Re: [PATCH v4 25/39] unwind_user/sframe: Show file name in debug output

Josh Poimboeuf
2025-02-04T19:10:21Z

On Thu, Jan 30, 2025 at 05:17:33PM +0100, Jens Remus wrote:
> On 22.01.2025 03:31, Josh Poimboeuf wrote:
> > When debugging sframe issues, the error messages aren't all that helpful
> > without knowing what file a corresponding .sframe section belongs to.
> > Prefix debug output strings with the file name.
> >
> > Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
>
> > diff --git a/kernel/unwind/sframe_debug.h b/kernel/unwind/sframe_debug.h
>
> > +static inline void dbg_init(struct sframe_section *sec)
> > +{
> > + struct mm_struct *mm = current->mm;
> > + struct vm_area_struct *vma;
> > +
> > + guard(mmap_read_lock)(mm);
> > + vma = vma_lookup(mm, sec->sframe_start);
> > + if (!vma)
> > + sec->filename = kstrdup("(vma gone???)", GFP_KERNEL);
> > + else if (vma->vm_file)
> > + sec->filename = kstrdup_quotable_file(vma->vm_file, GFP_KERNEL);
> > + else if (!vma->vm_mm)
>
> This condition does not appear to work for vdso on s390.

I had a fix for this which somehow got dropped:

diff --git a/kernel/unwind/sframe_debug.h b/kernel/unwind/sframe_debug.h
index 3bb3c5574aee..045e9c0b16c9 100644
--- a/kernel/unwind/sframe_debug.h
+++ b/kernel/unwind/sframe_debug.h
@@ -67,6 +67,10 @@ static inline void dbg_init(struct sframe_section *sec)
sec->filename = kstrdup("(vma gone???)", GFP_KERNEL);
else if (vma->vm_file)
sec->filename = kstrdup_quotable_file(vma->vm_file, GFP_KERNEL);
+ else if (vma->vm_ops && vma->vm_ops->name)
+ sec->filename = kstrdup(vma->vm_ops->name(vma), GFP_KERNEL);
+ else if (arch_vma_name(vma))
+ sec->filename = kstrdup(arch_vma_name(vma), GFP_KERNEL);
else if (!vma->vm_mm)
sec->filename = kstrdup("(vdso)", GFP_KERNEL);
else