All of lore.kernel.org
 help / color / mirror / Atom feed
From: Nicholas Piggin <npiggin@gmail.com>
To: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: [PATCH] tools/objtool: tolerate STT_NOTYPE symbols at end of section
Date: Tue, 20 Dec 2022 20:13:23 +1000	[thread overview]
Message-ID: <20221220101323.3119939-1-npiggin@gmail.com> (raw)

Hand-written asm often contains non-function symbols in executable
sections. _end symbols for finding the size of instruction blocks
for runtime processing is one such usage.

optprobe_template_end is one example that causes the warning:

  objtool: optprobe_template_end(): can't find starting instruction

This is because the symbol happens to be at the end of the file (and
therefore end of a section in the object file).

So ignore end-of-section STT_NOTYPE symbols instead of bailing out
because an instruction can't be found. While we're here, add a more
descriptive warning for STT_FUNC symbols found at the end of a
section.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 tools/objtool/check.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 4350be739f4f..4b7c8b33069e 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -427,6 +427,15 @@ static int decode_instructions(struct objtool_file *file)
 			if (func->type != STT_NOTYPE && func->type != STT_FUNC)
 				continue;
 
+			if (func->offset == sec->sh.sh_size) {
+				/* Heuristic: likely an "end" symbol */
+				if (func->type == STT_NOTYPE)
+					continue;
+				WARN("%s(): STT_FUNC at end of section",
+				     func->name);
+				return -1;
+			}
+
 			if (func->return_thunk || func->alias != func)
 				continue;
 
-- 
2.37.2


WARNING: multiple messages have this Message-ID (diff)
From: Nicholas Piggin <npiggin@gmail.com>
To: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
	Nicholas Piggin <npiggin@gmail.com>
Subject: [PATCH] tools/objtool: tolerate STT_NOTYPE symbols at end of section
Date: Tue, 20 Dec 2022 20:13:23 +1000	[thread overview]
Message-ID: <20221220101323.3119939-1-npiggin@gmail.com> (raw)

Hand-written asm often contains non-function symbols in executable
sections. _end symbols for finding the size of instruction blocks
for runtime processing is one such usage.

optprobe_template_end is one example that causes the warning:

  objtool: optprobe_template_end(): can't find starting instruction

This is because the symbol happens to be at the end of the file (and
therefore end of a section in the object file).

So ignore end-of-section STT_NOTYPE symbols instead of bailing out
because an instruction can't be found. While we're here, add a more
descriptive warning for STT_FUNC symbols found at the end of a
section.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 tools/objtool/check.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 4350be739f4f..4b7c8b33069e 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -427,6 +427,15 @@ static int decode_instructions(struct objtool_file *file)
 			if (func->type != STT_NOTYPE && func->type != STT_FUNC)
 				continue;
 
+			if (func->offset == sec->sh.sh_size) {
+				/* Heuristic: likely an "end" symbol */
+				if (func->type == STT_NOTYPE)
+					continue;
+				WARN("%s(): STT_FUNC at end of section",
+				     func->name);
+				return -1;
+			}
+
 			if (func->return_thunk || func->alias != func)
 				continue;
 
-- 
2.37.2


             reply	other threads:[~2022-12-20 10:14 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-20 10:13 Nicholas Piggin [this message]
2022-12-20 10:13 ` [PATCH] tools/objtool: tolerate STT_NOTYPE symbols at end of section Nicholas Piggin
2022-12-20 14:21 ` Christophe Leroy
2023-01-09 17:01 ` [tip: core/urgent] objtool: Tolerate " tip-bot2 for Nicholas Piggin

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20221220101323.3119939-1-npiggin@gmail.com \
    --to=npiggin@gmail.com \
    --cc=jpoimboe@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=peterz@infradead.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.