Re: [PATCH] objtool: continue if find_insn() fails in decode_instructions()

[Sathvika Vasireddy]

Hi Ingo, Happy New Year!

On 07/01/23 15:51, Ingo Molnar wrote:
> * Sathvika Vasireddy <sv@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Sathvika Vasireddy <sv@xxxxxxxxxxxxx>
> 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@xxxxxxxxxxxxxxxxxxxx>
>          Signed-off-by: First Co-Author <first@xxxxxxxxxxxxxxxxxxxx>
>          Co-developed-by: Second Co-Author <second@xxxxxxxxxxxxxxxxxxxx>
>          Signed-off-by: Second Co-Author <second@xxxxxxxxxxxxxxxxxxxx>
>
> [ 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. ]
Thank you for the clarification, and for bringing these points to my 
attention. I'll keep these things in mind. In this case, since both 
Naveen N. Rao and I developed the patch, the below tags
are applicable.

        Co-developed-by: First Co-Author <first@xxxxxxxxxxxxxxxxxxxx>
        Signed-off-by: First Co-Author <first@xxxxxxxxxxxxxxxxxxxx>
        Co-developed-by: Second Co-Author <second@xxxxxxxxxxxxxxxxxxxx>
        Signed-off-by: Second Co-Author <second@xxxxxxxxxxxxxxxxxxxx>

However, I would be dropping this particular patch, since I think Nick's 
patch [1] is better to fix the objtool issue.

[1] - 
https://lore.kernel.org/linuxppc-dev/20221220101323.3119939-1-npiggin@xxxxxxxxx/ 



Thanks for reviewing!

- Sathvika