /proc/iomem for the memory regions used by the kernel and for the region reserved for crash kernel. Note that on userspace the device tree is used to determine the system's memory layout so the "System RAM" on /proc/iomem is ignored.

I tested this on riscv64 qemu and works as expected, you may test it by triggering a crash through /proc/sysrq_trigger:

echo c > /proc/sysrq_trigger

v3:
* Move ELF_CORE_COPY_REGS to asm/elf.h instead of uapi/asm/elf.h
* Set stvec when disabling MMU
* Minor cleanups and re-base

v2:
* Properly populate the ioresources tree, so that it can be used later on for implementing strict /dev/mem.
* Minor cleanups and re-base

Signed-off-by Nick Kossifidis <[email protected]>

---
 arch/riscv/include/asm/elf.h        |  6 +++
 arch/riscv/include/asm/kexec.h      | 19 ++++---
 arch/riscv/kernel/Makefile          |  2 +-
 arch/riscv/kernel/crash_save_regs.S | 56 +++++++++++++++++++++
 arch/riscv/kernel/kexec_relocate.S  | 68 ++++++++++++++++++++++++-
 arch/riscv/kernel/machine_kexec.c   | 43 +++++++++-------
 arch/riscv/kernel/setup.c           | 11 ++++-
 arch/riscv/mm/init.c                | 77 +++++++++++++++++++++++++++++
 8 files changed, 255 insertions(+), 27 deletions(-)
 create mode 100644 arch/riscv/kernel/crash_save_regs.S

arch/riscv/include/asm/elf.h +6 -0

index 5c725e1df..f4b490cd0 100644
@@ -81,4 +81,10 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm,
 	int uses_interp);
 #endif /* CONFIG_MMU */
 
+#define ELF_CORE_COPY_REGS(dest, regs)			\
+do {							\
+	*(struct user_regs_struct *)&(dest) =		\
+		*(struct user_regs_struct *)regs;	\
+} while (0);
+
 #endif /* _ASM_RISCV_ELF_H */

arch/riscv/include/asm/kexec.h +13 -6

index efc69feb4..4fd583acc 100644
@@ -21,11 +21,16 @@
 
 #define KEXEC_ARCH KEXEC_ARCH_RISCV
 
+extern void riscv_crash_save_regs(struct pt_regs *newregs);
+
 static inline void
 crash_setup_regs(struct pt_regs *newregs,
 		 struct pt_regs *oldregs)
 {
-	/* Dummy implementation for now */
+	if (oldregs)
+		memcpy(newregs, oldregs, sizeof(struct pt_regs));
+	else
+		riscv_crash_save_regs(newregs);
 }
 
 

@@ -38,10 +43,12 @@ struct kimage_arch {
 const extern unsigned char riscv_kexec_relocate[];
 const extern unsigned int riscv_kexec_relocate_size;
 
-typedef void (*riscv_kexec_do_relocate)(unsigned long first_ind_entry,
-					unsigned long jump_addr,
-					unsigned long fdt_addr,
-					unsigned long hartid,
-					unsigned long va_pa_off);
+typedef void (*riscv_kexec_method)(unsigned long first_ind_entry,
+				   unsigned long jump_addr,
+				   unsigned long fdt_addr,
+				   unsigned long hartid,
+				   unsigned long va_pa_off);
+
+extern riscv_kexec_method riscv_kexec_norelocate;
 
 #endif

arch/riscv/kernel/Makefile +1 -1

index c2594018c..07f676ad3 100644
@@ -58,7 +58,7 @@ obj-$(CONFIG_SMP) += cpu_ops_sbi.o
 endif
 obj-$(CONFIG_HOTPLUG_CPU)	+= cpu-hotplug.o
 obj-$(CONFIG_KGDB)		+= kgdb.o
-obj-${CONFIG_KEXEC}		+= kexec_relocate.o machine_kexec.o
+obj-${CONFIG_KEXEC}		+= kexec_relocate.o crash_save_regs.o machine_kexec.o
 
 obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o
 

arch/riscv/kernel/crash_save_regs.S new file +56 -0

new file mode 100644
index 000000000..7832fb763
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020 FORTH-ICS/CARV
+ *  Nick Kossifidis <[email protected]>
+ */
+
+#include <asm/asm.h>    	/* For RISCV_* and REG_* macros */
+#include <asm/csr.h>		/* For CSR_* macros */
+#include <asm/asm-offsets.h>	/* For offsets on pt_regs */
+#include <linux/linkage.h>	/* For SYM_* macros */
+
+.section ".text"
+SYM_CODE_START(riscv_crash_save_regs)
+	REG_S ra,  PT_RA(a0)	/* x1 */
+	REG_S sp,  PT_SP(a0)	/* x2 */
+	REG_S gp,  PT_GP(a0)	/* x3 */
+	REG_S tp,  PT_TP(a0)	/* x4 */
+	REG_S t0,  PT_T0(a0)	/* x5 */
+	REG_S t1,  PT_T1(a0)	/* x6 */
+	REG_S t2,  PT_T2(a0)	/* x7 */
+	REG_S s0,  PT_S0(a0)	/* x8/fp */
+	REG_S s1,  PT_S1(a0)	/* x9 */
+	REG_S a0,  PT_A0(a0)	/* x10 */
+	REG_S a1,  PT_A1(a0)	/* x11 */
+	REG_S a2,  PT_A2(a0)	/* x12 */
+	REG_S a3,  PT_A3(a0)	/* x13 */
+	REG_S a4,  PT_A4(a0)	/* x14 */
+	REG_S a5,  PT_A5(a0)	/* x15 */
+	REG_S a6,  PT_A6(a0)	/* x16 */
+	REG_S a7,  PT_A7(a0)	/* x17 */
+	REG_S s2,  PT_S2(a0)	/* x18 */
+	REG_S s3,  PT_S3(a0)	/* x19 */
+	REG_S s4,  PT_S4(a0)	/* x20 */
+	REG_S s5,  PT_S5(a0)	/* x21 */
+	REG_S s6,  PT_S6(a0)	/* x22 */
+	REG_S s7,  PT_S7(a0)	/* x23 */
+	REG_S s8,  PT_S8(a0)	/* x24 */
+	REG_S s9,  PT_S9(a0)	/* x25 */
+	REG_S s10, PT_S10(a0)	/* x26 */
+	REG_S s11, PT_S11(a0)	/* x27 */
+	REG_S t3,  PT_T3(a0)	/* x28 */
+	REG_S t4,  PT_T4(a0)	/* x29 */
+	REG_S t5,  PT_T5(a0)	/* x30 */
+	REG_S t6,  PT_T6(a0)	/* x31 */
+
+	csrr t1, CSR_STATUS
+	csrr t2, CSR_EPC
+	csrr t3, CSR_TVAL
+	csrr t4, CSR_CAUSE
+
+	REG_S t1, PT_STATUS(a0)
+	REG_S t2, PT_EPC(a0)
+	REG_S t3, PT_BADADDR(a0)
+	REG_S t4, PT_CAUSE(a0)
+	ret
+SYM_CODE_END(riscv_crash_save_regs)

arch/riscv/kernel/kexec_relocate.S +67 -1

index 616c20771..14220f70f 100644
@@ -150,7 +150,73 @@ SYM_CODE_START(riscv_kexec_relocate)
 SYM_CODE_END(riscv_kexec_relocate)
 riscv_kexec_relocate_end:
 
-	.section ".rodata"
+
+/* Used for jumping to crashkernel */
+.section ".text"
+SYM_CODE_START(riscv_kexec_norelocate)
+	/*
+	 * s0: (const) Phys address to jump to
+	 * s1: (const) Phys address of the FDT image
+	 * s2: (const) The hartid of the current hart
+	 * s3: (const) va_pa_offset, used when switching MMU off
+	 */
+	mv	s0, a1
+	mv	s1, a2
+	mv	s2, a3
+	mv	s3, a4
+
+	/* Disable / cleanup interrupts */
+	csrw	sie, zero
+	csrw	sip, zero
+
+	/* Switch to physical addressing */
+	la	s4, 1f
+	sub	s4, s4, s3
+	csrw	stvec, s4
+	csrw	sptbr, zero
+
+.align 2
+1:
+	/* Pass the arguments to the next kernel  / Cleanup*/
+	mv	a0, s2
+	mv	a1, s1
+	mv	a2, s0
+
+	/* Cleanup */
+	mv	a3, zero
+	mv	a4, zero
+	mv	a5, zero
+	mv	a6, zero
+	mv	a7, zero
+
+	mv	s0, zero
+	mv	s1, zero
+	mv	s2, zero
+	mv	s3, zero
+	mv	s4, zero
+	mv	s5, zero
+	mv	s6, zero
+	mv	s7, zero
+	mv	s8, zero
+	mv	s9, zero
+	mv	s10, zero
+	mv	s11, zero
+
+	mv	t0, zero
+	mv	t1, zero
+	mv	t2, zero
+	mv	t3, zero
+	mv	t4, zero
+	mv	t5, zero
+	mv	t6, zero
+	csrw	sepc, zero
+	csrw	scause, zero
+	csrw	sscratch, zero
+
+	jalr	zero, a2, 0
+SYM_CODE_END(riscv_kexec_norelocate)
+
+.section ".rodata"
 SYM_DATA(riscv_kexec_relocate_size,
 	.long riscv_kexec_relocate_end - riscv_kexec_relocate)
 

arch/riscv/kernel/machine_kexec.c +25 -18

index 2ce6c3daf..e0596c0ac 100644
@@ -59,11 +59,6 @@ machine_kexec_prepare(struct kimage *image)
 
 	kexec_image_info(image);
 
