powerpc/ftrace: refactor and add support for -fpatchable-function-entry

The minimum level of gcc supported for building the kernel is v5.1. v5.x releases of gcc emitted a three instruction sequence for -mprofile-kernel:

	mflr	r0
	std	r0, 16(r1)
	bl	_mcount

It is only with the v6.x releases that gcc started emitting the two instruction sequence for -mprofile-kernel, omitting the second store instruction.

With the older three instruction sequence, the actual ftrace location can be the 5th instruction into a function. Update the allowed offset for ftrace location from 12 to 16 to accommodate the same.

Cc [email protected]

Fixes 7af82ff90a2b06 ("powerpc/ftrace: Ignore weak functions")

Signed-off-by Naveen N Rao <[email protected]>

---
  arch/powerpc/include/asm/ftrace.h | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

arch/powerpc/include/asm/ftrace.h +1 -1

index 91c049d51d0e10..2edc6269b1a357 100644
@@ -12,7 +12,7 @@
 
  /* Ignore unused weak functions which will have larger offsets */
  #ifdef CONFIG_MPROFILE_KERNEL
-#define FTRACE_MCOUNT_MAX_OFFSET	12
+#define FTRACE_MCOUNT_MAX_OFFSET	16
  #elif defined(CONFIG_PPC32)
  #define FTRACE_MCOUNT_MAX_OFFSET	8
  #endif

.ftrace.tramp section is not used for any purpose. This code was added all the way back in the original commit introducing support for dynamic ftrace on ppc64 modules. Remove it.

Signed-off-by Naveen N Rao <[email protected]>

---
  arch/powerpc/include/asm/module.h | 4 ----
  1 file changed, 4 deletions(-)

arch/powerpc/include/asm/module.h +0 -4

index ac53606c259430..a8e2e8339fb7f4 100644
@@ -75,10 +75,6 @@ struct mod_arch_specific {
  #endif
 
  #ifdef CONFIG_DYNAMIC_FTRACE
-#    ifdef MODULE
-	asm(".section .ftrace.tramp,\"ax\",@nobits; .align 3; .previous");
-#    endif	/* MODULE */
-
  int module_trampoline_target(struct module *mod, unsigned long trampoline,
  			     unsigned long *target);
  int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs);

ELFv1 support is deprecated and on the way out. Pre -mprofile-kernel ftrace support (-pg only) is very limited and is retained primarily for clang builds. It won't be necessary once clang lands support for -fpatchable-function-entry.

Copy the existing ftrace code supporting these into ftrace_pg.c. ftrace.c can then be refactored and enhanced with a focus on ppc32 and ppc64 ELFv2.

Signed-off-by Naveen N Rao <[email protected]>

---
  arch/powerpc/kernel/trace/Makefile    |  13 +-
  arch/powerpc/kernel/trace/ftrace.c    |  10 -
  arch/powerpc/kernel/trace/ftrace_pg.c | 846 ++++++++++++++++++++++++++
  3 files changed, 855 insertions(+), 14 deletions(-)

create mode 100644 arch/powerpc/kernel/trace/ftrace_pg.c

arch/powerpc/kernel/trace/Makefile +9 -4

index b16a9f9c0b35f2..342a2d1ae86cd0 100644
@@ -6,15 +6,16 @@
  ifdef CONFIG_FUNCTION_TRACER
  # do not trace tracer code
  CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE)
+CFLAGS_REMOVE_ftrace_pg.o = $(CC_FLAGS_FTRACE)
  endif
 
-obj32-$(CONFIG_FUNCTION_TRACER)		+= ftrace_mprofile.o
+obj32-$(CONFIG_FUNCTION_TRACER)		+= ftrace_mprofile.o ftrace.o
  ifdef CONFIG_MPROFILE_KERNEL
-obj64-$(CONFIG_FUNCTION_TRACER)		+= ftrace_mprofile.o
+obj64-$(CONFIG_FUNCTION_TRACER)		+= ftrace_mprofile.o ftrace.o
  else
-obj64-$(CONFIG_FUNCTION_TRACER)		+= ftrace_64_pg.o
+obj64-$(CONFIG_FUNCTION_TRACER)		+= ftrace_64_pg.o ftrace_pg.o
  endif
-obj-$(CONFIG_FUNCTION_TRACER)		+= ftrace_low.o ftrace.o
+obj-$(CONFIG_FUNCTION_TRACER)		+= ftrace_low.o
  obj-$(CONFIG_TRACING)			+= trace_clock.o
 
  obj-$(CONFIG_PPC64)			+= $(obj64-y)

@@ -25,3 +26,7 @@ GCOV_PROFILE_ftrace.o := n
  KCOV_INSTRUMENT_ftrace.o := n
  KCSAN_SANITIZE_ftrace.o := n
  UBSAN_SANITIZE_ftrace.o := n
+GCOV_PROFILE_ftrace_pg.o := n
+KCOV_INSTRUMENT_ftrace_pg.o := n
+KCSAN_SANITIZE_ftrace_pg.o := n
+UBSAN_SANITIZE_ftrace_pg.o := n

arch/powerpc/kernel/trace/ftrace.c +0 -10

index a47f303734233b..81a121b56c4d7f 100644
@@ -864,13 +864,3 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
  }
  #endif
  #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
-
-#ifdef CONFIG_PPC64_ELF_ABI_V1
-char *arch_ftrace_match_adjust(char *str, const char *search)
-{
-	if (str[0] == '.' && search[0] != '.')
-		return str + 1;
-	else
-		return str;
-}
-#endif /* CONFIG_PPC64_ELF_ABI_V1 */

