linux-kernel - [PATCH v4] scripts: Create objdump-func helper script

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Message-Id: <3eb3f091fd6bd9caba50392ceab98ce756804f3b.1650578171.git.jpoimboe@redhat.com>
Date:   Thu, 21 Apr 2022 14:56:55 -0700
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Miroslav Benes <mbenes@...e.cz>,
        Borislav Petkov <bp@...en8.de>, Borislav Petkov <bp@...e.de>
Subject: [PATCH v4] scripts: Create objdump-func helper script

Add a simple script which disassembles a single function from an object
file.  Comes in handy for objtool warnings and kernel stack traces.

Originally-by: Peter Zijlstra <peterz@...radead.org>
Acked-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
v4:
- allow extra args to be provided at the end
- match ".cold", etc

 scripts/objdump-func | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100755 scripts/objdump-func

diff --git a/scripts/objdump-func b/scripts/objdump-func
new file mode 100755
index 000000000000..4eb463dd9f52
--- /dev/null
+++ b/scripts/objdump-func
@@ -0,0 +1,29 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Disassemble a single function.
+#
+# usage: objdump-func <file> <func>
+
+set -o errexit
+set -o nounset
+
+OBJDUMP="${CROSS_COMPILE:-}objdump"
+
+command -v gawk >/dev/null 2>&1 || die "gawk isn't installed"
+
+usage() {
+	echo "usage: objdump-func <file> <func>" >&2
+	exit 1
+}
+
+[[ $# -lt 2 ]] && usage
+
+OBJ=$1; shift
+FUNC=$1; shift
+
+# Secret feature to allow adding extra objdump args at the end
+EXTRA_ARGS=$@
+
+# Note this also matches compiler-added suffixes like ".cold", etc
+${OBJDUMP} -wdr $EXTRA_ARGS $OBJ | gawk -M -v f=$FUNC '/^$/ { P=0; } $0 ~ "<" f "(\\..*)?>:" { P=1; O=strtonum("0x" $1); } { if (P) { o=strtonum("0x" $1); printf("%04x ", o-O); print $0; } }'
-- 
2.34.1