Compile error ppc64le: Cannot find symbol for section 11: .text.unlikely.

[Baoquan He]

On 11/24/21 at 01:47pm, Veronika Kabatova wrote:
> Hi,
> 
> for a while we've been seen the following error when compiling
> the mainline kernel with gcc 11.2 and binutils 2.37:
> 
> 00:02:32 Cannot find symbol for section 11: .text.unlikely.
> 00:02:32 kernel/kexec_file.o: failed
> 00:02:32 make[3]: *** [scripts/Makefile.build:287: kernel/kexec_file.o] Error 1
> 00:02:32 make[3]: *** Deleting file 'kernel/kexec_file.o'
> 00:02:32 make[2]: *** [Makefile:1846: kernel] Error 2
> 00:02:32 make[2]: *** Waiting for unfinished jobs....
> 
> The error only happens with ppc64le. I've tested this with cross
> compilation, but the only reference to the error I found suggests
> the same happens with the native compiles as well:
> 
> https://github.com/groeck/linux-build-test/commit/142cbefbc0d37962c9a6c7f28ee415ecd5fd1e98
> 
> In case it matters, the config used is the Fedora config with
> kselftest options enabled, which you can grab from
> 
> https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/cki-trusted-contributors/-/jobs/1760752896/artifacts/raw/artifacts/kernel-mainline.kernel.org-ppc64le-e4e737bb5c170df6135a127739a9e6148ee3da82.config
> 
> 
> I've reached out to the Fedora compiler folks and Nick Clifton
> suggested this is a problem with the kernel:
> 
>     This message comes from the recordmcount tool, which is part of the kernel
>     sources:
> 
>     linux/scripts/recordmcount.[ch]
> 
>     It appears to be triggered when a compiler update causes code to be
>     rearranged. The problem has been reported before in various forums,
>     but in particular I found this reference:
> 
>     https://lore.kernel.org/lkml/20201204165742.3815221-2-arnd@kernel.org/
> 
>     The point of which to me at least is that this is a kernel issue rather than
>     a compiler issue.  Ie there must be some weak symbols in kexec_file.o file
>     which need to be moved elsewhere.

It could be arch_kexec_kernel_verify_sig() in kernel/kexec_file.c which
is __weak, but not implemented in any ARCH. If true, this has been
pointed out by Eric in one patch thread from Coiby.

[PATCH v3 1/3] kexec: clean up arch_kexec_kernel_verify_sig
http://lkml.kernel.org/r/20211018083137.338757-2-coxu@redhat.com

Maybe Coiby can fetch above config file and run the test to check.

Thanks
Baoquan