linux-kernel - Re: [PATCH v2] x86/lib: Do not use local symbols with SYM_CODE_START

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Message-ID: <38e24fd4-9213-229d-9919-7ae3bfb113bb@intel.com>
Date:   Thu, 25 May 2023 12:05:42 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Nadav Amit <nadav.amit@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Nadav Amit <namit@...are.com>
Subject: Re: [PATCH v2] x86/lib: Do not use local symbols with
 SYM_CODE_START_LOCAL()

On 5/25/23 11:42, Nadav Amit wrote:
> From: Nadav Amit <namit@...are.com>
> 
> When SYM_CODE_START_LOCAL() is used, the symbols are local but need to
> be preserved in the object. However, using the ".L" label prefix does
> not retain the symbol in the object.
> 
> It is beneficial to be able to map instruction pointers back to symbols,
> for instance for profiling. Otherwise, there are code addresses that do
> not map back to any symbol.  Consequently, the ".L" label prefix should
> not be used when SYM_CODE_START_LOCAL() is used.
> 
> Few symbols, such as .Lbad_put_user_clac and currently have both the
> SYM_CODE_START_LOCAL() invocation and the ".L" prefix.  This commit
> removes the ".L" prefix from these symbols.
> 
> No functional change, other then emitting these symbols into the object,
> is intended.

Nadav, could you perhaps do a bit of research on how this situation came
to be?  Was it an accident or on purpose that these symbols came to be
.L?  Then, could you CC the folks who made this change and ask them
directly if they intended to induce the effects that you find undesirable?