arch/powerpc/kernel/trace/ftrace.c - linux-imx - Git at Google

 // 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/asm-prototypes.h>
 #include <asm/cacheflush.h>
 #include <asm/code-patching.h>
 #include <asm/ftrace.h>
 #include <asm/syscall.h>


 #ifdef CONFIG_DYNAMIC_FTRACE
 static unsigned int
 ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
 {
 	unsigned int op;

 	addr = ppc_function_entry((void *)addr);

 	/* if (link) set op to 'bl' else 'b' */
 	op = create_branch((unsigned int *)ip, addr, link ? 1 : 0);

 	return op;
 }

 static int
 ftrace_modify_code(unsigned long ip, unsigned int old, unsigned int new)
 {
 	unsigned int 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 (probe_kernel_read(&replaced, (void *)ip, MCOUNT_INSN_SIZE))
 		return -EFAULT;

 	/* Make sure it is what we expect it to be */
 	if (replaced != old) {
 		pr_err("%p: replaced (%#x) != old (%#x)",
 		(void *)ip, replaced, old);
 		return -EINVAL;
 	}

 	/* replace the text with the new text */
 	if (patch_instruction((unsigned int *)ip, new))
 		return -EPERM;

 	return 0;
 }

 /*
  * 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);

 	/* use the create_branch to verify that this offset can be branched */
 	return create_branch((unsigned int *)ip, addr, 0);
 }

 #ifdef CONFIG_MODULES

 static int is_bl_op(unsigned int op)
 {
 	return (op & 0xfc000003) == 0x48000001;
 }

 static unsigned long find_bl_target(unsigned long ip, unsigned int op)
 {
 	static int offset;

 	offset = (op & 0x03fffffc);
 	/* make it signed */
 	if (offset & 0x02000000)
 		offset |= 0xfe000000;

 	return ip + (long)offset;
 }

 #ifdef CONFIG_PPC64
 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;
 	unsigned int op, pop;

 	/* read where this goes */
 	if (probe_kernel_read(&op, (void *)ip, sizeof(int))) {
 		pr_err("Fetching opcode failed.\n");
 		return -EFAULT;
 	}

 	/* Make sure that that this is still a 24bit jump */
 	if (!is_bl_op(op)) {
 		pr_err("Not expected bl: opcode is %x\n", 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;
 	}

 #ifdef CC_USING_MPROFILE_KERNEL
 	/* When using -mkernel_profile there is no load to jump over */
 	pop = PPC_INST_NOP;

 	if (probe_kernel_read(&op, (void *)(ip - 4), 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 (op != PPC_INST_MFLR && op != PPC_INST_STD_LR) {
 		pr_err("Unexpected instruction %08x around bl _mcount\n", op);
 		return -EINVAL;
 	}
 #else
 	/*
 	 * 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.
 	 */

 	pop = PPC_INST_BRANCH | 8;	/* b +8 */

 	/*
 	 * 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 (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE)) {
 		pr_err("Fetching op failed.\n");
 		return -EFAULT;
 	}

 	if (op != PPC_INST_LD_TOC) {
 		pr_err("Expected %08x found %08x\n", PPC_INST_LD_TOC, op);
 		return -EINVAL;
 	}
 #endif /* CC_USING_MPROFILE_KERNEL */

 	if (patch_instruction((unsigned int *)ip, pop)) {
 		pr_err("Patching NOP failed.\n");
 		return -EPERM;
 	}

 	return 0;
 }

 #else /* !PPC64 */
 static int
 __ftrace_make_nop(struct module *mod,
 		  struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned int op;
 	unsigned int jmp[4];
 	unsigned long ip = rec->ip;
 	unsigned long tramp;

 	if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
 		return -EFAULT;

 	/* Make sure that that this is still a 24bit jump */
 	if (!is_bl_op(op)) {
 		pr_err("Not expected bl: opcode is %x\n", op);
 		return -EINVAL;
 	}

