Re: [PATCH v5 0/8] unwind, arm64: add sframe unwinder for kernel

[Mostafa Saleh <smostafa@google.com>]

On Tue, Apr 28, 2026 at 06:36:35PM +0000, Dylan Hatch wrote:
> Implement a generic kernel sframe-based [1] unwinder. The main goal is
> to improve reliable stacktrace on arm64 by unwinding across exception
> boundaries.
> 
> On x86, the ORC unwinder provides reliable stacktrace through similar
> methodology, but arm64 lacks the necessary support from objtool to
> create ORC unwind tables.
> 
> Currently, there's already a sframe unwinder proposed for userspace: [2].
> To maintain common definitions and algorithms for sframe lookup, a
> substantial portion of this patch series aims to refactor the sframe
> lookup code to support both kernel and userspace sframe sections.
> 
> Currently, only GNU Binutils support sframe. This series relies on the
> Sframe V3 format, which is supported in binutils 2.46.
> 
> These patches are based on Steven Rostedt's sframe/core branch [3],
> which is and aggregation of existing work done for x86 sframe userspace
> unwind, and contains [2]. This branch is, in turn, based on Linux
> v7.0-rc3. This full series (applied to the sframe/core branch) is
> available on github: [4].
> 

Not sure if related, but after updating my toolchain
(aarch64-linux-gnu-gcc (Debian 15.2.0-4) 15.2.0), I hit link errors:
ld.lld: error: arch/arm64/kernel/vdso/vgettimeofday.o:(.sframe) is being placed in '.sframe'
ld.lld: error: arch/arm64/kernel/vdso/vgetrandom.o:(.sframe) is being placed in '.sframe`

I applied this series hoping that fix it, but it doesn't, so far I
have this hack :
diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S
index 52314be29191..53bdf757ee44 100644
--- a/arch/arm64/kernel/vdso/vdso.lds.S
+++ b/arch/arm64/kernel/vdso/vdso.lds.S
@@ -77,7 +77,7 @@ SECTIONS
        /DISCARD/       : {
                *(.data .data.* .gnu.linkonce.d.* .sdata*)
                *(.bss .sbss .dynbss .dynsbss)
-               *(.eh_frame .eh_frame_hdr)
+               *(.eh_frame .eh_frame_hdr .sframe)
        }
 }

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 60c8c22fd3e4..759903acd6fc 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -1064,6 +1064,7 @@
        /* ld.bfd warns about .gnu.version* even when not emitted */    \
        *(.gnu.version*)                                                \
        *(__tracepoint_check)                                           \
+       *(.sframe)                                                      \

 #define DISCARDS                                                       \
        /DISCARD/ : {                                                   \


Thanks,
Mostafa