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

On Thu, Apr 30, 2026 at 3:11 AM Jens Remus <[email protected]> wrote:
>
> On 4/28/2026 8:36 PM, 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.
>
> Please add support to initialize the optional sframe unwinder debug
> information.  Either in the appropriate patches in this series or as a
> separate patch.

Sounds good, I'll add this in as a separate patch in the next version.

>
> Note that for the module case I wonder whether it would be preferable
> to somehow indicate that it is a module name in the string, e.g.
> "(<module-name>)" or "<module-name> (module)"?

I don't have a strong preference, though I agree it makes sense to
indicate that the section is from a module. For now I'll add the
parentheses "(<module-name>)".

>
> diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c
> --- a/kernel/unwind/sframe.c
> +++ b/kernel/unwind/sframe.c
> @@ -1028,6 +1028,8 @@ void __init init_sframe_table(void)
>         kernel_sfsec.text_start         = (unsigned long)_stext;
>         kernel_sfsec.text_end           = (unsigned long)_etext;
>
> +       dbg_init(&kernel_sfsec);
> +
>         if (WARN_ON(sframe_read_header(&kernel_sfsec)))
>                 return;
>         if (WARN_ON(sframe_validate_section(&kernel_sfsec)))
> @@ -1047,6 +1049,8 @@ void sframe_module_init(struct module *mod, void *sframe, size_t sframe_size,
>         sec->text_start   = (unsigned long)text;
>         sec->text_end     = (unsigned long)text + text_size;
>
> +       dbg_init(sec);
> +
>         if (WARN_ON(sframe_read_header(sec)))
>                 return;
>         if (WARN_ON(sframe_validate_section(sec)))
> diff --git a/kernel/unwind/sframe_debug.h b/kernel/unwind/sframe_debug.h
> --- a/kernel/unwind/sframe_debug.h
> +++ b/kernel/unwind/sframe_debug.h
> @@ -32,6 +32,18 @@ static inline void dbg_init(struct sframe_section *sec)
>         struct mm_struct *mm = current->mm;
>         struct vm_area_struct *vma;
>
> +       if (sec->sec_type == SFRAME_KERNEL) {
> +               if (sec == &kernel_sfsec) {
> +                       sec->filename = kstrdup("(vmlinux)", GFP_KERNEL);
> +               } else {
> +                       struct module *mod = container_of(sec, struct module,
> +                                                         arch.sframe_sec);
> +                       sec->filename = kstrdup(mod->name, GFP_KERNEL);
> +               }
> +
> +               return;
> +       }
> +
>         guard(mmap_read_lock)(mm);
>         vma = vma_lookup(mm, sec->sframe_start);
>         if (!vma)
>
> Regards,
> Jens
> --
> Jens Remus
> Linux on Z Development (D3303)
> [email protected] / [email protected]
>
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>

Thanks for the suggestion,
Dylan