-	if (image->type == KEXEC_TYPE_CRASH) {
-		pr_warn("Loading a crash kernel is unsupported for now.\n");
-		return -EINVAL;
-	}
-
 	/* Find the Flattened Device Tree and save its physical address */
 	for (i = 0; i < image->nr_segments; i++) {
 		if (image->segment[i].memsz <= sizeof(fdt))

@@ -85,17 +80,21 @@ machine_kexec_prepare(struct kimage *image)
 	}
 
 	/* Copy the assembler code for relocation to the control page */
-	control_code_buffer = page_address(image->control_code_page);
-	control_code_buffer_sz = page_size(image->control_code_page);
-	if (unlikely(riscv_kexec_relocate_size > control_code_buffer_sz)) {
-		pr_err("Relocation code doesn't fit within a control page\n");
-		return -EINVAL;
-	}
-	memcpy(control_code_buffer, riscv_kexec_relocate,
-		riscv_kexec_relocate_size);
+	if (image->type != KEXEC_TYPE_CRASH) {
+		control_code_buffer = page_address(image->control_code_page);
+		control_code_buffer_sz = page_size(image->control_code_page);
 
-	/* Mark the control page executable */
-	set_memory_x((unsigned long) control_code_buffer, 1);
+		if (unlikely(riscv_kexec_relocate_size > control_code_buffer_sz)) {
+			pr_err("Relocation code doesn't fit within a control page\n");
+			return -EINVAL;
+		}
+
+		memcpy(control_code_buffer, riscv_kexec_relocate,
+			riscv_kexec_relocate_size);
+
+		/* Mark the control page executable */
+		set_memory_x((unsigned long) control_code_buffer, 1);
+	}
 
 	return 0;
 }

@@ -147,6 +146,9 @@ void machine_shutdown(void)
 void
 machine_crash_shutdown(struct pt_regs *regs)
 {
+	crash_save_cpu(regs, smp_processor_id());
+	machine_shutdown();
+	pr_info("Starting crashdump kernel...\n");
 }
 
 /**

@@ -169,7 +171,12 @@ machine_kexec(struct kimage *image)
 	unsigned long this_hart_id = raw_smp_processor_id();
 	unsigned long fdt_addr = internal->fdt_addr;
 	void *control_code_buffer = page_address(image->control_code_page);
-	riscv_kexec_do_relocate do_relocate = control_code_buffer;
+	riscv_kexec_method kexec_method = NULL;
+
+	if (image->type != KEXEC_TYPE_CRASH)
+		kexec_method = control_code_buffer;
+	else
+		kexec_method = (riscv_kexec_method) &riscv_kexec_norelocate;
 
 	pr_notice("Will call new kernel at %08lx from hart id %lx\n",
 		  jump_addr, this_hart_id);

@@ -180,7 +187,7 @@ machine_kexec(struct kimage *image)
 
 	/* Jump to the relocation code */
 	pr_notice("Bye...\n");
-	do_relocate(first_ind_entry, jump_addr, fdt_addr,
-		    this_hart_id, va_pa_offset);
+	kexec_method(first_ind_entry, jump_addr, fdt_addr,
+		     this_hart_id, va_pa_offset);
 	unreachable();
 }

arch/riscv/kernel/setup.c +9 -1

index 030554bab..31866dce9 100644
@@ -20,6 +20,7 @@
 #include <linux/swiotlb.h>
 #include <linux/smp.h>
 #include <linux/efi.h>
+#include <linux/crash_dump.h>
 
 #include <asm/cpu_ops.h>
 #include <asm/early_ioremap.h>

@@ -160,6 +161,14 @@ static void __init init_resources(void)
 	if (ret < 0)
 		goto error;
 
+#ifdef CONFIG_KEXEC_CORE
+	if (crashk_res.start != crashk_res.end) {
+		ret = add_resource(&iomem_resource, &crashk_res);
+		if (ret < 0)
+			goto error;
+	}
+#endif
+
 	for_each_reserved_mem_region(region) {
 		res = &mem_res[res_idx--];
 

@@ -252,7 +261,6 @@ void __init setup_arch(char **cmdline_p)
 	efi_init();
 	setup_bootmem();
 	paging_init();
-	init_resources();
 #if IS_ENABLED(CONFIG_BUILTIN_DTB)
 	unflatten_and_copy_device_tree();
 #else

arch/riscv/kernel/setup.c +0 -0

 	if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))

arch/riscv/mm/init.c +77 -0

index 7f5036fbe..e71b35cec 100644
@@ -2,6 +2,8 @@
 /*
  * Copyright (C) 2012 Regents of the University of California
  * Copyright (C) 2019 Western Digital Corporation or its affiliates.
+ * Copyright (C) 2020 FORTH-ICS/CARV
+ *  Nick Kossifidis <[email protected]>
  */
 
