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Merge "Clean up the argc/argv/envp/auxv handling."

This commit is contained in:
Elliott Hughes 2013-02-07 19:48:16 +00:00 committed by Gerrit Code Review
parent d4187efd7f 42b2c6a5ee
commit 2f41531ff9
16 changed files with 383 additions and 417 deletions
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8
libc/Android.mk
View File

@ -177,7 +177,6 @@ libc_common_src_files := \
bionic/isatty.c \
bionic/issetugid.c \
bionic/ldexp.c \
bionic/libc_init_common.c \
bionic/logd_write.c \
bionic/lseek64.c \
bionic/md5.c \
@ -275,6 +274,7 @@ libc_bionic_src_files := \
bionic/__fgets_chk.cpp \
bionic/getauxval.cpp \
bionic/getcwd.cpp \
bionic/libc_init_common.cpp \
bionic/libgen.cpp \
bionic/__memcpy_chk.cpp \
bionic/__memmove_chk.cpp \
@ -824,7 +824,7 @@ include $(CLEAR_VARS)
LOCAL_SRC_FILES := \
$(libc_arch_static_src_files) \
$(libc_static_common_src_files) \
bionic/libc_init_static.c
bionic/libc_init_static.cpp
LOCAL_C_INCLUDES := $(libc_common_c_includes)
LOCAL_CFLAGS := $(libc_common_cflags) \
@ -849,7 +849,7 @@ LOCAL_SRC_FILES := \
$(libc_static_common_src_files) \
bionic/dlmalloc.c \
bionic/malloc_debug_common.cpp \
bionic/libc_init_static.c
bionic/libc_init_static.cpp
LOCAL_CFLAGS := $(libc_common_cflags) \
-DLIBC_STATIC \
@ -883,7 +883,7 @@ LOCAL_SRC_FILES := \
bionic/dlmalloc.c \
bionic/malloc_debug_common.cpp \
bionic/pthread_debug.cpp \
bionic/libc_init_dynamic.c
bionic/libc_init_dynamic.cpp
ifeq ($(TARGET_ARCH),arm)
LOCAL_NO_CRT := true

30
libc/arch-arm/bionic/crtbegin.c
View File

@ -26,21 +26,8 @@
* SUCH DAMAGE.
*/
typedef struct
{
void (**preinit_array)(void);
void (**init_array)(void);
void (**fini_array)(void);
} structors_array_t;
extern int main(int argc, char **argv, char **env);
extern void __libc_init(
unsigned int *elfdata,
void (*onexit)(void),
int (*slingshot)(int, char**, char**),
structors_array_t const * const structors
);
#include "../../bionic/libc_init_common.h"
#include <stddef.h>
__attribute__ ((section (".preinit_array")))
void (*__PREINIT_ARRAY__)(void) = (void (*)(void)) -1;
@ -51,17 +38,14 @@ void (*__INIT_ARRAY__)(void) = (void (*)(void)) -1;
__attribute__ ((section (".fini_array")))
void (*__FINI_ARRAY__)(void) = (void (*)(void)) -1;
__attribute__((visibility("hidden")))
void _start() {
__LIBC_HIDDEN__ void _start() {
structors_array_t array;
void *elfdata;
array.preinit_array = &__PREINIT_ARRAY__;
array.init_array = &__INIT_ARRAY__;
array.fini_array = &__FINI_ARRAY__;
array.init_array = &__INIT_ARRAY__;
array.fini_array = &__FINI_ARRAY__;
elfdata = __builtin_frame_address(0) + sizeof(void *);
__libc_init(elfdata, (void *) 0, &main, &array);
void* raw_args = __builtin_frame_address(0) + sizeof(void*);
__libc_init(raw_args, NULL, &main, &array);
}
#include "__dso_handle.h"

