arch/x86/kernel/ftrace.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Dynamic function tracing support.
  *
  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
  *
  * Thanks goes to Ingo Molnar, for suggesting the idea.
  * Mathieu Desnoyers, for suggesting postponing the modifications.
  * Arjan van de Ven, for keeping me straight, and explaining to me
  * the dangers of modifying code on the run.
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/spinlock.h>
 #include <linux/hardirq.h>
 #include <linux/uaccess.h>
 #include <linux/ftrace.h>
 #include <linux/percpu.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/memory.h>
 #include <linux/vmalloc.h>

 #include <trace/syscall.h>

 #include <asm/set_memory.h>
 #include <asm/kprobes.h>
 #include <asm/ftrace.h>
 #include <asm/nops.h>
 #include <asm/text-patching.h>

 #ifdef CONFIG_DYNAMIC_FTRACE

 static int ftrace_poke_late = 0;

 int ftrace_arch_code_modify_prepare(void)
     __acquires(&text_mutex)
 {
 	/*
 	 * Need to grab text_mutex to prevent a race from module loading
 	 * and live kernel patching from changing the text permissions while
 	 * ftrace has it set to "read/write".
 	 */
 	mutex_lock(&text_mutex);
 	ftrace_poke_late = 1;
 	return 0;
 }

 int ftrace_arch_code_modify_post_process(void)
     __releases(&text_mutex)
 {
 	/*
 	 * ftrace_make_{call,nop}() may be called during
 	 * module load, and we need to finish the text_poke_queue()
 	 * that they do, here.
 	 */
 	text_poke_finish();
 	ftrace_poke_late = 0;
 	mutex_unlock(&text_mutex);
 	return 0;
 }

 static const char *ftrace_nop_replace(void)
 {
 	return ideal_nops[NOP_ATOMIC5];
 }

 static const char *ftrace_call_replace(unsigned long ip, unsigned long addr)
 {
 	return text_gen_insn(CALL_INSN_OPCODE, (void *)ip, (void *)addr);
 }

 static int ftrace_verify_code(unsigned long ip, const char *old_code)
 {
 	char cur_code[MCOUNT_INSN_SIZE];

 	/*
 	 * 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_from_kernel_nofault(cur_code, (void *)ip, MCOUNT_INSN_SIZE)) {
 		WARN_ON(1);
 		return -EFAULT;
 	}

 	/* Make sure it is what we expect it to be */
 	if (memcmp(cur_code, old_code, MCOUNT_INSN_SIZE) != 0) {
 		WARN_ON(1);
 		return -EINVAL;
 	}

 	return 0;
 }

 /*
  * Marked __ref because it calls text_poke_early() which is .init.text. That is
  * ok because that call will happen early, during boot, when .init sections are
  * still present.
  */
 static int __ref
 ftrace_modify_code_direct(unsigned long ip, const char *old_code,
 			  const char *new_code)
 {
 	int ret = ftrace_verify_code(ip, old_code);
 	if (ret)
 		return ret;

 	/* replace the text with the new text */
 	if (ftrace_poke_late)
 		text_poke_queue((void *)ip, new_code, MCOUNT_INSN_SIZE, NULL);
 	else
 		text_poke_early((void *)ip, new_code, MCOUNT_INSN_SIZE);
 	return 0;
 }

 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned long ip = rec->ip;
 	const char *new, *old;

 	old = ftrace_call_replace(ip, addr);
 	new = ftrace_nop_replace();

 	/*
 	 * On boot up, and when modules are loaded, the MCOUNT_ADDR
 	 * is converted to a nop, and will never become MCOUNT_ADDR
 	 * again. This code is either running before SMP (on boot up)
 	 * or before the code will ever be executed (module load).
 	 * We do not want to use the breakpoint version in this case,
 	 * just modify the code directly.
 	 */
 	if (addr == MCOUNT_ADDR)
 		return ftrace_modify_code_direct(ip, old, new);

 	/*
 	 * x86 overrides ftrace_replace_code -- this function will never be used
 	 * in this case.
 	 */
 	WARN_ONCE(1, "invalid use of ftrace_make_nop");
 	return -EINVAL;
 }

 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned long ip = rec->ip;
 	const char *new, *old;

 	old = ftrace_nop_replace();
 	new = ftrace_call_replace(ip, addr);

 	/* Should only be called when module is loaded */
 	return ftrace_modify_code_direct(rec->ip, old, new);
 }

