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

Jens Remus
2025-02-05T10:26:10Z

On 04.02.2025 20:10, Josh Poimboeuf wrote:
> On Thu, Jan 30, 2025 at 05:17:33PM +0100, Jens Remus wrote:
>> On 22.01.2025 03:31, Josh Poimboeuf wrote:

>>> 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

Thanks! Your patch works fine on s390:

test_vdso 1087 104.721004: 10000 task-clock:ppp:
3ffd11f1702 __cvdso_clock_gettime_data.constprop.0+0x52 ([vdso])
3ffd11f14c6 __kernel_clock_gettime+0x16 ([vdso])
3ff8f6f113e clock_gettime@@GLIBC_2.17+0x1e (/usr/lib64/libc.so.6)
3ff8f6e20e8 __gettimeofday+0x38 (/usr/lib64/libc.so.6)
100066e main+0x1e (/root/test/vdso/test_vdso)
3ff8f63459c __libc_start_call_main+0x8c (/usr/lib64/libc.so.6)
3ff8f63469e __libc_start_main@@GLIBC_2.34+0xae (/usr/lib64/libc.so.6)
100073a _start+0x3a (/root/test/vdso/test_vdso)

Regards,
Jens
--
Jens Remus
Linux on Z Development (D3303)
+49-7031-16-1128 Office
jremus@de.ibm.com

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