29
libc/arch-x86/bionic/crtbegin.c
View File

@ -26,21 +26,8 @@
* SUCH DAMAGE.
*/
typedef struct
{
void (**preinit_array)(void);
void (**init_array)(void);
void (**fini_array)(void);
} structors_array_t;
extern int main(int argc, char **argv, char **env);
extern void __libc_init(
unsigned int *elfdata,
void (*onexit)(void),
int (*slingshot)(int, char**, char**),
structors_array_t const * const structors
);
#include "../../bionic/libc_init_common.h"
#include <stddef.h>
__attribute__ ((section (".preinit_array")))
void (*__PREINIT_ARRAY__)(void) = (void (*)(void)) -1;
@ -51,18 +38,16 @@ void (*__INIT_ARRAY__)(void) = (void (*)(void)) -1;
__attribute__ ((section (".fini_array")))
void (*__FINI_ARRAY__)(void) = (void (*)(void)) -1;
__attribute__((visibility("hidden")))
__LIBC_HIDDEN__
__attribute__((force_align_arg_pointer))
void _start() {
structors_array_t array;
void *elfdata;
array.preinit_array = &__PREINIT_ARRAY__;
array.init_array = &__INIT_ARRAY__;
array.fini_array = &__FINI_ARRAY__;
array.init_array = &__INIT_ARRAY__;
array.fini_array = &__FINI_ARRAY__;
elfdata = __builtin_frame_address(0) + sizeof(void *);
__libc_init(elfdata, (void *) 0, &main, &array);
void* raw_args = __builtin_frame_address(0) + sizeof(void*);
__libc_init(raw_args, NULL, &main, &array);
}
#include "__dso_handle.h"

8
libc/bionic/getauxval.cpp
View File

@ -32,17 +32,13 @@
#include <private/bionic_auxv.h>
#include <elf.h>
__LIBC_HIDDEN__
Elf32_auxv_t* __libc_auxv = NULL;
__LIBC_HIDDEN__ Elf32_auxv_t* __libc_auxv = NULL;
extern "C" unsigned long int getauxval(unsigned long int type) {
Elf32_auxv_t* v;
for (v = __libc_auxv; v->a_type != AT_NULL; v++) {
for (Elf32_auxv_t* v = __libc_auxv; v->a_type != AT_NULL; ++v) {
if (v->a_type == type) {
return v->a_un.a_val;
}
}
return 0;
}