 /*
  * Should never be called:
  *  As it is only called by __ftrace_replace_code() which is called by
  *  ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
  *  which is called to turn mcount into nops or nops into function calls
  *  but not to convert a function from not using regs to one that uses
  *  regs, which ftrace_modify_call() is for.
  */
 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 				 unsigned long addr)
 {
 	WARN_ON(1);
 	return -EINVAL;
 }

 int ftrace_update_ftrace_func(ftrace_func_t func)
 {
 	unsigned long ip;
 	const char *new;

 	ip = (unsigned long)(&ftrace_call);
 	new = ftrace_call_replace(ip, (unsigned long)func);
 	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);

 	ip = (unsigned long)(&ftrace_regs_call);
 	new = ftrace_call_replace(ip, (unsigned long)func);
 	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);

 	return 0;
 }

 void ftrace_replace_code(int enable)
 {
 	struct ftrace_rec_iter *iter;
 	struct dyn_ftrace *rec;
 	const char *new, *old;
 	int ret;

 	for_ftrace_rec_iter(iter) {
 		rec = ftrace_rec_iter_record(iter);

 		switch (ftrace_test_record(rec, enable)) {
 		case FTRACE_UPDATE_IGNORE:
 		default:
 			continue;

 		case FTRACE_UPDATE_MAKE_CALL:
 			old = ftrace_nop_replace();
 			break;

 		case FTRACE_UPDATE_MODIFY_CALL:
 		case FTRACE_UPDATE_MAKE_NOP:
 			old = ftrace_call_replace(rec->ip, ftrace_get_addr_curr(rec));
 			break;
 		}

 		ret = ftrace_verify_code(rec->ip, old);
 		if (ret) {
 			ftrace_bug(ret, rec);
 			return;
 		}
 	}

 	for_ftrace_rec_iter(iter) {
 		rec = ftrace_rec_iter_record(iter);

 		switch (ftrace_test_record(rec, enable)) {
 		case FTRACE_UPDATE_IGNORE:
 		default:
 			continue;

 		case FTRACE_UPDATE_MAKE_CALL:
 		case FTRACE_UPDATE_MODIFY_CALL:
 			new = ftrace_call_replace(rec->ip, ftrace_get_addr_new(rec));
 			break;

 		case FTRACE_UPDATE_MAKE_NOP:
 			new = ftrace_nop_replace();
 			break;
 		}

 		text_poke_queue((void *)rec->ip, new, MCOUNT_INSN_SIZE, NULL);
 		ftrace_update_record(rec, enable);
 	}
 	text_poke_finish();
 }

 void arch_ftrace_update_code(int command)
 {
 	ftrace_modify_all_code(command);
 }

 int __init ftrace_dyn_arch_init(void)
 {
 	return 0;
 }

 /* Currently only x86_64 supports dynamic trampolines */
 #ifdef CONFIG_X86_64

 #ifdef CONFIG_MODULES
 #include <linux/moduleloader.h>
 /* Module allocation simplifies allocating memory for code */
 static inline void *alloc_tramp(unsigned long size)
 {
 	return module_alloc(size);
 }
 static inline void tramp_free(void *tramp)
 {
 	module_memfree(tramp);
 }
 #else
 /* Trampolines can only be created if modules are supported */
 static inline void *alloc_tramp(unsigned long size)
 {
 	return NULL;
 }
 static inline void tramp_free(void *tramp) { }
 #endif

 /* Defined as markers to the end of the ftrace default trampolines */
 extern void ftrace_regs_caller_end(void);
 extern void ftrace_regs_caller_ret(void);
 extern void ftrace_caller_end(void);
 extern void ftrace_caller_op_ptr(void);
 extern void ftrace_regs_caller_op_ptr(void);

 /* movq function_trace_op(%rip), %rdx */
 /* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
 #define OP_REF_SIZE	7

 /*
  * The ftrace_ops is passed to the function callback. Since the
  * trampoline only services a single ftrace_ops, we can pass in
  * that ops directly.
  *
  * The ftrace_op_code_union is used to create a pointer to the
  * ftrace_ops that will be passed to the callback function.
  */
 union ftrace_op_code_union {
 	char code[OP_REF_SIZE];
 	struct {
 		char op[3];
 		int offset;
 	} __attribute__((packed));
 };

 #define RET_SIZE		1

 static unsigned long
 create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
 {
 	unsigned long start_offset;
 	unsigned long end_offset;
 	unsigned long op_offset;
 	unsigned long call_offset;
 	unsigned long offset;
 	unsigned long npages;
 	unsigned long size;
 	unsigned long retq;
 	unsigned long *ptr;
 	void *trampoline;
 	void *ip;
 	/* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
 	unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
 	union ftrace_op_code_union op_ptr;
 	int ret;

 	if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
 		start_offset = (unsigned long)ftrace_regs_caller;
 		end_offset = (unsigned long)ftrace_regs_caller_end;
 		op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
 		call_offset = (unsigned long)ftrace_regs_call;
 	} else {
 		start_offset = (unsigned long)ftrace_caller;
 		end_offset = (unsigned long)ftrace_caller_end;
 		op_offset = (unsigned long)ftrace_caller_op_ptr;
 		call_offset = (unsigned long)ftrace_call;
 	}

 	size = end_offset - start_offset;

