linux-kernel - Re: [PATCH 9/9] objtool: Collect all annotations in objtool.h

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Message-ID: <20241123131943.GD24774@noisy.programming.kicks-ass.net>
Date: Sat, 23 Nov 2024 14:19:43 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH 9/9] objtool: Collect all annotations in objtool.h

On Fri, Nov 22, 2024 at 09:54:45AM -0800, Josh Poimboeuf wrote:
> On Fri, Nov 22, 2024 at 01:10:25PM +0100, Peter Zijlstra wrote:
> > +#ifndef __ASSEMBLY__
> > +/*
> > + * Annotate away the various 'relocation to !ENDBR` complaints; knowing that
> > + * these relocations will never be used for indirect calls.
> > + */
> > +#define ANNOTATE_NOENDBR		ASM_ANNOTATE(ANNOTYPE_NOENDBR)
> > +/*
> > + * This should be used immediately before an indirect jump/call. It tells
> > + * objtool the subsequent indirect jump/call is vouched safe for retpoline
> > + * builds.
> > + */
> > +#define ANNOTATE_RETPOLINE_SAFE		ASM_ANNOTATE(ANNOTYPE_RETPOLINE_SAFE)
> > +/*
> > + * objtool annotation to ignore the alternatives and only consider the original
> > + * instruction(s).
> > + */
> > +#define ANNOTATE_IGNORE_ALTERNATIVE	ASM_ANNOTATE(ANNOTYPE_IGNORE_ALTS)
> 
> This is a good start, though it would be really nice to have them *all*
> together:
> 
>   - move ANNOTATE_INTRA_FUNCTION_CALL down next to those ^
> 
>   - similarly, create ANNOTATE_UNRET_BEGIN and just do
> 
>       #define VALIDATE_UNRET_BEGIN ANNOTATE_UNRET_BEGIN
>     
>     since the VALIDATE_* syntax is more descriptive.

Done these two.

>   - create ANNOTATE_INSTR_BEGIN and ANNOTATE_INSTR_END, and then do
>     
>       #define instrumentation_begin() ANNOTATE_INSTR_BEGIN
> 
>     to keep the existing syntax.  Then instrumentation.h is no longer
>     needed.  The nice comment there can go above ANNOTATE_INSTR_BEGIN.

Let me noodle a bit with this one, its a bit different from the rest.

> BTW, is there a reason .discard.[un]reachable weren't converted over?

Completely forgot/missed them. Let me add a patch.