[PATCH 1/1] perf symbols: Handle '1' symbols in /proc/kallsyms

[PATCH 1/1] perf symbols: Handle '1' symbols in /proc/kallsyms

[Arnaldo Carvalho de Melo]

Just FYI, I'm carrying this on the perf tools tree.

I started seeing this in recent Fedora 42 kernels:

  root@x1:~# uname -a
  Linux x1 6.17.4-200.fc42.x86_64 #1 SMP PREEMPT_DYNAMIC Sun Oct 19 18:47:49 UTC 2025 x86_64 GNU/Linux
  root@x1:~#

  root@x1:~# perf test 1
    1: vmlinux symtab matches kallsyms     : FAILED!
  root@x1:~#

Related to:

  root@x1:~# grep ' 1 ' /proc/kallsyms
  ffffffffb098bc00 1 __pfx__RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
  ffffffffb098bc10 1 _RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
  root@x1:~#

That is found in:

  root@x1:~# pahole --running_kernel_vmlinux
  /usr/lib/debug/lib/modules/6.17.4-200.fc42.x86_64/vmlinux
  root@x1:~#

  root@x1:~# readelf -sW /usr/lib/debug/lib/modules/6.17.4-200.fc42.x86_64/vmlinux | grep __pfx__RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
  150649: ffffffff81f8bc00    16 FUNC    LOCAL  DEFAULT    1 __pfx__RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
  root@x1:~#

But was being filtered out when reading /proc/kallsyms, as the '1'
symbol type was not being handled, do it, there are just two of them at
this point.

Cc: Alex Gaynor <alex.gaynor@gmail.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Andreas Hindborg <a.hindborg@kernel.org>
Cc: Benno Lossin <lossin@kernel.org>
Cc: Björn Roy Baron <bjorn3_gh@protonmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Gary Guo <gary@garyguo.net>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Trevor Gross <tmgross@umich.edu>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/symbol.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index cc26b7bf302b29d6..948d3e8ad782bc2a 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -112,9 +112,13 @@ static bool symbol_type__filter(char __symbol_type)
 	// 'N' first seen in:
 	// ffffffff9b35d130 N __pfx__RNCINvNtNtNtCsbDUBuN8AbD4_4core4iter8adapters3map12map_try_foldjNtCs6vVzKs5jPr6_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
 	// a seemingly Rust mangled name
+	// Ditto for '1':
+	// root@x1:~# grep ' 1 ' /proc/kallsyms
+	// ffffffffb098bc00 1 __pfx__RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
+	// ffffffffb098bc10 1 _RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
 	char symbol_type = toupper(__symbol_type);
 	return symbol_type == 'T' || symbol_type == 'W' || symbol_type == 'D' || symbol_type == 'B' ||
-	       __symbol_type == 'u' || __symbol_type == 'l' || __symbol_type == 'N';
+	       __symbol_type == 'u' || __symbol_type == 'l' || __symbol_type == 'N' || __symbol_type == '1';
 }
 
 static int prefix_underscores_count(const char *str)
-- 
2.51.1

Re: [PATCH 1/1] perf symbols: Handle '1' symbols in /proc/kallsyms

[Namhyung Kim]