 	/* lets find where the pointer goes */
 	tramp = find_bl_target(ip, op);

 	/*
 	 * On PPC32 the trampoline looks like:
 	 *  0x3d, 0x80, 0x00, 0x00  lis r12,sym@ha
 	 *  0x39, 0x8c, 0x00, 0x00  addi r12,r12,sym@l
 	 *  0x7d, 0x89, 0x03, 0xa6  mtctr r12
 	 *  0x4e, 0x80, 0x04, 0x20  bctr
 	 */

 	pr_devel("ip:%lx jumps to %lx", ip, tramp);

 	/* Find where the trampoline jumps to */
 	if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
 		pr_err("Failed to read %lx\n", tramp);
 		return -EFAULT;
 	}

 	pr_devel(" %08x %08x ", jmp[0], jmp[1]);

 	/* verify that this is what we expect it to be */
 	if (((jmp[0] & 0xffff0000) != 0x3d800000) ||
 	    ((jmp[1] & 0xffff0000) != 0x398c0000) ||
 	    (jmp[2] != 0x7d8903a6) ||
 	    (jmp[3] != 0x4e800420)) {
 		pr_err("Not a trampoline\n");
 		return -EINVAL;
 	}

 	tramp = (jmp[1] & 0xffff) |
 		((jmp[0] & 0xffff) << 16);
 	if (tramp & 0x8000)
 		tramp -= 0x10000;

 	pr_devel(" %lx ", tramp);

 	if (tramp != addr) {
 		pr_err("Trampoline location %08lx does not match addr\n",
 		       tramp);
 		return -EINVAL;
 	}

 	op = PPC_INST_NOP;

 	if (patch_instruction((unsigned int *)ip, op))
 		return -EPERM;

 	return 0;
 }
 #endif /* PPC64 */
 #endif /* CONFIG_MODULES */

 int ftrace_make_nop(struct module *mod,
 		    struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned long ip = rec->ip;
 	unsigned int 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_NOP;
 		return ftrace_modify_code(ip, old, new);
 	}

 #ifdef CONFIG_MODULES
 	/*
 	 * 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);
 #else
 	/* We should not get here without modules */
 	return -EINVAL;
 #endif /* CONFIG_MODULES */
 }

 #ifdef CONFIG_MODULES
 #ifdef CONFIG_PPC64
 /*
  * 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.
  */
 #ifndef CC_USING_MPROFILE_KERNEL
 static int
 expected_nop_sequence(void *ip, unsigned int op0, unsigned int op1)
 {
 	/*
 	 * We expect to see:
 	 *
 	 * b +8
 	 * ld r2,XX(r1)
 	 *
 	 * The load offset is different depending on the ABI. For simplicity
 	 * just mask it out when doing the compare.
 	 */
 	if ((op0 != 0x48000008) || ((op1 & 0xffff0000) != 0xe8410000))
 		return 0;
 	return 1;
 }
 #else
 static int
 expected_nop_sequence(void *ip, unsigned int op0, unsigned int op1)
 {
 	/* look for patched "NOP" on ppc64 with -mprofile-kernel */
 	if (op0 != PPC_INST_NOP)
 		return 0;
 	return 1;
 }
 #endif

 static int
 __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned int op[2];
 	void *ip = (void *)rec->ip;

 	/* read where this goes */
 	if (probe_kernel_read(op, ip, sizeof(op)))
 		return -EFAULT;

 	if (!expected_nop_sequence(ip, op[0], op[1])) {
 		pr_err("Unexpected call sequence at %p: %x %x\n",
 		ip, op[0], op[1]);
 		return -EINVAL;
 	}

 	/* If we never set up a trampoline to ftrace_caller, then bail */
 	if (!rec->arch.mod->arch.tramp) {
 		pr_err("No ftrace trampoline\n");
 		return -EINVAL;
 	}