 	/*
 	 * Allocate enough size to store the ftrace_caller code,
 	 * the iret , as well as the address of the ftrace_ops this
 	 * trampoline is used for.
 	 */
 	trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *));
 	if (!trampoline)
 		return 0;

 	*tramp_size = size + RET_SIZE + sizeof(void *);
 	npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);

 	/* Copy ftrace_caller onto the trampoline memory */
 	ret = copy_from_kernel_nofault(trampoline, (void *)start_offset, size);
 	if (WARN_ON(ret < 0))
 		goto fail;

 	ip = trampoline + size;

 	/* The trampoline ends with ret(q) */
 	retq = (unsigned long)ftrace_stub;
 	ret = copy_from_kernel_nofault(ip, (void *)retq, RET_SIZE);
 	if (WARN_ON(ret < 0))
 		goto fail;

 	if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
 		ip = trampoline + (ftrace_regs_caller_ret - ftrace_regs_caller);
 		ret = copy_from_kernel_nofault(ip, (void *)retq, RET_SIZE);
 		if (WARN_ON(ret < 0))
 			goto fail;
 	}

 	/*
 	 * The address of the ftrace_ops that is used for this trampoline
 	 * is stored at the end of the trampoline. This will be used to
 	 * load the third parameter for the callback. Basically, that
 	 * location at the end of the trampoline takes the place of
 	 * the global function_trace_op variable.
 	 */

 	ptr = (unsigned long *)(trampoline + size + RET_SIZE);
 	*ptr = (unsigned long)ops;

 	op_offset -= start_offset;
 	memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);

 	/* Are we pointing to the reference? */
 	if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0))
 		goto fail;

 	/* Load the contents of ptr into the callback parameter */
 	offset = (unsigned long)ptr;
 	offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;

 	op_ptr.offset = offset;

 	/* put in the new offset to the ftrace_ops */
 	memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);

 	/* put in the call to the function */
 	mutex_lock(&text_mutex);
 	call_offset -= start_offset;
 	memcpy(trampoline + call_offset,
 	       text_gen_insn(CALL_INSN_OPCODE,
 			     trampoline + call_offset,
 			     ftrace_ops_get_func(ops)), CALL_INSN_SIZE);
 	mutex_unlock(&text_mutex);

 	/* ALLOC_TRAMP flags lets us know we created it */
 	ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;

 	set_vm_flush_reset_perms(trampoline);

 	if (likely(system_state != SYSTEM_BOOTING))
 		set_memory_ro((unsigned long)trampoline, npages);
 	set_memory_x((unsigned long)trampoline, npages);
 	return (unsigned long)trampoline;
 fail:
 	tramp_free(trampoline);
 	return 0;
 }

 void set_ftrace_ops_ro(void)
 {
 	struct ftrace_ops *ops;
 	unsigned long start_offset;
 	unsigned long end_offset;
 	unsigned long npages;
 	unsigned long size;

 	do_for_each_ftrace_op(ops, ftrace_ops_list) {
 		if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
 			continue;

 		if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
 			start_offset = (unsigned long)ftrace_regs_caller;
 			end_offset = (unsigned long)ftrace_regs_caller_end;
 		} else {
 			start_offset = (unsigned long)ftrace_caller;
 			end_offset = (unsigned long)ftrace_caller_end;
 		}
 		size = end_offset - start_offset;
 		size = size + RET_SIZE + sizeof(void *);
 		npages = DIV_ROUND_UP(size, PAGE_SIZE);
 		set_memory_ro((unsigned long)ops->trampoline, npages);
 	} while_for_each_ftrace_op(ops);
 }

 static unsigned long calc_trampoline_call_offset(bool save_regs)
 {
 	unsigned long start_offset;
 	unsigned long call_offset;

 	if (save_regs) {
 		start_offset = (unsigned long)ftrace_regs_caller;
 		call_offset = (unsigned long)ftrace_regs_call;
 	} else {
 		start_offset = (unsigned long)ftrace_caller;
 		call_offset = (unsigned long)ftrace_call;
 	}

 	return call_offset - start_offset;
 }

 void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
 {
 	ftrace_func_t func;
 	unsigned long offset;
 	unsigned long ip;
 	unsigned int size;
 	const char *new;

 	if (!ops->trampoline) {
 		ops->trampoline = create_trampoline(ops, &size);
 		if (!ops->trampoline)
 			return;
 		ops->trampoline_size = size;
 		return;
 	}

 	/*
 	 * The ftrace_ops caller may set up its own trampoline.
 	 * In such a case, this code must not modify it.
 	 */
 	if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
 		return;

 	offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
 	ip = ops->trampoline + offset;
 	func = ftrace_ops_get_func(ops);

 	mutex_lock(&text_mutex);
 	/* Do a safe modify in case the trampoline is executing */
 	new = ftrace_call_replace(ip, (unsigned long)func);
 	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
 	mutex_unlock(&text_mutex);
 }

