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: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 8821cea..4282915 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -62,7 +62,6 @@
unsigned char *new_code)
{
unsigned char replaced[MCOUNT_INSN_SIZE];
- int ret;
/*
* Note: Due to modules and __init, code can
@@ -72,15 +71,16 @@
* 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();
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 0e95295..79fa10c 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -72,13 +72,33 @@
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);
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 1f54a94..b2de8de 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -596,22 +596,22 @@
{
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 @@
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;