 #include <linux/init.h>

@@ -14,6 +16,7 @@
 #include <linux/libfdt.h>
 #include <linux/set_memory.h>
 #include <linux/dma-map-ops.h>
+#include <linux/crash_dump.h>
 
 #include <asm/fixmap.h>
 #include <asm/tlbflush.h>

@@ -586,6 +589,77 @@ void mark_rodata_ro(void)
 }
 #endif
 
+#ifdef CONFIG_KEXEC_CORE
+/*
+ * reserve_crashkernel() - reserves memory for crash kernel
+ *
+ * This function reserves memory area given in "crashkernel=" kernel command
+ * line parameter. The memory reserved is used by dump capture kernel when
+ * primary kernel is crashing.
+ */
+static void __init reserve_crashkernel(void)
+{
+	unsigned long long crash_base = 0;
+	unsigned long long crash_size = 0;
+	unsigned long search_start = memblock_start_of_DRAM();
+	unsigned long search_end = memblock_end_of_DRAM();
+
+	int ret = 0;
+
+	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
+				&crash_size, &crash_base);
+	if (ret || !crash_size)
+		return;
+
+	crash_size = PAGE_ALIGN(crash_size);
+
+	if (crash_base == 0) {
+		/*
+		 * Current riscv boot protocol requires 2MB alignment for
+		 * RV64 and 4MB alignment for RV32 (hugepage size)
+		 */
+		crash_base = memblock_find_in_range(search_start, search_end,
+#ifdef CONFIG_64BIT
+						    crash_size, SZ_2M);
+#else
+						    crash_size, SZ_4M);
+#endif
+		if (crash_base == 0) {
+			pr_warn("crashkernel: couldn't allocate %lldKB\n",
+				crash_size >> 10);
+			return;
+		}
+	} else {
+		/* User specifies base address explicitly. */
+		if (!memblock_is_region_memory(crash_base, crash_size)) {
+			pr_warn("crashkernel: requested region is not memory\n");
+			return;
+		}
+
+		if (memblock_is_region_reserved(crash_base, crash_size)) {
+			pr_warn("crashkernel: requested region is reserved\n");
+			return;
+		}
+
+#ifdef CONFIG_64BIT
+		if (!IS_ALIGNED(crash_base, SZ_2M)) {
+#else
+		if (!IS_ALIGNED(crash_base, SZ_4M)) {
+#endif
+			pr_warn("crashkernel: requested region is misaligned\n");
+			return;
+		}
+	}
+	memblock_reserve(crash_base, crash_size);
+
+	pr_info("crashkernel: reserved 0x%016llx - 0x%016llx (%lld MB)\n",
+		crash_base, crash_base + crash_size, crash_size >> 20);
+
+	crashk_res.start = crash_base;
+	crashk_res.end = crash_base + crash_size - 1;
+}
+#endif /* CONFIG_KEXEC_CORE */
+
 void __init paging_init(void)
 {
 	setup_vm_final();

@@ -598,6 +672,9 @@ void __init misc_mem_init(void)
 	arch_numa_init();
 	sparse_init();
 	zone_sizes_init();
+#ifdef CONFIG_KEXEC_CORE
+	reserve_crashkernel();
+#endif
 	memblock_dump_all();
 }

From: Nick Kossifidis <[email protected]>

This patch allows Linux to act as a crash kernel for use with kdump. Userspace will let the crash kernel know about the memory region it can use through linux,usable-memory property on the /memory node (overriding its reg property), and about the memory region where the elf core header of the previous kernel is saved, through a reserved-memory node with a compatible string of "linux,elfcorehdr". This approach is the least invasive and re-uses functionality already present.

I tested this on riscv64 qemu and it works as expected, you may test it by retrieving the dmesg of the previous kernel through /proc/vmcore, using the vmcore-dmesg utility from kexec-tools.

v3:
* Rebase

v2:
* Use linux,usable-memory on /memory instead of a new binding
* Use a reserved-memory node for ELF core header

Signed-off-by Nick Kossifidis <[email protected]>

---
 arch/riscv/Kconfig             | 10 ++++++++
 arch/riscv/kernel/Makefile     |  1 +
 arch/riscv/kernel/crash_dump.c | 46 ++++++++++++++++++++++++++++++++++
 arch/riscv/kernel/setup.c      | 12 +++++++++
 arch/riscv/mm/init.c           | 33 ++++++++++++++++++++++++
 5 files changed, 102 insertions(+)
 create mode 100644 arch/riscv/kernel/crash_dump.c

arch/riscv/Kconfig +10 -0

index 3716262ef..553c2dced 100644
@@ -403,6 +403,16 @@ config KEXEC
 
 	  The name comes from the similarity to the exec system call.
 
