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

["Doebel, Bjoern" <doebel@xxxxxxxxx>]

On 02.03.22 15:27, Roger Pau Monne wrote:
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> Do not attempt to modify the build system if CFLAGS are not set in
> Rules.mk, and instead rely on CONFIG_LIVEPATCH already setting
> -f{function,data}-sections.
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> This depends on getting the patch to add -f{function,data}-sections
> when using CONFIG_LIVEPATCH accepted.
> ---
>   livepatch-build | 22 ++++++++++++++--------
>   1 file changed, 14 insertions(+), 8 deletions(-)
>
> 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
This means we are still breaking livepatch builds for all Xen versions 
between your recent patch and the original patch that moved CFLAGS to 
xen/Makefile (commit 2740d96efdd3009f8adb40aacdbcf05cfe8d1bbb, Fri Apr 
24 14:57:10 2020 +0200).
Is this acceptable? (I mean, no one seems to have noticed...)

> +         # 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
>
>       unset LIVEPATCH_BUILD_DIR
>       unset LIVEPATCH_CAPTURE_DIR
Bjoern



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