From: Srikar Dronamraju <srikar@linux.ibm.com>
To: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Brian Johannesmeyer <bjohannesmeyer@gmail.com>,
Madhavan Srinivasan <maddy@linux.ibm.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Revert "scripts/faddr2line: Combine three readelf calls into one"
Date: Tue, 15 Sep 2026 07:45:37 +0530 [thread overview]
Message-ID: <aqiqScJg8Ey5QnKl@linux.ibm.com> (raw)
In-Reply-To: <aqhDm60zSZIazrnC@jpoimboe>
* Josh Poimboeuf <jpoimboe@kernel.org> [2026-09-14 12:00:26]:
> > It could be a bug in Powerpc readelf that this line doesnt get printed.
> > However since its breaking with existing readelf, its better to be
> > reverted.
> >
> > With the revert, we end up calling readelf three times but this should
> > still be fine since calling faddr2line is a debug tool.
> >
> > Fixes: b8d9d9496c1e ("scripts/faddr2line: Combine three readelf calls into one")
> > Signed-off-by: Srikar Dronamraju <srikar@linux.ibm.com>
>
> Can you run
>
> bash -x scripts/faddr2line ./vmlinux need_active_balance+0x1d4/0x21c
>
+ set -o errexit
+ set -o nounset
+ UTIL_SUFFIX=
+ [[ '' == '' ]]
+ UTIL_PREFIX=
+ READELF=readelf
+ ADDR2LINE=addr2line
+ AWK=awk
+ GREP=grep
+ export LC_ALL=C
+ LC_ALL=C
+ command -v awk
+ command -v readelf
+ command -v addr2line
+ [[ 2 -lt 2 ]]
+ objfile=./vmlinux
+ LIST=0
+ [[ ./vmlinux == \-\-\l\i\s\t ]]
+ [[ ! -f ./vmlinux ]]
+ shift
+ run_readelf ./vmlinux
+ local objfile=./vmlinux
+ local tmpfile
++ mktemp
+ tmpfile=/tmp/tmp.BGkKH2pxoy
+ readelf --file-header --section-headers --symbols --wide ./vmlinux
++ sed -n '/There are [0-9]* section headers, starting at offset\|Section Headers:/q;p' /tmp/tmp.BGkKH2pxoy
+ ELF_FILEHEADER='ELF Header:
Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class: ELF64
Data: 2'\''s complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: EXEC (Executable file)
Machine: PowerPC64
Version: 0x1
Entry point address: 0xc000000000000000
Start of program headers: 64 (bytes into file)
Start of section headers: 425572840 (bytes into file)
Flags: 0x2, abiv2
Size of this header: 64 (bytes)
Size of program headers: 56 (bytes)
Number of program headers: 2
Size of section headers: 64 (bytes)
Number of section headers: 61
Section header string table index: 60'
++ sed -n '/Symbol table .* contains [0-9]* entries:/q;p'
++ sed -n '/There are [0-9]* section headers, starting at offset\|Section Headers:/,$p' /tmp/tmp.BGkKH2pxoy
+ ELF_SECHEADERS='Section Headers:
[Nr] Name Type Address Off Size ES Flg Lk Inf Al
[ 0] NULL 0000000000000000 000000 000000 00 0 0 0
[ 1] .head.text PROGBITS c000000000000000 010000 008000 00 AX 0 0 128
[ 2] .text PROGBITS c000000000008000 018000 1474ed4 00 AX 0 0 256
[ 3] .rodata PROGBITS c000000001480000 1490000 6217ce 00 WA 0 0 65536
[ 4] .pci_fixup PROGBITS c000000001aa17d0 1ab17d0 004590 00 WA 0 0 8
[ 5] .printk_index PROGBITS c000000001aa5d60 1ab5d60 00f770 00 WA 0 0 8
[ 6] __ksymtab PROGBITS c000000001ab54d0 1ac54d0 045120 00 A 0 0 8
[ 7] __kcrctab PROGBITS c000000001afa5f0 1b0a5f0 00b830 00 A 0 0 4
[ 8] __kflagstab PROGBITS c000000001b05e20 1b15e20 002e0c 00 A 0 0 1
[ 9] __ksymtab_strings PROGBITS c000000001b08c2c 1b18c2c 039a9c 01 AMS 0 0 1
[10] __param PROGBITS c000000001b426c8 1b526c8 002e18 00 WA 0 0 8
[11] __modver PROGBITS c000000001b454e0 1b554e0 0005a0 00 WA 0 0 8
[12] __ex_table PROGBITS c000000001b45a80 1b55a80 002ab8 00 A 0 0 4
[13] .notes NOTE c000000001b48538 1b58538 000088 00 A 0 0 4
[14] .BTF PROGBITS c000000001b50000 1b60000 4d833d 00 A 0 0 1
