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Re: [ARM/FDPIC v5 05/21] [ARM] FDPIC: Fix __do_global_dtors_aux and frame_dummy generation


Christophe Lyon <christophe.lyon@st.com> writes:
> In FDPIC, we need to make sure __do_global_dtors_aux and frame_dummy
> are referenced by their address, not by pointers to the function
> descriptors.
>
> 2019-XX-XX  Christophe Lyon  <christophe.lyon@st.com>
> 	Mickaël Guêné <mickael.guene@st.com>
>
> 	* libgcc/crtstuff.c: Add support for FDPIC.
>
> Change-Id: I0bc4b1232fbf3c69068fb23a1b9cafc895d141b1
>
> diff --git a/libgcc/crtstuff.c b/libgcc/crtstuff.c
> index 4927a9f..159b461 100644
> --- a/libgcc/crtstuff.c
> +++ b/libgcc/crtstuff.c
> @@ -429,9 +429,18 @@ __do_global_dtors_aux (void)
>  #ifdef FINI_SECTION_ASM_OP
>  CRT_CALL_STATIC_FUNCTION (FINI_SECTION_ASM_OP, __do_global_dtors_aux)
>  #elif defined (FINI_ARRAY_SECTION_ASM_OP)
> +#if defined(__FDPIC__)
> +__asm__(
> +    "   .section .fini_array\n"
> +    "   .align 2\n"
> +    "   .word __do_global_dtors_aux\n"
> +);
> +asm (TEXT_SECTION_ASM_OP);
> +#else /* defined(__FDPIC__) */
>  static func_ptr __do_global_dtors_aux_fini_array_entry[]
>    __attribute__ ((__used__, section(".fini_array"), aligned(sizeof(func_ptr))))
>    = { __do_global_dtors_aux };
> +#endif /* defined(__FDPIC__) */
>  #else /* !FINI_SECTION_ASM_OP && !FINI_ARRAY_SECTION_ASM_OP */
>  static void __attribute__((used))
>  __do_global_dtors_aux_1 (void)

It'd be good to avoid hard-coding the pointer size.  Would it work to do:

__asm__("\t.equ\.t__do_global_dtors_aux_alias, __do_global_dtors_aux\n");
extern char __do_global_dtors_aux_alias;
static void *__do_global_dtors_aux_fini_array_entry[]
   __attribute__ ((__used__, section(".fini_array"), aligned(sizeof(void *))))
   = { &__do_global_dtors_aux_alias };

?  Similarly for the init_array.

AFAICT this and 02/21 are the only patches that aren't Arm-specific,
is that right?

Thanks,
Richard


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