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authorPetr Mladek <pmladek@suse.cz>2014-02-24 17:12:22 +0100
committerSteven Rostedt <rostedt@goodmis.org>2014-03-07 10:06:16 -0500
commit7f11f5ecf4ae09815dc2de267c5e04d1de01d862 (patch)
tree51014fbc43d559884d4c95d57d86b8c69426718c
parentcd21067f69240041d36e491ff5597e0217615465 (diff)
ftrace/x86: BUG when ftrace recovery fails
Ftrace modifies function calls using Int3 breakpoints on x86. The breakpoints are handled only when the patching is in progress. If something goes wrong, there is a recovery code that removes the breakpoints. If this fails, the system might get silently rebooted when a remaining break is not handled or an invalid instruction is proceed. We should BUG() when the breakpoint could not be removed. Otherwise, the system silently crashes when the function finishes the Int3 handler is disabled. Note that we need to modify remove_breakpoint() to return non-zero value only when there is an error. The return value was ignored before, so it does not cause any troubles. Link: http://lkml.kernel.org/r/1393258342-29978-4-git-send-email-pmladek@suse.cz Signed-off-by: Petr Mladek <pmladek@suse.cz> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
-rw-r--r--arch/x86/kernel/ftrace.c18
1 files changed, 15 insertions, 3 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 4b66adf17369..52819e816f87 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -425,7 +425,7 @@ static int remove_breakpoint(struct dyn_ftrace *rec)
/* If this does not have a breakpoint, we are done */
if (ins[0] != brk)
- return -1;
+ return 0;
nop = ftrace_nop_replace();
@@ -625,7 +625,12 @@ void ftrace_replace_code(int enable)
printk(KERN_WARNING "Failed on %s (%d):\n", report, count);
for_ftrace_rec_iter(iter) {
rec = ftrace_rec_iter_record(iter);
- remove_breakpoint(rec);
+ /*
+ * Breakpoints are handled only when this function is in
+ * progress. The system could not work with them.
+ */
+ if (remove_breakpoint(rec))
+ BUG();
}
run_sync();
}
@@ -649,12 +654,19 @@ ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
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:
- ftrace_write(ip, old_code, 1);
+ /* Also here the system could not work with the breakpoint */
+ if (ftrace_write(ip, old_code, 1))
+ BUG();
goto out;
}