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Switch to inline assembler in crtbegin. 

Using __builtin_frame_address was clever, but didn't work for arm64 (for
reasons which were never investigated) and the ChromeOS folks claim it
causes trouble for x86 with ARC++ (though without a reproduceable test case).

Naked functions turn out to be quite unevenly supported: some architectures
do the right thing, others don't; some architectures warn, others don't (and
the warnings don't always match the platforms that _actually_ have problems).

Inline assembler also removes the guessing games: everyone knows what the
couple of instructions _ought_ to be, and now we don't have to reason about
what the compiler will actually do (yet still keep the majority of the code
in C).

Bug: N/A
Test: builds, boots
Change-Id: I14207ef50ca46b6eca273c3cb7509c311146a3ca
This commit is contained in:
Elliott Hughes 2017-05-23 11:03:58 -07:00
parent 4767bc4a6c
commit 94072fbb4e
3 changed files with 22 additions and 99 deletions
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16
libc/Android.bp
View File

@ -1984,14 +1984,6 @@ cc_object {
srcs: ["arch-common/bionic/crtbegin.c"],
arch: {
arm64: {
srcs: [
"arch-arm64/bionic/crtbegin.c",
],
exclude_srcs: [
"arch-common/bionic/crtbegin.c",
],
},
mips: {
srcs: [
"arch-mips/bionic/crtbegin.c",
@ -2029,14 +2021,6 @@ cc_object {
srcs: ["arch-common/bionic/crtbegin.c"],
arch: {
arm64: {
srcs: [
"arch-arm64/bionic/crtbegin.c",
],
exclude_srcs: [
"arch-common/bionic/crtbegin.c",
],
},
mips: {
srcs: [
"arch-mips/bionic/crtbegin.c",

70
libc/arch-arm64/bionic/crtbegin.c
View File

@ -1,70 +0,0 @@
/*
* Copyright (C) 2013 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "../../bionic/libc_init_common.h"
#include <stddef.h>
#include <stdint.h>
__attribute__ ((section (".preinit_array")))
void (*__PREINIT_ARRAY__)(void) = (void (*)(void)) -1;
__attribute__ ((section (".init_array")))
void (*__INIT_ARRAY__)(void) = (void (*)(void)) -1;
__attribute__ ((section (".fini_array")))
void (*__FINI_ARRAY__)(void) = (void (*)(void)) -1;
__LIBC_HIDDEN__ void do_arm64_start(void* raw_args) {
structors_array_t array;
array.preinit_array = &__PREINIT_ARRAY__;
array.init_array = &__INIT_ARRAY__;
array.fini_array = &__FINI_ARRAY__;
__libc_init(raw_args, NULL, &main, &array);
}
/*
* Put the value of sp in x0 and call do_arm64_init(). The latter will then
* then be able to access the stack as prepared by the kernel's execve system
* call (via the first argument).
*/
__asm__ (
" .text \n"
" .align 2 \n"
" .global _start \n"
" .hidden _start \n"
" .type _start, %function \n"
"_start: \n"
" add x0, sp, xzr \n"
" b do_arm64_start \n"
" .size _start, .-_start \n"
);
#include "../../arch-common/bionic/__dso_handle.h"
#include "../../arch-common/bionic/atexit.h"
#include "../../arch-common/bionic/pthread_atfork.h"

35
libc/arch-common/bionic/crtbegin.c
View File

@ -30,33 +30,42 @@
#include <stddef.h>
#include <stdint.h>
__attribute__ ((section (".preinit_array")))
__attribute__((__section__(".preinit_array")))
void (*__PREINIT_ARRAY__)(void) = (void (*)(void)) -1;
__attribute__ ((section (".init_array")))
__attribute__((__section__(".init_array")))
void (*__INIT_ARRAY__)(void) = (void (*)(void)) -1;
__attribute__ ((section (".fini_array")))
__attribute__((__section__(".fini_array")))
void (*__FINI_ARRAY__)(void) = (void (*)(void)) -1;
__LIBC_HIDDEN__
#ifdef __i386__
__attribute__((force_align_arg_pointer))
#endif
void _start() {
static void _start_main(void* raw_args) {
structors_array_t array;
array.preinit_array = &__PREINIT_ARRAY__;
array.init_array = &__INIT_ARRAY__;
array.fini_array = &__FINI_ARRAY__;
void* raw_args = (void*) ((uintptr_t) __builtin_frame_address(0) + sizeof(void*));
#ifdef __x86_64__
// 16-byte stack alignment is required by x86_64 ABI
asm("andq $~15, %rsp");
#endif
__libc_init(raw_args, NULL, &main, &array);
}
#define PRE ".text; .global _start; .type _start,%function; _start:"
#define POST "; .size _start, .-_start"
#if defined(__aarch64__)
__asm__(PRE "mov x0,sp; b _start_main" POST);
#elif defined(__arm__)
__asm__(PRE "mov r0,sp; b _start_main" POST);
#elif defined(__i386__)
__asm__(PRE "movl %esp,%eax; andl $~0xf,%esp; pushl %eax; calll _start_main" POST);
#elif defined(__x86_64__)
__asm__(PRE "movq %rsp,%rdi; andq $~0xf,%rsp; callq _start_main" POST);
#else
#error unsupported architecture
#endif
#undef PRE
#undef POST
#include "__dso_handle.h"
#include "atexit.h"
#include "pthread_atfork.h"