linux-kernel - [PATCH v3] x86/tools: fix line number reported for malformed lines

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Date: Fri, 29 Mar 2024 12:31:58 +0100
From: Valentin Obst <kernel@...entinobst.de>
To: Borislav Petkov <bp@...en8.de>, 
 Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, 
 Ingo Molnar <mingo@...nel.org>, Ingo Molnar <mingo@...hat.com>, 
 Thomas Gleixner <tglx@...utronix.de>
Cc: Andreas Hindborg <a.hindborg@...sung.com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 John Baublitz <john.m.baublitz@...il.com>, 
 Masami Hiramatsu <mhiramat@...nel.org>, Miguel Ojeda <ojeda@...nel.org>, 
 Peter Zijlstra <peterz@...radead.org>, 
 Sergio González Collado <sergio.collado@...il.com>, 
 linux-kernel@...r.kernel.org, x86@...nel.org, stable@...r.kernel.org, 
 Valentin Obst <kernel@...entinobst.de>
Subject: [PATCH v3] x86/tools: fix line number reported for malformed lines

Commit 35039eb6b199 ("x86: Show symbol name if insn decoder test failed")
included symbol lines in the post-processed objdump output consumed by
the insn decoder test. This broke the `instuction lines == total lines`
property that `insn_decoder_test.c` relied upon to print the offending
line's number in error messages. This has the consequence that the line
number reported on a test failure is unreated to, and much smaller than,
the line that actually caused the problem.

Add a new variable that counts the combined (insn+symbol) line count and
report this in the error message.

Fixes: 35039eb6b199 ("x86: Show symbol name if insn decoder test failed")
Cc: stable@...r.kernel.org
Reviewed-by: Miguel Ojeda <ojeda@...nel.org>
Tested-by: Miguel Ojeda <ojeda@...nel.org>
Reported-by: John Baublitz <john.m.baublitz@...il.com>
Debugged-by: John Baublitz <john.m.baublitz@...il.com>
Signed-off-by: Valentin Obst <kernel@...entinobst.de>
---
See v2's commit message and [1] for context why this bug made debugging a
test failure harder than necessary.

[1]: https://rust-for-linux.zulipchat.com/#narrow/stream/291565-Help/topic/insn_decoder_test.20failure/near/421075039

Changes in v3:
- Add Cc stable tag in sign-off area.
- Make commit message less verbose.
- Link to v2: https://lore.kernel.org/r/20240223-x86-insn-decoder-line-fix-v2-1-cde49c69f402@valentinobst.de

Changes in v2:
- Added tags 'Reviewed-by', 'Tested-by', 'Reported-by', 'Debugged-by',
  'Link', and 'Fixes'.
- Explain why this patch fixes the commit mentioned in the 'Fixes' tag.
- CCed the stable list and sent to all x86 maintainers.
- Link to v1: https://lore.kernel.org/r/20240221-x86-insn-decoder-line-fix-v1-1-47cd5a1718c6@valentinobst.de
---
 arch/x86/tools/insn_decoder_test.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/tools/insn_decoder_test.c b/arch/x86/tools/insn_decoder_test.c
index 472540aeabc2..727017a3c3c7 100644
--- a/arch/x86/tools/insn_decoder_test.c
+++ b/arch/x86/tools/insn_decoder_test.c
@@ -114,6 +114,7 @@ int main(int argc, char **argv)
 	unsigned char insn_buff[16];
 	struct insn insn;
 	int insns = 0;
+	int lines = 0;
 	int warnings = 0;

 	parse_args(argc, argv);
@@ -123,6 +124,8 @@ int main(int argc, char **argv)
 		int nb = 0, ret;
 		unsigned int b;

+		lines++;
+
 		if (line[0] == '<') {
 			/* Symbol line */
 			strcpy(sym, line);
@@ -134,12 +137,12 @@ int main(int argc, char **argv)
 		strcpy(copy, line);
 		tab1 = strchr(copy, '\t');
 		if (!tab1)
-			malformed_line(line, insns);
+			malformed_line(line, lines);
 		s = tab1 + 1;
 		s += strspn(s, " ");
 		tab2 = strchr(s, '\t');
 		if (!tab2)
-			malformed_line(line, insns);
+			malformed_line(line, lines);
 		*tab2 = '\0';	/* Characters beyond tab2 aren't examined */
 		while (s < tab2) {
 			if (sscanf(s, "%x", &b) == 1) {

---
base-commit: 4cece764965020c22cff7665b18a012006359095
change-id: 20240221-x86-insn-decoder-line-fix-7b1f2e1732ff

Best regards,
--
Valentin Obst <kernel@...entinobst.de>