Re: [PATCH 5.15 5.10 5.4 v2] kbuild: fix Build ID if CONFIG_MODVERSIONS

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Dec 15, 2022 at 04:18:18PM -0700, Tom Saeger wrote:
> Backport of:
> commit 0d362be5b142 ("Makefile: link with -z noexecstack --no-warn-rwx-segments")
> breaks arm64 Build ID when CONFIG_MODVERSIONS=y for all kernels
> from: commit e4484a495586 ("Merge tag 'kbuild-fixes-v5.0' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild")
> until: commit df202b452fe6 ("Merge tag 'kbuild-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild")
> 
> Linus's tree doesn't have this issue since 0d362be5b142 was merged
> after df202b452fe6 which included:
> commit 7b4537199a4a ("kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS")

Why can't we add this one instead of a custom change?

> 
> This kernel's KBUILD CONFIG_MODVERSIONS tooling compiles and links .S targets
> with relocatable (-r) and now (-z noexecstack)
> which results in ld adding a .note.GNU-stack section to .o files.
> Final linking of vmlinux should add a .NOTES segment containing the
> Build ID, but does NOT (on some architectures like arm64) if a
> .note.GNU-stack section is found in .o's supplied during link
> of vmlinux.
> 
> DISCARD .note.GNU-stack sections of .S targets.  Final link of
> vmlinux then properly adds .NOTES segment containing Build ID that can
> be read using tools like 'readelf -n'.
> 
> Fixes: 0d362be5b142 ("Makefile: link with -z noexecstack --no-warn-rwx-segments")
> Cc: <stable@vger.kernel.org> # 5.15, 5.10, 5.4
> Cc: <linux-kbuild@vger.kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Michal Marek <michal.lkml@markovi.net>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Signed-off-by: Tom Saeger <tom.saeger@oracle.com>
> ---
> 
> v2:
>   - Changed approach to append DISCARD section to generated linker script.
>     - ld no longer emits warning (which was intent of 0d362b35b142) this
>       addresses Nick's v1 feedback.
>     - this is applied to all arches, not just arm64
>   - added commit refs and notes why this doesn't occur in Linus's tree
>     to address Greg's v1 feedback.
>   - added Fixes: 0d362b35b142 requested by Nick
>   - added note to changelog for 7b4537199a4a requested by Nick
>   - build tested on arm64 and x86
>    
>    version           works(vmlinux contains Build ID)
>    v4.14.302         x86, arm64
>    v4.14.302.patched x86, arm64
>    v4.19.269         x86, arm64
>    v4.19.269.patched x86, arm64
>    v5.4.227          x86
>    v5.4.227.patched  x86, arm64
>    v5.10.159         x86
>    v5.10.159.patched x86, arm64
>    v5.15.83          x86
>    v5.15.83.patched  x86, arm64
> 
> v1: https://lore.kernel.org/all/cover.1670358255.git.tom.saeger@oracle.com/
> 
> 
>  scripts/Makefile.build | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 17aa8ef2d52a..e3939676eeb5 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -379,6 +379,8 @@ cmd_modversions_S =								\
>  	if $(OBJDUMP) -h $@ | grep -q __ksymtab; then				\
>  		$(call cmd_gensymtypes_S,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))	\
>  		    > $(@D)/.tmp_$(@F:.o=.ver);					\
> +		echo "SECTIONS { /DISCARD/ : { *(.note.GNU-stack) } }"		\
> +		>> $(@D)/.tmp_$(@F:.o=.ver); 					\
>  										\
>  		$(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@ 		\
>  			-T $(@D)/.tmp_$(@F:.o=.ver);				\
> 
> base-commit: fd6d66840b4269da4e90e1ea807ae3197433bc66
> -- 
> 2.38.1
> 


I need some acks from some developers/maintainers before I can take
this... {hint}

thanks,

greg k-h