Commit 0f69dc29 authored Aug 23, 2024 by Luca Ceresoli Committed by Andrew Morton Sep 01, 2024

scripts/decode_stacktrace.sh: remove find_module recursion and improve error reporting

Patch series "scripts/decode_stacktrace.sh: improve error reporting and
usability", v2.

This small series improves usability of scripts/decode_stacktrace.sh by
improving the usage text and correctly reporting when modules are built
without debugging symbols.


This patch (of 3):

The find_module() function can fail for two reasons:

 * the module was not found
 * the module was found but without debugging info

In both cases the user is reported the same error:

   WARNING! Modules path isn't set, but is needed to parse this symbol

This is misleading in case the modules path is set correctly.

find_module() is currently implemented as a recursive function based on
global variables in order to check up to 4 different paths.  This is not
straightforward to read and even less to modify.

Besides, the debuginfo code at the beginning of find_module() is executed
identically every time the function is entered, i.e.  up to 4 times per
each module search due to recursion.

To be able to improve error reporting, first rewrite the find_module()
function to remove recursion.  The new version of the function iterates
over all the same (up to 4) paths as before and for each of them does the
same checks as before.  At the end of the iteration it is now able to
print an appropriate error message, so that has been moved from the caller
into find_module().

Finally, when the module is found but without debugging info, mention the
two Kconfig variables one needs to set in order to have the needed
debugging symbols.

Link: https://lkml.kernel.org/r/20240823-decode_stacktrace-find_module-improvements-v2-0-d7a57d35558b@bootlin.com
Link: https://lkml.kernel.org/r/20240823-decode_stacktrace-find_module-improvements-v2-1-d7a57d35558b@bootlin.com


Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Cc: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Luca Ceresoli <luca.ceresoli@bootlin.com>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent 38676d9e

scripts/decode_stacktrace.sh

+20 −20

Original line number	Diff line number	Diff line
		@@ -89,31 +89,32 @@ find_module() {
		fi
		fi

		if [[ "$modpath" != "" ]] ; then
		for fn in $(find "$modpath" -name "${module//_/[-_]}.ko*") ; do
		if [ -z $release ] ; then
		release=$(gdb -ex 'print init_uts_ns.name.release' -ex 'quit' -quiet -batch "$vmlinux" 2>/dev/null \| sed -n 's/\$1 = "$.$"./\1/p')
		fi
		if [ -n "${release}" ] ; then
		release_dirs="/usr/lib/debug/lib/modules/$release /lib/modules/$release"
		fi

		found_without_debug_info=false
		for dir in "$modpath" "$(dirname "$vmlinux")" ${release_dirs}; do
		if [ -n "${dir}" ] && [ -e "${dir}" ]; then
		for fn in $(find "$dir" -name "${module//_/[-_]}.ko*") ; do
		if ${READELF} -WS "$fn" \| grep -qwF .debug_line ; then
		echo $fn
		return
		fi
		found_without_debug_info=true
		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 "$vmlinux" 2>/dev/null \| sed -n 's/\$1 = "$.$"./\1/p')
		fi
		done

		for dn in {/usr/lib/debug,}/lib/modules/$release ; do
		if [ -e "$dn" ] ; then
		modpath="$dn"
		find_module && return
		if [[ ${found_without_debug_info} == true ]]; then
		echo "WARNING! No debugging info in module ${module}, rebuild with DEBUG_KERNEL and DEBUG_INFO" >&2
		else
		echo "WARNING! Cannot find .ko for module ${module}, please pass a valid module path" >&2
		fi
		done

		modpath=""
		return 1
		}

		@@ -131,7 +132,6 @@ parse_symbol() {
		else
		local objfile=$(find_module)
		if [[ $objfile == "" ]] ; then
		echo "WARNING! Modules path isn't set, but is needed to parse this symbol" >&2
		return
		fi
		if [[ $aarray_support == true ]]; then