Re: objtool failure caused some kernel functionality not working

[Josh Poimboeuf]

On Wed, Jan 29, 2025 at 11:10:14PM -0800, Yonghong Song wrote:
> The llvm18 does not have issues. I tried to bisect what changed in llvm19 and
> found the following llvm patch is responsible:
> 
> https://github.com/llvm/llvm-project/pull/96089
> 
> Basically, the compiler might be able to create a jump target which actually
> not possible at runtime. For example, in one of examples in the above llvm patch, something
> like
>    if i >= 3 goto out;  /* i unsigned */
>    switch i, label default_unreachable:
>      case 0:  goto label1;
>      case 1:  goto label2;
>      case 2:  goto label3;
>    label1: ...; return;
>    label2: ...; return;
>    label3: ...; return;
>    default_unreachable:
> 
> I think that this should be a valid code from compiler perspective.
> 
> Can we fix objtool to handle jump target which is immediately after the func body?Thanks, Yonghong

I actually have a fix for that, can you try this?

  https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git/commit/?h=objtool/core&id=fbb454b7bb39955c324693e73a5cf7e448632553

-- 
Josh