 /* Return the address of the function the trampoline calls */
 static void *addr_from_call(void *ptr)
 {
 	union text_poke_insn call;
 	int ret;

 	ret = copy_from_kernel_nofault(&call, ptr, CALL_INSN_SIZE);
 	if (WARN_ON_ONCE(ret < 0))
 		return NULL;

 	/* Make sure this is a call */
 	if (WARN_ON_ONCE(call.opcode != CALL_INSN_OPCODE)) {
 		pr_warn("Expected E8, got %x\n", call.opcode);
 		return NULL;
 	}

 	return ptr + CALL_INSN_SIZE + call.disp;
 }

 void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
 			   unsigned long frame_pointer);

 /*
  * If the ops->trampoline was not allocated, then it probably
  * has a static trampoline func, or is the ftrace caller itself.
  */
 static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
 {
 	unsigned long offset;
 	bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
 	void *ptr;

 	if (ops && ops->trampoline) {
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 		/*
 		 * We only know about function graph tracer setting as static
 		 * trampoline.
 		 */
 		if (ops->trampoline == FTRACE_GRAPH_ADDR)
 			return (void *)prepare_ftrace_return;
 #endif
 		return NULL;
 	}

 	offset = calc_trampoline_call_offset(save_regs);

 	if (save_regs)
 		ptr = (void *)FTRACE_REGS_ADDR + offset;
 	else
 		ptr = (void *)FTRACE_ADDR + offset;

 	return addr_from_call(ptr);
 }

 void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
 {
 	unsigned long offset;

 	/* If we didn't allocate this trampoline, consider it static */
 	if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
 		return static_tramp_func(ops, rec);

 	offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
 	return addr_from_call((void *)ops->trampoline + offset);
 }

 void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
 {
 	if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
 		return;

 	tramp_free((void *)ops->trampoline);
 	ops->trampoline = 0;
 }

 #endif /* CONFIG_X86_64 */
 #endif /* CONFIG_DYNAMIC_FTRACE */

 #ifdef CONFIG_FUNCTION_GRAPH_TRACER

 #ifdef CONFIG_DYNAMIC_FTRACE
 extern void ftrace_graph_call(void);

 static const char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
 {
 	return text_gen_insn(JMP32_INSN_OPCODE, (void *)ip, (void *)addr);
 }

 static int ftrace_mod_jmp(unsigned long ip, void *func)
 {
 	const char *new;

 	new = ftrace_jmp_replace(ip, (unsigned long)func);
 	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
 	return 0;
 }

 int ftrace_enable_ftrace_graph_caller(void)
 {
 	unsigned long ip = (unsigned long)(&ftrace_graph_call);

 	return ftrace_mod_jmp(ip, &ftrace_graph_caller);
 }

 int ftrace_disable_ftrace_graph_caller(void)
 {
 	unsigned long ip = (unsigned long)(&ftrace_graph_call);

 	return ftrace_mod_jmp(ip, &ftrace_stub);
 }

 #endif /* !CONFIG_DYNAMIC_FTRACE */

 /*
  * Hook the return address and push it in the stack of return addrs
  * in current thread info.
  */
 void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
 			   unsigned long frame_pointer)
 {
 	unsigned long return_hooker = (unsigned long)&return_to_handler;
 	unsigned long old;
 	int faulted;

 	/*
 	 * When resuming from suspend-to-ram, this function can be indirectly
 	 * called from early CPU startup code while the CPU is in real mode,
 	 * which would fail miserably.  Make sure the stack pointer is a
 	 * virtual address.
 	 *
 	 * This check isn't as accurate as virt_addr_valid(), but it should be
 	 * good enough for this purpose, and it's fast.
 	 */
 	if (unlikely((long)__builtin_frame_address(0) >= 0))
 		return;

 	if (unlikely(ftrace_graph_is_dead()))
 		return;

 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		return;

 	/*
 	 * Protect against fault, even if it shouldn't
 	 * happen. This tool is too much intrusive to
 	 * ignore such a protection.
 	 */
 	asm volatile(
 		"1: " _ASM_MOV " (%[parent]), %[old]\n"
 		"2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
 		"   movl $0, %[faulted]\n"
 		"3:\n"

 		".section .fixup, \"ax\"\n"
 		"4: movl $1, %[faulted]\n"
 		"   jmp 3b\n"
 		".previous\n"

 		_ASM_EXTABLE(1b, 4b)
 		_ASM_EXTABLE(2b, 4b)

