linux-kernel - Re: [PATCH v2 1/2] unwind_user/x86: Enable frame pointer unwinding on x86

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Message-ID: <20250923082059.15fc17bc@batman.local.home>
Date: Tue, 23 Sep 2025 08:20:59 -0400
From: Steven Rostedt <rostedt@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 x86@...nel.org, Masami Hiramatsu <mhiramat@...nel.org>, Mark Rutland
 <mark.rutland@....com>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Thomas Gleixner
 <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov
 <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, Linus Torvalds
 <torvalds@...ux-foundation.org>, Josh Poimboeuf <jpoimboe@...nel.org>
Subject: Re: [PATCH v2 1/2] unwind_user/x86: Enable frame pointer unwinding
 on x86

On Tue, 23 Sep 2025 12:51:30 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> Moo, and now you have me look at unwind/user.c:
> 
>         /* Make sure that the address is word aligned */
>         shift = sizeof(long) == 4 ? 2 : 3;
>         if (cfa & ((1 << shift) - 1))
>                 return -EINVAL;
> 
> Isn't that just:
> 
> 	if (cfa & (sizeof(long) - 1))
> 
> ?
> 
> Let me go add a patch to clean that up...

Sure, as long as it's commented.

Thanks,

-- Steve