+config CRASH_DUMP
+	bool "Build kdump crash kernel"
+	help
+	  Generate crash dump after being started by kexec. This should
+	  be normally only set in special crash dump kernels which are
+	  loaded in the main kernel with kexec-tools into a specially
+	  reserved region and then later executed after a crash by
+	  kdump/kexec.
+
+	  For more details see Documentation/admin-guide/kdump/kdump.rst
 
 endmenu
 

arch/riscv/kernel/Makefile +1 -0

index 07f676ad3..bd66d2ce0 100644
@@ -59,6 +59,7 @@ endif
 obj-$(CONFIG_HOTPLUG_CPU)	+= cpu-hotplug.o
 obj-$(CONFIG_KGDB)		+= kgdb.o
 obj-${CONFIG_KEXEC}		+= kexec_relocate.o crash_save_regs.o machine_kexec.o
+obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 
 obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o
 

arch/riscv/kernel/crash_dump.c new file +46 -0

new file mode 100644
index 000000000..86cc0ada5
@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This code comes from arch/arm64/kernel/crash_dump.c
+ * Created by: AKASHI Takahiro <[email protected]>
+ * Copyright (C) 2017 Linaro Limited
+ */
+
+#include <linux/crash_dump.h>
+#include <linux/io.h>
+
+/**
+ * copy_oldmem_page() - copy one page from old kernel memory
+ * @pfn: page frame number to be copied
+ * @buf: buffer where the copied page is placed
+ * @csize: number of bytes to copy
+ * @offset: offset in bytes into the page
+ * @userbuf: if set, @buf is in a user address space
+ *
+ * This function copies one page from old kernel memory into buffer pointed by
+ * @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
+ * copied or negative error in case of failure.
+ */
+ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
+			 size_t csize, unsigned long offset,
+			 int userbuf)
+{
+	void *vaddr;
+
+	if (!csize)
+		return 0;
+
+	vaddr = memremap(__pfn_to_phys(pfn), PAGE_SIZE, MEMREMAP_WB);
+	if (!vaddr)
+		return -ENOMEM;
+
+	if (userbuf) {
+		if (copy_to_user((char __user *)buf, vaddr + offset, csize)) {
+			memunmap(vaddr);
+			return -EFAULT;
+		}
+	} else
+		memcpy(buf, vaddr + offset, csize);
+
+	memunmap(vaddr);
+	return csize;
+}

arch/riscv/kernel/setup.c +12 -0

index 31866dce9..ff398a3d8 100644
@@ -66,6 +66,9 @@ static struct resource code_res = { .name = "Kernel code", };
 static struct resource data_res = { .name = "Kernel data", };
 static struct resource rodata_res = { .name = "Kernel rodata", };
 static struct resource bss_res = { .name = "Kernel bss", };
+#ifdef CONFIG_CRASH_DUMP
+static struct resource elfcorehdr_res = { .name = "ELF Core hdr", };
+#endif
 
 static int __init add_resource(struct resource *parent,
 				struct resource *res)

@@ -169,6 +172,15 @@ static void __init init_resources(void)
 	}
 #endif
 
+#ifdef CONFIG_CRASH_DUMP
+	if (elfcorehdr_size > 0) {
+		elfcorehdr_res.start = elfcorehdr_addr;
+		elfcorehdr_res.end = elfcorehdr_addr + elfcorehdr_size - 1;
+		elfcorehdr_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+		add_resource(&iomem_resource, &elfcorehdr_res);
+	}
+#endif
+
 	for_each_reserved_mem_region(region) {
 		res = &mem_res[res_idx--];
 

arch/riscv/mm/init.c +33 -0

index e71b35cec..f66011816 100644
@@ -13,6 +13,7 @@
 #include <linux/swap.h>
 #include <linux/sizes.h>
 #include <linux/of_fdt.h>
+#include <linux/of_reserved_mem.h>
 #include <linux/libfdt.h>
 #include <linux/set_memory.h>
 #include <linux/dma-map-ops.h>

@@ -606,6 +607,18 @@ static void __init reserve_crashkernel(void)
 
 	int ret = 0;
 
+	/*
+	 * Don't reserve a region for a crash kernel on a crash kernel
+	 * since it doesn't make much sense and we have limited memory
+	 * resources.
+	 */
+#ifdef CONFIG_CRASH_DUMP
+	if (is_kdump_kernel()) {
+		pr_info("crashkernel: ignoring reservation request\n");
+		return;
+	}
+#endif
+
 	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
 				&crash_size, &crash_base);
 	if (ret || !crash_size)

@@ -660,6 +673,26 @@ static void __init reserve_crashkernel(void)
 }
 #endif /* CONFIG_KEXEC_CORE */
 
