Re: [PATCH 1/3] libgcc: Mark AArch64 asm features with build attributes

On Mai 21 2026, Muhammad Kamran wrote:

> @@ -92,14 +91,39 @@
>    .word 0;				\
>    .previous
>  
> +#ifdef __ARM_BUILDATTR64_FV
> +/* Add AArch64 feature bits build attributes.  */
> +# define FEATURE_1_AND_MARK(value)					\
> +    .aeabi_subsection aeabi_feature_and_bits, optional, ULEB128;	\
> +    .if ((value) & FEATURE_1_BTI);					\
> +    .aeabi_attribute Tag_Feature_BTI, 1;				\
> +    .else;								\
> +    .aeabi_attribute Tag_Feature_BTI, 0;				\
> +    .endif;								\
> +    .if ((value) & FEATURE_1_PAC);					\
> +    .aeabi_attribute Tag_Feature_PAC, 1;				\
> +    .else;								\
> +    .aeabi_attribute Tag_Feature_PAC, 0;				\
> +    .endif;								\
> +    .if ((value) & FEATURE_1_GCS);					\
> +    .aeabi_attribute Tag_Feature_GCS, 1;				\
> +    .else;								\
> +    .aeabi_attribute Tag_Feature_GCS, 0;				\
> +    .endif;								\
> +    .previous

This does not work.  The .previous directive will not undo the
.aeabi_subsection switch, instead it will switch to the .note.GNU-stack
section ...

> +#else
> +/* Add a NT_GNU_PROPERTY_TYPE_0 note.  */
> +# define FEATURE_1_AND_MARK(value) GNU_PROPERTY (FEATURE_1_AND, value)
> +#endif
> +
>  #if defined(__linux__) || defined(__FreeBSD__)
>  /* Do not require executable stack.  */
>  .section .note.GNU-stack, "", %progbits
>  .previous

... which was temporarily entered here.  Thus all the rest of the code
will end up there instead of .text.

> -/* Add GNU property note if built with branch protection.  */
> +/* Add marking if built with branch protection.  */
>  # if (BTI_FLAG|PAC_FLAG|GCS_FLAG) != 0
> -GNU_PROPERTY (FEATURE_1_AND, BTI_FLAG|PAC_FLAG|GCS_FLAG)
> +FEATURE_1_AND_MARK (BTI_FLAG|PAC_FLAG|GCS_FLAG)
>  # endif
>  #endif

-- 
Andreas Schwab, SUSE Labs, [email protected]
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."