Re: [PATCH] xen/x86: prevent addition of .note.gnu.property if livepatch is enabled

[Jan Beulich <jbeulich@xxxxxxxx>]

On 07.11.2024 15:59, Roger Pau Monne wrote:
> GNU assembly that supports such feature will unconditionally add a
> .note.gnu.property section to object files.  The content of that section can
> change depending on the generated instructions.  The current logic in
> livepatch-build-tools doesn't know how to deal with such section changing
> as a result of applying a patch and rebuilding.
> 
> Since .note.gnu.property is not consumed by the Xen build, suppress its
> addition when livepatch support is enabled.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Just one thing though:

> --- a/xen/arch/x86/arch.mk
> +++ b/xen/arch/x86/arch.mk
> @@ -26,6 +26,12 @@ $(call as-option-add,CFLAGS,CC,"invpcid 
> (%rax)$(comma)%rax",-DHAVE_AS_INVPCID)
>  $(call as-option-add,CFLAGS,CC,"movdiri %rax$(comma)(%rax)",-DHAVE_AS_MOVDIR)
>  $(call as-option-add,CFLAGS,CC,"enqcmd (%rax)$(comma)%rax",-DHAVE_AS_ENQCMD)
>  
> +# Disable the addition of a .note.gnu.property section to object files when
> +# livepatch support is enabled.  The contents of that section can change
> +# depending on the instructions used, and livepatch-build-tools doesn't know
> +# how to deal with such changes.
> +$(call 
> cc-option-add,CFLAGS-$(CONFIG_LIVEPATCH),CC,-Wa$$(comma)-mx86-used-note=no)
> +
>  # Check to see whether the assmbler supports the .nop directive.
>  $(call as-option-add,CFLAGS,CC,\
>      ".L1: .L2: .nops (.L2 - .L1)$(comma)9",-DHAVE_AS_NOPS_DIRECTIVE)

I don't really like this being squashed between two as-option-add invocations.
Can this be moved down, e.g. before or after the XEN_IBT chunk? Happy to move
while committing ...

Jan