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

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Message-ID: <20250204191017.iqrew5zgxg7eh4s2@jpoimboe>
Date: Tue, 4 Feb 2025 11:10:17 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Jens Remus <jremus@...ux.ibm.com>
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 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@...nel.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