- 根目录:
- arch
- x86
- kernel
- ftrace.c
/*
* Code for replacing ftrace calls with jumps.
*
* 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 <trace/syscall.h>
#include <asm/cacheflush.h>
#include <asm/kprobes.h>
#include <asm/ftrace.h>
#include <asm/nops.h>
#ifdef CONFIG_DYNAMIC_FTRACE
int ftrace_arch_code_modify_prepare(void)
{
set_kernel_text_rw();
set_all_modules_text_rw();
return 0;
}
int ftrace_arch_code_modify_post_process(void)
{
set_all_modules_text_ro();
set_kernel_text_ro();
return 0;
}
union ftrace_code_union {
char code[MCOUNT_INSN_SIZE];
struct {
unsigned char e8;
int offset;
} __attribute__((packed));
};
static int ftrace_calc_offset(long ip, long addr)
{
return (int)(addr - ip);
}
static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
{
static union ftrace_code_union calc;
calc.e8 = 0xe8;
calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
/*
* No locking needed, this must be called via kstop_machine
* which in essence is like running on a uniprocessor machine.
*/
return calc.code;
}
static inline int
within(unsigned long addr, unsigned long start, unsigned long end)
{
return addr >= start && addr < end;
}
static unsigned long text_ip_addr(unsigned long ip)
{
/*
* On x86_64, kernel text mappings are mapped read-only with
* CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead
* of the kernel text mapping to modify the kernel text.
*
* For 32bit kernels, these mappings are same and we can use
* kernel identity mapping to modify code.
*/
if (within(ip, (unsigned long)_text, (unsigned long)_etext))
ip = (unsigned long)__va(__pa_symbol(ip));
return ip;
}
static const unsigned char *ftrace_nop_replace(void)
{
return ideal_nops[NOP_ATOMIC5];
}
static int
ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
unsigned const char *new_code)
{
unsigned char replaced[MCOUNT_INSN_SIZE];
/*
* Note: Due to modules and __init, code can
* disappear and change, we need to protect against faulting
* as well as code changing. We do this by using the
* probe_kernel_* functions.
*
* No real locking needed, this code is run through
* kstop_machine, or before SMP starts.
*/
/* 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 (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
return -EINVAL;
ip = text_ip_addr(ip);
/* replace the text with the new text */
if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
return -EPERM;
sync_core();
return 0;
}
int ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
unsigned const char *new, *old;
unsigned long ip = rec->ip;
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(rec->ip, old, new);
/* Normal cases use add_brk_on_nop */
WARN_ONCE(1, "invalid use of ftrace_make_nop");
return -EINVAL;
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned const char *new, *old;
unsigned long ip = rec->ip;
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);
}
/*
* The modifying_ftrace_code is used to tell the breakpoint
* handler to call ftrace_int3_handler(). If it fails to
* call this handler for a breakpoint added by ftrace, then
* the kernel may crash.
*
* As atomic_writes on x86 do not need a barrier, we do not
* need to add smp_mb()s for this to work. It is also considered
* that we can not read the modifying_ftrace_code before
* executing the breakpoint. That would be quite remarkable if
* it could do that. Here's the flow that is required:
*
* CPU-0 CPU-1
*
* atomic_inc(mfc);
* write int3s
* <trap-int3> // implicit (r)mb
* if (atomic_read(mfc))
* call ftrace_int3_handler()
*
* Then when we are finished:
*
* atomic_dec(mfc);
*
* If we hit a breakpoint that was not set by ftrace, it does not
* matter if ftrace_int3_handler() is called or not. It will
* simply be ignored. But it is crucial that a ftrace nop/caller
* breakpoint is handled. No other user should ever place a
* breakpoint on an ftrace nop/caller location. It must only
* be done by this code.
