[edk2-devel] [PATCH 1/2] ArmPkg/AsmMacroIoLibV8: Introduce ASM_FUNC_ALIGN()
Leif Lindholm
quic_llindhol at quicinc.com
Mon Apr 17 19:52:02 UTC 2023
Hi Marvin,
First of all - many thanks for tracking down the bug that creates the
need for this.
On Mon, Apr 17, 2023 at 18:09:15 +0000, Marvin Häuser wrote:
> With the current ASM_FUNC() macro, there is no good way to declare an
> alignment constraint for a function. As ASM_FUNC() switches sections,
> declaring the constraint before the macro invocation applies it to the
> current location in the previous section. Declaring the constraint after
> the macro invocation lets the function label point to the location prior
> to alignment. Depending on toolchain behaviour, this may cause the label
> to point to alignment padding preceding the actual function definition.
>
> To address these issues, introduce the ASM_FUNC_ALIGN() macro, which
> declares the alignment constraint right before the function label.
>
> Signed-off-by: Marvin Häuser <mhaeuser at posteo.de>
> Cc: Leif Lindholm <quic_llindhol at quicinc.com>
> Cc: Ard Biesheuvel <ardb+tianocore at kernel.org>
> Cc: Sami Mujawar <sami.mujawar at arm.com>
> Cc: Vitaly Cheptsov <vit9696 at protonmail.com>
> ---
> ArmPkg/Include/AsmMacroIoLibV8.h | 22 ++++++++++++++++++----
> 1 file changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/ArmPkg/Include/AsmMacroIoLibV8.h b/ArmPkg/Include/AsmMacroIoLibV8.h
> index 135aaeca5d0b..919edc70384d 100644
> --- a/ArmPkg/Include/AsmMacroIoLibV8.h
> +++ b/ArmPkg/Include/AsmMacroIoLibV8.h
> @@ -34,15 +34,29 @@
> cbnz SAFE_XREG, 1f ;\
> b . ;// We should never get here
>
> -#define _ASM_FUNC(Name, Section) \
> - .global Name ; \
> - .section #Section, "ax" ; \
> - .type Name, %function ; \
> +#define _ASM_FUNC_HDR(Name, Section) \
> + .global Name ; \
> + .section #Section, "ax" ; \
> + .type Name, %function
> +
> +#define _ASM_FUNC_FTR(Name) \
> Name: ; \
> AARCH64_BTI(c)
>
> +#define _ASM_FUNC(Name, Section) \
> + _ASM_FUNC_HDR(Name, Section) ; \
> + _ASM_FUNC_FTR(Name)
> +
> +#define _ASM_FUNC_ALIGN(Name, Section, Align) \
I like this solution, but I'd like to hear Ard's opinion.
I probably want to bikeshed some of the implementation details:
Although I generally dislike duplicate definitions, I think I would
prefer having _ASM_FUNC and _ASM_FUNC_ALIGN defined self-contained,
without _HDR and _FTR.
If we do keep the reused primitives, we need better language; the
footer of the header is not a footer of the function.
/
Leif
> + _ASM_FUNC_HDR(Name, Section) ; \
> + .balign Align ; \
> + _ASM_FUNC_FTR(Name)
> +
> #define ASM_FUNC(Name) _ASM_FUNC(ASM_PFX(Name), .text. ## Name)
>
> +#define ASM_FUNC_ALIGN(Name, Align) \
> + _ASM_FUNC_ALIGN(ASM_PFX(Name), .text. ## Name, Align)
> +
> #define MOV32(Reg, Val) \
> movz Reg, (Val) >> 16, lsl #16 ; \
> movk Reg, (Val) & 0xffff
> --
> 2.40.0
>
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