[PATCH 03/12 v3] ftrace: return error on failed modified text.

Steven Rostedt
2008-10-23T13:38:18Z

[-- Attachment #1: ftrace-return-error-on-mod-code.patch --]
[-- Type: text/plain, Size: 4494 bytes --]

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>
---
arch/x86/kernel/ftrace.c | 12 +++++++-----
include/linux/ftrace.h | 24 ++++++++++++++++++++++--
kernel/trace/ftrace.c | 21 +++++++++++++++------
3 files changed, 44 insertions(+), 13 deletions(-)

Index: linux-compile.git/arch/x86/kernel/ftrace.c
===================================================================
--- linux-compile.git.orig/arch/x86/kernel/ftrace.c 2008-10-23 09:13:39.000000000 -0400
+++ linux-compile.git/arch/x86/kernel/ftrace.c 2008-10-23 09:27:46.000000000 -0400
@@ -71,14 +71,16 @@ ftrace_modify_code(unsigned long ip, uns
* 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;

- WARN_ON_ONCE(__copy_to_user_inatomic((char __user *)ip, new_code,
- MCOUNT_INSN_SIZE));
+ if (__copy_to_user_inatomic((char __user *)ip, new_code,
+ MCOUNT_INSN_SIZE))
+ return -EPERM;

sync_core();

Index: linux-compile.git/kernel/trace/ftrace.c
===================================================================
--- linux-compile.git.orig/kernel/trace/ftrace.c 2008-10-23 09:13:39.000000000 -0400
+++ linux-compile.git/kernel/trace/ftrace.c 2008-10-23 09:20:55.000000000 -0400
@@ -591,22 +591,22 @@ ftrace_code_disable(struct dyn_ftrace *r
{
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);
@@ -615,6 +615,15 @@ ftrace_code_disable(struct dyn_ftrace *r
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;
Index: linux-compile.git/include/linux/ftrace.h
===================================================================
--- linux-compile.git.orig/include/linux/ftrace.h 2008-10-23 09:13:39.000000000 -0400
+++ linux-compile.git/include/linux/ftrace.h 2008-10-23 09:21:23.000000000 -0400
@@ -72,13 +72,33 @@ extern unsigned char *ftrace_nop_replace
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);

--