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


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>
	Mickaël Guêné <mickael.guene@st.com>

	libgcc/
	* libgcc/crtstuff.c: Add support for FDPIC.

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 */
 
-- 
2.6.3


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