arch/powerpc/kernel/trace/ftrace_pg.c new file +846 -0

new file mode 100644
index 00000000000000..7b85c3b460a3c0
@@ -0,0 +1,846 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Code for replacing ftrace calls with jumps.
+ *
+ * Copyright (C) 2007-2008 Steven Rostedt <[email protected]>
+ *
+ * Thanks goes out to P.A. Semi, Inc for supplying me with a PPC64 box.
+ *
+ * Added function graph tracer code, taken from x86 that was written
+ * by Frederic Weisbecker, and ported to PPC by Steven Rostedt.
+ *
+ */
+
+#define pr_fmt(fmt) "ftrace-powerpc: " fmt
+
+#include <linux/spinlock.h>
+#include <linux/hardirq.h>
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <linux/ftrace.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
+#include <linux/list.h>
+
+#include <asm/cacheflush.h>
+#include <asm/code-patching.h>
+#include <asm/ftrace.h>
+#include <asm/syscall.h>
+#include <asm/inst.h>
+
+/*
+ * We generally only have a single long_branch tramp and at most 2 or 3 plt
+ * tramps generated. But, we don't use the plt tramps currently. We also allot
+ * 2 tramps after .text and .init.text. So, we only end up with around 3 usable
+ * tramps in total. Set aside 8 just to be sure.
+ */
+#define	NUM_FTRACE_TRAMPS	8
+static unsigned long ftrace_tramps[NUM_FTRACE_TRAMPS];
+
+static ppc_inst_t
+ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
+{
+	ppc_inst_t op;
+
+	addr = ppc_function_entry((void *)addr);
+
+	/* if (link) set op to 'bl' else 'b' */
+	create_branch(&op, (u32 *)ip, addr, link ? BRANCH_SET_LINK : 0);
+
+	return op;
+}
+
+static inline int
+ftrace_modify_code(unsigned long ip, ppc_inst_t old, ppc_inst_t new)
+{
+	ppc_inst_t replaced;
+
+	/*
+	 * Note:
+	 * We are paranoid about modifying text, as if a bug was to happen, it
+	 * could cause us to read or write to someplace that could cause harm.
+	 * Carefully read and modify the code with probe_kernel_*(), and make
+	 * sure what we read is what we expected it to be before modifying it.
+	 */
+
+	/* read the text we want to modify */
+	if (copy_inst_from_kernel_nofault(&replaced, (void *)ip))
+		return -EFAULT;
+
+	/* Make sure it is what we expect it to be */
+	if (!ppc_inst_equal(replaced, old)) {
+		pr_err("%p: replaced (%08lx) != old (%08lx)", (void *)ip,
+		       ppc_inst_as_ulong(replaced), ppc_inst_as_ulong(old));
+		return -EINVAL;
+	}
+
+	/* replace the text with the new text */
+	return patch_instruction((u32 *)ip, new);
+}
+
+/*
+ * Helper functions that are the same for both PPC64 and PPC32.
+ */
+static int test_24bit_addr(unsigned long ip, unsigned long addr)
+{
+	addr = ppc_function_entry((void *)addr);
+
+	return is_offset_in_branch_range(addr - ip);
+}
+
+static int is_bl_op(ppc_inst_t op)
+{
+	return (ppc_inst_val(op) & ~PPC_LI_MASK) == PPC_RAW_BL(0);
+}
+
+static int is_b_op(ppc_inst_t op)
+{
+	return (ppc_inst_val(op) & ~PPC_LI_MASK) == PPC_RAW_BRANCH(0);
+}
+
+static unsigned long find_bl_target(unsigned long ip, ppc_inst_t op)
+{
+	int offset;
+
+	offset = PPC_LI(ppc_inst_val(op));
+	/* make it signed */
+	if (offset & 0x02000000)
+		offset |= 0xfe000000;
+
+	return ip + (long)offset;
+}
+
+#ifdef CONFIG_MODULES
+static int
+__ftrace_make_nop(struct module *mod,
+		  struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned long entry, ptr, tramp;
+	unsigned long ip = rec->ip;
+	ppc_inst_t op, pop;
+
+	/* read where this goes */
+	if (copy_inst_from_kernel_nofault(&op, (void *)ip)) {
+		pr_err("Fetching opcode failed.\n");
+		return -EFAULT;
+	}
+
+	/* Make sure that this is still a 24bit jump */
+	if (!is_bl_op(op)) {
+		pr_err("Not expected bl: opcode is %08lx\n", ppc_inst_as_ulong(op));
+		return -EINVAL;
+	}
+
+	/* lets find where the pointer goes */
+	tramp = find_bl_target(ip, op);
+
+	pr_devel("ip:%lx jumps to %lx", ip, tramp);
+
+	if (module_trampoline_target(mod, tramp, &ptr)) {
+		pr_err("Failed to get trampoline target\n");
+		return -EFAULT;
+	}
+
+	pr_devel("trampoline target %lx", ptr);
+
+	entry = ppc_global_function_entry((void *)addr);
+	/* This should match what was called */
+	if (ptr != entry) {
+		pr_err("addr %lx does not match expected %lx\n", ptr, entry);
+		return -EINVAL;
+	}
+
+	if (IS_ENABLED(CONFIG_MPROFILE_KERNEL)) {
+		if (copy_inst_from_kernel_nofault(&op, (void *)(ip - 4))) {
+			pr_err("Fetching instruction at %lx failed.\n", ip - 4);
+			return -EFAULT;
+		}
+
+		/* We expect either a mflr r0, or a std r0, LRSAVE(r1) */
+		if (!ppc_inst_equal(op, ppc_inst(PPC_RAW_MFLR(_R0))) &&
+		    !ppc_inst_equal(op, ppc_inst(PPC_INST_STD_LR))) {
+			pr_err("Unexpected instruction %08lx around bl _mcount\n",
+			       ppc_inst_as_ulong(op));
+			return -EINVAL;
+		}
+	} else if (IS_ENABLED(CONFIG_PPC64)) {
+		/*
+		 * Check what is in the next instruction. We can see ld r2,40(r1), but
+		 * on first pass after boot we will see mflr r0.
+		 */
+		if (copy_inst_from_kernel_nofault(&op, (void *)(ip + 4))) {
+			pr_err("Fetching op failed.\n");
+			return -EFAULT;
+		}
+
+		if (!ppc_inst_equal(op,  ppc_inst(PPC_INST_LD_TOC))) {
+			pr_err("Expected %08lx found %08lx\n", PPC_INST_LD_TOC,
+			       ppc_inst_as_ulong(op));
+			return -EINVAL;
+		}
+	}
+
+	/*
+	 * When using -mprofile-kernel or PPC32 there is no load to jump over.
+	 *
+	 * Otherwise our original call site looks like:
+	 *
+	 * bl <tramp>
+	 * ld r2,XX(r1)
+	 *
+	 * Milton Miller pointed out that we can not simply nop the branch.
+	 * If a task was preempted when calling a trace function, the nops
+	 * will remove the way to restore the TOC in r2 and the r2 TOC will
+	 * get corrupted.
+	 *
+	 * Use a b +8 to jump over the load.
+	 */
+	if (IS_ENABLED(CONFIG_MPROFILE_KERNEL) || IS_ENABLED(CONFIG_PPC32))
+		pop = ppc_inst(PPC_RAW_NOP());
+	else
+		pop = ppc_inst(PPC_RAW_BRANCH(8));	/* b +8 */
+
+	if (patch_instruction((u32 *)ip, pop)) {
+		pr_err("Patching NOP failed.\n");
+		return -EPERM;
+	}
+
+	return 0;
+}
+#else
+static int __ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
+{
+	return 0;
+}
+#endif /* CONFIG_MODULES */
+
+static unsigned long find_ftrace_tramp(unsigned long ip)
+{
+	int i;
+
+	/*
+	 * We have the compiler generated long_branch tramps at the end
+	 * and we prefer those
+	 */
+	for (i = NUM_FTRACE_TRAMPS - 1; i >= 0; i--)
+		if (!ftrace_tramps[i])
+			continue;
+		else if (is_offset_in_branch_range(ftrace_tramps[i] - ip))
+			return ftrace_tramps[i];
+
+	return 0;
+}
+
+static int add_ftrace_tramp(unsigned long tramp)
+{
+	int i;
+
+	for (i = 0; i < NUM_FTRACE_TRAMPS; i++)
+		if (!ftrace_tramps[i]) {
+			ftrace_tramps[i] = tramp;
+			return 0;
+		}
+
+	return -1;
+}
+
+/*
+ * If this is a compiler generated long_branch trampoline (essentially, a
+ * trampoline that has a branch to _mcount()), we re-write the branch to
+ * instead go to ftrace_[regs_]caller() and note down the location of this
+ * trampoline.
+ */
+static int setup_mcount_compiler_tramp(unsigned long tramp)
+{
+	int i;
+	ppc_inst_t op;
+	unsigned long ptr;
+
+	/* Is this a known long jump tramp? */
+	for (i = 0; i < NUM_FTRACE_TRAMPS; i++)
+		if (ftrace_tramps[i] == tramp)
+			return 0;
+
+	/* New trampoline -- read where this goes */
+	if (copy_inst_from_kernel_nofault(&op, (void *)tramp)) {
+		pr_debug("Fetching opcode failed.\n");
+		return -1;
+	}
+
+	/* Is this a 24 bit branch? */
+	if (!is_b_op(op)) {
+		pr_debug("Trampoline is not a long branch tramp.\n");
+		return -1;
+	}
+
+	/* lets find where the pointer goes */
+	ptr = find_bl_target(tramp, op);
+
+	if (ptr != ppc_global_function_entry((void *)_mcount)) {
+		pr_debug("Trampoline target %p is not _mcount\n", (void *)ptr);
+		return -1;
+	}
+
+	/* Let's re-write the tramp to go to ftrace_[regs_]caller */
+	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
+		ptr = ppc_global_function_entry((void *)ftrace_regs_caller);
+	else
+		ptr = ppc_global_function_entry((void *)ftrace_caller);
+
+	if (patch_branch((u32 *)tramp, ptr, 0)) {
+		pr_debug("REL24 out of range!\n");
+		return -1;
+	}
+
+	if (add_ftrace_tramp(tramp)) {
+		pr_debug("No tramp locations left\n");
+		return -1;
+	}
+
+	return 0;
+}
+
+static int __ftrace_make_nop_kernel(struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned long tramp, ip = rec->ip;
+	ppc_inst_t op;
+
+	/* Read where this goes */
+	if (copy_inst_from_kernel_nofault(&op, (void *)ip)) {
+		pr_err("Fetching opcode failed.\n");
+		return -EFAULT;
+	}
+
+	/* Make sure that this is still a 24bit jump */
+	if (!is_bl_op(op)) {
+		pr_err("Not expected bl: opcode is %08lx\n", ppc_inst_as_ulong(op));
+		return -EINVAL;
+	}
+
+	/* Let's find where the pointer goes */
+	tramp = find_bl_target(ip, op);
+
+	pr_devel("ip:%lx jumps to %lx", ip, tramp);
+
+	if (setup_mcount_compiler_tramp(tramp)) {
+		/* Are other trampolines reachable? */
+		if (!find_ftrace_tramp(ip)) {
+			pr_err("No ftrace trampolines reachable from %ps\n",
+					(void *)ip);
+			return -EINVAL;
+		}
+	}
+
+	if (patch_instruction((u32 *)ip, ppc_inst(PPC_RAW_NOP()))) {
+		pr_err("Patching NOP failed.\n");
+		return -EPERM;
+	}
+
+	return 0;
+}
+
+int ftrace_make_nop(struct module *mod,
+		    struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned long ip = rec->ip;
+	ppc_inst_t old, new;
+
+	/*
+	 * If the calling address is more that 24 bits away,
+	 * then we had to use a trampoline to make the call.
+	 * Otherwise just update the call site.
+	 */
+	if (test_24bit_addr(ip, addr)) {
+		/* within range */
+		old = ftrace_call_replace(ip, addr, 1);
+		new = ppc_inst(PPC_RAW_NOP());
+		return ftrace_modify_code(ip, old, new);
+	} else if (core_kernel_text(ip)) {
+		return __ftrace_make_nop_kernel(rec, addr);
+	} else if (!IS_ENABLED(CONFIG_MODULES)) {
+		return -EINVAL;
+	}
+
+	/*
+	 * Out of range jumps are called from modules.
+	 * We should either already have a pointer to the module
+	 * or it has been passed in.
+	 */
+	if (!rec->arch.mod) {
+		if (!mod) {
+			pr_err("No module loaded addr=%lx\n", addr);
+			return -EFAULT;
+		}
+		rec->arch.mod = mod;
+	} else if (mod) {
+		if (mod != rec->arch.mod) {
+			pr_err("Record mod %p not equal to passed in mod %p\n",
+			       rec->arch.mod, mod);
+			return -EINVAL;
+		}
+		/* nothing to do if mod == rec->arch.mod */
+	} else
+		mod = rec->arch.mod;
+
+	return __ftrace_make_nop(mod, rec, addr);
+}
+
+#ifdef CONFIG_MODULES
+/*
+ * Examine the existing instructions for __ftrace_make_call.
+ * They should effectively be a NOP, and follow formal constraints,
+ * depending on the ABI. Return false if they don't.
+ */
+static bool expected_nop_sequence(void *ip, ppc_inst_t op0, ppc_inst_t op1)
+{
+	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
+		return ppc_inst_equal(op0, ppc_inst(PPC_RAW_NOP()));
+	else
+		return ppc_inst_equal(op0, ppc_inst(PPC_RAW_BRANCH(8))) &&
+		       ppc_inst_equal(op1, ppc_inst(PPC_INST_LD_TOC));
+}
+
+static int
+__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+	ppc_inst_t op[2];
+	void *ip = (void *)rec->ip;
+	unsigned long entry, ptr, tramp;
+	struct module *mod = rec->arch.mod;
+
+	/* read where this goes */
+	if (copy_inst_from_kernel_nofault(op, ip))
+		return -EFAULT;
+
+	if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) &&
+	    copy_inst_from_kernel_nofault(op + 1, ip + 4))
+		return -EFAULT;
+
+	if (!expected_nop_sequence(ip, op[0], op[1])) {
+		pr_err("Unexpected call sequence at %p: %08lx %08lx\n", ip,
+		       ppc_inst_as_ulong(op[0]), ppc_inst_as_ulong(op[1]));
+		return -EINVAL;
+	}
+
+	/* If we never set up ftrace trampoline(s), then bail */
+	if (!mod->arch.tramp ||
+	    (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) && !mod->arch.tramp_regs)) {
+		pr_err("No ftrace trampoline\n");
+		return -EINVAL;
+	}
+
+	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) && rec->flags & FTRACE_FL_REGS)
+		tramp = mod->arch.tramp_regs;
+	else
+		tramp = mod->arch.tramp;
+
+	if (module_trampoline_target(mod, tramp, &ptr)) {
+		pr_err("Failed to get trampoline target\n");
+		return -EFAULT;
+	}
+
+	pr_devel("trampoline target %lx", ptr);
+
+	entry = ppc_global_function_entry((void *)addr);
+	/* This should match what was called */
+	if (ptr != entry) {
+		pr_err("addr %lx does not match expected %lx\n", ptr, entry);
+		return -EINVAL;
+	}
+
+	if (patch_branch(ip, tramp, BRANCH_SET_LINK)) {
+		pr_err("REL24 out of range!\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+#else
+static int __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+	return 0;
+}
+#endif /* CONFIG_MODULES */
+
+static int __ftrace_make_call_kernel(struct dyn_ftrace *rec, unsigned long addr)
+{
+	ppc_inst_t op;
+	void *ip = (void *)rec->ip;
+	unsigned long tramp, entry, ptr;
+
+	/* Make sure we're being asked to patch branch to a known ftrace addr */
+	entry = ppc_global_function_entry((void *)ftrace_caller);
+	ptr = ppc_global_function_entry((void *)addr);
+
+	if (ptr != entry && IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
+		entry = ppc_global_function_entry((void *)ftrace_regs_caller);
+
+	if (ptr != entry) {
+		pr_err("Unknown ftrace addr to patch: %ps\n", (void *)ptr);
+		return -EINVAL;
+	}
+
+	/* Make sure we have a nop */
+	if (copy_inst_from_kernel_nofault(&op, ip)) {
+		pr_err("Unable to read ftrace location %p\n", ip);
+		return -EFAULT;
+	}
+
+	if (!ppc_inst_equal(op, ppc_inst(PPC_RAW_NOP()))) {
+		pr_err("Unexpected call sequence at %p: %08lx\n",
+		       ip, ppc_inst_as_ulong(op));
+		return -EINVAL;
+	}
+
+	tramp = find_ftrace_tramp((unsigned long)ip);
+	if (!tramp) {
+		pr_err("No ftrace trampolines reachable from %ps\n", ip);
+		return -EINVAL;
+	}
+
+	if (patch_branch(ip, tramp, BRANCH_SET_LINK)) {
+		pr_err("Error patching branch to ftrace tramp!\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned long ip = rec->ip;
+	ppc_inst_t old, new;
+
+	/*
+	 * If the calling address is more that 24 bits away,
+	 * then we had to use a trampoline to make the call.
+	 * Otherwise just update the call site.
+	 */
+	if (test_24bit_addr(ip, addr)) {
+		/* within range */
+		old = ppc_inst(PPC_RAW_NOP());
+		new = ftrace_call_replace(ip, addr, 1);
+		return ftrace_modify_code(ip, old, new);
+	} else if (core_kernel_text(ip)) {
+		return __ftrace_make_call_kernel(rec, addr);
+	} else if (!IS_ENABLED(CONFIG_MODULES)) {
+		/* We should not get here without modules */
+		return -EINVAL;
+	}
+
+	/*
+	 * Out of range jumps are called from modules.
+	 * Being that we are converting from nop, it had better
+	 * already have a module defined.
+	 */
+	if (!rec->arch.mod) {
+		pr_err("No module loaded\n");
+		return -EINVAL;
+	}
+
+	return __ftrace_make_call(rec, addr);
+}
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+#ifdef CONFIG_MODULES
+static int
+__ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+					unsigned long addr)
+{
+	ppc_inst_t op;
+	unsigned long ip = rec->ip;
+	unsigned long entry, ptr, tramp;
+	struct module *mod = rec->arch.mod;
+
+	/* If we never set up ftrace trampolines, then bail */
+	if (!mod->arch.tramp || !mod->arch.tramp_regs) {
+		pr_err("No ftrace trampoline\n");
+		return -EINVAL;
+	}
+
+	/* read where this goes */
+	if (copy_inst_from_kernel_nofault(&op, (void *)ip)) {
+		pr_err("Fetching opcode failed.\n");
+		return -EFAULT;
+	}
+
+	/* Make sure that this is still a 24bit jump */
+	if (!is_bl_op(op)) {
+		pr_err("Not expected bl: opcode is %08lx\n", ppc_inst_as_ulong(op));
+		return -EINVAL;
+	}
+
+	/* lets find where the pointer goes */
+	tramp = find_bl_target(ip, op);
+	entry = ppc_global_function_entry((void *)old_addr);
+
+	pr_devel("ip:%lx jumps to %lx", ip, tramp);
+
+	if (tramp != entry) {
+		/* old_addr is not within range, so we must have used a trampoline */
+		if (module_trampoline_target(mod, tramp, &ptr)) {
+			pr_err("Failed to get trampoline target\n");
+			return -EFAULT;
+		}
+
+		pr_devel("trampoline target %lx", ptr);
+
+		/* This should match what was called */
+		if (ptr != entry) {
+			pr_err("addr %lx does not match expected %lx\n", ptr, entry);
+			return -EINVAL;
+		}
+	}
+
+	/* The new target may be within range */
+	if (test_24bit_addr(ip, addr)) {
+		/* within range */
+		if (patch_branch((u32 *)ip, addr, BRANCH_SET_LINK)) {
+			pr_err("REL24 out of range!\n");
+			return -EINVAL;
+		}
+
+		return 0;
+	}
+
+	if (rec->flags & FTRACE_FL_REGS)
+		tramp = mod->arch.tramp_regs;
+	else
+		tramp = mod->arch.tramp;
+
+	if (module_trampoline_target(mod, tramp, &ptr)) {
+		pr_err("Failed to get trampoline target\n");
+		return -EFAULT;
+	}
+
+	pr_devel("trampoline target %lx", ptr);
+
+	entry = ppc_global_function_entry((void *)addr);
+	/* This should match what was called */
+	if (ptr != entry) {
+		pr_err("addr %lx does not match expected %lx\n", ptr, entry);
+		return -EINVAL;
+	}
+
+	if (patch_branch((u32 *)ip, tramp, BRANCH_SET_LINK)) {
+		pr_err("REL24 out of range!\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+#else
+static int __ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr)
+{
+	return 0;
+}
+#endif
+
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+			unsigned long addr)
+{
+	unsigned long ip = rec->ip;
+	ppc_inst_t old, new;
+
+	/*
+	 * If the calling address is more that 24 bits away,
+	 * then we had to use a trampoline to make the call.
+	 * Otherwise just update the call site.
+	 */
+	if (test_24bit_addr(ip, addr) && test_24bit_addr(ip, old_addr)) {
+		/* within range */
+		old = ftrace_call_replace(ip, old_addr, 1);
+		new = ftrace_call_replace(ip, addr, 1);
+		return ftrace_modify_code(ip, old, new);
+	} else if (core_kernel_text(ip)) {
+		/*
+		 * We always patch out of range locations to go to the regs
+		 * variant, so there is nothing to do here
+		 */
+		return 0;
+	} else if (!IS_ENABLED(CONFIG_MODULES)) {
+		/* We should not get here without modules */
+		return -EINVAL;
+	}
+
+	/*
+	 * Out of range jumps are called from modules.
+	 */
+	if (!rec->arch.mod) {
+		pr_err("No module loaded\n");
+		return -EINVAL;
+	}
+
+	return __ftrace_modify_call(rec, old_addr, addr);
+}
+#endif
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+	unsigned long ip = (unsigned long)(&ftrace_call);
+	ppc_inst_t old, new;
+	int ret;
+
+	old = ppc_inst_read((u32 *)&ftrace_call);
+	new = ftrace_call_replace(ip, (unsigned long)func, 1);
+	ret = ftrace_modify_code(ip, old, new);
+
+	/* Also update the regs callback function */
+	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) && !ret) {
+		ip = (unsigned long)(&ftrace_regs_call);
+		old = ppc_inst_read((u32 *)&ftrace_regs_call);
+		new = ftrace_call_replace(ip, (unsigned long)func, 1);
+		ret = ftrace_modify_code(ip, old, new);
+	}
+
+	return ret;
+}
+
+/*
+ * Use the default ftrace_modify_all_code, but without
+ * stop_machine().
+ */
+void arch_ftrace_update_code(int command)
+{
+	ftrace_modify_all_code(command);
+}
+
+#ifdef CONFIG_PPC64
+#define PACATOC offsetof(struct paca_struct, kernel_toc)
+
+extern unsigned int ftrace_tramp_text[], ftrace_tramp_init[];
+
+void ftrace_free_init_tramp(void)
+{
+	int i;
+
+	for (i = 0; i < NUM_FTRACE_TRAMPS && ftrace_tramps[i]; i++)
+		if (ftrace_tramps[i] == (unsigned long)ftrace_tramp_init) {
+			ftrace_tramps[i] = 0;
+			return;
+		}
+}
+
+int __init ftrace_dyn_arch_init(void)
+{
+	int i;
+	unsigned int *tramp[] = { ftrace_tramp_text, ftrace_tramp_init };
+	u32 stub_insns[] = {
+		PPC_RAW_LD(_R12, _R13, PACATOC),
+		PPC_RAW_ADDIS(_R12, _R12, 0),
+		PPC_RAW_ADDI(_R12, _R12, 0),
+		PPC_RAW_MTCTR(_R12),
+		PPC_RAW_BCTR()
+	};
+	unsigned long addr;
+	long reladdr;
+
+	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
+		addr = ppc_global_function_entry((void *)ftrace_regs_caller);
+	else
+		addr = ppc_global_function_entry((void *)ftrace_caller);
+
+	reladdr = addr - kernel_toc_addr();
+
+	if (reladdr >= SZ_2G || reladdr < -(long)SZ_2G) {
+		pr_err("Address of %ps out of range of kernel_toc.\n",
+				(void *)addr);
+		return -1;
+	}
+
+	for (i = 0; i < 2; i++) {
+		memcpy(tramp[i], stub_insns, sizeof(stub_insns));
+		tramp[i][1] |= PPC_HA(reladdr);
+		tramp[i][2] |= PPC_LO(reladdr);
+		add_ftrace_tramp((unsigned long)tramp[i]);
+	}
+
+	return 0;
+}
+#endif
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+
+extern void ftrace_graph_call(void);
+extern void ftrace_graph_stub(void);
+
+static int ftrace_modify_ftrace_graph_caller(bool enable)
+{
+	unsigned long ip = (unsigned long)(&ftrace_graph_call);
+	unsigned long addr = (unsigned long)(&ftrace_graph_caller);
+	unsigned long stub = (unsigned long)(&ftrace_graph_stub);
+	ppc_inst_t old, new;
+
+	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_ARGS))
+		return 0;
+
+	old = ftrace_call_replace(ip, enable ? stub : addr, 0);
+	new = ftrace_call_replace(ip, enable ? addr : stub, 0);
+
+	return ftrace_modify_code(ip, old, new);
+}
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+	return ftrace_modify_ftrace_graph_caller(true);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+	return ftrace_modify_ftrace_graph_caller(false);
+}
+
+/*
+ * Hook the return address and push it in the stack of return addrs
+ * in current thread info. Return the address we want to divert to.
+ */
+static unsigned long
+__prepare_ftrace_return(unsigned long parent, unsigned long ip, unsigned long sp)
+{
+	unsigned long return_hooker;
+	int bit;
+
+	if (unlikely(ftrace_graph_is_dead()))
+		goto out;
+
+	if (unlikely(atomic_read(&current->tracing_graph_pause)))
+		goto out;
+
+	bit = ftrace_test_recursion_trylock(ip, parent);
+	if (bit < 0)
+		goto out;
+
+	return_hooker = ppc_function_entry(return_to_handler);
+
+	if (!function_graph_enter(parent, ip, 0, (unsigned long *)sp))
+		parent = return_hooker;
+
+	ftrace_test_recursion_unlock(bit);
+out:
+	return parent;
+}
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+		       struct ftrace_ops *op, struct ftrace_regs *fregs)
+{
+	fregs->regs.link = __prepare_ftrace_return(parent_ip, ip, fregs->regs.gpr[1]);
+}
+#else
+unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
+				    unsigned long sp)
+{
+	return __prepare_ftrace_return(parent, ip, sp);
+}
+#endif
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
+#ifdef CONFIG_PPC64_ELF_ABI_V1
+char *arch_ftrace_match_adjust(char *str, const char *search)
+{
+	if (str[0] == '.' && search[0] != '.')
+		return str + 1;
+	else
+		return str;
+}
+#endif /* CONFIG_PPC64_ELF_ABI_V1 */