 		: [old] "=&r" (old), [faulted] "=r" (faulted)
 		: [parent] "r" (parent), [return_hooker] "r" (return_hooker)
 		: "memory"
 	);

 	if (unlikely(faulted)) {
 		ftrace_graph_stop();
 		WARN_ON(1);
 		return;
 	}

 	if (function_graph_enter(old, self_addr, frame_pointer, parent))
 		*parent = old;
 }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Dynamic function tracing support.
	*
	* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
	*
	* Thanks goes to Ingo Molnar, for suggesting the idea.
	* Mathieu Desnoyers, for suggesting postponing the modifications.
	* Arjan van de Ven, for keeping me straight, and explaining to me
	* the dangers of modifying code on the run.
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/spinlock.h>
	#include <linux/hardirq.h>
	#include <linux/uaccess.h>
	#include <linux/ftrace.h>
	#include <linux/percpu.h>
	#include <linux/sched.h>
	#include <linux/slab.h>
	#include <linux/init.h>
	#include <linux/list.h>
	#include <linux/module.h>
	#include <linux/memory.h>
	#include <linux/vmalloc.h>

	#include <trace/syscall.h>

	#include <asm/set_memory.h>
	#include <asm/kprobes.h>
	#include <asm/ftrace.h>
	#include <asm/nops.h>
	#include <asm/text-patching.h>

	#ifdef CONFIG_DYNAMIC_FTRACE

	static int ftrace_poke_late = 0;

	int ftrace_arch_code_modify_prepare(void)
	__acquires(&text_mutex)
	{
	/*
	* Need to grab text_mutex to prevent a race from module loading
	* and live kernel patching from changing the text permissions while
	* ftrace has it set to "read/write".
	*/
	mutex_lock(&text_mutex);
	ftrace_poke_late = 1;
	return 0;
	}

	int ftrace_arch_code_modify_post_process(void)
	__releases(&text_mutex)
	{
	/*
	* ftrace_make_{call,nop}() may be called during
	* module load, and we need to finish the text_poke_queue()
	* that they do, here.
	*/
	text_poke_finish();
	ftrace_poke_late = 0;
	mutex_unlock(&text_mutex);
	return 0;
	}

	static const char *ftrace_nop_replace(void)
	{
	return ideal_nops[NOP_ATOMIC5];
	}

	static const char *ftrace_call_replace(unsigned long ip, unsigned long addr)
	{
	return text_gen_insn(CALL_INSN_OPCODE, (void )ip, (void )addr);
	}

	static int ftrace_verify_code(unsigned long ip, const char *old_code)
	{
	char cur_code[MCOUNT_INSN_SIZE];

	/*
	* 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_from_kernel_nofault(cur_code, (void *)ip, MCOUNT_INSN_SIZE)) {
	WARN_ON(1);
	return -EFAULT;
	}

	/* Make sure it is what we expect it to be */
	if (memcmp(cur_code, old_code, MCOUNT_INSN_SIZE) != 0) {
	WARN_ON(1);
	return -EINVAL;
	}

	return 0;
	}

	/*
	* Marked __ref because it calls text_poke_early() which is .init.text. That is
	* ok because that call will happen early, during boot, when .init sections are
	* still present.
	*/
	static int __ref
	ftrace_modify_code_direct(unsigned long ip, const char *old_code,
	const char *new_code)
	{
	int ret = ftrace_verify_code(ip, old_code);
	if (ret)
	return ret;

	/* replace the text with the new text */
	if (ftrace_poke_late)
	text_poke_queue((void *)ip, new_code, MCOUNT_INSN_SIZE, NULL);
	else
	text_poke_early((void *)ip, new_code, MCOUNT_INSN_SIZE);
	return 0;
	}

	int ftrace_make_nop(struct module mod, struct dyn_ftrace rec, unsigned long addr)
	{
	unsigned long ip = rec->ip;
	const char new, old;

	old = ftrace_call_replace(ip, addr);
	new = ftrace_nop_replace();

	/*
	* On boot up, and when modules are loaded, the MCOUNT_ADDR
	* is converted to a nop, and will never become MCOUNT_ADDR
	* again. This code is either running before SMP (on boot up)
	* or before the code will ever be executed (module load).
	* We do not want to use the breakpoint version in this case,
	* just modify the code directly.
	*/
	if (addr == MCOUNT_ADDR)
	return ftrace_modify_code_direct(ip, old, new);

	/*
	* x86 overrides ftrace_replace_code -- this function will never be used
	* in this case.
	*/
	WARN_ONCE(1, "invalid use of ftrace_make_nop");
	return -EINVAL;
	}

	int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
	{
	unsigned long ip = rec->ip;
	const char new, old;

	old = ftrace_nop_replace();
	new = ftrace_call_replace(ip, addr);

	/* Should only be called when module is loaded */
	return ftrace_modify_code_direct(rec->ip, old, new);
	}

