From: Petr Mladek <[email protected]>
If a failure occurs while modifying ftrace function, it bails out and will
remove the tracepoints to be back to what the code originally was.
There is missing the final sync run across the CPUs after the fix up is done
and before the ftrace int3 handler flag is reset.
Here's the description of the problem:
CPU0 CPU1
---- ----
remove_breakpoint();
modifying_ftrace_code = 0;
[still sees breakpoint]
<takes trap>
[sees modifying_ftrace_code as zero]
[no breakpoint handler]
[goto failed case]
[trap exception - kernel breakpoint, no
handler]
BUG()
Link: http://lkml.kernel.org/r/[email protected]
Fixes: 8a4d0a687a5 "ftrace: Use breakpoint method to update ftrace caller"
Acked-by: Frederic Weisbecker <[email protected]>
Acked-by: H. Peter Anvin <[email protected]>
Signed-off-by: Petr Mladek <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
---
arch/x86/kernel/ftrace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 6b566c8..69885e2 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -660,8 +660,8 @@ ftrace_modify_code(unsigned long ip, unsigned const char
*old_code,
ret = -EPERM;
goto out;
}
- run_sync();
out:
+ run_sync();
return ret;
fail_update:
--
1.8.5.3
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