+#ifdef CONFIG_CRASH_DUMP
+/*
+ * We keep track of the ELF core header of the crashed
+ * kernel with a reserved-memory region with compatible
+ * string "linux,elfcorehdr". Here we register a callback
+ * to populate elfcorehdr_addr/size when this region is
+ * present. Note that this region will be marked as
+ * reserved once we call early_init_fdt_scan_reserved_mem()
+ * later on.
+ */
+static int elfcore_hdr_setup(struct reserved_mem *rmem)
+{
+	elfcorehdr_addr = rmem->base;
+	elfcorehdr_size = rmem->size;
+	return 0;
+}
+
+RESERVEDMEM_OF_DECLARE(elfcorehdr, "linux,elfcorehdr", elfcore_hdr_setup);
+#endif
+
 void __init paging_init(void)
 {
 	setup_vm_final();

This patch series adds kexec/kdump and crash kernel support on RISC-V. For testing the patches a patched version of kexec-tools is needed (still a work in progress) which can be found at:

https://riscv.ics.forth.gr/kexec-tools-patched.tar.xz

v3:
* Rebase on newer kernel tree
* Minor cleanups
* Split UAPI changes to a separate patch
* Improve / cleanup init_resources
* Resolve Palmer's comments

v2:
* Rebase on newer kernel tree
* Minor cleanups
* Properly populate the ioresources tre, so that it can be used later on for implementing strict /dev/mem
* Use linux,usable-memory on /memory instead of a new binding
* USe a reserved-memory node for ELF core header

Nick Kossifidis (5):
RISC-V: Add EM_RISCV to kexec UAPI header
RISC-V: Add kexec support
RISC-V: Improve init_resources
RISC-V: Add kdump support
RISC-V: Add crash kernel support

  arch/riscv/Kconfig                  |  25 ++++
  arch/riscv/include/asm/elf.h        |   6 +
  arch/riscv/include/asm/kexec.h      |  54 +++++++
  arch/riscv/kernel/Makefile          |   6 +
  arch/riscv/kernel/crash_dump.c      |  46 ++++++
  arch/riscv/kernel/crash_save_regs.S |  56 +++++++
  arch/riscv/kernel/kexec_relocate.S  | 222 ++++++++++++++++++++++++++++
  arch/riscv/kernel/machine_kexec.c   | 193 ++++++++++++++++++++++++
  arch/riscv/kernel/setup.c           | 113 ++++++++------
  arch/riscv/mm/init.c                | 110 ++++++++++++++
  include/uapi/linux/kexec.h          |   1 +
  11 files changed, 787 insertions(+), 45 deletions(-)

create mode 100644 arch/riscv/include/asm/kexec.h create mode 100644 arch/riscv/kernel/crash_dump.c create mode 100644 arch/riscv/kernel/crash_save_regs.S create mode 100644 arch/riscv/kernel/kexec_relocate.S create mode 100644 arch/riscv/kernel/machine_kexec.c

This patch series adds kexec/kdump and crash kernel support on RISC-V. For testing the patches a patched version of kexec-tools is needed (still a work in progress) which can be found at:

https://riscv.ics.forth.gr/kexec-tools-patched.tar.xz

v3:
* Rebase on newer kernel tree
* Minor cleanups
* Split UAPI changes to a separate patch
* Improve / cleanup init_resources
* Resolve Palmer's comments

v2:
* Rebase on newer kernel tree
* Minor cleanups
* Properly populate the ioresources tre, so that it can be used later on for implementing strict /dev/mem
* Use linux,usable-memory on /memory instead of a new binding

Quoted 14 lines

This patch series adds kexec/kdump and crash kernel support on RISC-V. For testing the patches a patched version of kexec-tools is needed (still a work in progress) which can be found at:

https://riscv.ics.forth.gr/kexec-tools-patched.tar.xz

v3:
* Rebase on newer kernel tree
* Minor cleanups
* Split UAPI changes to a separate patch
* Improve / cleanup init_resources
* Resolve Palmer's comments

Quoted 6 lines

v2:
* Rebase on newer kernel tree
* Minor cleanups
* Properly populate the ioresources tre, so that it can be used later on for implementing strict /dev/mem
* Use linux,usable-memory on /memory instead of a new binding

Where? In any case, that's not going to work well with EFI support assuming like arm64, 'memory' is passed in UEFI structures instead of DT. That's why there's now a /chosen linux,usable-memory-ranges property.

Isn't the preferred kexec interface the file based interface? I'd expect a new arch to only support that. And there's common kexec DT handling for that pending for 5.13.

