[03/17] powerpc64/ftrace: Move ELFv1 and -pg support code into a separate file

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 <naveen@kernel.org>
---
 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

Le 19/06/2023 à 11:47, Naveen N Rao a écrit :
> 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 <naveen@kernel.org>

Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>

> ---
>   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
> 
> diff --git a/arch/powerpc/kernel/trace/Makefile b/arch/powerpc/kernel/trace/Makefile
> index b16a9f9c0b35f2..342a2d1ae86cd0 100644
> --- a/arch/powerpc/kernel/trace/Makefile
> +++ b/arch/powerpc/kernel/trace/Makefile
> @@ -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
> diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
> index a47f303734233b..81a121b56c4d7f 100644
> --- a/arch/powerpc/kernel/trace/ftrace.c
> +++ b/arch/powerpc/kernel/trace/ftrace.c
> @@ -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 */
> diff --git a/arch/powerpc/kernel/trace/ftrace_pg.c b/arch/powerpc/kernel/trace/ftrace_pg.c
> new file mode 100644
> index 00000000000000..7b85c3b460a3c0
> --- /dev/null
> +++ b/arch/powerpc/kernel/trace/ftrace_pg.c
> @@ -0,0 +1,846 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Code for replacing ftrace calls with jumps.
> + *
> + * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
> + *
> + * 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 */