linux-kernel - Re: [PATCH 04/13] objtool: Update documentation

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Message-ID: <alpine.LSU.2.21.2503171143290.4236@pobox.suse.cz>
Date: Mon, 17 Mar 2025 11:46:53 +0100 (CET)
From: Miroslav Benes <mbenes@...e.cz>
To: Josh Poimboeuf <jpoimboe@...nel.org>
cc: x86@...nel.org, linux-kernel@...r.kernel.org, 
    Peter Zijlstra <peterz@...radead.org>, 
    Brendan Jackman <jackmanb@...gle.com>, 
    Nathan Chancellor <nathan@...nel.org>
Subject: Re: [PATCH 04/13] objtool: Update documentation

Hi,

>  1. Each callable function must be annotated as such with the ELF
>     function type.  In asm code, this is typically done using the
> -   ENTRY/ENDPROC macros.  If objtool finds a return instruction
> +   SYM_FUNC_{START,END} macros.  If objtool finds a return instruction
>     outside of a function, it flags an error since that usually indicates
>     callable code which should be annotated accordingly.

there is one more occurrence of ENDPROC/END under "1. file.o: warning: 
objtool: func()+0x128: call without frame pointer save/setup" section 
which might be nice to update as well.

> @@ -339,23 +351,21 @@ the objtool maintainers.
>  
>     This is a kernel entry/exit instruction like sysenter or iret.  Such
>     instructions aren't allowed in a callable function, and are most
> -   likely part of the kernel entry code.  They should usually not have
> -   the callable function annotation (ENDPROC) and should always be
> -   annotated with the unwind hint macros in asm/unwind_hints.h.
> +   likely part of the kernel entry code.  Such code should probably be
> +   placed in a SYM_FUNC_CODE block with unwind hints.

SYM_CODE_{START,END} block?

>  7. file: warning: objtool: func()+0x5c: stack state mismatch
> @@ -371,8 +381,8 @@ the objtool maintainers.
>  
>     Another possibility is that the code has some asm or inline asm which
>     does some unusual things to the stack or the frame pointer.  In such
> -   cases it's probably appropriate to use the unwind hint macros in
> -   asm/unwind_hints.h.
> +   cases it's probably appropriate to use SYM_FUNC_CODE with unwind
> +   hints.

dtto

Miroslav