 	/* Ensure branch is within 24 bits */
 	if (!create_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
 		pr_err("Branch out of range\n");
 		return -EINVAL;
 	}

 	if (patch_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
 		pr_err("REL24 out of range!\n");
 		return -EINVAL;
 	}

 	return 0;
 }

 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 			unsigned long addr)
 {
 	return ftrace_make_call(rec, addr);
 }
 #endif

 #else  /* !CONFIG_PPC64: */
 static int
 __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned int op;
 	unsigned long ip = rec->ip;

 	/* read where this goes */
 	if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
 		return -EFAULT;

 	/* It should be pointing to a nop */
 	if (op != PPC_INST_NOP) {
 		pr_err("Expected NOP but have %x\n", op);
 		return -EINVAL;
 	}

 	/* If we never set up a trampoline to ftrace_caller, then bail */
 	if (!rec->arch.mod->arch.tramp) {
 		pr_err("No ftrace trampoline\n");
 		return -EINVAL;
 	}

 	/* create the branch to the trampoline */
 	op = create_branch((unsigned int *)ip,
 			   rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
 	if (!op) {
 		pr_err("REL24 out of range!\n");
 		return -EINVAL;
 	}

 	pr_devel("write to %lx\n", rec->ip);

 	if (patch_instruction((unsigned int *)ip, op))
 		return -EPERM;

 	return 0;
 }
 #endif /* CONFIG_PPC64 */
 #endif /* CONFIG_MODULES */

 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned long ip = rec->ip;
 	unsigned int 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_NOP;
 		new = ftrace_call_replace(ip, addr, 1);
 		return ftrace_modify_code(ip, old, new);
 	}

 #ifdef CONFIG_MODULES
 	/*
 	 * 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);
 #else
 	/* We should not get here without modules */
 	return -EINVAL;
 #endif /* CONFIG_MODULES */
 }

 int ftrace_update_ftrace_func(ftrace_func_t func)
 {
 	unsigned long ip = (unsigned long)(&ftrace_call);
 	unsigned int old, new;
 	int ret;

 	old = *(unsigned int *)&ftrace_call;
 	new = ftrace_call_replace(ip, (unsigned long)func, 1);
 	ret = ftrace_modify_code(ip, old, new);

 	return ret;
 }

 static int __ftrace_replace_code(struct dyn_ftrace *rec, int enable)
 {
 	unsigned long ftrace_addr = (unsigned long)FTRACE_ADDR;
 	int ret;

 	ret = ftrace_update_record(rec, enable);

 	switch (ret) {
 	case FTRACE_UPDATE_IGNORE:
 		return 0;
 	case FTRACE_UPDATE_MAKE_CALL:
 		return ftrace_make_call(rec, ftrace_addr);
 	case FTRACE_UPDATE_MAKE_NOP:
 		return ftrace_make_nop(NULL, rec, ftrace_addr);
 	}

 	return 0;
 }

 void ftrace_replace_code(int enable)
 {
 	struct ftrace_rec_iter *iter;
 	struct dyn_ftrace *rec;
 	int ret;

 	for (iter = ftrace_rec_iter_start(); iter;
 	     iter = ftrace_rec_iter_next(iter)) {
 		rec = ftrace_rec_iter_record(iter);
 		ret = __ftrace_replace_code(rec, enable);
 		if (ret) {
 			ftrace_bug(ret, rec);
 			return;
 		}
 	}
 }

 /*
  * Use the default ftrace_modify_all_code, but without
  * stop_machine().
  */
 void arch_ftrace_update_code(int command)
 {
 	ftrace_modify_all_code(command);
 }

 int __init ftrace_dyn_arch_init(void)
 {
 	return 0;
 }
 #endif /* CONFIG_DYNAMIC_FTRACE */