*/
atomic_t modifying_ftrace_code __read_mostly;
static int
ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
unsigned const char *new_code);
/*
* 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;
}
static unsigned long ftrace_update_func;
static int update_ftrace_func(unsigned long ip, void *new)
{
unsigned char old[MCOUNT_INSN_SIZE];
int ret;
memcpy(old, (void *)ip, MCOUNT_INSN_SIZE);
ftrace_update_func = ip;
/* Make sure the breakpoints see the ftrace_update_func update */
smp_wmb();
/* See comment above by declaration of modifying_ftrace_code */
atomic_inc(&modifying_ftrace_code);
ret = ftrace_modify_code(ip, old, new);
atomic_dec(&modifying_ftrace_code);
return ret;
}
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned long ip = (unsigned long)(&ftrace_call);
unsigned char *new;
int ret;
new = ftrace_call_replace(ip, (unsigned long)func);
ret = update_ftrace_func(ip, new);
/* Also update the regs callback function */
if (!ret) {
ip = (unsigned long)(&ftrace_regs_call);
new = ftrace_call_replace(ip, (unsigned long)func);
ret = update_ftrace_func(ip, new);
}
return ret;
}
static int is_ftrace_caller(unsigned long ip)
{
if (ip == ftrace_update_func)
return 1;
return 0;
}
/*
* A breakpoint was added to the code address we are about to
* modify, and this is the handle that will just skip over it.
* We are either changing a nop into a trace call, or a trace
* call to a nop. While the change is taking place, we treat
* it just like it was a nop.
*/
int ftrace_int3_handler(struct pt_regs *regs)
{
unsigned long ip;
if (WARN_ON_ONCE(!regs))
return 0;
ip = regs->ip - 1;
if (!ftrace_location(ip) && !is_ftrace_caller(ip))
return 0;
regs->ip += MCOUNT_INSN_SIZE - 1;
return 1;
}
static int ftrace_write(unsigned long ip, const char *val, int size)
{
ip = text_ip_addr(ip);
if (probe_kernel_write((void *)ip, val, size))
return -EPERM;
return 0;
}
static int add_break(unsigned long ip, const char *old)
{
unsigned char replaced[MCOUNT_INSN_SIZE];
unsigned char brk = BREAKPOINT_INSTRUCTION;
if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
return -EFAULT;
/* Make sure it is what we expect it to be */
if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0)
return -EINVAL;
return ftrace_write(ip, &brk, 1);
}
static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned const char *old;
unsigned long ip = rec->ip;
old = ftrace_call_replace(ip, addr);
return add_break(rec->ip, old);
}
static int add_brk_on_nop(struct dyn_ftrace *rec)
{
unsigned const char *old;
old = ftrace_nop_replace();
return add_break(rec->ip, old);
}
static int add_breakpoints(struct dyn_ftrace *rec, int enable)
{
unsigned long ftrace_addr;
int ret;
ftrace_addr = ftrace_get_addr_curr(rec);
ret = ftrace_test_record(rec, enable);
switch (ret) {
case FTRACE_UPDATE_IGNORE:
return 0;
case FTRACE_UPDATE_MAKE_CALL:
/* converting nop to call */
return add_brk_on_nop(rec);
case FTRACE_UPDATE_MODIFY_CALL:
case FTRACE_UPDATE_MAKE_NOP:
/* converting a call to a nop */
return add_brk_on_call(rec, ftrace_addr);
}
return 0;
}
/*
* On error, we need to remove breakpoints. This needs to
* be done caefully. If the address does not currently have a
* breakpoint, we know we are done. Otherwise, we look at the
* remaining 4 bytes of the instruction. If it matches a nop
* we replace the breakpoint with the nop. Otherwise we replace
* it with the call instruction.
*/
static int remove_breakpoint(struct dyn_ftrace *rec)
{
unsigned char ins[MCOUNT_INSN_SIZE];
unsigned char brk = BREAKPOINT_INSTRUCTION;
const unsigned char *nop;
unsigned long ftrace_addr;
unsigned long ip = rec->ip;
/* If we fail the read, just give up */
if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE))
return -EFAULT;
/* If this does not have a breakpoint, we are done */
if (ins[0] != brk)
return 0;
nop = ftrace_nop_replace();
/*
* If the last 4 bytes of the instruction do not match
* a nop, then we assume that this is a call to ftrace_addr.
*/
if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) {
/*
* For extra paranoidism, we check if the breakpoint is on
* a call that would actually jump to the ftrace_addr.
* If not, don't touch the breakpoint, we make just create
* a disaster.
