Re: [PATCH 4/4] livepatch: differentiate between old and new build systems

[Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>]

On 02/03/2022 14:27, Roger Pau Monne wrote:
> diff --git a/livepatch-build b/livepatch-build
> index 38a92be..656cdac 100755
> --- a/livepatch-build
> +++ b/livepatch-build
> @@ -98,14 +98,20 @@ function build_special()
>  
>      # Build with special GCC flags
>      cd "${SRCDIR}/xen" || die
> -    sed -i 's/CFLAGS += -nostdinc/CFLAGS += -nostdinc -ffunction-sections 
> -fdata-sections/' Rules.mk
> -    cp -p arch/x86/Makefile arch/x86/Makefile.bak
> -    sed -i 's/--section-alignment=0x200000/--section-alignment=0x1000/' 
> arch/x86/Makefile
> -    # Restore timestamps to prevent spurious rebuilding
> -    touch --reference=arch/x86/Makefile.bak arch/x86/Makefile
> -    make "-j$CPUS" $XEN_DEBUG &> "${OUTPUT}/build_${name}_compile.log" || die
> -    sed -i 's/CFLAGS += -nostdinc -ffunction-sections -fdata-sections/CFLAGS 
> += -nostdinc/' Rules.mk
> -    mv -f arch/x86/Makefile.bak arch/x86/Makefile
> +    if grep -q 'nostdinc' Rules.mk; then
> +         # Support for old build system, attempt to set 
> -f{function,data}-sections and rebuild
> +        sed -i 's/CFLAGS += -nostdinc/CFLAGS += -nostdinc 
> -ffunction-sections -fdata-sections/' Rules.mk
> +        cp -p arch/x86/Makefile arch/x86/Makefile.bak
> +        sed -i 's/--section-alignment=0x200000/--section-alignment=0x1000/' 
> arch/x86/Makefile
> +        # Restore timestamps to prevent spurious rebuilding
> +        touch --reference=arch/x86/Makefile.bak arch/x86/Makefile
> +        make "-j$CPUS" $XEN_DEBUG &> "${OUTPUT}/build_${name}_compile.log" 
> || die
> +        sed -i 's/CFLAGS += -nostdinc -ffunction-sections 
> -fdata-sections/CFLAGS += -nostdinc/' Rules.mk
> +        mv -f arch/x86/Makefile.bak arch/x86/Makefile
> +    else
> +        # -f{function,data}-sections set by CONFIG_LIVEPATCH
> +        make "-j$CPUS" $XEN_DEBUG &> "${OUTPUT}/build_${name}_compile.log" 
> || die
> +    fi

This really ought to be the other way around, by spotting the thing we
know is good, and then falling back to the heuristics.  In light of the
updates to the Xen side, something like:

if grep -q CC_SPLIT_SECTIONS Kconfig; then
    # -f{function,data}-sections set by CONFIG_LIVEPATCH
    make "-j$CPUS" $XEN_DEBUG &> "${OUTPUT}/build_${name}_compile.log"
|| die
else
    # Support for old build system, attempt to set
-f{function,data}-sections and rebuild
    ...
fi

?
~Andrew