 #ifdef CONFIG_FUNCTION_GRAPH_TRACER

 #ifdef CONFIG_DYNAMIC_FTRACE
 extern void ftrace_graph_call(void);
 extern void ftrace_graph_stub(void);

 int ftrace_enable_ftrace_graph_caller(void)
 {
 	unsigned long ip = (unsigned long)(&ftrace_graph_call);
 	unsigned long addr = (unsigned long)(&ftrace_graph_caller);
 	unsigned long stub = (unsigned long)(&ftrace_graph_stub);
 	unsigned int old, new;

 	old = ftrace_call_replace(ip, stub, 0);
 	new = ftrace_call_replace(ip, addr, 0);

 	return ftrace_modify_code(ip, old, new);
 }

 int ftrace_disable_ftrace_graph_caller(void)
 {
 	unsigned long ip = (unsigned long)(&ftrace_graph_call);
 	unsigned long addr = (unsigned long)(&ftrace_graph_caller);
 	unsigned long stub = (unsigned long)(&ftrace_graph_stub);
 	unsigned int old, new;

 	old = ftrace_call_replace(ip, addr, 0);
 	new = ftrace_call_replace(ip, stub, 0);

 	return ftrace_modify_code(ip, old, new);
 }
 #endif /* CONFIG_DYNAMIC_FTRACE */

 /*
  * 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.
  */
 unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
 {
 	struct ftrace_graph_ent trace;
 	unsigned long return_hooker;

 	if (unlikely(ftrace_graph_is_dead()))
 		goto out;

 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		goto out;

 	return_hooker = ppc_function_entry(return_to_handler);

 	trace.func = ip;
 	trace.depth = current->curr_ret_stack + 1;

 	/* Only trace if the calling function expects to */
 	if (!ftrace_graph_entry(&trace))
 		goto out;

 	if (ftrace_push_return_trace(parent, ip, &trace.depth, 0,
 				     NULL) == -EBUSY)
 		goto out;

 	parent = return_hooker;
 out:
 	return parent;
 }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */

 #if defined(CONFIG_FTRACE_SYSCALLS) && defined(CONFIG_PPC64)
 unsigned long __init arch_syscall_addr(int nr)
 {
 	return sys_call_table[nr*2];
 }
 #endif /* CONFIG_FTRACE_SYSCALLS && CONFIG_PPC64 */

 #ifdef 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 /* PPC64_ELF_ABI_v1 */
	// 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/asm-prototypes.h>
	#include <asm/cacheflush.h>
	#include <asm/code-patching.h>
	#include <asm/ftrace.h>
	#include <asm/syscall.h>


	#ifdef CONFIG_DYNAMIC_FTRACE
	static unsigned int
	ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
	{
	unsigned int op;

	addr = ppc_function_entry((void *)addr);

	/* if (link) set op to 'bl' else 'b' */
	op = create_branch((unsigned int *)ip, addr, link ? 1 : 0);

	return op;
	}

	static int
	ftrace_modify_code(unsigned long ip, unsigned int old, unsigned int new)
	{
	unsigned int 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 (probe_kernel_read(&replaced, (void *)ip, MCOUNT_INSN_SIZE))
	return -EFAULT;

	/* Make sure it is what we expect it to be */
	if (replaced != old) {
	pr_err("%p: replaced (%#x) != old (%#x)",
	(void *)ip, replaced, old);
	return -EINVAL;
	}

	/* replace the text with the new text */
	if (patch_instruction((unsigned int *)ip, new))
	return -EPERM;

	return 0;
	}

	/*
	* 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);

	/* use the create_branch to verify that this offset can be branched */
	return create_branch((unsigned int *)ip, addr, 0);
	}

	#ifdef CONFIG_MODULES

	static int is_bl_op(unsigned int op)
	{
	return (op & 0xfc000003) == 0x48000001;
	}

	static unsigned long find_bl_target(unsigned long ip, unsigned int op)
	{
	static int offset;

	offset = (op & 0x03fffffc);
	/* make it signed */
	if (offset & 0x02000000)
	offset \|= 0xfe000000;

	return ip + (long)offset;
	}

	#ifdef CONFIG_PPC64
	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;
	unsigned int op, pop;

