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

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Message-ID: <48231957-ef84-4329-9337-411a8fbf5fe6@linux.ibm.com>
Date: Wed, 5 Feb 2025 11:04:55 +0100
From: Jens Remus <jremus@...ux.ibm.com>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-kernel@...r.kernel.org, Indu Bhagat <indu.bhagat@...cle.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, Mark Brown <broonie@...nel.org>,
        linux-toolchains@...r.kernel.org, Jordan Rome <jordalgo@...a.com>,
        Sam James <sam@...too.org>, linux-trace-kernel@...r.kernel.org,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Florian Weimer <fweimer@...hat.com>, Andy Lutomirski <luto@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>, Weinan Liu <wnliu@...gle.com>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>
Subject: Re: [PATCH v4 25/39] unwind_user/sframe: Show file name in debug
 output

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@...ibm.com

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