Hi Arnaldo,

On Mon, Nov 03, 2025 at 03:03:23PM -0300, Arnaldo Carvalho de Melo wrote:
> Just FYI, I'm carrying this on the perf tools tree.
> 
> I started seeing this in recent Fedora 42 kernels:
> 
>   root@x1:~# uname -a
>   Linux x1 6.17.4-200.fc42.x86_64 #1 SMP PREEMPT_DYNAMIC Sun Oct 19 18:47:49 UTC 2025 x86_64 GNU/Linux
>   root@x1:~#
> 
>   root@x1:~# perf test 1
>     1: vmlinux symtab matches kallsyms     : FAILED!
>   root@x1:~#
> 
> Related to:
> 
>   root@x1:~# grep ' 1 ' /proc/kallsyms
>   ffffffffb098bc00 1 __pfx__RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
>   ffffffffb098bc10 1 _RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
>   root@x1:~#
> 
> That is found in:
> 
>   root@x1:~# pahole --running_kernel_vmlinux
>   /usr/lib/debug/lib/modules/6.17.4-200.fc42.x86_64/vmlinux
>   root@x1:~#
> 
>   root@x1:~# readelf -sW /usr/lib/debug/lib/modules/6.17.4-200.fc42.x86_64/vmlinux | grep __pfx__RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
>   150649: ffffffff81f8bc00    16 FUNC    LOCAL  DEFAULT    1 __pfx__RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
>   root@x1:~#
> 
> But was being filtered out when reading /proc/kallsyms, as the '1'
> symbol type was not being handled, do it, there are just two of them at
> this point.

Do you know what the type '1' means?  It seems they are from Rust.

Thanks,
Namhyung

> 
> Cc: Alex Gaynor <alex.gaynor@gmail.com>
> Cc: Alice Ryhl <aliceryhl@google.com>
> Cc: Andreas Hindborg <a.hindborg@kernel.org>
> Cc: Benno Lossin <lossin@kernel.org>
> Cc: Björn Roy Baron <bjorn3_gh@protonmail.com>
> Cc: Boqun Feng <boqun.feng@gmail.com>
> Cc: Danilo Krummrich <dakr@kernel.org>
> Cc: Gary Guo <gary@garyguo.net>
> Cc: Miguel Ojeda <ojeda@kernel.org>
> Cc: Trevor Gross <tmgross@umich.edu>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> ---
>  tools/perf/util/symbol.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index cc26b7bf302b29d6..948d3e8ad782bc2a 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -112,9 +112,13 @@ static bool symbol_type__filter(char __symbol_type)
>  	// 'N' first seen in:
>  	// ffffffff9b35d130 N __pfx__RNCINvNtNtNtCsbDUBuN8AbD4_4core4iter8adapters3map12map_try_foldjNtCs6vVzKs5jPr6_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
>  	// a seemingly Rust mangled name
> +	// Ditto for '1':
> +	// root@x1:~# grep ' 1 ' /proc/kallsyms
> +	// ffffffffb098bc00 1 __pfx__RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
> +	// ffffffffb098bc10 1 _RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
>  	char symbol_type = toupper(__symbol_type);
>  	return symbol_type == 'T' || symbol_type == 'W' || symbol_type == 'D' || symbol_type == 'B' ||
> -	       __symbol_type == 'u' || __symbol_type == 'l' || __symbol_type == 'N';
> +	       __symbol_type == 'u' || __symbol_type == 'l' || __symbol_type == 'N' || __symbol_type == '1';
>  }
>  
>  static int prefix_underscores_count(const char *str)
> -- 
> 2.51.1
> 

Re: [PATCH 1/1] perf symbols: Handle '1' symbols in /proc/kallsyms

[Arnaldo Carvalho de Melo]

On Mon, Nov 03, 2025 at 07:06:45PM -0800, Namhyung Kim wrote:
> On Mon, Nov 03, 2025 at 03:03:23PM -0300, Arnaldo Carvalho de Melo wrote:
> > Just FYI, I'm carrying this on the perf tools tree.

> > I started seeing this in recent Fedora 42 kernels:

> >   root@x1:~# uname -a
> >   Linux x1 6.17.4-200.fc42.x86_64 #1 SMP PREEMPT_DYNAMIC Sun Oct 19 18:47:49 UTC 2025 x86_64 GNU/Linux
> >   root@x1:~#

> >   root@x1:~# perf test 1
> >     1: vmlinux symtab matches kallsyms     : FAILED!
> >   root@x1:~#

> > Related to:

> >   root@x1:~# grep ' 1 ' /proc/kallsyms
> >   ffffffffb098bc00 1 __pfx__RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
> >   ffffffffb098bc10 1 _RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
> >   root@x1:~#

> > That is found in:
 
