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

[Richard Sandiford <richard.sandiford@arm.com>]

Christophe Lyon <christophe.lyon@st.com> writes:
> On 12/07/2019 08:06, Richard Sandiford wrote:
>> 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.
>> 
> OK, done.
>
>> AFAICT this and 02/21 are the only patches that aren't Arm-specific,
>> is that right?
>> 
>> Thanks,
>> Richard
>> .
>> 
>
> From ea0eee1ddeddef92277ae68eac4af28994c2902c Mon Sep 17 00:00:00 2001
> From: Christophe Lyon <christophe.lyon@linaro.org>
> Date: Thu, 8 Feb 2018 11:12:52 +0100
> Subject: [ARM/FDPIC v6 05/24] [ARM] FDPIC: Fix __do_global_dtors_aux and
>  frame_dummy generation
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
>
> 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>
> 	Micka«l Guªn© <mickael.guene@st.com>
>
> 	libgcc/
> 	* libgcc/crtstuff.c: Add support for FDPIC.

OK, thanks.

Richard

>
> Change-Id: I0bc4b1232fbf3c69068fb23a1b9cafc895d141b1
>
> diff --git a/libgcc/crtstuff.c b/libgcc/crtstuff.c
> index 4927a9f..6659039 100644
> --- a/libgcc/crtstuff.c
> +++ b/libgcc/crtstuff.c
> @@ -429,9 +429,17 @@ __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__("\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 };
> +#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)
> @@ -473,9 +481,17 @@ frame_dummy (void)
>  #ifdef __LIBGCC_INIT_SECTION_ASM_OP__
>  CRT_CALL_STATIC_FUNCTION (__LIBGCC_INIT_SECTION_ASM_OP__, frame_dummy)
>  #else /* defined(__LIBGCC_INIT_SECTION_ASM_OP__) */
> +#if defined(__FDPIC__)
> +__asm__("\t.equ\t__frame_dummy_alias, frame_dummy\n");
> +extern char __frame_dummy_alias;
> +static void *__frame_dummy_init_array_entry[]
> +__attribute__ ((__used__, section(".init_array"), aligned(sizeof(void *))))
> +     = { &__frame_dummy_alias };
> +#else /* defined(__FDPIC__) */
>  static func_ptr __frame_dummy_init_array_entry[]
>    __attribute__ ((__used__, section(".init_array"), aligned(sizeof(func_ptr))))
>    = { frame_dummy };
> +#endif /* defined(__FDPIC__) */
>  #endif /* !defined(__LIBGCC_INIT_SECTION_ASM_OP__) */
>  #endif /* USE_EH_FRAME_REGISTRY || USE_TM_CLONE_REGISTRY */