	/*
	* Should never be called:
	* As it is only called by __ftrace_replace_code() which is called by
	* ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
	* which is called to turn mcount into nops or nops into function calls
	* but not to convert a function from not using regs to one that uses
	* regs, which ftrace_modify_call() is for.
	*/
	int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
	unsigned long addr)
	{
	WARN_ON(1);
	return -EINVAL;
	}

	int ftrace_update_ftrace_func(ftrace_func_t func)
	{
	unsigned long ip;
	const char *new;

	ip = (unsigned long)(&ftrace_call);
	new = ftrace_call_replace(ip, (unsigned long)func);
	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);

	ip = (unsigned long)(&ftrace_regs_call);
	new = ftrace_call_replace(ip, (unsigned long)func);
	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);

	return 0;
	}

	void ftrace_replace_code(int enable)
	{
	struct ftrace_rec_iter *iter;
	struct dyn_ftrace *rec;
	const char new, old;
	int ret;

	for_ftrace_rec_iter(iter) {
	rec = ftrace_rec_iter_record(iter);

	switch (ftrace_test_record(rec, enable)) {
	case FTRACE_UPDATE_IGNORE:
	default:
	continue;

	case FTRACE_UPDATE_MAKE_CALL:
	old = ftrace_nop_replace();
	break;

	case FTRACE_UPDATE_MODIFY_CALL:
	case FTRACE_UPDATE_MAKE_NOP:
	old = ftrace_call_replace(rec->ip, ftrace_get_addr_curr(rec));
	break;
	}

	ret = ftrace_verify_code(rec->ip, old);
	if (ret) {
	ftrace_bug(ret, rec);
	return;
	}
	}

	for_ftrace_rec_iter(iter) {
	rec = ftrace_rec_iter_record(iter);

	switch (ftrace_test_record(rec, enable)) {
	case FTRACE_UPDATE_IGNORE:
	default:
	continue;

	case FTRACE_UPDATE_MAKE_CALL:
	case FTRACE_UPDATE_MODIFY_CALL:
	new = ftrace_call_replace(rec->ip, ftrace_get_addr_new(rec));
	break;

	case FTRACE_UPDATE_MAKE_NOP:
	new = ftrace_nop_replace();
	break;
	}

	text_poke_queue((void *)rec->ip, new, MCOUNT_INSN_SIZE, NULL);
	ftrace_update_record(rec, enable);
	}
	text_poke_finish();
	}

	void arch_ftrace_update_code(int command)
	{
	ftrace_modify_all_code(command);
	}

	int __init ftrace_dyn_arch_init(void)
	{
	return 0;
	}

	/* Currently only x86_64 supports dynamic trampolines */
	#ifdef CONFIG_X86_64

	#ifdef CONFIG_MODULES
	#include <linux/moduleloader.h>
	/* Module allocation simplifies allocating memory for code */
	static inline void *alloc_tramp(unsigned long size)
	{
	return module_alloc(size);
	}
	static inline void tramp_free(void *tramp)
	{
	module_memfree(tramp);
	}
	#else
	/* Trampolines can only be created if modules are supported */
	static inline void *alloc_tramp(unsigned long size)
	{
	return NULL;
	}
	static inline void tramp_free(void *tramp) { }
	#endif

	/* Defined as markers to the end of the ftrace default trampolines */
	extern void ftrace_regs_caller_end(void);
	extern void ftrace_regs_caller_ret(void);
	extern void ftrace_caller_end(void);
	extern void ftrace_caller_op_ptr(void);
	extern void ftrace_regs_caller_op_ptr(void);

	/* movq function_trace_op(%rip), %rdx */
	/* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
	#define OP_REF_SIZE 7

	/*
	* The ftrace_ops is passed to the function callback. Since the
	* trampoline only services a single ftrace_ops, we can pass in
	* that ops directly.
	*
	* The ftrace_op_code_union is used to create a pointer to the
	* ftrace_ops that will be passed to the callback function.
	*/
	union ftrace_op_code_union {
	char code[OP_REF_SIZE];
	struct {
	char op[3];
	int offset;
	} __attribute__((packed));
	};

	#define RET_SIZE 1

	static unsigned long
	create_trampoline(struct ftrace_ops ops, unsigned int tramp_size)
	{
	unsigned long start_offset;
	unsigned long end_offset;
	unsigned long op_offset;
	unsigned long call_offset;
	unsigned long offset;
	unsigned long npages;
	unsigned long size;
	unsigned long retq;
	unsigned long *ptr;
	void *trampoline;
	void *ip;
	/* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
	unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
	union ftrace_op_code_union op_ptr;
	int ret;

	if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
	start_offset = (unsigned long)ftrace_regs_caller;
	end_offset = (unsigned long)ftrace_regs_caller_end;
	op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
	call_offset = (unsigned long)ftrace_regs_call;
	} else {
	start_offset = (unsigned long)ftrace_caller;
	end_offset = (unsigned long)ftrace_caller_end;
	op_offset = (unsigned long)ftrace_caller_op_ptr;
	call_offset = (unsigned long)ftrace_call;
	}

	size = end_offset - start_offset;

