patches/old/scripts-decode_stacktracesh-optionally-use-llvm-utilities.patch

From: Carlos Llamas <cmllamas@google.com>
Subject: scripts/decode_stacktrace.sh: optionally use LLVM utilities
Date: Fri, 29 Sep 2023 03:48:17 +0000

GNU's addr2line can have problems parsing a vmlinux built with LLVM,
particularly when LTO was used.  In order to decode the traces correctly
this patch adds the ability to switch to LLVM's utilities readelf and
addr2line.  The same approach is followed by Will in [1].

Before:
  $ scripts/decode_stacktrace.sh vmlinux < kernel.log
  [17716.240635] Call trace:
  [17716.240646] skb_cow_data (??:?)
  [17716.240654] esp6_input (ld-temp.o:?)
  [17716.240666] xfrm_input (ld-temp.o:?)
  [17716.240674] xfrm6_rcv (??:?)
  [...]

After:
  $ LLVM=1 scripts/decode_stacktrace.sh vmlinux < kernel.log
  [17716.240635] Call trace:
  [17716.240646] skb_cow_data (include/linux/skbuff.h:2172 net/core/skbuff.c:4503)
  [17716.240654] esp6_input (net/ipv6/esp6.c:977)
  [17716.240666] xfrm_input (net/xfrm/xfrm_input.c:659)
  [17716.240674] xfrm6_rcv (net/ipv6/xfrm6_input.c:172)
  [...]

Note that one could set CROSS_COMPILE=llvm- instead to hack around this
issue.  However, doing so can break the decodecode routine as it will
force the selection of other LLVM utilities down the line e.g.  llvm-as.

[1] https://lore.kernel.org/all/20230914131225.13415-3-will@kernel.org/

Link: https://lkml.kernel.org/r/20230929034836.403735-1-cmllamas@google.com
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Elliot Berman <quic_eberman@quicinc.com>
Tested-by: Justin Stitt <justinstitt@google.com>
Cc: Will Deacon <will@kernel.org>
Cc: John Stultz <jstultz@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Tom Rix <trix@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 scripts/decode_stacktrace.sh |   19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

--- a/scripts/decode_stacktrace.sh~scripts-decode_stacktracesh-optionally-use-llvm-utilities
+++ a/scripts/decode_stacktrace.sh
@@ -16,6 +16,21 @@ elif type c++filt >/dev/null 2>&1 ; then
 	cppfilt_opts=-i
 fi
 
+UTIL_SUFFIX=
+if [[ -z ${LLVM:-} ]]; then
+	UTIL_PREFIX=${CROSS_COMPILE:-}
+else
+	UTIL_PREFIX=llvm-
+	if [[ ${LLVM} == */ ]]; then
+		UTIL_PREFIX=${LLVM}${UTIL_PREFIX}
+	elif [[ ${LLVM} == -* ]]; then
+		UTIL_SUFFIX=${LLVM}
+	fi
+fi
+
+READELF=${UTIL_PREFIX}readelf${UTIL_SUFFIX}
+ADDR2LINE=${UTIL_PREFIX}addr2line${UTIL_SUFFIX}
+
 if [[ $1 == "-r" ]] ; then
 	vmlinux=""
 	basepath="auto"
@@ -75,7 +90,7 @@ find_module() {
 
 	if [[ "$modpath" != "" ]] ; then
 		for fn in $(find "$modpath" -name "${module//_/[-_]}.ko*") ; do
-			if readelf -WS "$fn" | grep -qwF .debug_line ; then
+			if ${READELF} -WS "$fn" | grep -qwF .debug_line ; then
 				echo $fn
 				return
 			fi
@@ -169,7 +184,7 @@ parse_symbol() {
 	if [[ $aarray_support == true && "${cache[$module,$address]+isset}" == "isset" ]]; then
 		local code=${cache[$module,$address]}
 	else
-		local code=$(${CROSS_COMPILE}addr2line -i -e "$objfile" "$address" 2>/dev/null)
+		local code=$(${ADDR2LINE} -i -e "$objfile" "$address" 2>/dev/null)
 		if [[ $aarray_support == true ]]; then
 			cache[$module,$address]=$code
 		fi
_