	/* read where this goes */
	if (probe_kernel_read(&op, (void *)ip, sizeof(int))) {
	pr_err("Fetching opcode failed.\n");
	return -EFAULT;
	}

	/* Make sure that that this is still a 24bit jump */
	if (!is_bl_op(op)) {
	pr_err("Not expected bl: opcode is %x\n", 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;
	}

	#ifdef CC_USING_MPROFILE_KERNEL
	/* When using -mkernel_profile there is no load to jump over */
	pop = PPC_INST_NOP;

	if (probe_kernel_read(&op, (void *)(ip - 4), 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 (op != PPC_INST_MFLR && op != PPC_INST_STD_LR) {
	pr_err("Unexpected instruction %08x around bl _mcount\n", op);
	return -EINVAL;
	}
	#else
	/*
	* 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.
	*/

	pop = PPC_INST_BRANCH \| 8; /* b +8 */

	/*
	* 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 (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE)) {
	pr_err("Fetching op failed.\n");
	return -EFAULT;
	}

	if (op != PPC_INST_LD_TOC) {
	pr_err("Expected %08x found %08x\n", PPC_INST_LD_TOC, op);
	return -EINVAL;
	}
	#endif /* CC_USING_MPROFILE_KERNEL */

	if (patch_instruction((unsigned int *)ip, pop)) {
	pr_err("Patching NOP failed.\n");
	return -EPERM;
	}

	return 0;
	}

	#else /* !PPC64 */
	static int
	__ftrace_make_nop(struct module *mod,
	struct dyn_ftrace *rec, unsigned long addr)
	{
	unsigned int op;
	unsigned int jmp[4];
	unsigned long ip = rec->ip;
	unsigned long tramp;

	if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
	return -EFAULT;

	/* Make sure that that this is still a 24bit jump */
	if (!is_bl_op(op)) {
	pr_err("Not expected bl: opcode is %x\n", op);
	return -EINVAL;
	}

	/* lets find where the pointer goes */
	tramp = find_bl_target(ip, op);

	/*
	* On PPC32 the trampoline looks like:
	* 0x3d, 0x80, 0x00, 0x00 lis r12,sym@ha
	* 0x39, 0x8c, 0x00, 0x00 addi r12,r12,sym@l
	* 0x7d, 0x89, 0x03, 0xa6 mtctr r12
	* 0x4e, 0x80, 0x04, 0x20 bctr
	*/

	pr_devel("ip:%lx jumps to %lx", ip, tramp);

	/* Find where the trampoline jumps to */
	if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
	pr_err("Failed to read %lx\n", tramp);
	return -EFAULT;
	}

	pr_devel(" %08x %08x ", jmp[0], jmp[1]);

	/* verify that this is what we expect it to be */
	if (((jmp[0] & 0xffff0000) != 0x3d800000) \|\|
	((jmp[1] & 0xffff0000) != 0x398c0000) \|\|
	(jmp[2] != 0x7d8903a6) \|\|
	(jmp[3] != 0x4e800420)) {
	pr_err("Not a trampoline\n");
	return -EINVAL;
	}

	tramp = (jmp[1] & 0xffff) \|
	((jmp[0] & 0xffff) << 16);
	if (tramp & 0x8000)
	tramp -= 0x10000;

	pr_devel(" %lx ", tramp);

	if (tramp != addr) {
	pr_err("Trampoline location %08lx does not match addr\n",
	tramp);
	return -EINVAL;
	}

	op = PPC_INST_NOP;

	if (patch_instruction((unsigned int *)ip, op))
	return -EPERM;

	return 0;
	}
	#endif /* PPC64 */
	#endif /* CONFIG_MODULES */

	int ftrace_make_nop(struct module *mod,
	struct dyn_ftrace *rec, unsigned long addr)
	{
	unsigned long ip = rec->ip;
	unsigned int 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_NOP;
	return ftrace_modify_code(ip, old, new);
	}

