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

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On Wed, 12 Dec 2018 at 13:36, Leif Lindholm <leif.lindholm@linaro.org> wrote:
>
> On Wed, Dec 12, 2018 at 01:19:31PM +0100, 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.
>
> Do we know how ling that flag has been around for? I find a post from
> 2009 referring to as "new", so I guess we're safe for anything we care
> about.
> Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
>

I accidentally pushed this, and failed to add the tags as well.

Given that this only affects 32-bit ARM, I guess few people are going
to mind, so I am going to leave this as-is unless anyone complains.

> > Contributed-under: TianoCore Contribution Agreement 1.1
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > ---
> >  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)
> > --
> > 2.19.2
> >