From 94072fbb4e42a195cd6cec97f9af15ff45cb84ee Mon Sep 17 00:00:00 2001 From: Elliott Hughes Date: Tue, 23 May 2017 11:03:58 -0700 Subject: [PATCH] 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 --- libc/Android.bp | 16 ------- libc/arch-arm64/bionic/crtbegin.c | 70 ------------------------------ libc/arch-common/bionic/crtbegin.c | 35 +++++++++------ 3 files changed, 22 insertions(+), 99 deletions(-) delete mode 100644 libc/arch-arm64/bionic/crtbegin.c diff --git a/libc/Android.bp b/libc/Android.bp index 38771455a..cda9eaae4 100644 --- a/libc/Android.bp +++ b/libc/Android.bp @@ -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", diff --git a/libc/arch-arm64/bionic/crtbegin.c b/libc/arch-arm64/bionic/crtbegin.c deleted file mode 100644 index 7e2c5d766..000000000 --- a/libc/arch-arm64/bionic/crtbegin.c +++ /dev/null @@ -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 -#include - -__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" diff --git a/libc/arch-common/bionic/crtbegin.c b/libc/arch-common/bionic/crtbegin.c index c46405c4f..fc5866e97 100644 --- a/libc/arch-common/bionic/crtbegin.c +++ b/libc/arch-common/bionic/crtbegin.c @@ -30,33 +30,42 @@ #include #include -__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"