	#ifdef CONFIG_MODULES
	/*
	* 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);
	#else
	/* We should not get here without modules */
	return -EINVAL;
	#endif /* CONFIG_MODULES */
	}

	#ifdef CONFIG_MODULES
	#ifdef CONFIG_PPC64
	/*
	* 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.
	*/
	#ifndef CC_USING_MPROFILE_KERNEL
	static int
	expected_nop_sequence(void *ip, unsigned int op0, unsigned int op1)
	{
	/*
	* We expect to see:
	*
	* b +8
	* ld r2,XX(r1)
	*
	* The load offset is different depending on the ABI. For simplicity
	* just mask it out when doing the compare.
	*/
	if ((op0 != 0x48000008) \|\| ((op1 & 0xffff0000) != 0xe8410000))
	return 0;
	return 1;
	}
	#else
	static int
	expected_nop_sequence(void *ip, unsigned int op0, unsigned int op1)
	{
	/* look for patched "NOP" on ppc64 with -mprofile-kernel */
	if (op0 != PPC_INST_NOP)
	return 0;
	return 1;
	}
	#endif

	static int
	__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
	{
	unsigned int op[2];
	void ip = (void )rec->ip;

	/* read where this goes */
	if (probe_kernel_read(op, ip, sizeof(op)))
	return -EFAULT;

	if (!expected_nop_sequence(ip, op[0], op[1])) {
	pr_err("Unexpected call sequence at %p: %x %x\n",
	ip, op[0], op[1]);
	return -EINVAL;
	}

	/* If we never set up a trampoline to ftrace_caller, then bail */
	if (!rec->arch.mod->arch.tramp) {
	pr_err("No ftrace trampoline\n");
	return -EINVAL;
	}

	/* Ensure branch is within 24 bits */
	if (!create_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
	pr_err("Branch out of range\n");
	return -EINVAL;
	}

	if (patch_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
	pr_err("REL24 out of range!\n");
	return -EINVAL;
	}

	return 0;
	}

	#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
	int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
	unsigned long addr)
	{
	return ftrace_make_call(rec, addr);
	}
	#endif

	#else /* !CONFIG_PPC64: */
	static int
	__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
	{
	unsigned int op;
	unsigned long ip = rec->ip;

	/* read where this goes */
	if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
	return -EFAULT;

	/* It should be pointing to a nop */
	if (op != PPC_INST_NOP) {
	pr_err("Expected NOP but have %x\n", op);
	return -EINVAL;
	}

	/* If we never set up a trampoline to ftrace_caller, then bail */
	if (!rec->arch.mod->arch.tramp) {
	pr_err("No ftrace trampoline\n");
	return -EINVAL;
	}

	/* create the branch to the trampoline */
	op = create_branch((unsigned int *)ip,
	rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
	if (!op) {
	pr_err("REL24 out of range!\n");
	return -EINVAL;
	}

	pr_devel("write to %lx\n", rec->ip);

	if (patch_instruction((unsigned int *)ip, op))
	return -EPERM;

	return 0;
	}
	#endif /* CONFIG_PPC64 */
	#endif /* CONFIG_MODULES */

	int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
	{
	unsigned long ip = rec->ip;
	unsigned int 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_NOP;
	new = ftrace_call_replace(ip, addr, 1);
	return ftrace_modify_code(ip, old, new);
	}