Since we now support DYNAMIC_FTRACE_WITH_ARGS across ppc32 and ppc64 ELFv2, we can simplify function_graph tracer support code in ftrace.c

Signed-off-by Naveen N Rao <[email protected]>

---
  arch/powerpc/kernel/trace/ftrace.c | 64 ++++--------------------------
  1 file changed, 7 insertions(+), 57 deletions(-)

arch/powerpc/kernel/trace/ftrace.c +7 -57

index 81a121b56c4d7f..f117124c30325f 100644
@@ -790,44 +790,10 @@ int __init ftrace_dyn_arch_init(void)
  #endif
 
  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
-
-extern void ftrace_graph_call(void);
-extern void ftrace_graph_stub(void);
-
-static int ftrace_modify_ftrace_graph_caller(bool enable)
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+		       struct ftrace_ops *op, struct ftrace_regs *fregs)
  {
-	unsigned long ip = (unsigned long)(&ftrace_graph_call);
-	unsigned long addr = (unsigned long)(&ftrace_graph_caller);
-	unsigned long stub = (unsigned long)(&ftrace_graph_stub);
-	ppc_inst_t old, new;
-
-	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_ARGS))
-		return 0;
-
-	old = ftrace_call_replace(ip, enable ? stub : addr, 0);
-	new = ftrace_call_replace(ip, enable ? addr : stub, 0);
-
-	return ftrace_modify_code(ip, old, new);
-}
-
-int ftrace_enable_ftrace_graph_caller(void)
-{
-	return ftrace_modify_ftrace_graph_caller(true);
-}
-
-int ftrace_disable_ftrace_graph_caller(void)
-{
-	return ftrace_modify_ftrace_graph_caller(false);
-}
-
-/*
- * Hook the return address and push it in the stack of return addrs
- * in current thread info. Return the address we want to divert to.
- */
-static unsigned long
-__prepare_ftrace_return(unsigned long parent, unsigned long ip, unsigned long sp)
-{
-	unsigned long return_hooker;
+	unsigned long sp = fregs->regs.gpr[1];
  	int bit;
 
  	if (unlikely(ftrace_graph_is_dead()))

