[PATCH] scripts/faddr2line: Fix regression in name resolution on ppc64le

* [PATCH] scripts/faddr2line: Fix regression in name resolution on ppc64le
@ 2022-09-27  7:52 Srikar Dronamraju
  2022-09-27 11:19 ` Thadeu Lima de Souza Cascardo
  0 siblings, 1 reply; 5+ messages in thread
From: Srikar Dronamraju @ 2022-09-27  7:52 UTC (permalink / raw)
  To: LKML
  Cc: Thadeu Lima de Souza Cascardo, Srikar Dronamraju, Peter Zijlstra,
	Jiri Olsa, Josh Poimboeuf, Naveen N. Rao, linuxppc-dev

Commit 1d1a0e7c5100 ("scripts/faddr2line: Fix overlapping text section failures")
can cause scripts/faddr2line to fail on ppc64le machines on few
distributions, while working on other distributions. The failure can be
attributed to difference in readelf output on various distributions.

$ ./scripts/faddr2line vmlinux find_busiest_group+0x00
no match for find_busiest_group+0x00

Expected output was:
$ ./scripts/faddr2line vmlinux find_busiest_group+0x00
find_busiest_group+0x00/0x3d0:
find_busiest_group at kernel/sched/fair.c:9595

On ppc64le, readelf adds localentry tag before the symbol name on few
distributions and adds the localentry tag after the symbol name on few
other distributions. This problem has been discussed in the reference
URL given below. This problem can be overcome by filtering out
localentry tags in readelf output. Similar fixes are already present in
kernel by way of commits:

1fd6cee127e2 ("libbpf: Fix VERSIONED_SYM_COUNT number parsing")
aa915931ac3e ("libbpf: Fix readelf output parsing for Fedora")

Fixes: 1d1a0e7c5100 ("scripts/faddr2line: Fix overlapping text section failures")
Reference: https://lore.kernel.org/bpf/20191211160133.GB4580@calabresa/
Cc: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
 scripts/faddr2line | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/scripts/faddr2line b/scripts/faddr2line
index 5514c23f45c2..0e73aca4f908 100755
--- a/scripts/faddr2line
+++ b/scripts/faddr2line
@@ -74,7 +74,8 @@ command -v ${ADDR2LINE} >/dev/null 2>&1 || die "${ADDR2LINE} isn't installed"
 find_dir_prefix() {
 	local objfile=$1
 
-	local start_kernel_addr=$(${READELF} --symbols --wide $objfile | ${AWK} '$8 == "start_kernel" {printf "0x%s", $2}')
+	local start_kernel_addr=$(${READELF} --symbols --wide $objfile | sed 's/\[.*\]//' |
+		${AWK} '$8 == "start_kernel" {printf "0x%s", $2}')
 	[[ -z $start_kernel_addr ]] && return
 
 	local file_line=$(${ADDR2LINE} -e $objfile $start_kernel_addr)
@@ -178,7 +179,7 @@ __faddr2line() {
 				found=2
 				break
 			fi
-		done < <(${READELF} --symbols --wide $objfile | ${AWK} -v sec=$sym_sec '$7 == sec' | sort --key=2)
+		done < <(${READELF} --symbols --wide $objfile | sed 's/\[.*\]//' | ${AWK} -v sec=$sym_sec '$7 == sec' | sort --key=2)
 
 		if [[ $found = 0 ]]; then
 			warn "can't find symbol: sym_name: $sym_name sym_sec: $sym_sec sym_addr: $sym_addr sym_elf_size: $sym_elf_size"
@@ -259,7 +260,7 @@ __faddr2line() {
 
 		DONE=1
 
-	done < <(${READELF} --symbols --wide $objfile | ${AWK} -v fn=$sym_name '$4 == "FUNC" && $8 == fn')
+	done < <(${READELF} --symbols --wide $objfile | sed 's/\[.*\]//' | ${AWK} -v fn=$sym_name '$4 == "FUNC" && $8 == fn')
 }
 
 [[ $# -lt 2 ]] && usage

base-commit: bf682942cd26ce9cd5e87f73ae099b383041e782
-- 
2.31.1


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