This patch series adds kexec/kdump and crash kernel support on RISC-V. For testing the patches a patched version of kexec-tools is needed (still a work in progress) which can be found at:

https://riscv.ics.forth.gr/kexec-tools-patched.tar.xz

v3:
* Rebase on newer kernel tree
* Minor cleanups
* Split UAPI changes to a separate patch
* Improve / cleanup init_resources
* Resolve Palmer's comments

v2:
* Rebase on newer kernel tree
* Minor cleanups
* Properly populate the ioresources tre, so that it can be used later on for implementing strict /dev/mem
* Use linux,usable-memory on /memory instead of a new binding
* USe a reserved-memory node for ELF core header

Nick Kossifidis (5):
RISC-V: Add EM_RISCV to kexec UAPI header
RISC-V: Add kexec support
RISC-V: Improve init_resources
RISC-V: Add kdump support
RISC-V: Add crash kernel support

 arch/riscv/Kconfig                  |  25 ++++
 arch/riscv/include/asm/elf.h        |   6 +
 arch/riscv/include/asm/kexec.h      |  54 +++++++
 arch/riscv/kernel/Makefile          |   6 +
 arch/riscv/kernel/crash_dump.c      |  46 ++++++
 arch/riscv/kernel/crash_save_regs.S |  56 +++++++
 arch/riscv/kernel/kexec_relocate.S  | 222 ++++++++++++++++++++++++++++
 arch/riscv/kernel/machine_kexec.c   | 193 ++++++++++++++++++++++++
 arch/riscv/kernel/setup.c           | 113 ++++++++------

 arch/riscv/mm/init.c                | 110 ++++++++++++++
 include/uapi/linux/kexec.h          |   1 +
 11 files changed, 787 insertions(+), 45 deletions(-)
 create mode 100644 arch/riscv/include/asm/kexec.h
 create mode 100644 arch/riscv/kernel/crash_dump.c
 create mode 100644 arch/riscv/kernel/crash_save_regs.S
 create mode 100644 arch/riscv/kernel/kexec_relocate.S
 create mode 100644 arch/riscv/kernel/machine_kexec.c

Quoted 39 lines

This patch series adds kexec/kdump and crash kernel support on RISC-V. For testing the patches a patched version of kexec-tools is needed (still a work in progress) which can be found at:

https://riscv.ics.forth.gr/kexec-tools-patched.tar.xz

v3:
* Rebase on newer kernel tree
* Minor cleanups
* Split UAPI changes to a separate patch
* Improve / cleanup init_resources
* Resolve Palmer's comments

v2:
* Rebase on newer kernel tree
* Minor cleanups
* Properly populate the ioresources tre, so that it can be used later on for implementing strict /dev/mem
* Use linux,usable-memory on /memory instead of a new binding
* USe a reserved-memory node for ELF core header

Nick Kossifidis (5):
RISC-V: Add EM_RISCV to kexec UAPI header
RISC-V: Add kexec support
RISC-V: Improve init_resources
RISC-V: Add kdump support
RISC-V: Add crash kernel support

 arch/riscv/Kconfig                  |  25 ++++
 arch/riscv/include/asm/elf.h        |   6 +
 arch/riscv/include/asm/kexec.h      |  54 +++++++
 arch/riscv/kernel/Makefile          |   6 +
 arch/riscv/kernel/crash_dump.c      |  46 ++++++
 arch/riscv/kernel/crash_save_regs.S |  56 +++++++
 arch/riscv/kernel/kexec_relocate.S  | 222 
++++++++++++++++++++++++++++
 arch/riscv/kernel/machine_kexec.c   | 193 ++++++++++++++++++++++++
 arch/riscv/kernel/setup.c           | 113 ++++++++------

Quoted 8 lines

 arch/riscv/mm/init.c                | 110 ++++++++++++++
 include/uapi/linux/kexec.h          |   1 +
 11 files changed, 787 insertions(+), 45 deletions(-)
 create mode 100644 arch/riscv/include/asm/kexec.h
 create mode 100644 arch/riscv/kernel/crash_dump.c
 create mode 100644 arch/riscv/kernel/crash_save_regs.S
 create mode 100644 arch/riscv/kernel/kexec_relocate.S
 create mode 100644 arch/riscv/kernel/machine_kexec.c

Thanks. There were some minor issues and some merge conflicts, I put this on for-next with some fixups.

Στις 2021-04-23 06:30, Palmer Dabbelt έγραψε:

Quoted 49 lines · On Mon, 05 Apr 2021 01:57:07 PDT (-0700), [email protected] wrote:

Quoted 47 lines

This patch series adds kexec/kdump and crash kernel support on RISC-V. For testing the patches a patched version of kexec-tools is needed (still a work in progress) which can be found at:

https://riscv.ics.forth.gr/kexec-tools-patched.tar.xz

v3:
* Rebase on newer kernel tree
* Minor cleanups
* Split UAPI changes to a separate patch
* Improve / cleanup init_resources
* Resolve Palmer's comments

v2:
* Rebase on newer kernel tree
* Minor cleanups
* Properly populate the ioresources tre, so that it can be used later on for implementing strict /dev/mem
* Use linux,usable-memory on /memory instead of a new binding
* USe a reserved-memory node for ELF core header

