Re: [PATCH] BaseTools/tools_def ARM: emit PIC veneers

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 12/12/18 1:19 PM, Ard Biesheuvel wrote:
> The ARM linker may emit veneers, i.e., trampolines, when ordinary
> direct relative branches cannot be used, e.g., for Thumb interworking
> or branch targets that are out of range.
> 
> Usually, such veneers carry an absolute reference to the branch
> target, which is problematic for us, since these absolute references
> are not covered by annotations that are visible to GenFw in the
> PE/COFF conversion, and so these absolute references are not fixed
> up by the PE/COFF loader at runtime.
> 
> So switch to all ARM GNU ld toolchains to position independent veneers.
> 
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
>  BaseTools/Conf/tools_def.template | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template
> index 2ba833e1fb06..902680c24c85 100755
> --- a/BaseTools/Conf/tools_def.template
> +++ b/BaseTools/Conf/tools_def.template
> @@ -4150,7 +4150,7 @@ DEFINE GCC_DLINK_FLAGS_COMMON      = -nostdlib --pie
>  DEFINE GCC_DLINK2_FLAGS_COMMON     = -Wl,--script=$(EDK_TOOLS_PATH)/Scripts/GccBase.lds
>  DEFINE GCC_IA32_X64_DLINK_COMMON   = DEF(GCC_DLINK_FLAGS_COMMON) --gc-sections
>  DEFINE GCC_ARM_AARCH64_DLINK_COMMON= -Wl,--emit-relocs -nostdlib -Wl,--gc-sections -u $(IMAGE_ENTRY_POINT) -Wl,-e,$(IMAGE_ENTRY_POINT),-Map,$(DEST_DIR_DEBUG)/$(BASE_NAME).map
> -DEFINE GCC_ARM_DLINK_FLAGS         = DEF(GCC_ARM_AARCH64_DLINK_COMMON) -z common-page-size=0x20
> +DEFINE GCC_ARM_DLINK_FLAGS         = DEF(GCC_ARM_AARCH64_DLINK_COMMON) -z common-page-size=0x20 -Wl,--pic-veneer
>  DEFINE GCC_AARCH64_DLINK_FLAGS     = DEF(GCC_ARM_AARCH64_DLINK_COMMON) -z common-page-size=0x20
>  DEFINE GCC_ARM_AARCH64_ASLDLINK_FLAGS = -Wl,--defsym=PECOFF_HEADER_SIZE=0 DEF(GCC_DLINK2_FLAGS_COMMON) -z common-page-size=0x20
>  DEFINE GCC_IA32_X64_ASLDLINK_FLAGS = DEF(GCC_IA32_X64_DLINK_COMMON) --entry _ReferenceAcpiTable -u $(IMAGE_ENTRY_POINT)
>