@@ -836,31 +802,15 @@ __prepare_ftrace_return(unsigned long parent, unsigned long ip, unsigned long sp
  	if (unlikely(atomic_read(&current->tracing_graph_pause)))
  		goto out;
 
-	bit = ftrace_test_recursion_trylock(ip, parent);
+	bit = ftrace_test_recursion_trylock(ip, parent_ip);
  	if (bit < 0)
  		goto out;
 
-	return_hooker = ppc_function_entry(return_to_handler);
-
-	if (!function_graph_enter(parent, ip, 0, (unsigned long *)sp))
-		parent = return_hooker;
+	if (!function_graph_enter(parent_ip, ip, 0, (unsigned long *)sp))
+		parent_ip = ppc_function_entry(return_to_handler);
 
  	ftrace_test_recursion_unlock(bit);
  out:
-	return parent;
+	fregs->regs.link = parent_ip;
  }
-
-#ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
-void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
-		       struct ftrace_ops *op, struct ftrace_regs *fregs)
-{
-	fregs->regs.link = __prepare_ftrace_return(parent_ip, ip, fregs->regs.gpr[1]);
-}
-#else
-unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
-				    unsigned long sp)
-{
-	return __prepare_ftrace_return(parent, ip, sp);
-}
-#endif
  #endif /* CONFIG_FUNCTION_GRAPH_TRACER */

Instead of keying off DYNAMIC_FTRACE_WITH_REGS, use FTRACE_REGS_ADDR to identify the proper ftrace trampoline address to use.

Signed-off-by Naveen N Rao <[email protected]>

---
  arch/powerpc/kernel/trace/ftrace.c | 7 +------
  1 file changed, 1 insertion(+), 6 deletions(-)

arch/powerpc/kernel/trace/ftrace.c +1 -6

index f117124c30325f..5aa36272617a03 100644
@@ -745,14 +745,9 @@ int __init ftrace_dyn_arch_init(void)
  	};
  #endif
 
-	unsigned long addr;
+	unsigned long addr = FTRACE_REGS_ADDR;
  	long reladdr;
 
-	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
-		addr = ppc_global_function_entry((void *)ftrace_regs_caller);
-	else
-		addr = ppc_global_function_entry((void *)ftrace_caller);
-
  	if (IS_ENABLED(CONFIG_PPC_KERNEL_PCREL)) {
  		for (i = 0; i < 2; i++) {
  			reladdr = addr - (unsigned long)tramp[i];

Commit 67361cf8071286 ("powerpc/ftrace: Handle large kernel configs") added ftrace support for ppc64 kernel images with a text section larger than 32MB. The approach itself isn't specific to ppc64, so extend the same to also work on ppc32.

While at it, reduce the space reserved for the stub from 64 bytes to 32 bytes since the different stub variants are all less than 8 instructions.

To reduce use of #ifdef, a stub implementation is provided for kernel_toc_address() and -SZ_2G is cast to 'long long' to prevent errors on ppc32.

Signed-off-by Naveen N Rao <[email protected]>

---
  arch/powerpc/include/asm/ftrace.h      | 10 +++++--
  arch/powerpc/include/asm/sections.h    |  2 ++
  arch/powerpc/kernel/trace/ftrace.c     | 39 ++++++++++++++------------
  arch/powerpc/kernel/trace/ftrace_low.S |  6 ++--
  arch/powerpc/kernel/vmlinux.lds.S      |  4 ---
  5 files changed, 32 insertions(+), 29 deletions(-)

arch/powerpc/include/asm/ftrace.h +7 -3

index 2edc6269b1a357..702aaf2efa966c 100644
@@ -124,15 +124,19 @@ static inline u8 this_cpu_get_ftrace_enabled(void)
  {
  	return get_paca()->ftrace_enabled;
  }
-
-void ftrace_free_init_tramp(void);
  #else /* CONFIG_PPC64 */
  static inline void this_cpu_disable_ftrace(void) { }
  static inline void this_cpu_enable_ftrace(void) { }
  static inline void this_cpu_set_ftrace_enabled(u8 ftrace_enabled) { }
  static inline u8 this_cpu_get_ftrace_enabled(void) { return 1; }
-static inline void ftrace_free_init_tramp(void) { }
  #endif /* CONFIG_PPC64 */
+
+#ifdef CONFIG_FUNCTION_TRACER
+extern unsigned int ftrace_tramp_text[], ftrace_tramp_init[];
+void ftrace_free_init_tramp(void);
+#else
+static inline void ftrace_free_init_tramp(void) { }
+#endif
  #endif /* !__ASSEMBLY__ */
 
  #endif /* _ASM_POWERPC_FTRACE */

arch/powerpc/include/asm/sections.h +2 -0

index 4e1f548c8d373d..ea26665f82cfc8 100644
@@ -74,6 +74,8 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
  		(unsigned long)_stext < end;
  }
 
+#else
+static inline unsigned long kernel_toc_addr(void) { BUILD_BUG(); return -1UL; }
  #endif
 
  #endif /* __KERNEL__ */

arch/powerpc/kernel/trace/ftrace.c +21 -18

index 5aa36272617a03..913c7aa63d3fa3 100644
@@ -707,11 +707,6 @@ void arch_ftrace_update_code(int command)
  	ftrace_modify_all_code(command);
  }
 
-#ifdef CONFIG_PPC64
-#define PACATOC offsetof(struct paca_struct, kernel_toc)
-
-extern unsigned int ftrace_tramp_text[], ftrace_tramp_init[];
-
  void ftrace_free_init_tramp(void)
  {
  	int i;

@@ -725,28 +720,30 @@ void ftrace_free_init_tramp(void)
 
  int __init ftrace_dyn_arch_init(void)
  {
-	int i;
  	unsigned int *tramp[] = { ftrace_tramp_text, ftrace_tramp_init };
-#ifdef CONFIG_PPC_KERNEL_PCREL
+	unsigned long addr = FTRACE_REGS_ADDR;
+	long reladdr;
+	int i;
  	u32 stub_insns[] = {
+#ifdef CONFIG_PPC_KERNEL_PCREL
  		/* pla r12,addr */
  		PPC_PREFIX_MLS | __PPC_PRFX_R(1),
  		PPC_INST_PADDI | ___PPC_RT(_R12),
  		PPC_RAW_MTCTR(_R12),
  		PPC_RAW_BCTR()
-	};
-#else
-	u32 stub_insns[] = {
-		PPC_RAW_LD(_R12, _R13, PACATOC),
+#elif defined(CONFIG_PPC64)
+		PPC_RAW_LD(_R12, _R13, offsetof(struct paca_struct, kernel_toc)),
  		PPC_RAW_ADDIS(_R12, _R12, 0),
  		PPC_RAW_ADDI(_R12, _R12, 0),
  		PPC_RAW_MTCTR(_R12),
  		PPC_RAW_BCTR()
-	};
+#else
+		PPC_RAW_LIS(_R12, 0),
+		PPC_RAW_ADDI(_R12, _R12, 0),
+		PPC_RAW_MTCTR(_R12),
+		PPC_RAW_BCTR()
  #endif
-
-	unsigned long addr = FTRACE_REGS_ADDR;
-	long reladdr;
+	};
 
  	if (IS_ENABLED(CONFIG_PPC_KERNEL_PCREL)) {
  		for (i = 0; i < 2; i++) {

@@ -763,10 +760,10 @@ int __init ftrace_dyn_arch_init(void)
  			tramp[i][1] |= IMM_L(reladdr);
  			add_ftrace_tramp((unsigned long)tramp[i]);
  		}
-	} else {
+	} else if (IS_ENABLED(CONFIG_PPC64)) {
  		reladdr = addr - kernel_toc_addr();
 
-		if (reladdr >= (long)SZ_2G || reladdr < -(long)SZ_2G) {
+		if (reladdr >= (long)SZ_2G || reladdr < -(long long)SZ_2G) {
  			pr_err("Address of %ps out of range of kernel_toc.\n",
  				(void *)addr);
  			return -1;

@@ -778,11 +775,17 @@ int __init ftrace_dyn_arch_init(void)
  			tramp[i][2] |= PPC_LO(reladdr);
  			add_ftrace_tramp((unsigned long)tramp[i]);
  		}
+	} else {
+		for (i = 0; i < 2; i++) {
+			memcpy(tramp[i], stub_insns, sizeof(stub_insns));
+			tramp[i][0] |= PPC_HA(addr);
+			tramp[i][1] |= PPC_LO(addr);
+			add_ftrace_tramp((unsigned long)tramp[i]);
+		}
  	}
 
  	return 0;
  }
-#endif
 
  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,

arch/powerpc/kernel/trace/ftrace_low.S +2 -4

index 294d1e05958aae..2fc7dd0a5ae968 100644
@@ -10,19 +10,17 @@
  #include <asm/ppc-opcode.h>
  #include <asm/export.h>
 
-#ifdef CONFIG_PPC64
  .pushsection ".tramp.ftrace.text","aw",@progbits;
  .globl ftrace_tramp_text
  ftrace_tramp_text:
-	.space 64
+	.space 32
  .popsection
 
  .pushsection ".tramp.ftrace.init","aw",@progbits;
  .globl ftrace_tramp_init
  ftrace_tramp_init:
-	.space 64
+	.space 32
  .popsection
-#endif
 
  _GLOBAL(mcount)
  _GLOBAL(_mcount)

arch/powerpc/kernel/vmlinux.lds.S +0 -4

index 13614f0b269cf4..1c5970df323366 100644
@@ -107,9 +107,7 @@ SECTIONS
  #endif
  		/* careful! __ftr_alt_* sections need to be close to .text */
  		*(.text.hot .text.hot.* TEXT_MAIN .text.fixup .text.unlikely .text.unlikely.* .fixup __ftr_alt_* .ref.text);
-#ifdef CONFIG_PPC64
  		*(.tramp.ftrace.text);
-#endif
  		NOINSTR_TEXT
  		SCHED_TEXT
  		LOCK_TEXT

@@ -276,9 +274,7 @@ SECTIONS
  		 */
  		. = ALIGN(PAGE_SIZE);
  		_einittext = .;
-#ifdef CONFIG_PPC64
  		*(.tramp.ftrace.init);
-#endif
  	} :text
 
  	/* .exit.text is discarded at runtime, not link time,

ftrace_low.S has just the _mcount stub and return_to_handler(). Merge this back into ftrace_mprofile.S and ftrace_64_pg.S to keep all ftrace code together, and to allow those to evolve independently.

ftrace_mprofile.S is also not an entirely accurate name since this also holds ppc32 code. This will be all the more incorrect once support for -fpatchable-function-entry is added. Rename files here to more accurately describe the code:
- ftrace_mprofile.S is renamed to ftrace_entry.S
- ftrace_pg.c is renamed to ftrace_64_pg.c
- ftrace_64_pg.S is rename to ftrace_64_pg_entry.S