Nick Kossifidis (5):
RISC-V: Add EM_RISCV to kexec UAPI header
RISC-V: Add kexec support
RISC-V: Improve init_resources
RISC-V: Add kdump support
RISC-V: Add crash kernel support

 arch/riscv/Kconfig                  |  25 ++++
 arch/riscv/include/asm/elf.h        |   6 +
 arch/riscv/include/asm/kexec.h      |  54 +++++++
 arch/riscv/kernel/Makefile          |   6 +
 arch/riscv/kernel/crash_dump.c      |  46 ++++++
 arch/riscv/kernel/crash_save_regs.S |  56 +++++++
 arch/riscv/kernel/kexec_relocate.S  | 222
++++++++++++++++++++++++++++
 arch/riscv/kernel/machine_kexec.c   | 193 ++++++++++++++++++++++++
 arch/riscv/kernel/setup.c           | 113 ++++++++------
 arch/riscv/mm/init.c                | 110 ++++++++++++++
 include/uapi/linux/kexec.h          |   1 +
 11 files changed, 787 insertions(+), 45 deletions(-)
 create mode 100644 arch/riscv/include/asm/kexec.h
 create mode 100644 arch/riscv/kernel/crash_dump.c
 create mode 100644 arch/riscv/kernel/crash_save_regs.S
 create mode 100644 arch/riscv/kernel/kexec_relocate.S
 create mode 100644 arch/riscv/kernel/machine_kexec.c

Quoted 2 lines

Thanks. There were some minor issues and some merge conflicts, I put this on for-next with some fixups.

I've sent a v4 that shouldn't have merge conflicts, addressing some comments from Alex as well, could you use that instead or is it too late ?

Quoted 50 lines

Στις 2021-04-23 06:30, Palmer Dabbelt έγραψε:

Quoted 49 lines · On Mon, 05 Apr 2021 01:57:07 PDT (-0700), [email protected] wrote:

Quoted 47 lines

This patch series adds kexec/kdump and crash kernel support on RISC-V. For testing the patches a patched version of kexec-tools is needed (still a work in progress) which can be found at:

https://riscv.ics.forth.gr/kexec-tools-patched.tar.xz

v3:
* Rebase on newer kernel tree
* Minor cleanups
* Split UAPI changes to a separate patch
* Improve / cleanup init_resources
* Resolve Palmer's comments

v2:
* Rebase on newer kernel tree
* Minor cleanups
* Properly populate the ioresources tre, so that it can be used later on for implementing strict /dev/mem
* Use linux,usable-memory on /memory instead of a new binding
* USe a reserved-memory node for ELF core header

Nick Kossifidis (5):
RISC-V: Add EM_RISCV to kexec UAPI header
RISC-V: Add kexec support
RISC-V: Improve init_resources
RISC-V: Add kdump support
RISC-V: Add crash kernel support

 arch/riscv/Kconfig                  |  25 ++++
 arch/riscv/include/asm/elf.h        |   6 +
 arch/riscv/include/asm/kexec.h      |  54 +++++++
 arch/riscv/kernel/Makefile          |   6 +
 arch/riscv/kernel/crash_dump.c      |  46 ++++++
 arch/riscv/kernel/crash_save_regs.S |  56 +++++++
 arch/riscv/kernel/kexec_relocate.S  | 222
++++++++++++++++++++++++++++
 arch/riscv/kernel/machine_kexec.c   | 193 ++++++++++++++++++++++++
 arch/riscv/kernel/setup.c           | 113 ++++++++------
 arch/riscv/mm/init.c                | 110 ++++++++++++++
 include/uapi/linux/kexec.h          |   1 +
 11 files changed, 787 insertions(+), 45 deletions(-)
 create mode 100644 arch/riscv/include/asm/kexec.h
 create mode 100644 arch/riscv/kernel/crash_dump.c
 create mode 100644 arch/riscv/kernel/crash_save_regs.S
 create mode 100644 arch/riscv/kernel/kexec_relocate.S
 create mode 100644 arch/riscv/kernel/machine_kexec.c

Quoted 6 lines

Quoted 2 lines

Thanks. There were some minor issues and some merge conflicts, I put this on for-next with some fixups.

I've sent a v4 that shouldn't have merge conflicts, addressing some comments from Alex as well, could you use that instead or is it too late ?

Thanks, for some reason I didn't see it when poking around. There was still that one init_resources() merge conflict and I fixed up some of the commit texts, it's now on for-next as

b94394119804 (HEAD -> for-next, riscv/for-next) RISC-V: Add crash kernel support 6e8451782c90 RISC-V: Add kdump support
0a0652429bdb RISC-V: Improve init_resources()
d9a8897d6b5d RISC-V: Add kexec support
f59938095b94 RISC-V: Add EM_RISCV to kexec UAPI header