[15] .BTF_ids PROGBITS c000000002030000 2040000 00138c 00 A 0 0 1
[16] .branch_lt PROGBITS c000000002040000 2050000 003030 00 WA 0 0 8
[17] .got PROGBITS c000000002043100 2053100 000380 08 WA 0 0 256
[18] __soft_mask_table PROGBITS c000000002043480 2053480 000080 00 A 0 0 8
[19] __restart_table PROGBITS c000000002043500 2053500 0000c0 00 A 0 0 8
[20] __stf_entry_barrier_fixup PROGBITS c0000000020435c0 20535c0 0001e8 00 A 0 0 4
[21] __uaccess_flush_fixup PROGBITS c0000000020437a8 20537a8 000008 00 A 0 0 4
[22] __entry_flush_fixup PROGBITS c0000000020437b0 20537b0 0001d8 00 A 0 0 4
[23] __scv_entry_flush_fixup PROGBITS c000000002043988 2053988 000010 00 A 0 0 4
[24] __stf_exit_barrier_fixup PROGBITS c000000002043998 2053998 000060 00 A 0 0 4
[25] __rfi_flush_fixup PROGBITS c0000000020439f8 20539f8 000060 00 A 0 0 4
[26] __spec_barrier_fixup PROGBITS c000000002043a58 2053a58 000690 00 A 0 0 4
[27] .init.text PROGBITS c000000003000000 3010000 0b0000 00 WAX 0 0 32
[28] .exit.text PROGBITS c0000000030b0000 30c0000 004158 00 AX 0 0 32
[29] .init.data PROGBITS c0000000030c0000 30d0000 1c4580 00 WA 0 0 65536
[30] __ftr_fixup PROGBITS c000000003284580 3294580 00eaf0 00 A 0 0 8
[31] __mmu_ftr_fixup PROGBITS c000000003293070 32a3070 001830 00 A 0 0 8
[32] __lwsync_fixup PROGBITS c0000000032948a0 32a48a0 000dc8 00 A 0 0 4
[33] .data..percpu PROGBITS c0000000032a0000 32b0000 1e0e58 00 WA 0 0 4096
[34] .machine.desc PROGBITS c000000003480e58 3490e58 000410 00 WA 0 0 8
[35] .dynsym DYNSYM c000000003481268 3491268 000048 18 A 36 3 8
[36] .dynstr STRTAB c0000000034812b0 34912b0 000001 00 A 0 0 1
[37] .dynamic DYNAMIC c0000000034812b8 34912b8 000120 10 WA 36 0 8
[38] .gnu.hash GNU_HASH c0000000034813d8 34913d8 00001c 00 A 35 0 8
[39] .rela.dyn RELA c0000000034813f8 34913f8 519030 18 A 35 0 8
[40] .data PROGBITS c0000000039a0000 39b0000 610100 00 WA 0 0 128
[41] .data..init_task NOBITS c000000003fb4000 3fc0100 004000 00 WA 0 0 1
[42] .data..page_aligned PROGBITS c000000003fc0000 3fd0000 010000 00 WA 0 0 65536
[43] .data..cacheline_aligned PROGBITS c000000003fd0000 3fe0000 023500 00 WA 0 0 128
[44] .data..read_mostly PROGBITS c000000003ff3500 4003500 03cb80 00 WA 0 0 128
[45] .data_nosave PROGBITS c000000004040000 407bcec 000000 00 W 0 0 1
[46] __bug_table PROGBITS c000000004040000 4050000 02bcec 00 WA 0 0 1
[47] .bss NOBITS c000000004070000 407bcec 725338 00 WA 0 0 65536
[48] .debug_aranges PROGBITS 0000000000000000 407bcf0 0279d0 00 0 0 16
[49] .debug_info PROGBITS 0000000000000000 40a36c0 fa4d575 00 0 0 1
[50] .debug_abbrev PROGBITS 0000000000000000 13af0c35 673114 00 0 0 1
[51] .debug_line PROGBITS 0000000000000000 14163d49 211a8e7 00 0 0 1
[52] .debug_frame PROGBITS 0000000000000000 1627e630 3ba1f8 00 0 0 8
[53] .debug_str PROGBITS 0000000000000000 16638828 426e36 01 MS 0 0 1
[54] .debug_line_str PROGBITS 0000000000000000 16a5f65e 0004f5 01 MS 0 0 1
[55] .debug_loclists PROGBITS 0000000000000000 16a5fb53 1efdaf5 00 0 0 1
[56] .debug_rnglists PROGBITS 0000000000000000 1895d648 4d9186 00 0 0 1
[57] .comment PROGBITS 0000000000000000 18e367ce 00002e 01 MS 0 0 1
[58] .symtab SYMTAB 0000000000000000 18e36800 42b670 18 59 150524 8
[59] .strtab STRTAB 0000000000000000 19261e70 379870 00 0 0 1
[60] .shstrtab STRTAB 0000000000000000 195db6e0 000302 00 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
L (link order), O (extra OS processing required), G (group), T (TLS),
C (compressed), x (unknown), o (OS specific), E (exclude),
D (mbind), p (processor specific)'
> to see what line it's failing at?