Signed-off-by Naveen N Rao <[email protected]>

---
  arch/powerpc/kernel/trace/Makefile            | 17 +++--
  arch/powerpc/kernel/trace/ftrace_64_pg.S      | 67 -------------------
  .../trace/{ftrace_pg.c => ftrace_64_pg.c}     |  0
  .../{ftrace_low.S => ftrace_64_pg_entry.S}    | 58 +++++++++++++++-
  .../{ftrace_mprofile.S => ftrace_entry.S}     | 65 ++++++++++++++++++
  5 files changed, 130 insertions(+), 77 deletions(-)

delete mode 100644 arch/powerpc/kernel/trace/ftrace_64_pg.S rename arch/powerpc/kernel/trace/{ftrace_pg.c => ftrace_64_pg.c} (100%) rename arch/powerpc/kernel/trace/{ftrace_low.S => ftrace_64_pg_entry.S} (55%) rename arch/powerpc/kernel/trace/{ftrace_mprofile.S => ftrace_entry.S} (83%)

arch/powerpc/kernel/trace/Makefile +8 -9

index 342a2d1ae86cd0..125f4ca588b98a 100644
@@ -6,16 +6,15 @@
  ifdef CONFIG_FUNCTION_TRACER
  # do not trace tracer code
  CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE)
-CFLAGS_REMOVE_ftrace_pg.o = $(CC_FLAGS_FTRACE)
+CFLAGS_REMOVE_ftrace_64_pg.o = $(CC_FLAGS_FTRACE)
  endif
 
-obj32-$(CONFIG_FUNCTION_TRACER)		+= ftrace_mprofile.o ftrace.o
+obj32-$(CONFIG_FUNCTION_TRACER)		+= ftrace.o ftrace_entry.o
  ifdef CONFIG_MPROFILE_KERNEL
-obj64-$(CONFIG_FUNCTION_TRACER)		+= ftrace_mprofile.o ftrace.o
+obj64-$(CONFIG_FUNCTION_TRACER)		+= ftrace.o ftrace_entry.o
  else
-obj64-$(CONFIG_FUNCTION_TRACER)		+= ftrace_64_pg.o ftrace_pg.o
+obj64-$(CONFIG_FUNCTION_TRACER)		+= ftrace_64_pg.o ftrace_64_pg_entry.o
  endif
-obj-$(CONFIG_FUNCTION_TRACER)		+= ftrace_low.o
  obj-$(CONFIG_TRACING)			+= trace_clock.o
 
  obj-$(CONFIG_PPC64)			+= $(obj64-y)

@@ -26,7 +25,7 @@ GCOV_PROFILE_ftrace.o := n
  KCOV_INSTRUMENT_ftrace.o := n
  KCSAN_SANITIZE_ftrace.o := n
  UBSAN_SANITIZE_ftrace.o := n
-GCOV_PROFILE_ftrace_pg.o := n
-KCOV_INSTRUMENT_ftrace_pg.o := n
-KCSAN_SANITIZE_ftrace_pg.o := n
-UBSAN_SANITIZE_ftrace_pg.o := n
+GCOV_PROFILE_ftrace_64_pg.o := n
+KCOV_INSTRUMENT_ftrace_64_pg.o := n
+KCSAN_SANITIZE_ftrace_64_pg.o := n
+UBSAN_SANITIZE_ftrace_64_pg.o := n

arch/powerpc/kernel/trace/ftrace_64_pg.S deleted +0 -67

deleted file mode 100644
index 6708e24db0aba8..00000000000000
@@ -1,67 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-or-later */
-/*
- * Split from ftrace_64.S
- */
-
-#include <linux/magic.h>
-#include <asm/ppc_asm.h>
-#include <asm/asm-offsets.h>
-#include <asm/ftrace.h>
-#include <asm/ppc-opcode.h>
-#include <asm/export.h>
-
-_GLOBAL_TOC(ftrace_caller)
-	lbz	r3, PACA_FTRACE_ENABLED(r13)
-	cmpdi	r3, 0
-	beqlr
-
-	/* Taken from output of objdump from lib64/glibc */
-	mflr	r3
-	ld	r11, 0(r1)
-	stdu	r1, -112(r1)
-	std	r3, 128(r1)
-	ld	r4, 16(r11)
-	subi	r3, r3, MCOUNT_INSN_SIZE
-.globl ftrace_call
-ftrace_call:
-	bl	ftrace_stub
-	nop
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-.globl ftrace_graph_call
-ftrace_graph_call:
-	b	ftrace_graph_stub
-_GLOBAL(ftrace_graph_stub)
-#endif
-	ld	r0, 128(r1)
-	mtlr	r0
-	addi	r1, r1, 112
-
-_GLOBAL(ftrace_stub)
-	blr
-
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-_GLOBAL(ftrace_graph_caller)
-	addi	r5, r1, 112
-	/* load r4 with local address */
-	ld	r4, 128(r1)
-	subi	r4, r4, MCOUNT_INSN_SIZE
-
-	/* Grab the LR out of the caller stack frame */
-	ld	r11, 112(r1)
-	ld	r3, 16(r11)
-
-	bl	prepare_ftrace_return
-	nop
-
-	/*
-	 * prepare_ftrace_return gives us the address we divert to.
-	 * Change the LR in the callers stack frame to this.
-	 */
-	ld	r11, 112(r1)
-	std	r3, 16(r11)
-
-	ld	r0, 128(r1)
-	mtlr	r0
-	addi	r1, r1, 112
-	blr
-#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

arch/powerpc/kernel/trace/ftrace_64_pg.c renamed from arch/powerpc/kernel/trace/ftrace_pg.c +0 -0

similarity index 100%
rename from arch/powerpc/kernel/trace/ftrace_pg.c
rename to arch/powerpc/kernel/trace/ftrace_64_pg.c

arch/powerpc/kernel/trace/ftrace_64_pg_entry.S renamed from arch/powerpc/kernel/trace/ftrace_low.S +57 -1

similarity index 55%
rename from arch/powerpc/kernel/trace/ftrace_low.S
rename to arch/powerpc/kernel/trace/ftrace_64_pg_entry.S
index 2fc7dd0a5ae968..81dbaf70b1513a 100644
@@ -1,6 +1,6 @@
  /* SPDX-License-Identifier: GPL-2.0-or-later */
  /*
- * Split from entry_64.S
+ * Split from ftrace_64.S
   */
 
  #include <linux/magic.h>

@@ -10,6 +10,62 @@
  #include <asm/ppc-opcode.h>
  #include <asm/export.h>
 
+_GLOBAL_TOC(ftrace_caller)
+	lbz	r3, PACA_FTRACE_ENABLED(r13)
+	cmpdi	r3, 0
+	beqlr
+
+	/* Taken from output of objdump from lib64/glibc */
+	mflr	r3
+	ld	r11, 0(r1)
+	stdu	r1, -112(r1)
+	std	r3, 128(r1)
+	ld	r4, 16(r11)
+	subi	r3, r3, MCOUNT_INSN_SIZE
+.globl ftrace_call
+ftrace_call:
+	bl	ftrace_stub
+	nop
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+.globl ftrace_graph_call
+ftrace_graph_call:
+	b	ftrace_graph_stub
+_GLOBAL(ftrace_graph_stub)
+#endif
+	ld	r0, 128(r1)
+	mtlr	r0
+	addi	r1, r1, 112
+
+_GLOBAL(ftrace_stub)
+	blr
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+_GLOBAL(ftrace_graph_caller)
+	addi	r5, r1, 112
+	/* load r4 with local address */
+	ld	r4, 128(r1)
+	subi	r4, r4, MCOUNT_INSN_SIZE
+
+	/* Grab the LR out of the caller stack frame */
+	ld	r11, 112(r1)
+	ld	r3, 16(r11)
+
+	bl	prepare_ftrace_return
+	nop
+
+	/*
+	 * prepare_ftrace_return gives us the address we divert to.
+	 * Change the LR in the callers stack frame to this.
+	 */
+	ld	r11, 112(r1)
+	std	r3, 16(r11)
+
+	ld	r0, 128(r1)
+	mtlr	r0
+	addi	r1, r1, 112
+	blr
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
  .pushsection ".tramp.ftrace.text","aw",@progbits;
  .globl ftrace_tramp_text
  ftrace_tramp_text:

arch/powerpc/kernel/trace/ftrace_entry.S renamed from arch/powerpc/kernel/trace/ftrace_mprofile.S +65 -0

similarity index 83%
rename from arch/powerpc/kernel/trace/ftrace_mprofile.S
rename to arch/powerpc/kernel/trace/ftrace_entry.S
index ffb1db38684998..e8339706e735b1 100644
@@ -249,3 +249,68 @@ livepatch_handler:
  	/* Return to original caller of live patched function */
  	blr
  #endif /* CONFIG_LIVEPATCH */
+
+_GLOBAL(mcount)
+_GLOBAL(_mcount)
+EXPORT_SYMBOL(_mcount)
+	mflr	r12
+	mtctr	r12
+	mtlr	r0
+	bctr
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+_GLOBAL(return_to_handler)
+	/* need to save return values */
+#ifdef CONFIG_PPC64
+	std	r4,  -32(r1)
+	std	r3,  -24(r1)
+	/* save TOC */
+	std	r2,  -16(r1)
+	std	r31, -8(r1)
+	mr	r31, r1
+	stdu	r1, -112(r1)
+
+	/*
+	 * We might be called from a module.
+	 * Switch to our TOC to run inside the core kernel.
+	 */
+	LOAD_PACA_TOC()
+#else
+	stwu	r1, -16(r1)
+	stw	r3, 8(r1)
+	stw	r4, 12(r1)
+#endif
+
+	bl	ftrace_return_to_handler
+	nop
+
+	/* return value has real return address */
+	mtlr	r3
+
+#ifdef CONFIG_PPC64
+	ld	r1, 0(r1)
+	ld	r4,  -32(r1)
+	ld	r3,  -24(r1)
+	ld	r2,  -16(r1)
+	ld	r31, -8(r1)
+#else
+	lwz	r3, 8(r1)
+	lwz	r4, 12(r1)
+	addi	r1, r1, 16
+#endif
+
+	/* Jump back to real return address */
+	blr
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
+.pushsection ".tramp.ftrace.text","aw",@progbits;
+.globl ftrace_tramp_text
+ftrace_tramp_text:
+	.space 32
+.popsection
+
+.pushsection ".tramp.ftrace.init","aw",@progbits;
+.globl ftrace_tramp_init
+ftrace_tramp_init:
+	.space 32
+.popsection

Le 19/06/2023 à 11:47, Naveen N Rao a écrit :

Quoted 11 lines

ftrace_low.S has just the _mcount stub and return_to_handler(). Merge this back into ftrace_mprofile.S and ftrace_64_pg.S to keep all ftrace code together, and to allow those to evolve independently.

ftrace_mprofile.S is also not an entirely accurate name since this also holds ppc32 code. This will be all the more incorrect once support for -fpatchable-function-entry is added. Rename files here to more accurately describe the code:
- ftrace_mprofile.S is renamed to ftrace_entry.S
- ftrace_pg.c is renamed to ftrace_64_pg.c
- ftrace_64_pg.S is rename to ftrace_64_pg_entry.S

