linux-kernel - Re: [PATCH v10 00/14] unwind_user: x86: Deferred unwinding infrastructure

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Message-ID: <ldnmzsofhpy7rxk7rslgs5mevep7s22ltaqd7pxuoshs67flvm@cakolwpjdkwm>
Date: Thu, 12 Jun 2025 15:02:05 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org, bpf@...r.kernel.org, x86@...nel.org, 
	Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...nel.org>, 
	Namhyung Kim <namhyung@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, 
	Andrii Nakryiko <andrii@...nel.org>, Indu Bhagat <indu.bhagat@...cle.com>, 
	"Jose E. Marchesi" <jemarch@....org>, Beau Belgrave <beaub@...ux.microsoft.com>, 
	Jens Remus <jremus@...ux.ibm.com>, Linus Torvalds <torvalds@...ux-foundation.org>, 
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v10 00/14] unwind_user: x86: Deferred unwinding
 infrastructure

On Thu, Jun 12, 2025 at 02:44:18PM -0700, Andrii Nakryiko wrote:
> On Tue, Jun 10, 2025 at 6:03 PM Steven Rostedt <rostedt@...dmis.org> wrote:
> >
> >
> > Hi Peter and Ingo,
> >
> > This is the first patch series of a set that will make it possible to be able
> > to use SFrames[1] in the Linux kernel. A quick recap of the motivation for
> > doing this.
> >
> > Currently the only way to get a user space stack trace from a stack
> > walk (and not just copying large amount of user stack into the kernel
> > ring buffer) is to use frame pointers. This has a few issues. The biggest
> > one is that compiling frame pointers into every application and library
> > has been shown to cause performance overhead.
> >
> > Another issue is that the format of the frames may not always be consistent
> > between different compilers and some architectures (s390) has no defined
> > format to do a reliable stack walk. The only way to perform user space
> > profiling on these architectures is to copy the user stack into the kernel
> > buffer.
> >
> > SFrames is now supported in gcc binutils and soon will also be supported
> > by LLVM. SFrames acts more like ORC, and lives in the ELF executable
> 
> Is there any upstream PR or discussion for SFrames support in LLVM to
> keep track of?

https://github.com/llvm/llvm-project/issues/64449

-- 
Josh