>
As you can see, the last executed line line is
ELF_SECHEADERS=$(sed -n '/There are [0-9]* section headers, starting at offset\|Section Headers:/,$p' "$tmpfile" | sed -n '/Symbol table .* contains [0-9]* entries:/q;p')
which it self is called from run_readelf
since sed -o errexit is set in the script, sed returns an non-zero error
and that causes the script to exit if the line is not found.
The other options are
1. to reset sed -o errexit in run_readelf
diff --git a/scripts/faddr2line b/scripts/faddr2line
index 622875396bcf..f1b83913d08c 100755
--- a/scripts/faddr2line
+++ b/scripts/faddr2line
@@ -116,12 +116,14 @@ run_readelf() {
${READELF} --file-header --section-headers --symbols --wide "$objfile" > "$tmpfile"
+ set +o errexit
# This assumes that readelf first prints the file header, then the section headers, then the symbols.
# Note: It seems that GNU readelf does not prefix section headers with the "There are X section headers"
# line when multiple options are given, so let's also match with the "Section Headers:" line.
ELF_FILEHEADER=$(sed -n '/There are [0-9]* section headers, starting at offset\|Section Headers:/q;p' "$tmpfile")
ELF_SECHEADERS=$(sed -n '/There are [0-9]* section headers, starting at offset\|Section Headers:/,$p' "$tmpfile" | sed -n '/Symbol table .* contains [0-9]* entries:/q;p')
ELF_SYMS=$(sed -n '/Symbol table .* contains [0-9]* entries:/,$p' "$tmpfile")
+ set -o errexit
rm -f -- "$tmpfile"
}
2. or use || true with sed, so that it doesn't fail.
diff --git a/scripts/faddr2line b/scripts/faddr2line
index 622875396bcf..6e867b053ac4 100755
--- a/scripts/faddr2line
+++ b/scripts/faddr2line
@@ -119,9 +119,9 @@ run_readelf() {
# This assumes that readelf first prints the file header, then the section headers, then the symbols.
# Note: It seems that GNU readelf does not prefix section headers with the "There are X section headers"
# line when multiple options are given, so let's also match with the "Section Headers:" line.
- ELF_FILEHEADER=$(sed -n '/There are [0-9]* section headers, starting at offset\|Section Headers:/q;p' "$tmpfile")
- ELF_SECHEADERS=$(sed -n '/There are [0-9]* section headers, starting at offset\|Section Headers:/,$p' "$tmpfile" | sed -n '/Symbol table .* contains [0-9]* entries:/q;p')
- ELF_SYMS=$(sed -n '/Symbol table .* contains [0-9]* entries:/,$p' "$tmpfile")
+ ELF_FILEHEADER=$(sed -n '/There are [0-9]* section headers, starting at offset\|Section Headers:/q;p' "$tmpfile" || true)
+ ELF_SECHEADERS=$(sed -n '/There are [0-9]* section headers, starting at offset\|Section Headers:/,$p' "$tmpfile" | sed -n '/Symbol table .* contains [0-9]* entries:/q;p' || true)
+ ELF_SYMS=$(sed -n '/Symbol table .* contains [0-9]* entries:/,$p' "$tmpfile" || true)
rm -f -- "$tmpfile"
}
Note: only the SECHEADERS line needs true but adding true to just that line looks hacky.
3. remove set -o errexit for the entire file.
diff --git a/scripts/faddr2line b/scripts/faddr2line
index 622875396bcf..174ab098750f 100755
--- a/scripts/faddr2line
+++ b/scripts/faddr2line
@@ -41,7 +41,6 @@
# free_reserved_area at mm/page_alloc.c:6429 (discriminator 2)
-set -o errexit
set -o nounset
usage() {
4. patch I sent before, use readelf multiple times.
I have tried and verified these options work correctly too.
However I feel option 4, where we run readelf 3 times is the cleanest.
> Any chance the below fixes it?
>
> diff --git a/scripts/faddr2line b/scripts/faddr2line
> index 622875396bcfc..550c0f9b9d473 100755
> --- a/scripts/faddr2line
> +++ b/scripts/faddr2line
> @@ -78,7 +78,7 @@ GREP="grep"
>
> # Enforce ASCII-only output from tools like readelf
> # ensuring sed processes strings correctly.
> -export LANG=C
> +export LC_ALL=C
>
As you can see above from the log, I have tried this but this doesn't help
> command -v ${AWK} >/dev/null 2>&1 || die "${AWK} isn't installed"
> command -v ${READELF} >/dev/null 2>&1 || die "${READELF} isn't installed"
--
Thanks and Regards
Srikar Dronamraju
prev parent reply other threads:[~2026-09-15 2:15 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-05 1:24 Srikar Dronamraju
2026-09-14 19:00 ` Josh Poimboeuf
2026-09-15 2:15 ` Srikar Dronamraju [this message]
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