linux-kernel - Re: [PATCH] objtool: continue if find_insn() fails in decode

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Date:   Sat, 7 Jan 2023 11:21:39 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Sathvika Vasireddy <sv@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        jpoimboe@...hat.com, peterz@...radead.org, aik@...abs.ru,
        mpe@...erman.id.au, mingo@...hat.com, christophe.leroy@...roup.eu,
        mbenes@...e.cz, npiggin@...il.com, chenzhongjin@...wei.com,
        sfr@...b.auug.org.au, naveen.n.rao@...ux.vnet.ibm.com
Subject: Re: [PATCH] objtool: continue if find_insn() fails in
 decode_instructions()


* Sathvika Vasireddy <sv@...ux.ibm.com> wrote:

> Currently, decode_instructions() is failing if it is not able to find
> instruction, and this is happening since commit dbcdbdfdf137b4
> ("objtool: Rework instruction -> symbol mapping") because it is
> expecting instruction for STT_NOTYPE symbols.
> 
> Due to this, the following objtool warnings are seen:
>  [1] arch/powerpc/kernel/optprobes_head.o: warning: objtool: optprobe_template_end(): can't find starting instruction
>  [2] arch/powerpc/kernel/kvm_emul.o: warning: objtool: kvm_template_end(): can't find starting instruction
>  [3] arch/powerpc/kernel/head_64.o: warning: objtool: end_first_256B(): can't find starting instruction
> 
> The warnings are thrown because find_insn() is failing for symbols that
> are at the end of the file, or at the end of the section. Given how
> STT_NOTYPE symbols are currently handled in decode_instructions(),
> continue if the instruction is not found, instead of throwing warning
> and returning.
> 
> Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
> Signed-off-by: Sathvika Vasireddy <sv@...ux.ibm.com>

The SOB chain doesn't look valid: is Naveen N. Rao, the first SOB line, the 
author of the patch? If yes then a matching From: line is needed.

Or if two people developed the patch, then Co-developed-by should be used:

        Co-developed-by: First Co-Author <first@...uthor.example.org>
        Signed-off-by: First Co-Author <first@...uthor.example.org>
        Co-developed-by: Second Co-Author <second@...uthor.example.org>
        Signed-off-by: Second Co-Author <second@...uthor.example.org>

[ In this SOB sequence "Second Co-Author" is the one who submits the patch. ]

[ Please only use Co-developed-by if actual lines of code were written by 
  the co-author that created copyrightable material - it's not a courtesy 
  tag. Reviewed-by/Acked-by/Tested-by can be used to credit non-code 
  contributions. ]

Thanks,

	Ingo