The stats from git do not match., it says {ftrace_low.S => ftrace_64_pg_entry.S

Quoted 3 lines

Signed-off-by Naveen N Rao <[email protected]>

Reviewed-by Christophe Leroy <[email protected]>

Quoted 281 lines

---
  arch/powerpc/kernel/trace/Makefile            | 17 +++--
  arch/powerpc/kernel/trace/ftrace_64_pg.S      | 67 -------------------
  .../trace/{ftrace_pg.c => ftrace_64_pg.c}     |  0
  .../{ftrace_low.S => ftrace_64_pg_entry.S}    | 58 +++++++++++++++-
  .../{ftrace_mprofile.S => ftrace_entry.S}     | 65 ++++++++++++++++++
  5 files changed, 130 insertions(+), 77 deletions(-)

delete mode 100644 arch/powerpc/kernel/trace/ftrace_64_pg.S rename arch/powerpc/kernel/trace/{ftrace_pg.c => ftrace_64_pg.c} (100%) rename arch/powerpc/kernel/trace/{ftrace_low.S => ftrace_64_pg_entry.S} (55%) rename arch/powerpc/kernel/trace/{ftrace_mprofile.S => ftrace_entry.S} (83%)

arch/powerpc/kernel/trace/Makefile +8 -9

index 342a2d1ae86cd0..125f4ca588b98a 100644
@@ -6,16 +6,15 @@
  ifdef CONFIG_FUNCTION_TRACER
  # do not trace tracer code
  CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE)
-CFLAGS_REMOVE_ftrace_pg.o = $(CC_FLAGS_FTRACE)
+CFLAGS_REMOVE_ftrace_64_pg.o = $(CC_FLAGS_FTRACE)
  endif
 
-obj32-$(CONFIG_FUNCTION_TRACER)		+= ftrace_mprofile.o ftrace.o
+obj32-$(CONFIG_FUNCTION_TRACER)		+= ftrace.o ftrace_entry.o
  ifdef CONFIG_MPROFILE_KERNEL
-obj64-$(CONFIG_FUNCTION_TRACER)		+= ftrace_mprofile.o ftrace.o
+obj64-$(CONFIG_FUNCTION_TRACER)		+= ftrace.o ftrace_entry.o
  else
-obj64-$(CONFIG_FUNCTION_TRACER)		+= ftrace_64_pg.o ftrace_pg.o
+obj64-$(CONFIG_FUNCTION_TRACER)		+= ftrace_64_pg.o ftrace_64_pg_entry.o
  endif
-obj-$(CONFIG_FUNCTION_TRACER)		+= ftrace_low.o
  obj-$(CONFIG_TRACING)			+= trace_clock.o
 
  obj-$(CONFIG_PPC64)			+= $(obj64-y)

@@ -26,7 +25,7 @@ GCOV_PROFILE_ftrace.o := n
  KCOV_INSTRUMENT_ftrace.o := n
  KCSAN_SANITIZE_ftrace.o := n
  UBSAN_SANITIZE_ftrace.o := n
-GCOV_PROFILE_ftrace_pg.o := n
-KCOV_INSTRUMENT_ftrace_pg.o := n
-KCSAN_SANITIZE_ftrace_pg.o := n
-UBSAN_SANITIZE_ftrace_pg.o := n
+GCOV_PROFILE_ftrace_64_pg.o := n
+KCOV_INSTRUMENT_ftrace_64_pg.o := n
+KCSAN_SANITIZE_ftrace_64_pg.o := n
+UBSAN_SANITIZE_ftrace_64_pg.o := n

arch/powerpc/kernel/trace/ftrace_64_pg.S deleted +0 -67

deleted file mode 100644
index 6708e24db0aba8..00000000000000
@@ -1,67 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-or-later */
-/*
- * Split from ftrace_64.S
- */
-
-#include <linux/magic.h>
-#include <asm/ppc_asm.h>
-#include <asm/asm-offsets.h>
-#include <asm/ftrace.h>
-#include <asm/ppc-opcode.h>
-#include <asm/export.h>
-
-_GLOBAL_TOC(ftrace_caller)
-	lbz	r3, PACA_FTRACE_ENABLED(r13)
-	cmpdi	r3, 0
-	beqlr
-
-	/* Taken from output of objdump from lib64/glibc */
-	mflr	r3
-	ld	r11, 0(r1)
-	stdu	r1, -112(r1)
-	std	r3, 128(r1)
-	ld	r4, 16(r11)
-	subi	r3, r3, MCOUNT_INSN_SIZE
-.globl ftrace_call
-ftrace_call:
-	bl	ftrace_stub
-	nop
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-.globl ftrace_graph_call
-ftrace_graph_call:
-	b	ftrace_graph_stub
-_GLOBAL(ftrace_graph_stub)
-#endif
-	ld	r0, 128(r1)
-	mtlr	r0
-	addi	r1, r1, 112
-
-_GLOBAL(ftrace_stub)
-	blr
-
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-_GLOBAL(ftrace_graph_caller)
-	addi	r5, r1, 112
-	/* load r4 with local address */
-	ld	r4, 128(r1)
-	subi	r4, r4, MCOUNT_INSN_SIZE
-
-	/* Grab the LR out of the caller stack frame */
-	ld	r11, 112(r1)
-	ld	r3, 16(r11)
-
-	bl	prepare_ftrace_return
-	nop
-
-	/*
-	 * prepare_ftrace_return gives us the address we divert to.
-	 * Change the LR in the callers stack frame to this.
-	 */
-	ld	r11, 112(r1)
-	std	r3, 16(r11)
-
-	ld	r0, 128(r1)
-	mtlr	r0
-	addi	r1, r1, 112
-	blr
-#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

arch/powerpc/kernel/trace/ftrace_64_pg.c renamed from arch/powerpc/kernel/trace/ftrace_pg.c +0 -0

similarity index 100%
rename from arch/powerpc/kernel/trace/ftrace_pg.c
rename to arch/powerpc/kernel/trace/ftrace_64_pg.c

arch/powerpc/kernel/trace/ftrace_64_pg_entry.S renamed from arch/powerpc/kernel/trace/ftrace_low.S +57 -1

similarity index 55%
rename from arch/powerpc/kernel/trace/ftrace_low.S
rename to arch/powerpc/kernel/trace/ftrace_64_pg_entry.S
index 2fc7dd0a5ae968..81dbaf70b1513a 100644
@@ -1,6 +1,6 @@
  /* SPDX-License-Identifier: GPL-2.0-or-later */
  /*
- * Split from entry_64.S
+ * Split from ftrace_64.S
   */
 
  #include <linux/magic.h>

@@ -10,6 +10,62 @@
  #include <asm/ppc-opcode.h>
  #include <asm/export.h>
 
+_GLOBAL_TOC(ftrace_caller)
+	lbz	r3, PACA_FTRACE_ENABLED(r13)
+	cmpdi	r3, 0
+	beqlr
+
+	/* Taken from output of objdump from lib64/glibc */
+	mflr	r3
+	ld	r11, 0(r1)
+	stdu	r1, -112(r1)
+	std	r3, 128(r1)
+	ld	r4, 16(r11)
+	subi	r3, r3, MCOUNT_INSN_SIZE
+.globl ftrace_call
+ftrace_call:
+	bl	ftrace_stub
+	nop
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+.globl ftrace_graph_call
+ftrace_graph_call:
+	b	ftrace_graph_stub
+_GLOBAL(ftrace_graph_stub)
+#endif
+	ld	r0, 128(r1)
+	mtlr	r0
+	addi	r1, r1, 112
+
+_GLOBAL(ftrace_stub)
+	blr
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+_GLOBAL(ftrace_graph_caller)
+	addi	r5, r1, 112
+	/* load r4 with local address */
+	ld	r4, 128(r1)
+	subi	r4, r4, MCOUNT_INSN_SIZE
+
+	/* Grab the LR out of the caller stack frame */
+	ld	r11, 112(r1)
+	ld	r3, 16(r11)
+
+	bl	prepare_ftrace_return
+	nop
+
+	/*
+	 * prepare_ftrace_return gives us the address we divert to.
+	 * Change the LR in the callers stack frame to this.
+	 */
+	ld	r11, 112(r1)
+	std	r3, 16(r11)
+
+	ld	r0, 128(r1)
+	mtlr	r0
+	addi	r1, r1, 112
+	blr
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
  .pushsection ".tramp.ftrace.text","aw",@progbits;
  .globl ftrace_tramp_text
  ftrace_tramp_text:

arch/powerpc/kernel/trace/ftrace_entry.S renamed from arch/powerpc/kernel/trace/ftrace_mprofile.S +65 -0

similarity index 83%
rename from arch/powerpc/kernel/trace/ftrace_mprofile.S
rename to arch/powerpc/kernel/trace/ftrace_entry.S
index ffb1db38684998..e8339706e735b1 100644
@@ -249,3 +249,68 @@ livepatch_handler:
  	/* Return to original caller of live patched function */
  	blr
  #endif /* CONFIG_LIVEPATCH */
+
+_GLOBAL(mcount)
+_GLOBAL(_mcount)
+EXPORT_SYMBOL(_mcount)
+	mflr	r12
+	mtctr	r12
+	mtlr	r0
+	bctr
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+_GLOBAL(return_to_handler)
+	/* need to save return values */
+#ifdef CONFIG_PPC64
+	std	r4,  -32(r1)
+	std	r3,  -24(r1)
+	/* save TOC */
+	std	r2,  -16(r1)
+	std	r31, -8(r1)
+	mr	r31, r1
+	stdu	r1, -112(r1)
+
+	/*
+	 * We might be called from a module.
+	 * Switch to our TOC to run inside the core kernel.
+	 */
+	LOAD_PACA_TOC()
+#else
+	stwu	r1, -16(r1)
+	stw	r3, 8(r1)
+	stw	r4, 12(r1)
+#endif
+
+	bl	ftrace_return_to_handler
+	nop
+
+	/* return value has real return address */
+	mtlr	r3
+
+#ifdef CONFIG_PPC64
+	ld	r1, 0(r1)
+	ld	r4,  -32(r1)
+	ld	r3,  -24(r1)
+	ld	r2,  -16(r1)
+	ld	r31, -8(r1)
+#else
+	lwz	r3, 8(r1)
+	lwz	r4, 12(r1)
+	addi	r1, r1, 16
+#endif
+
+	/* Jump back to real return address */
+	blr
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
+.pushsection ".tramp.ftrace.text","aw",@progbits;
+.globl ftrace_tramp_text
+ftrace_tramp_text:
+	.space 32
+.popsection
+
+.pushsection ".tramp.ftrace.init","aw",@progbits;
+.globl ftrace_tramp_init
+ftrace_tramp_init:
+	.space 32
+.popsection

Split up ftrace_modify_code() into a few helpers for future use. Also update error messages accordingly.

