On Mon, Mar 27, 2023 at 15:12:29 +0100, Pedro Falcato wrote:
> On Mon, Mar 27, 2023 at 12:01 PM Ard Biesheuvel <a...@kernel.org> wrote:
> >
> > Implement a CPP macro that can be called from .S files to emit the .note
> > section carrying the annotation that informs the linker that the object
> > file is compatible with BTI control flow integrity checks.
> >
> > Signed-off-by: Ard Biesheuvel <a...@kernel.org>
> > ---
> > MdePkg/Include/AArch64/ProcessorBind.h | 31 ++++++++++++++++++++
> > 1 file changed, 31 insertions(+)
> >
> > diff --git a/MdePkg/Include/AArch64/ProcessorBind.h
> > b/MdePkg/Include/AArch64/ProcessorBind.h
> > index abe2571245c665f3..11814f1ffaef698a 100644
> > --- a/MdePkg/Include/AArch64/ProcessorBind.h
> > +++ b/MdePkg/Include/AArch64/ProcessorBind.h
> > @@ -186,6 +186,37 @@ typedef INT64 INTN;
> > #define GCC_ASM_IMPORT(func__) \
> > .extern _CONCATENATE (__USER_LABEL_PREFIX__, func__)
> >
> > +#if defined(__ARM_FEATURE_BTI_DEFAULT) && __ARM_FEATURE_BTI_DEFAULT == 1
> > +#define AARCH64_BTI(__type) \
> > + .ifnc __type, ;\
> > + bti __type ;\
> > + .endif ;\
> > + .ifndef .Lgnu_bti_notesize ;\
> > + .pushsection .note.gnu.property, "a" ;\
> > + .set NT_GNU_PROPERTY_TYPE_0, 0x5 ;\
> > + .set GNU_PROPERTY_AARCH64_FEATURE_1_AND, 0xc0000000 ;\
> > + .set GNU_PROPERTY_AARCH64_FEATURE_1_BTI, 0x1 ;\
> > + .align 3 ;\
> > + .long .Lnamesize ;\
> > + .long .Lgnu_bti_notesize ;\
> > + .long NT_GNU_PROPERTY_TYPE_0 ;\
> > +0: .asciz "GNU" ;\
> > + .set .Lnamesize, . - 0b ;\
> > + .align 3 ;\
> > +1: .long GNU_PROPERTY_AARCH64_FEATURE_1_AND ;\
> > + .long .Lvalsize ;\
> > +2: .long GNU_PROPERTY_AARCH64_FEATURE_1_BTI ;\
> > + .set .Lvalsize, . - 2b ;\
> > + .align 3 ;\
> > + .set .Lgnu_bti_notesize, . - 1b ;\
> > + .popsection ;\
> > + .endif
> > +#endif
> > +
> > +#endif
> > +
> > +#ifndef AARCH64_BTI
> > +#define AARCH64_BTI(__type)
> > #endif
> >
> > /**
> > --
> > 2.39.2
>
> Patch-set wide comment: is there any chance we could take this
> opportunity to introduce a global ASM_FUNC (or a more Linux-named
> ENTRY(FuncName))?
> It seems to be that the current way is a bit error prone and you end
> up repeating yourself quite a bit with:
>
> ASM_PFX(Foo):
> AARCH64_BTI(c)
> <code>
>
> having a:
> ASM_FUNC(Foo)
> <code>
>
> that does proper PFX and BTI expansion internally seems better to me.
I was thinking while looking at this patch that ASM_FUNC could
probably do with moving over to this file from AsmMacroIoLibV8.h.
I didn't take the thought far enough to consider including the BTI
bits in that, but I guess that could make sense.
/
Leif
>
> --
> Pedro
>
>
>
>
>
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