> >   root@x1:~# pahole --running_kernel_vmlinux
> >   /usr/lib/debug/lib/modules/6.17.4-200.fc42.x86_64/vmlinux
> >   root@x1:~#
 
> >   root@x1:~# readelf -sW /usr/lib/debug/lib/modules/6.17.4-200.fc42.x86_64/vmlinux | grep __pfx__RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
> >   150649: ffffffff81f8bc00    16 FUNC    LOCAL  DEFAULT    1 __pfx__RNCINvNtNtNtCsfwaGRd4cjqE_4core4iter8adapters3map12map_try_foldjNtCskFudTml27HW_12drm_panic_qr7VersionuINtNtNtBa_3ops12control_flow11ControlFlowB10_ENcB10_0NCINvNvNtNtNtB8_6traits8iterator8Iterator4find5checkB10_NCNvMB12_B10_13from_segments0E0E0B12_
> >   root@x1:~#
> > 
> > But was being filtered out when reading /proc/kallsyms, as the '1'
> > symbol type was not being handled, do it, there are just two of them at
> > this point.
> 
> Do you know what the type '1' means?  It seems they are from Rust.

They are related to anonymous Rust closures in the QR encoder for the
DRM panic, this part:

drivers/gpu/drm/drm_panic_qr.rs

    fn from_segments(segments: &[&Segment<'_>]) -> Option<Version> {
        (1..=40)
            .map(Version)
            .find(|&v| v.max_data() * 8 >= segments.iter().map(|s| s.total_size_bits(v)).sum())
    }

That 

Using rustfilt we get:

core::iter::adapters::map::map_try_fold::<usize, drm_panic_qr::Version, (), core::ops::control_flow::ControlFlow<drm_panic_qr::Version>, drm_panic_qr::Version, core::iter::traits::iterator::Iterator::find::check<drm_panic_qr::Version, <drm_panic_qr::Version>::from_segments::{closure#0}>::{closure#0}>::{closure#0}
#

Both are for the same symbol, the __pfx__ is to do some stack probing.
LLVM may introduce this for other reasons.

So far, '1' symbols are Rust symbols, in the Linux kernel, for unnamed
closures and its prefix code checking for stack space, Miguel, do you
have something to add?

- Arnaldo

Re: [PATCH 1/1] perf symbols: Handle '1' symbols in /proc/kallsyms

[Miguel Ojeda]

On Thu, Nov 6, 2025 at 9:25 PM Arnaldo Carvalho de Melo <acme@kernel.org> wrote:
>
> So far, '1' symbols are Rust symbols, in the Linux kernel, for unnamed
> closures and its prefix code checking for stack space, Miguel, do you
> have something to add?

Wait, is `1` the symbol type? I don't know what that is. That column
in `readelf` isn't the symbol type, no?

And if I use `nm` on Fedora's `vmlinux`, I get a `t` (and the
`System.map` has the same). Something is fishy in `/proc/kallsyms`.

We don't handle the big symbol double-byte... I will send a patch.

Cheers,
Miguel

Re: [PATCH 1/1] perf symbols: Handle '1' symbols in /proc/kallsyms

[Miguel Ojeda]

On Fri, Nov 7, 2025 at 2:35 AM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> We don't handle the big symbol double-byte... I will send a patch.

For (cross-)reference, I sent this patch a few days ago:

    https://lore.kernel.org/rust-for-linux/20251107050414.511648-1-ojeda@kernel.org/

And then Gary told me today (thanks!) there was a similar path a year ago:

    https://lore.kernel.org/lkml/20241011143853.3022643-1-zhengyejian@huaweicloud.com/

So I think we should take Zheng's (Cc'd).

Thanks!

Cheers,
Miguel

Re: [PATCH 1/1] perf symbols: Handle '1' symbols in /proc/kallsyms

[Miguel Ojeda]

On Tue, Nov 11, 2025 at 10:16 PM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> So I think we should take Zheng's (Cc'd).

Trying another address, since that one failed...

Cheers,
Miguel