*/
ftrace_addr = ftrace_get_addr_new(rec);
nop = ftrace_call_replace(ip, ftrace_addr);
if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) == 0)
goto update;
/* Check both ftrace_addr and ftrace_old_addr */
ftrace_addr = ftrace_get_addr_curr(rec);
nop = ftrace_call_replace(ip, ftrace_addr);
if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0)
return -EINVAL;
}
update:
return ftrace_write(ip, nop, 1);
}
static int add_update_code(unsigned long ip, unsigned const char *new)
{
/* skip breakpoint */
ip++;
new++;
return ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1);
}
static int add_update_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long ip = rec->ip;
unsigned const char *new;
new = ftrace_call_replace(ip, addr);
return add_update_code(ip, new);
}
static int add_update_nop(struct dyn_ftrace *rec)
{
unsigned long ip = rec->ip;
unsigned const char *new;
new = ftrace_nop_replace();
return add_update_code(ip, new);
}
static int add_update(struct dyn_ftrace *rec, int enable)
{
unsigned long ftrace_addr;
int ret;
ret = ftrace_test_record(rec, enable);
ftrace_addr = ftrace_get_addr_new(rec);
switch (ret) {
case FTRACE_UPDATE_IGNORE:
return 0;
case FTRACE_UPDATE_MODIFY_CALL:
case FTRACE_UPDATE_MAKE_CALL:
/* converting nop to call */
return add_update_call(rec, ftrace_addr);
case FTRACE_UPDATE_MAKE_NOP:
/* converting a call to a nop */
return add_update_nop(rec);
}
return 0;
}
static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long ip = rec->ip;
unsigned const char *new;
new = ftrace_call_replace(ip, addr);
return ftrace_write(ip, new, 1);
}
static int finish_update_nop(struct dyn_ftrace *rec)
{
unsigned long ip = rec->ip;
unsigned const char *new;
new = ftrace_nop_replace();
return ftrace_write(ip, new, 1);
}
static int finish_update(struct dyn_ftrace *rec, int enable)
{
unsigned long ftrace_addr;
int ret;
ret = ftrace_update_record(rec, enable);
ftrace_addr = ftrace_get_addr_new(rec);
switch (ret) {
case FTRACE_UPDATE_IGNORE:
return 0;
case FTRACE_UPDATE_MODIFY_CALL:
case FTRACE_UPDATE_MAKE_CALL:
/* converting nop to call */
return finish_update_call(rec, ftrace_addr);
case FTRACE_UPDATE_MAKE_NOP:
/* converting a call to a nop */
return finish_update_nop(rec);
}
return 0;
}
static void do_sync_core(void *data)
{
sync_core();
}
static void run_sync(void)
{
int enable_irqs = irqs_disabled();
/* We may be called with interrupts disbled (on bootup). */
if (enable_irqs)
local_irq_enable();
on_each_cpu(do_sync_core, NULL, 1);
if (enable_irqs)
local_irq_disable();
}
void ftrace_replace_code(int enable)
{
struct ftrace_rec_iter *iter;
struct dyn_ftrace *rec;
const char *report = "adding breakpoints";
int count = 0;
int ret;
for_ftrace_rec_iter(iter) {
rec = ftrace_rec_iter_record(iter);
ret = add_breakpoints(rec, enable);
if (ret)
goto remove_breakpoints;
count++;
}
run_sync();
report = "updating code";
count = 0;
for_ftrace_rec_iter(iter) {
rec = ftrace_rec_iter_record(iter);
ret = add_update(rec, enable);
if (ret)
goto remove_breakpoints;
count++;
}
run_sync();
report = "removing breakpoints";
count = 0;
for_ftrace_rec_iter(iter) {
rec = ftrace_rec_iter_record(iter);
ret = finish_update(rec, enable);
if (ret)
goto remove_breakpoints;
count++;
}
run_sync();
return;
remove_breakpoints:
pr_warn("Failed on %s (%d):\n", report, count);
ftrace_bug(ret, rec);
for_ftrace_rec_iter(iter) {
rec = ftrace_rec_iter_record(iter);
/*
* Breakpoints are handled only when this function is in
* progress. The system could not work with them.
*/
if (remove_breakpoint(rec))
BUG();
}
run_sync();
}
static int
ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
unsigned const char *new_code)
{
int ret;
ret = add_break(ip, old_code);
if (ret)
goto out;
run_sync();
ret = add_update_code(ip, new_code);
if (ret)
goto fail_update;
run_sync();
ret = ftrace_write(ip, new_code, 1);
/*
* The breakpoint is handled only when this function is in progress.
* The system could not work if we could not remove it.
