2022-02-02 02:04:29

by Changbin Du

Subject: [PATCH] kallsyms: ignore all local labels prefixed by '.L'

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 <[email protected]>
---
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

2022-02-03 16:43:24

by Nathan Chancellor

Subject: Re: [PATCH] kallsyms: ignore all local labels prefixed by '.L'

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 <[email protected]>

Does not seem too unreasonable to me.

Reviewed-by: Nathan Chancellor <[email protected]>

> ---
> 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
>
>

2022-02-03 18:34:57

by Nick Desaulniers

Subject: Re: [PATCH] kallsyms: ignore all local labels prefixed by '.L'

On Mon, Jan 31, 2022 at 5:33 PM Changbin Du <[email protected]> wrote:

Make sure to mark the version of your patches (this is v2, IIUC). `git
format-patch -v2 HEAD~`

Reviewed-by: Nick Desaulniers <[email protected]>

>
> 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 <[email protected]>
> ---
> 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
>


--
Thanks,
~Nick Desaulniers

2022-02-04 08:40:43

by Changbin Du

Subject: Re: [PATCH] kallsyms: ignore all local labels prefixed by '.L'

On Tue, Feb 01, 2022 at 11:42:59AM -0800, Nick Desaulniers wrote:
> On Mon, Jan 31, 2022 at 5:33 PM Changbin Du <[email protected]> wrote:
>
> Make sure to mark the version of your patches (this is v2, IIUC). `git
> format-patch -v2 HEAD~`
>
Sure, I fogot to add version NO. this time. Thanks for your reminding.

> Reviewed-by: Nick Desaulniers <[email protected]>
>
> >
> > 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 <[email protected]>
> > ---
> > 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
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers

--
Cheers,
Changbin Du

2022-02-21 18:27:41

by Masahiro Yamada

Subject: Re: [PATCH] kallsyms: ignore all local labels prefixed by '.L'

On Mon, Feb 21, 2022 at 11:38 PM Changbin Du <[email protected]> wrote:
>
> 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 <[email protected]>

Now applied to linux-kbuild. Thanks.



> > ---
> > 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



--
Best Regards
Masahiro Yamada

2022-02-22 05:22:06

by Changbin Du

Subject: Re: [PATCH] kallsyms: ignore all local labels prefixed by '.L'

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 <[email protected]>
> ---
> 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