	/*
	* Allocate enough size to store the ftrace_caller code,
	* the iret , as well as the address of the ftrace_ops this
	* trampoline is used for.
	*/
	trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *));
	if (!trampoline)
	return 0;

	tramp_size = size + RET_SIZE + sizeof(void );
	npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);

	/* Copy ftrace_caller onto the trampoline memory */
	ret = copy_from_kernel_nofault(trampoline, (void *)start_offset, size);
	if (WARN_ON(ret < 0))
	goto fail;

	ip = trampoline + size;

	/* The trampoline ends with ret(q) */
	retq = (unsigned long)ftrace_stub;
	ret = copy_from_kernel_nofault(ip, (void *)retq, RET_SIZE);
	if (WARN_ON(ret < 0))
	goto fail;

	if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
	ip = trampoline + (ftrace_regs_caller_ret - ftrace_regs_caller);
	ret = copy_from_kernel_nofault(ip, (void *)retq, RET_SIZE);
	if (WARN_ON(ret < 0))
	goto fail;
	}

	/*
	* The address of the ftrace_ops that is used for this trampoline
	* is stored at the end of the trampoline. This will be used to
	* load the third parameter for the callback. Basically, that
	* location at the end of the trampoline takes the place of
	* the global function_trace_op variable.
	*/

	ptr = (unsigned long *)(trampoline + size + RET_SIZE);
	*ptr = (unsigned long)ops;

	op_offset -= start_offset;
	memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);

	/* Are we pointing to the reference? */
	if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0))
	goto fail;

	/* Load the contents of ptr into the callback parameter */
	offset = (unsigned long)ptr;
	offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;

	op_ptr.offset = offset;

	/* put in the new offset to the ftrace_ops */
	memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);

	/* put in the call to the function */
	mutex_lock(&text_mutex);
	call_offset -= start_offset;
	memcpy(trampoline + call_offset,
	text_gen_insn(CALL_INSN_OPCODE,
	trampoline + call_offset,
	ftrace_ops_get_func(ops)), CALL_INSN_SIZE);
	mutex_unlock(&text_mutex);

	/* ALLOC_TRAMP flags lets us know we created it */
	ops->flags \|= FTRACE_OPS_FL_ALLOC_TRAMP;

	set_vm_flush_reset_perms(trampoline);

	if (likely(system_state != SYSTEM_BOOTING))
	set_memory_ro((unsigned long)trampoline, npages);
	set_memory_x((unsigned long)trampoline, npages);
	return (unsigned long)trampoline;
	fail:
	tramp_free(trampoline);
	return 0;
	}

	void set_ftrace_ops_ro(void)
	{
	struct ftrace_ops *ops;
	unsigned long start_offset;
	unsigned long end_offset;
	unsigned long npages;
	unsigned long size;

	do_for_each_ftrace_op(ops, ftrace_ops_list) {
	if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
	continue;

	if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
	start_offset = (unsigned long)ftrace_regs_caller;
	end_offset = (unsigned long)ftrace_regs_caller_end;
	} else {
	start_offset = (unsigned long)ftrace_caller;
	end_offset = (unsigned long)ftrace_caller_end;
	}
	size = end_offset - start_offset;
	size = size + RET_SIZE + sizeof(void *);
	npages = DIV_ROUND_UP(size, PAGE_SIZE);
	set_memory_ro((unsigned long)ops->trampoline, npages);
	} while_for_each_ftrace_op(ops);
	}

	static unsigned long calc_trampoline_call_offset(bool save_regs)
	{
	unsigned long start_offset;
	unsigned long call_offset;

	if (save_regs) {
	start_offset = (unsigned long)ftrace_regs_caller;
	call_offset = (unsigned long)ftrace_regs_call;
	} else {
	start_offset = (unsigned long)ftrace_caller;
	call_offset = (unsigned long)ftrace_call;
	}

	return call_offset - start_offset;
	}

	void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
	{
	ftrace_func_t func;
	unsigned long offset;
	unsigned long ip;
	unsigned int size;
	const char *new;

	if (!ops->trampoline) {
	ops->trampoline = create_trampoline(ops, &size);
	if (!ops->trampoline)
	return;
	ops->trampoline_size = size;
	return;
	}

	/*
	* The ftrace_ops caller may set up its own trampoline.
	* In such a case, this code must not modify it.
	*/
	if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
	return;

	offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
	ip = ops->trampoline + offset;
	func = ftrace_ops_get_func(ops);

	mutex_lock(&text_mutex);
	/* Do a safe modify in case the trampoline is executing */
	new = ftrace_call_replace(ip, (unsigned long)func);
	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
	mutex_unlock(&text_mutex);
	}