*/
BUG_ON(ret);
out:
run_sync();
return ret;
fail_update:
/* Also here the system could not work with the breakpoint */
if (ftrace_write(ip, old_code, 1))
BUG();
goto out;
}
void arch_ftrace_update_code(int command)
{
/* See comment above by declaration of modifying_ftrace_code */
atomic_inc(&modifying_ftrace_code);
ftrace_modify_all_code(command);
atomic_dec(&modifying_ftrace_code);
}
int __init ftrace_dyn_arch_init(void)
{
return 0;
}
#if defined(CONFIG_X86_64) || defined(CONFIG_FUNCTION_GRAPH_TRACER)
static unsigned char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
{
static union ftrace_code_union calc;
/* Jmp not a call (ignore the .e8) */
calc.e8 = 0xe9;
calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
/*
* ftrace external locks synchronize the access to the static variable.
*/
return calc.code;
}
#endif
/* 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_caller_end(void);
extern void ftrace_regs_caller_end(void);
extern void ftrace_return(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));
};
static unsigned long
create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
{
unsigned const char *jmp;
unsigned long start_offset;
unsigned long end_offset;
unsigned long op_offset;
unsigned long offset;
unsigned long size;
unsigned long ip;
unsigned long *ptr;
void *trampoline;
/* 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;
} else {
start_offset = (unsigned long)ftrace_caller;
end_offset = (unsigned long)ftrace_caller_end;
op_offset = (unsigned long)ftrace_caller_op_ptr;
}
size = end_offset - start_offset;
/*
* Allocate enough size to store the ftrace_caller code,
* the jmp to ftrace_return, as well as the address of
* the ftrace_ops this trampoline is used for.
*/
trampoline = alloc_tramp(size + MCOUNT_INSN_SIZE + sizeof(void *));
if (!trampoline)
return 0;
*tramp_size = size + MCOUNT_INSN_SIZE + sizeof(void *);
/* Copy ftrace_caller onto the trampoline memory */
ret = probe_kernel_read(trampoline, (void *)start_offset, size);
if (WARN_ON(ret < 0)) {
tramp_free(trampoline);
return 0;
}
ip = (unsigned long)trampoline + size;
/* The trampoline ends with a jmp to ftrace_return */
jmp = ftrace_jmp_replace(ip, (unsigned long)ftrace_return);
memcpy(trampoline + size, jmp, MCOUNT_INSN_SIZE);
/*
* 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 + MCOUNT_INSN_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)) {
tramp_free(trampoline);
return 0;
}
/* 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);
/* ALLOC_TRAMP flags lets us know we created it */
ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
return (unsigned long)trampoline;
}
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 char *new;
unsigned long offset;
unsigned long ip;
unsigned int size;
int ret;
if (ops->trampoline) {
/*
* 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;
} else {
ops->trampoline = create_trampoline(ops, &size);
if (!ops->trampoline)
return;
ops->trampoline_size = size;
}
offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
ip = ops->trampoline + offset;
func = ftrace_ops_get_func(ops);
/* Do a safe modify in case the trampoline is executing */
new = ftrace_call_replace(ip, (unsigned long)func);
ret = update_ftrace_func(ip, new);
/* The update should never fail */
WARN_ON(ret);
}
/* Return the address of the function the trampoline calls */
static void *addr_from_call(void *ptr)
{
union ftrace_code_union calc;
int ret;
ret = probe_kernel_read(&calc, ptr, MCOUNT_INSN_SIZE);
if (WARN_ON_ONCE(ret < 0))
return NULL;
/* Make sure this is a call */
if (WARN_ON_ONCE(calc.e8 != 0xe8)) {
pr_warn("Expected e8, got %x\n", calc.e8);
return NULL;
}
return ptr + MCOUNT_INSN_SIZE + calc.offset;
}
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 int ftrace_mod_jmp(unsigned long ip, void *func)
{
unsigned char *new;
new = ftrace_jmp_replace(ip, (unsigned long)func);
return update_ftrace_func(ip, new);
}
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 old;
int faulted;
struct ftrace_graph_ent trace;
unsigned long return_hooker = (unsigned long)
&return_to_handler;
if (unlikely(ftrace_graph_is_dead()))
return;
if (unlikely(atomic_read(¤t->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;
}
trace.func = self_addr;
trace.depth = current->curr_ret_stack + 1;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace)) {
*parent = old;
return;
}
if (ftrace_push_return_trace(old, self_addr, &trace.depth,
frame_pointer) == -EBUSY) {
*parent = old;
return;
}
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */