Re: [PATCH 0/2] Fix CFI failures with GCOV_PROFILE_ALL

[Peter Zijlstra]

On Fri, Jun 23, 2023 at 12:11:41AM +0000, Sami Tolvanen wrote:
> Hi folks,
> 
> The following two patches fix CFI failures with GCOV_PROFILE_ALL,
> where the compiler injects indirectly called functions to object
> files that otherwise contain no executable code, and are not
> processed by objtool or don't have CFI enabled. This results in
> missing or incorrect type hashes during boot and when modules are
> loaded.
> 
> Sami Tolvanen (2):
>   kbuild: Fix CFI failures with GCOV
>   kbuild: Disable GCOV for *.mod.o
> 
>  init/Makefile             | 1 +
>  scripts/Makefile.modfinal | 2 +-
>  scripts/Makefile.vmlinux  | 1 +
>  3 files changed, 3 insertions(+), 1 deletion(-)
> 

Urgh, tricky stuff this.

Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

And yes, objtool essentially assumes vmlinux.o is complete and does LTO
like passes. Is there something kbuild can do to ensure noting else gets
linked in after this?