[for-next][PATCH 03/25] ftrace/x86: Add back ftrace_expected for ftrace bug reports

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>

After someone reported a bug report with a failed modification due to the
expected value not matching what was found, it came to my attention that
the ftrace_expected is no longer set when that happens. This makes for
debugging the issue a bit more difficult.

Set ftrace_expected to the expected code before calling ftrace_bug, so
that it shows what was expected and why it failed.

Link: https://lore.kernel.org/all/CA+wXwBQ-VhK+hpBtYtyZP-NiX4g8fqRRWithFOHQW-0coQ3vLg@xxxxxxxxxxxxxx/
Link: https://lore.kernel.org/linux-trace-kernel/20221209105247.01d4e51d@xxxxxxxxxxxxxxxxxx

Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "x86@xxxxxxxxxx" <x86@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 768ae4406a5c ("x86/ftrace: Use text_poke()")
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
 arch/x86/kernel/ftrace.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index bd165004776d..e07234ec7e23 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -217,7 +217,9 @@ void ftrace_replace_code(int enable)
 
 		ret = ftrace_verify_code(rec->ip, old);
 		if (ret) {
+			ftrace_expected = old;
 			ftrace_bug(ret, rec);
+			ftrace_expected = NULL;
 			return;
 		}
 	}
-- 
2.35.1