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ftrace: return error on failed modified text.

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Have the ftrace_modify_code return error values:

  -EFAULT on error of reading the address

  -EINVAL if what is read does not match what it expected

  -EPERM  if the write fails to update after a successful match.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Steven Rostedt 2008-10-23 09:32:59 -04:00 committed by Ingo Molnar
parent 34698bcbdf
commit 593eb8a2d6
3 changed files with 44 additions and 15 deletions
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14
arch/x86/kernel/ftrace.c
View file

@ -62,7 +62,6 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code,
unsigned char *new_code)
{
unsigned char replaced[MCOUNT_INSN_SIZE];
int ret;
/*
* Note: Due to modules and __init, code can
@ -72,15 +71,16 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code,
* No real locking needed, this code is run through
* kstop_machine, or before SMP starts.
*/
if (__copy_from_user_inatomic(replaced, (char __user *)ip, MCOUNT_INSN_SIZE))
return 1;
if (__copy_from_user_inatomic(replaced, (char __user *)ip,
MCOUNT_INSN_SIZE))
return -EFAULT;
if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
return 2;
return -EINVAL;
ret = __copy_to_user_inatomic((char __user *)ip, new_code,
MCOUNT_INSN_SIZE);
WARN_ON_ONCE(ret);
if (__copy_to_user_inatomic((char __user *)ip, new_code,
MCOUNT_INSN_SIZE))
return -EPERM;
sync_core();

24
include/linux/ftrace.h
View file

@ -72,13 +72,33 @@ extern unsigned char *ftrace_nop_replace(void);
extern unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr);
extern int ftrace_dyn_arch_init(void *data);
extern int ftrace_mcount_set(unsigned long *data);
extern int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
unsigned char *new_code);
extern int ftrace_update_ftrace_func(ftrace_func_t func);
extern void ftrace_caller(void);
extern void ftrace_call(void);
extern void mcount_call(void);
/**
* ftrace_modify_code - modify code segment
* @ip: the address of the code segment
* @old_code: the contents of what is expected to be there
* @new_code: the code to patch in
*
* This is a very sensitive operation and great care needs
* to be taken by the arch. The operation should carefully
* read the location, check to see if what is read is indeed
* what we expect it to be, and then on success of the compare,
* it should write to the location.
*
* Return must be:
* 0 on success
* -EFAULT on error reading the location
* -EINVAL on a failed compare of the contents
* -EPERM on error writing to the location
* Any other value will be considered a failure.
*/
extern int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
unsigned char *new_code);
extern int skip_trace(unsigned long ip);
extern void ftrace_release(void *start, unsigned long size);

21
kernel/trace/ftrace.c
View file

@ -596,22 +596,22 @@ ftrace_code_disable(struct dyn_ftrace *rec)
{
unsigned long ip;
unsigned char *nop, *call;
int failed;
int ret;
ip = rec->ip;
nop = ftrace_nop_replace();
call = ftrace_call_replace(ip, mcount_addr);
failed = ftrace_modify_code(ip, call, nop);
if (failed) {
switch (failed) {
case 1:
ret = ftrace_modify_code(ip, call, nop);
if (ret) {
switch (ret) {
case -EFAULT:
WARN_ON_ONCE(1);
pr_info("ftrace faulted on modifying ");
print_ip_sym(ip);
break;
case 2:
case -EINVAL:
WARN_ON_ONCE(1);
pr_info("ftrace failed to modify ");
print_ip_sym(ip);
@ -620,6 +620,15 @@ ftrace_code_disable(struct dyn_ftrace *rec)
print_ip_ins(" replace: ", nop);
printk(KERN_CONT "\n");
break;
case -EPERM:
WARN_ON_ONCE(1);
pr_info("ftrace faulted on writing ");
print_ip_sym(ip);
break;
default:
WARN_ON_ONCE(1);
pr_info("ftrace faulted on unknown error ");
print_ip_sym(ip);
}
rec->flags |= FTRACE_FL_FAILED;