> -Original Message-
> From: Szabolcs Nagy
> Sent: 08 July 2020 17:28
> To: gcc-patches@gcc.gnu.org
> Cc: Richard Earnshaw ; Kyrylo Tkachov
>
> Subject: [PATCH 6/6] aarch64: Fix BTI support in libitm
>
> sjlj.S did not have the GNU property note markup and the BTI c
> instructions that are necessary when it is built with branch
> protection.
>
> The notes are only added when libitm is built with branch
> protection, because old linkers mishandle the note (merge
> them incorrectly or emit warnings), the BTI instructions
> are added unconditionally.
>
> libitm/ChangeLog:
>
> 2020-07-08 Szabolcs Nagy
>
> * config/aarch64/sjlj.S: Add BTI marking and related definitions,
> and add BTI c to function entries.
>
> ---
> Note: there is some redundancy: the libgcc fixup patch needed
> the same macro definitions, but i did not find a convenient
> place from where both libgcc and libitm can include them. Since
> this is a common problem i expect a change in the assembler
> that will be able to add the note without doing this manually,
> until then i think we can live with the code duplication.
Ok.
Thanks,
Kyrill
> ---
> libitm/config/aarch64/sjlj.S | 27 +++
> 1 file changed, 27 insertions(+)
>
> diff --git a/libitm/config/aarch64/sjlj.S b/libitm/config/aarch64/sjlj.S
> index 5b97b973e27..e2093ca1a97 100644
> --- a/libitm/config/aarch64/sjlj.S
> +++ b/libitm/config/aarch64/sjlj.S
> @@ -24,6 +24,8 @@
>
> #include "asmcfi.h"
>
> +#define BTI_Chint34
> +
> .text
> .align 2
> .global _ITM_beginTransaction
> @@ -31,6 +33,7 @@
>
> _ITM_beginTransaction:
> cfi_startproc
> + BTI_C
> mov x1, sp
> stp x29, x30, [sp, -11*16]!
> cfi_adjust_cfa_offset(11*16)
> @@ -70,6 +73,7 @@ GTM_longjmp:
> /* The first parameter becomes the return value (x0).
> The third parameter is ignored for now. */
> cfi_startproc
> + BTI_C
> ldp x19, x20, [x1, 1*16]
> ldp x21, x22, [x1, 2*16]
> ldp x23, x24, [x1, 3*16]
> @@ -87,6 +91,29 @@ GTM_longjmp:
> cfi_endproc
> .size GTM_longjmp, . - GTM_longjmp
>
> +/* GNU_PROPERTY_AARCH64_* macros from elf.h for use in asm code. */
> +#define FEATURE_1_AND 0xc000
> +#define FEATURE_1_BTI 1
> +#define FEATURE_1_PAC 2
> +
> +/* Add a NT_GNU_PROPERTY_TYPE_0 note. */
> +#define GNU_PROPERTY(type, value)\
> + .section .note.gnu.property, "a"; \
> + .p2align 3;\
> + .word 4; \
> + .word 16; \
> + .word 5; \
> + .asciz "GNU"; \
> + .word type;\
> + .word 4; \
> + .word value; \
> + .word 0;
> +
> #if defined(__linux__) || defined(__FreeBSD__)
> .section .note.GNU-stack, "", %progbits
> +
> +/* Add GNU property note if built with branch protection. */
> +# ifdef __ARM_FEATURE_BTI_DEFAULT
> +GNU_PROPERTY (FEATURE_1_AND, FEATURE_1_BTI)
> +# endif
> #endif
> --
> 2.17.1
