[PATCH] kallsyms: ignore all local labels prefixed by '.L'
Changbin Du
changbin.du at gmail.com
Mon Feb 21 06:37:58 PST 2022
Hi, Masahiro,
Could you consider picking up this change if you have no objection?
On Tue, Feb 01, 2022 at 09:32:57AM +0800, Changbin Du wrote:
> The llvm compiler can generate lots of local labels ('.LBB', '.Ltmpxxx',
> '.L__unnamed_xx', etc.). These symbols usually are useless for debugging.
> And they might overlap with handwritten symbols.
>
> Before this change, a dumpstack shows a local symbol for epc:
> [ 0.040341][ T0] Hardware name: riscv-virtio,qemu (DT)
> [ 0.040376][ T0] epc : .LBB6_14+0x22/0x6a
> [ 0.040452][ T0] ra : restore_all+0x12/0x6e
>
> The simple solution is that we can ignore all local labels prefixed by '.L'.
> For handwritten symbols which need to be preserved should drop the '.L'
> prefix.
>
> After this change, the C defined symbol is shown so we can locate the
> problematical code immediately:
> [ 0.035795][ T0] Hardware name: riscv-virtio,qemu (DT)
> [ 0.036332][ T0] epc : trace_hardirqs_on+0x54/0x13c
> [ 0.036567][ T0] ra : restore_all+0x12/0x6e
>
> Signed-off-by: Changbin Du <changbin.du at gmail.com>
> ---
> scripts/kallsyms.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
> index 54ad86d13784..8caabddf817c 100644
> --- a/scripts/kallsyms.c
> +++ b/scripts/kallsyms.c
> @@ -108,7 +108,7 @@ static bool is_ignored_symbol(const char *name, char type)
> /* Symbol names that begin with the following are ignored.*/
> static const char * const ignored_prefixes[] = {
> "$", /* local symbols for ARM, MIPS, etc. */
> - ".LASANPC", /* s390 kasan local symbols */
> + ".L", /* local labels, .LBB,.Ltmpxxx,.L__unnamed_xx,.LASANPC, etc. */
> "__crc_", /* modversions */
> "__efistub_", /* arm64 EFI stub namespace */
> "__kvm_nvhe_", /* arm64 non-VHE KVM namespace */
> --
> 2.32.0
>
--
Cheers,
Changbin Du
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