linux-kernel - [PATCH] ftrace/x86: Add back ftrace

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Message-ID: <20220726101851.069d2e70@gandalf.local.home>
Date:   Tue, 26 Jul 2022 10:18:51 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     "x86@...nel.org" <x86@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] ftrace/x86: Add back ftrace_expected assignment

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

When a ftrace_bug happens (where ftrace fails to modify a location) it is
helpful to have what was at that location as well as what was expected to
be there.

But with the conversion to text_poke() the variable that assigns the
expected for debugging was dropped. Unfortunately, I noticed this when I
needed it. Add it back.

Cc: stable@...r.kernel.org
Fixes: 768ae4406a5c ("x86/ftrace: Use text_poke()")
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 arch/x86/kernel/ftrace.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 5b4efc927d80..f5cdb5f675b3 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -91,6 +91,7 @@ static int ftrace_verify_code(unsigned long ip, const char *old_code)
 
 	/* Make sure it is what we expect it to be */
 	if (memcmp(cur_code, old_code, MCOUNT_INSN_SIZE) != 0) {
+		ftrace_expected = old_code;
 		WARN_ON(1);
 		return -EINVAL;
 	}
-- 
2.35.1