	/* Return the address of the function the trampoline calls */
	static void addr_from_call(void ptr)
	{
	union text_poke_insn call;
	int ret;

	ret = copy_from_kernel_nofault(&call, ptr, CALL_INSN_SIZE);
	if (WARN_ON_ONCE(ret < 0))
	return NULL;

	/* Make sure this is a call */
	if (WARN_ON_ONCE(call.opcode != CALL_INSN_OPCODE)) {
	pr_warn("Expected E8, got %x\n", call.opcode);
	return NULL;
	}

	return ptr + CALL_INSN_SIZE + call.disp;
	}

	void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
	unsigned long frame_pointer);

	/*
	* If the ops->trampoline was not allocated, then it probably
	* has a static trampoline func, or is the ftrace caller itself.
	*/
	static void static_tramp_func(struct ftrace_ops ops, struct dyn_ftrace *rec)
	{
	unsigned long offset;
	bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
	void *ptr;

	if (ops && ops->trampoline) {
	#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	/*
	* We only know about function graph tracer setting as static
	* trampoline.
	*/
	if (ops->trampoline == FTRACE_GRAPH_ADDR)
	return (void *)prepare_ftrace_return;
	#endif
	return NULL;
	}

	offset = calc_trampoline_call_offset(save_regs);

	if (save_regs)
	ptr = (void *)FTRACE_REGS_ADDR + offset;
	else
	ptr = (void *)FTRACE_ADDR + offset;

	return addr_from_call(ptr);
	}

	void arch_ftrace_trampoline_func(struct ftrace_ops ops, struct dyn_ftrace *rec)
	{
	unsigned long offset;

	/* If we didn't allocate this trampoline, consider it static */
	if (!ops \|\| !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
	return static_tramp_func(ops, rec);

	offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
	return addr_from_call((void *)ops->trampoline + offset);
	}

	void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
	{
	if (!ops \|\| !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
	return;

	tramp_free((void *)ops->trampoline);
	ops->trampoline = 0;
	}

	#endif /* CONFIG_X86_64 */
	#endif /* CONFIG_DYNAMIC_FTRACE */

	#ifdef CONFIG_FUNCTION_GRAPH_TRACER

	#ifdef CONFIG_DYNAMIC_FTRACE
	extern void ftrace_graph_call(void);

	static const char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
	{
	return text_gen_insn(JMP32_INSN_OPCODE, (void )ip, (void )addr);
	}

	static int ftrace_mod_jmp(unsigned long ip, void *func)
	{
	const char *new;

	new = ftrace_jmp_replace(ip, (unsigned long)func);
	text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
	return 0;
	}

	int ftrace_enable_ftrace_graph_caller(void)
	{
	unsigned long ip = (unsigned long)(&ftrace_graph_call);

	return ftrace_mod_jmp(ip, &ftrace_graph_caller);
	}

	int ftrace_disable_ftrace_graph_caller(void)
	{
	unsigned long ip = (unsigned long)(&ftrace_graph_call);

	return ftrace_mod_jmp(ip, &ftrace_stub);
	}

	#endif /* !CONFIG_DYNAMIC_FTRACE */

	/*
	* Hook the return address and push it in the stack of return addrs
	* in current thread info.
	*/
	void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
	unsigned long frame_pointer)
	{
	unsigned long return_hooker = (unsigned long)&return_to_handler;
	unsigned long old;
	int faulted;

	/*
	* When resuming from suspend-to-ram, this function can be indirectly
	* called from early CPU startup code while the CPU is in real mode,
	* which would fail miserably. Make sure the stack pointer is a
	* virtual address.
	*
	* This check isn't as accurate as virt_addr_valid(), but it should be
	* good enough for this purpose, and it's fast.
	*/
	if (unlikely((long)__builtin_frame_address(0) >= 0))
	return;

	if (unlikely(ftrace_graph_is_dead()))
	return;

	if (unlikely(atomic_read(&current->tracing_graph_pause)))
	return;

	/*
	* Protect against fault, even if it shouldn't
	* happen. This tool is too much intrusive to
	* ignore such a protection.
	*/
	asm volatile(
	"1: " _ASM_MOV " (%[parent]), %[old]\n"
	"2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
	" movl $0, %[faulted]\n"
	"3:\n"

	".section .fixup, \"ax\"\n"
	"4: movl $1, %[faulted]\n"
	" jmp 3b\n"
	".previous\n"

	_ASM_EXTABLE(1b, 4b)
	_ASM_EXTABLE(2b, 4b)

	: [old] "=&r" (old), [faulted] "=r" (faulted)
	: [parent] "r" (parent), [return_hooker] "r" (return_hooker)
	: "memory"
	);

	if (unlikely(faulted)) {
	ftrace_graph_stop();
	WARN_ON(1);
	return;
	}

	if (function_graph_enter(old, self_addr, frame_pointer, parent))
	*parent = old;
	}
	#endif /* CONFIG_FUNCTION_GRAPH_TRACER */