	#ifdef CONFIG_MODULES
	/*
	* 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);
	#else
	/* We should not get here without modules */
	return -EINVAL;
	#endif /* CONFIG_MODULES */
	}

	int ftrace_update_ftrace_func(ftrace_func_t func)
	{
	unsigned long ip = (unsigned long)(&ftrace_call);
	unsigned int old, new;
	int ret;

	old = (unsigned int )&ftrace_call;
	new = ftrace_call_replace(ip, (unsigned long)func, 1);
	ret = ftrace_modify_code(ip, old, new);

	return ret;
	}

	static int __ftrace_replace_code(struct dyn_ftrace *rec, int enable)
	{
	unsigned long ftrace_addr = (unsigned long)FTRACE_ADDR;
	int ret;

	ret = ftrace_update_record(rec, enable);

	switch (ret) {
	case FTRACE_UPDATE_IGNORE:
	return 0;
	case FTRACE_UPDATE_MAKE_CALL:
	return ftrace_make_call(rec, ftrace_addr);
	case FTRACE_UPDATE_MAKE_NOP:
	return ftrace_make_nop(NULL, rec, ftrace_addr);
	}

	return 0;
	}

	void ftrace_replace_code(int enable)
	{
	struct ftrace_rec_iter *iter;
	struct dyn_ftrace *rec;
	int ret;

	for (iter = ftrace_rec_iter_start(); iter;
	iter = ftrace_rec_iter_next(iter)) {
	rec = ftrace_rec_iter_record(iter);
	ret = __ftrace_replace_code(rec, enable);
	if (ret) {
	ftrace_bug(ret, rec);
	return;
	}
	}
	}

	/*
	* Use the default ftrace_modify_all_code, but without
	* stop_machine().
	*/
	void arch_ftrace_update_code(int command)
	{
	ftrace_modify_all_code(command);
	}

	int __init ftrace_dyn_arch_init(void)
	{
	return 0;
	}
	#endif /* CONFIG_DYNAMIC_FTRACE */

	#ifdef CONFIG_FUNCTION_GRAPH_TRACER

	#ifdef CONFIG_DYNAMIC_FTRACE
	extern void ftrace_graph_call(void);
	extern void ftrace_graph_stub(void);

	int ftrace_enable_ftrace_graph_caller(void)
	{
	unsigned long ip = (unsigned long)(&ftrace_graph_call);
	unsigned long addr = (unsigned long)(&ftrace_graph_caller);
	unsigned long stub = (unsigned long)(&ftrace_graph_stub);
	unsigned int old, new;

	old = ftrace_call_replace(ip, stub, 0);
	new = ftrace_call_replace(ip, addr, 0);

	return ftrace_modify_code(ip, old, new);
	}

	int ftrace_disable_ftrace_graph_caller(void)
	{
	unsigned long ip = (unsigned long)(&ftrace_graph_call);
	unsigned long addr = (unsigned long)(&ftrace_graph_caller);
	unsigned long stub = (unsigned long)(&ftrace_graph_stub);
	unsigned int old, new;

	old = ftrace_call_replace(ip, addr, 0);
	new = ftrace_call_replace(ip, stub, 0);

	return ftrace_modify_code(ip, old, new);
	}
	#endif /* CONFIG_DYNAMIC_FTRACE */

	/*
	* 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.
	*/
	unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
	{
	struct ftrace_graph_ent trace;
	unsigned long return_hooker;

	if (unlikely(ftrace_graph_is_dead()))
	goto out;

	if (unlikely(atomic_read(&current->tracing_graph_pause)))
	goto out;

	return_hooker = ppc_function_entry(return_to_handler);

	trace.func = ip;
	trace.depth = current->curr_ret_stack + 1;

	/* Only trace if the calling function expects to */
	if (!ftrace_graph_entry(&trace))
	goto out;

	if (ftrace_push_return_trace(parent, ip, &trace.depth, 0,
	NULL) == -EBUSY)
	goto out;

	parent = return_hooker;
	out:
	return parent;
	}
	#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

	#if defined(CONFIG_FTRACE_SYSCALLS) && defined(CONFIG_PPC64)
	unsigned long __init arch_syscall_addr(int nr)
	{
	return sys_call_table[nr*2];
	}
	#endif /* CONFIG_FTRACE_SYSCALLS && CONFIG_PPC64 */

	#ifdef 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 /* PPC64_ELF_ABI_v1 */