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Commit 593eb8a2 authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
Browse files

ftrace: return error on failed modified text. 



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: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 34698bcb

arch/x86/kernel/ftrace.c

+7 −7
Original line number Diff line number Diff line
@@ -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();

include/linux/ftrace.h

+22 −2
Original line number Diff line number Diff line
@@ -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);

kernel/trace/ftrace.c

+15 −6
Original line number Diff line number Diff line
@@ -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;