Signed-off-by Naveen N Rao <[email protected]>

---
  arch/powerpc/kernel/trace/ftrace.c | 51 +++++++++++++++++-------------
  1 file changed, 29 insertions(+), 22 deletions(-)

arch/powerpc/kernel/trace/ftrace.c +29 -22

index 913c7aa63d3fa3..ef4e49c2c37781 100644
@@ -50,32 +50,39 @@ ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
  	return op;
  }
 
-static inline int
-ftrace_modify_code(unsigned long ip, ppc_inst_t old, ppc_inst_t new)
+static inline int ftrace_read_inst(unsigned long ip, ppc_inst_t *op)
  {
-	ppc_inst_t replaced;
-
-	/*
-	 * Note:
-	 * We are paranoid about modifying text, as if a bug was to happen, it
-	 * could cause us to read or write to someplace that could cause harm.
-	 * Carefully read and modify the code with probe_kernel_*(), and make
-	 * sure what we read is what we expected it to be before modifying it.
-	 */
-
-	/* read the text we want to modify */
-	if (copy_inst_from_kernel_nofault(&replaced, (void *)ip))
+	if (copy_inst_from_kernel_nofault(op, (void *)ip)) {
+		pr_err("0x%lx: fetching instruction failed\n", ip);
  		return -EFAULT;
-
-	/* Make sure it is what we expect it to be */
-	if (!ppc_inst_equal(replaced, old)) {
-		pr_err("%p: replaced (%08lx) != old (%08lx)", (void *)ip,
-		       ppc_inst_as_ulong(replaced), ppc_inst_as_ulong(old));
-		return -EINVAL;
  	}
 
-	/* replace the text with the new text */
-	return patch_instruction((u32 *)ip, new);
+	return 0;
+}
+
+static inline int ftrace_validate_inst(unsigned long ip, ppc_inst_t inst)
+{
+	ppc_inst_t op;
+	int ret;
+
+	ret = ftrace_read_inst(ip, &op);
+	if (!ret && !ppc_inst_equal(op, inst)) {
+		pr_err("0x%lx: expected (%08lx) != found (%08lx)\n",
+		       ip, ppc_inst_as_ulong(inst), ppc_inst_as_ulong(op));
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+static inline int ftrace_modify_code(unsigned long ip, ppc_inst_t old, ppc_inst_t new)
+{
+	int ret = ftrace_validate_inst(ip, old);
+
+	if (!ret)
+		ret = patch_instruction((u32 *)ip, new);
+
+	return ret;
  }
 
  /*

Commit 67361cf8071286 ("powerpc/ftrace: Handle large kernel configs") added ftrace support for ppc64 kernel images with a text section larger than 32MB. The patch did two things:
1. Add stubs at the end of .text to branch into ftrace_[regs_]caller for functions that were out of branch range.
2. Re-purpose linker-generated long branches to _mcount to instead branch to ftrace_[regs_]caller.

Before that, we only supported kernel .text up to ~32MB. With the above, we now support up to ~96MB:
- The first 32MB of kernel text can branch directly into ftrace_[regs_]caller since that symbol is usually at the beginning.
- The modified long_branch from (2) above is used by the next 32MB of kernel text.
- The next 32MB of kernel text can use the stub at the end of text to branch back to ftrace_[regs_]caller.

While re-purposing the long branch works in practice, it still restricts ftrace to kernel text up to ~96MB. The stub at the end of kernel text from (1) already enables us to extend ftrace support for kernel text up to 64MB, which fulfils the original requirement. Further, once we switch to -fpatchable-function-entry, there will not be a long branch that we can use.

Stop re-purposing the linker-generated long branches for ftrace to simplify the code. If there are good reasons to support ftrace on kernels beyond 64MB, we can consider adding support by using -fpatchable-function-entry.

Signed-off-by Naveen N Rao <[email protected]>

---
  arch/powerpc/kernel/trace/ftrace.c | 110 +++++------------------------
  1 file changed, 17 insertions(+), 93 deletions(-)

arch/powerpc/kernel/trace/ftrace.c +17 -93

index ef4e49c2c37781..278bf8e52b6e89 100644
@@ -28,13 +28,7 @@
  #include <asm/syscall.h>
  #include <asm/inst.h>
 
-/*
- * We generally only have a single long_branch tramp and at most 2 or 3 plt
- * tramps generated. But, we don't use the plt tramps currently. We also allot
- * 2 tramps after .text and .init.text. So, we only end up with around 3 usable
- * tramps in total. Set aside 8 just to be sure.
- */
-#define	NUM_FTRACE_TRAMPS	8
+#define	NUM_FTRACE_TRAMPS	2
  static unsigned long ftrace_tramps[NUM_FTRACE_TRAMPS];
 
  static ppc_inst_t

@@ -100,11 +94,6 @@ static int is_bl_op(ppc_inst_t op)
  	return (ppc_inst_val(op) & ~PPC_LI_MASK) == PPC_RAW_BL(0);
  }
 
-static int is_b_op(ppc_inst_t op)
-{
-	return (ppc_inst_val(op) & ~PPC_LI_MASK) == PPC_RAW_BRANCH(0);
-}
-
  static unsigned long find_bl_target(unsigned long ip, ppc_inst_t op)
  {
  	int offset;

@@ -227,11 +216,7 @@ static unsigned long find_ftrace_tramp(unsigned long ip)
  {
  	int i;
 
-	/*
-	 * We have the compiler generated long_branch tramps at the end
-	 * and we prefer those
-	 */
-	for (i = NUM_FTRACE_TRAMPS - 1; i >= 0; i--)
+	for (i = 0; i < NUM_FTRACE_TRAMPS; i++)
  		if (!ftrace_tramps[i])
  			continue;
  		else if (is_offset_in_branch_range(ftrace_tramps[i] - ip))

@@ -240,75 +225,6 @@ static unsigned long find_ftrace_tramp(unsigned long ip)
  	return 0;
  }
 
-static int add_ftrace_tramp(unsigned long tramp)
-{
-	int i;
-
-	for (i = 0; i < NUM_FTRACE_TRAMPS; i++)
-		if (!ftrace_tramps[i]) {
-			ftrace_tramps[i] = tramp;
-			return 0;
-		}
-
-	return -1;
-}
-
-/*
- * If this is a compiler generated long_branch trampoline (essentially, a
- * trampoline that has a branch to _mcount()), we re-write the branch to
- * instead go to ftrace_[regs_]caller() and note down the location of this
- * trampoline.
- */
-static int setup_mcount_compiler_tramp(unsigned long tramp)
-{
-	int i;
-	ppc_inst_t op;
-	unsigned long ptr;
-
-	/* Is this a known long jump tramp? */
-	for (i = 0; i < NUM_FTRACE_TRAMPS; i++)
-		if (ftrace_tramps[i] == tramp)
-			return 0;
-
-	/* New trampoline -- read where this goes */
-	if (copy_inst_from_kernel_nofault(&op, (void *)tramp)) {
-		pr_debug("Fetching opcode failed.\n");
-		return -1;
-	}
-
-	/* Is this a 24 bit branch? */
-	if (!is_b_op(op)) {
-		pr_debug("Trampoline is not a long branch tramp.\n");
-		return -1;
-	}
-
-	/* lets find where the pointer goes */
-	ptr = find_bl_target(tramp, op);
-
-	if (ptr != ppc_global_function_entry((void *)_mcount)) {
-		pr_debug("Trampoline target %p is not _mcount\n", (void *)ptr);
-		return -1;
-	}
-
-	/* Let's re-write the tramp to go to ftrace_[regs_]caller */
-	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
-		ptr = ppc_global_function_entry((void *)ftrace_regs_caller);
-	else
-		ptr = ppc_global_function_entry((void *)ftrace_caller);
-
-	if (patch_branch((u32 *)tramp, ptr, 0)) {
-		pr_debug("REL24 out of range!\n");
-		return -1;
-	}
-
-	if (add_ftrace_tramp(tramp)) {
-		pr_debug("No tramp locations left\n");
-		return -1;
-	}
-
-	return 0;
-}
-
  static int __ftrace_make_nop_kernel(struct dyn_ftrace *rec, unsigned long addr)
  {
  	unsigned long tramp, ip = rec->ip;

@@ -331,13 +247,10 @@ static int __ftrace_make_nop_kernel(struct dyn_ftrace *rec, unsigned long addr)
 
  	pr_devel("ip:%lx jumps to %lx", ip, tramp);
 
-	if (setup_mcount_compiler_tramp(tramp)) {
-		/* Are other trampolines reachable? */
-		if (!find_ftrace_tramp(ip)) {
-			pr_err("No ftrace trampolines reachable from %ps\n",
-					(void *)ip);
-			return -EINVAL;
-		}
+	/* Are ftrace trampolines reachable? */
+	if (!find_ftrace_tramp(ip)) {
+		pr_err("No ftrace trampolines reachable from %ps\n", (void *)ip);
+		return -EINVAL;
  	}
 
  	if (patch_instruction((u32 *)ip, ppc_inst(PPC_RAW_NOP()))) {

@@ -725,6 +638,17 @@ void ftrace_free_init_tramp(void)
  		}
  }
 
+static void __init add_ftrace_tramp(unsigned long tramp)
+{
+	int i;
+
+	for (i = 0; i < NUM_FTRACE_TRAMPS; i++)
+		if (!ftrace_tramps[i]) {
+			ftrace_tramps[i] = tramp;
+			return;
+		}
+}
+
  int __init ftrace_dyn_arch_init(void)
  {
  	unsigned int *tramp[] = { ftrace_tramp_text, ftrace_tramp_init };

Currently, we validate instructions around the ftrace location every time we have to enable/disable ftrace. Introduce ftrace_init_nop() to instead perform all the validation during ftrace initialization. This allows us to simply patch the necessary instructions during enabling/disabling ftrace.

Signed-off-by Naveen N Rao <[email protected]>

---
  arch/powerpc/include/asm/ftrace.h  |  6 +++
  arch/powerpc/kernel/trace/ftrace.c | 71 ++++++++++++++++++++++++++++++
  2 files changed, 77 insertions(+)

arch/powerpc/include/asm/ftrace.h +6 -0

index 702aaf2efa966c..ef9f0b97670d1c 100644
@@ -29,11 +29,17 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)
  unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
  				    unsigned long sp);
 
+struct module;
+struct dyn_ftrace;
  struct dyn_arch_ftrace {
  	struct module *mod;
  };
 
  #ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
+#define ftrace_need_init_nop()	(true)
+int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
+#define ftrace_init_nop ftrace_init_nop
+
  struct ftrace_regs {
  	struct pt_regs regs;
  };

arch/powerpc/kernel/trace/ftrace.c +71 -0

index 278bf8e52b6e89..98bd099c428ee0 100644
@@ -31,6 +31,16 @@
  #define	NUM_FTRACE_TRAMPS	2
  static unsigned long ftrace_tramps[NUM_FTRACE_TRAMPS];
 
+static ppc_inst_t ftrace_create_branch_inst(unsigned long ip, unsigned long addr, int link)
+{
+	ppc_inst_t op;
+
+	WARN_ON(!is_offset_in_branch_range(addr - ip));
+	create_branch(&op, (u32 *)ip, addr, link ? BRANCH_SET_LINK : 0);
+
+	return op;
+}
+
  static ppc_inst_t
  ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
  {

@@ -597,6 +607,67 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
  }
  #endif
 
+int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
+{
+	unsigned long addr, ip = rec->ip;
+	ppc_inst_t old, new;
+	int ret = 0;
+
+	/* Verify instructions surrounding the ftrace location */
+	if (IS_ENABLED(CONFIG_PPC32)) {
+		/* Expected sequence: 'mflr r0', 'stw r0,4(r1)', 'bl _mcount' */
+		ret = ftrace_validate_inst(ip - 8, ppc_inst(PPC_RAW_MFLR(_R0)));
+		if (!ret)
+			ret = ftrace_validate_inst(ip - 4, ppc_inst(PPC_RAW_STW(_R0, _R1, 4)));
+	} else if (IS_ENABLED(CONFIG_MPROFILE_KERNEL)) {
+		/* Expected sequence: 'mflr r0', ['std r0,16(r1)'], 'bl _mcount' */
+		ret = ftrace_read_inst(ip - 4, &old);
+		if (!ret && !ppc_inst_equal(old, ppc_inst(PPC_RAW_MFLR(_R0)))) {
+			ret = ftrace_validate_inst(ip - 8, ppc_inst(PPC_RAW_MFLR(_R0)));
+			ret |= ftrace_validate_inst(ip - 4, ppc_inst(PPC_RAW_STD(_R0, _R1, 16)));
+		}
+	} else {
+		return -EINVAL;
+	}
+
+	if (ret)
+		return ret;
+
+	if (!core_kernel_text(ip)) {
+		if (!mod) {
+			pr_err("0x%lx: No module provided for non-kernel address\n", ip);
+			return -EFAULT;
+		}
+		rec->arch.mod = mod;
+	}
+
+	/* Nop-out the ftrace location */
+	new = ppc_inst(PPC_RAW_NOP());
+	addr = MCOUNT_ADDR;
+	if (is_offset_in_branch_range(addr - ip)) {
+		/* Within range */
+		old = ftrace_create_branch_inst(ip, addr, 1);
+		ret = ftrace_modify_code(ip, old, new);
+	} else if (core_kernel_text(ip) || (IS_ENABLED(CONFIG_MODULES) && mod)) {
+		/*
+		 * We would be branching to a linker-generated stub, or to the module _mcount
+		 * stub. Let's just confirm we have a 'bl' here.
+		 */
+		ret = ftrace_read_inst(ip, &old);
+		if (ret)
+			return ret;
+		if (!is_bl_op(old)) {
+			pr_err("0x%lx: expected (bl) != found (%08lx)\n", ip, ppc_inst_as_ulong(old));
+			return -EINVAL;
+		}
+		ret = patch_instruction((u32 *)ip, new);
+	} else {
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
  int ftrace_update_ftrace_func(ftrace_func_t func)
  {
  	unsigned long ip = (unsigned long)(&ftrace_call);

Now that we validate the ftrace location during initialization in ftrace_init_nop(), we can simplify ftrace_make_nop() to patch-in the nop without worrying about the instructions surrounding the ftrace location. Note that we continue to ensure that we have a bl to ftrace_[regs_]caller at the ftrace location before nop-ing it out.

Signed-off-by Naveen N Rao <[email protected]>

---
  arch/powerpc/kernel/trace/ftrace.c | 220 +++++------------------------
  1 file changed, 32 insertions(+), 188 deletions(-)

arch/powerpc/kernel/trace/ftrace.c +32 -188

index 98bd099c428ee0..05153a1038fdff 100644
@@ -116,112 +116,6 @@ static unsigned long find_bl_target(unsigned long ip, ppc_inst_t op)
  	return ip + (long)offset;
  }
 
-#ifdef CONFIG_MODULES
-static int
-__ftrace_make_nop(struct module *mod,
-		  struct dyn_ftrace *rec, unsigned long addr)
-{
-	unsigned long entry, ptr, tramp;
-	unsigned long ip = rec->ip;
-	ppc_inst_t op, pop;
-
-	/* read where this goes */
-	if (copy_inst_from_kernel_nofault(&op, (void *)ip)) {
-		pr_err("Fetching opcode failed.\n");
-		return -EFAULT;
-	}
-
-	/* Make sure that this is still a 24bit jump */
-	if (!is_bl_op(op)) {
-		pr_err("Not expected bl: opcode is %08lx\n", ppc_inst_as_ulong(op));
-		return -EINVAL;
-	}
-
-	/* lets find where the pointer goes */
-	tramp = find_bl_target(ip, op);
-
-	pr_devel("ip:%lx jumps to %lx", ip, tramp);
-
-	if (module_trampoline_target(mod, tramp, &ptr)) {
-		pr_err("Failed to get trampoline target\n");
-		return -EFAULT;
-	}
-
-	pr_devel("trampoline target %lx", ptr);
-
-	entry = ppc_global_function_entry((void *)addr);
-	/* This should match what was called */
-	if (ptr != entry) {
-		pr_err("addr %lx does not match expected %lx\n", ptr, entry);
-		return -EINVAL;
-	}
-
-	if (IS_ENABLED(CONFIG_MPROFILE_KERNEL)) {
-		if (copy_inst_from_kernel_nofault(&op, (void *)(ip - 4))) {
-			pr_err("Fetching instruction at %lx failed.\n", ip - 4);
-			return -EFAULT;
-		}
-
-		/* We expect either a mflr r0, or a std r0, LRSAVE(r1) */
-		if (!ppc_inst_equal(op, ppc_inst(PPC_RAW_MFLR(_R0))) &&
-		    !ppc_inst_equal(op, ppc_inst(PPC_INST_STD_LR))) {
-			pr_err("Unexpected instruction %08lx around bl _mcount\n",
-			       ppc_inst_as_ulong(op));
-			return -EINVAL;
-		}
-	} else if (IS_ENABLED(CONFIG_PPC64)) {
-		/*
-		 * Check what is in the next instruction. We can see ld r2,40(r1), but
-		 * on first pass after boot we will see mflr r0.
-		 */
-		if (copy_inst_from_kernel_nofault(&op, (void *)(ip + 4))) {
-			pr_err("Fetching op failed.\n");
-			return -EFAULT;
-		}
-
-		if (!ppc_inst_equal(op,  ppc_inst(PPC_INST_LD_TOC))) {
-			pr_err("Expected %08lx found %08lx\n", PPC_INST_LD_TOC,
-			       ppc_inst_as_ulong(op));
-			return -EINVAL;
-		}
-	}
-
-	/*
-	 * When using -mprofile-kernel or PPC32 there is no load to jump over.
-	 *
-	 * Otherwise our original call site looks like:
-	 *
-	 * bl <tramp>
-	 * ld r2,XX(r1)
-	 *
-	 * Milton Miller pointed out that we can not simply nop the branch.
-	 * If a task was preempted when calling a trace function, the nops
-	 * will remove the way to restore the TOC in r2 and the r2 TOC will
-	 * get corrupted.
-	 *
-	 * Use a b +8 to jump over the load.
-	 * XXX: could make PCREL depend on MPROFILE_KERNEL
-	 * XXX: check PCREL && MPROFILE_KERNEL calling sequence
-	 */
-	if (IS_ENABLED(CONFIG_MPROFILE_KERNEL) || IS_ENABLED(CONFIG_PPC32))
-		pop = ppc_inst(PPC_RAW_NOP());
-	else
-		pop = ppc_inst(PPC_RAW_BRANCH(8));	/* b +8 */
-
-	if (patch_instruction((u32 *)ip, pop)) {
-		pr_err("Patching NOP failed.\n");
-		return -EPERM;
-	}
-
-	return 0;
-}
-#else
-static int __ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
-{
-	return 0;
-}
-#endif /* CONFIG_MODULES */
-
  static unsigned long find_ftrace_tramp(unsigned long ip)
  {
  	int i;

@@ -235,88 +129,6 @@ static unsigned long find_ftrace_tramp(unsigned long ip)
  	return 0;
  }
 
-static int __ftrace_make_nop_kernel(struct dyn_ftrace *rec, unsigned long addr)
-{
-	unsigned long tramp, ip = rec->ip;
-	ppc_inst_t op;
-
-	/* Read where this goes */
-	if (copy_inst_from_kernel_nofault(&op, (void *)ip)) {
-		pr_err("Fetching opcode failed.\n");
-		return -EFAULT;
-	}
-
-	/* Make sure that this is still a 24bit jump */
-	if (!is_bl_op(op)) {
-		pr_err("Not expected bl: opcode is %08lx\n", ppc_inst_as_ulong(op));
-		return -EINVAL;
-	}
-
-	/* Let's find where the pointer goes */
-	tramp = find_bl_target(ip, op);
-
-	pr_devel("ip:%lx jumps to %lx", ip, tramp);
-
-	/* Are ftrace trampolines reachable? */
-	if (!find_ftrace_tramp(ip)) {
-		pr_err("No ftrace trampolines reachable from %ps\n", (void *)ip);
-		return -EINVAL;
-	}
-
-	if (patch_instruction((u32 *)ip, ppc_inst(PPC_RAW_NOP()))) {
-		pr_err("Patching NOP failed.\n");
-		return -EPERM;
-	}
-
-	return 0;
-}
-
-int ftrace_make_nop(struct module *mod,
-		    struct dyn_ftrace *rec, unsigned long addr)
-{
-	unsigned long ip = rec->ip;
-	ppc_inst_t old, new;
-
-	/*
-	 * If the calling address is more that 24 bits away,
-	 * then we had to use a trampoline to make the call.
-	 * Otherwise just update the call site.
-	 */
-	if (test_24bit_addr(ip, addr)) {
-		/* within range */
-		old = ftrace_call_replace(ip, addr, 1);
-		new = ppc_inst(PPC_RAW_NOP());
-		return ftrace_modify_code(ip, old, new);
-	} else if (core_kernel_text(ip)) {
-		return __ftrace_make_nop_kernel(rec, addr);
-	} else if (!IS_ENABLED(CONFIG_MODULES)) {
-		return -EINVAL;
-	}
-
-	/*
-	 * Out of range jumps are called from modules.
-	 * We should either already have a pointer to the module
-	 * or it has been passed in.
-	 */
-	if (!rec->arch.mod) {
-		if (!mod) {
-			pr_err("No module loaded addr=%lx\n", addr);
-			return -EFAULT;
-		}
-		rec->arch.mod = mod;
-	} else if (mod) {
-		if (mod != rec->arch.mod) {
-			pr_err("Record mod %p not equal to passed in mod %p\n",
-			       rec->arch.mod, mod);
-			return -EINVAL;
-		}
-		/* nothing to do if mod == rec->arch.mod */
-	} else
-		mod = rec->arch.mod;
-
-	return __ftrace_make_nop(mod, rec, addr);
-}
-
  #ifdef CONFIG_MODULES
  /*
   * Examine the existing instructions for __ftrace_make_call.

@@ -607,6 +419,38 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
  }
  #endif
 
+int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned long tramp, ip = rec->ip;
+	ppc_inst_t old, new;
+
+	/* Nop-out the ftrace location */
+	new = ppc_inst(PPC_RAW_NOP());
+	if (is_offset_in_branch_range(addr - ip)) {
+		/* Within range */
+		old = ftrace_create_branch_inst(ip, addr, 1);
+		return ftrace_modify_code(ip, old, new);
+	} else if (core_kernel_text(ip)) {
+		/* We would be branching to one of our ftrace tramps */
+		tramp = find_ftrace_tramp(ip);
+		if (!tramp) {
+			pr_err("0x%lx: No ftrace trampolines reachable\n", ip);
+			return -EINVAL;
+		}
+		old = ftrace_create_branch_inst(ip, tramp, 1);
+		return ftrace_modify_code(ip, old, new);
+	} else if (IS_ENABLED(CONFIG_MODULES)) {
+		/* Module code would be going to one of the module stubs */
+		if (!mod)
+			mod = rec->arch.mod;
+		tramp = (addr == (unsigned long)ftrace_caller ? mod->arch.tramp : mod->arch.tramp_regs);
+		old = ftrace_create_branch_inst(ip, tramp, 1);
+		return ftrace_modify_code(ip, old, new);
+	}
+
+	return -EINVAL;
+}
+
  int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
  {
  	unsigned long addr, ip = rec->ip;