758 lines
17 KiB
C
Executable File
758 lines
17 KiB
C
Executable File
/*
|
|
* 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/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 {
|
|
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";
|
|
|
|
for_ftrace_rec_iter(iter) {
|
|
rec = ftrace_rec_iter_record(iter);
|
|
|
|
ret = add_update(rec, enable);
|
|
if (ret)
|
|
goto remove_breakpoints;
|
|
}
|
|
|
|
run_sync();
|
|
|
|
report = "removing breakpoints";
|
|
|
|
for_ftrace_rec_iter(iter) {
|
|
rec = ftrace_rec_iter_record(iter);
|
|
|
|
ret = finish_update(rec, enable);
|
|
if (ret)
|
|
goto remove_breakpoints;
|
|
}
|
|
|
|
run_sync();
|
|
|
|
return;
|
|
|
|
remove_breakpoints:
|
|
pr_warn("Failed on %s (%d):\n", report, count);
|
|
ftrace_bug(ret, rec ? rec->ip : 0);
|
|
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;
|
|
}
|
|
#endif
|
|
|
|
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
|
|
|
|
#ifdef CONFIG_DYNAMIC_FTRACE
|
|
extern void ftrace_graph_call(void);
|
|
|
|
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;
|
|
}
|
|
|
|
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 *parent, unsigned long self_addr,
|
|
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 */
|