linux-kernel - [PATCH 3/4] scripts/decode_stacktrace: guess path to modules

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Date:   Mon, 22 Jun 2020 15:33:50 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     linux-kernel@...r.kernel.org, Sasha Levin <sashal@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 3/4] scripts/decode_stacktrace: guess path to modules

Try to find module in directory with vmlinux (for fresh build).
Then try standard paths where debuginfo are usually placed.
Pick first file which have elf section '.debug_line'.

Before:

$ echo 'tap_open+0x0/0x0 [tap]' |
  ./scripts/decode_stacktrace.sh /usr/lib/debug/boot/vmlinux-5.4.0-37-generic
WARNING! Modules path isn't set, but is needed to parse this symbol
tap_open+0x0/0x0 tap

After:

$ echo 'tap_open+0x0/0x0 [tap]' |
  ./scripts/decode_stacktrace.sh /usr/lib/debug/boot/vmlinux-5.4.0-37-generic
tap_open (drivers/net/tap.c:502) tap

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
---
 scripts/decode_stacktrace.sh |   36 +++++++++++++++++++++++++++++++++---
 1 file changed, 33 insertions(+), 3 deletions(-)

diff --git a/scripts/decode_stacktrace.sh b/scripts/decode_stacktrace.sh
index b1b85a7b2115..7f18ac10af03 100755
--- a/scripts/decode_stacktrace.sh
+++ b/scripts/decode_stacktrace.sh
@@ -12,9 +12,40 @@ fi
 vmlinux=$1
 basepath=${2-auto}
 modpath=$3
+release=""
+
 declare -A cache
 declare -A modcache
 
+find_module() {
+	if [[ "$modpath" != "" ]] ; then
+		for fn in $(find "$modpath" -name "${module//_/[-_]}.ko*") ; do
+			if readelf -WS "$fn" | grep -qwF .debug_line ; then
+				echo $fn
+				return
+			fi
+		done
+		return 1
+	fi
+
+	modpath=$(dirname "$vmlinux")
+	find_module && return
+
+	if [[ $release == "" ]] ; then
+		release=$(gdb -ex 'print init_uts_ns.name.release' -ex 'quit' -quiet -batch "$vmlinux" | sed -n 's/\$1 = "\(.*\)".*/\1/p')
+	fi
+
+	for dn in {/usr/lib/debug,}/lib/modules/$release ; do
+		if [ -e "$dn" ] ; then
+			modpath="$dn"
+			find_module && return
+		fi
+	done
+
+	modpath=""
+	return 1
+}
+
 parse_symbol() {
 	# The structure of symbol at this point is:
 	#   ([name]+[offset]/[total length])
@@ -27,12 +58,11 @@ parse_symbol() {
 	elif [[ "${modcache[$module]+isset}" == "isset" ]]; then
 		local objfile=${modcache[$module]}
 	else
-		if [[ $modpath == "" ]]; then
+		local objfile=$(find_module)
+		if [[ $objfile == "" ]] ; then
 			echo "WARNING! Modules path isn't set, but is needed to parse this symbol" >&2
 			return
 		fi
-		local objfile=$(find "$modpath" -name "${module//_/[-_]}.ko*" -print -quit)
-		[[ $objfile == "" ]] && return
 		modcache[$module]=$objfile
 	fi