50
libc/bionic/libc_init_common.c → libc/bionic/libc_init_common.cpp
View File

@ -30,29 +30,31 @@
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <elf.h>
#include <asm/page.h>
#include "pthread_internal.h"
#include "atexit.h"
#include "KernelArgumentBlock.h"
#include "libc_init_common.h"
#include <bionic_tls.h>
#include <errno.h>
#include <private/bionic_auxv.h>
extern unsigned __get_sp(void);
extern pid_t gettid(void);
extern "C" unsigned __get_sp(void);
extern "C" int __system_properties_init(void);
char* __progname;
// Not public, but well-known in the BSDs.
char* __progname;
// Declared in <unistd.h>
char** environ;
/* from asm/page.h */
// Declared in <asm/page.h>.
unsigned int __page_size = PAGE_SIZE;
unsigned int __page_shift = PAGE_SHIFT;
int __system_properties_init(void);
/* Init TLS for the initial thread. Called by the linker _before_ libc is mapped
* in memory. Beware: all writes to libc globals from this function will
* apply to linker-private copies and will not be visible from libc later on.
@ -61,10 +63,10 @@ int __system_properties_init(void);
* stores the pointer in TLS, but does not add it to pthread's gThreadList. This
* has to be done later from libc itself (see __libc_init_common).
*
* This function also stores the elf_data argument in a specific TLS slot to be later
* This function also stores a pointer to the kernel argument block in a TLS slot to be
* picked up by the libc constructor.
*/
void __libc_init_tls(unsigned** elf_data) {
extern "C" void __libc_init_tls(void* kernel_argument_block) {
unsigned stack_top = (__get_sp() & ~(PAGE_SIZE - 1)) + PAGE_SIZE;
unsigned stack_size = 128 * 1024;
unsigned stack_bottom = stack_top - stack_size;
@ -78,33 +80,21 @@ void __libc_init_tls(unsigned** elf_data) {
static void* tls_area[BIONIC_TLS_SLOTS];
__init_tls(tls_area, &thread);
tls_area[TLS_SLOT_BIONIC_PREINIT] = elf_data;
tls_area[TLS_SLOT_BIONIC_PREINIT] = kernel_argument_block;
}
void __libc_init_common(uintptr_t* elf_data) {
int argc = *elf_data;
char** argv = (char**) (elf_data + 1);
char** envp = argv + argc + 1;
void __libc_init_common(KernelArgumentBlock& args) {
// Initialize various globals.
environ = args.envp;
errno = 0;
__libc_auxv = args.auxv;
__progname = args.argv[0] ? args.argv[0] : const_cast<char*>("<unknown>");
// Get the main thread from TLS and add it to the thread list.
pthread_internal_t* main_thread = __get_thread();
main_thread->allocated_on_heap = false;
_pthread_internal_add(main_thread);
// Set various globals.
errno = 0;
__progname = argv[0] ? argv[0] : "<unknown>";
environ = envp;
// The auxiliary vector is at the end of the environment block
while(*envp != NULL) {
envp++;
}
/* The end of the environment block is marked by two NULL pointers */
envp++;
__libc_auxv = (Elf32_auxv_t*) envp;
__system_properties_init(); // Requires 'environ'.
}
@ -116,7 +106,7 @@ void __libc_init_common(uintptr_t* elf_data) {
* entry in the list has value -1, the last one has value 0.
*/
void __libc_fini(void* array) {
void** fini_array = array;
void** fini_array = reinterpret_cast<void**>(array);
const size_t minus1 = ~(size_t)0; /* ensure proper sign extension */
/* Sanity check - first entry must be -1 */
@ -135,7 +125,7 @@ void __libc_fini(void* array) {
/* Now call each destructor in reverse order. */
while (count > 0) {
void (*func)() = (void (*)) fini_array[--count];
void (*func)() = (void (*)()) fini_array[--count];
/* Sanity check, any -1 in the list is ignored */
if ((size_t)func == minus1) {

29
libc/bionic/libc_init_common.h
View File

@ -28,16 +28,29 @@
#ifndef LIBC_INIT_COMMON_H
#define LIBC_INIT_COMMON_H
#include <stdint.h>
#include <sys/cdefs.h>
typedef struct
{
void (**preinit_array)(void);
void (**init_array)(void);
void (**fini_array)(void);
typedef struct {
void (**preinit_array)(void);
void (**init_array)(void);
void (**fini_array)(void);
} structors_array_t;
extern void __libc_init_common(uintptr_t *elfdata);
extern void __libc_fini(void* finit_array);
__BEGIN_DECLS
extern int main(int argc, char** argv, char** env);
__noreturn void __libc_init(void* raw_args,
void (*onexit)(void),
int (*slingshot)(int, char**, char**),
structors_array_t const * const structors);
void __libc_fini(void* finit_array);
__END_DECLS
#if defined(__cplusplus)
struct KernelArgumentBlock;
void __libc_init_common(KernelArgumentBlock& args);
#endif
#endif

127
libc/bionic/libc_init_dynamic.c
View File

@ -1,127 +0,0 @@
/*
* Copyright (C) 2008 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.
*/
/*
* libc_init_dynamic.c
*
* This source files provides two important functions for dynamic
* executables:
*
* - a C runtime initializer (__libc_preinit), which is called by
* the dynamic linker when libc.so is loaded. This happens before
* any other initializer (e.g. static C++ constructors in other
* shared libraries the program depends on).
*
* - a program launch function (__libc_init), which is called after
* all dynamic linking has been performed. Technically, it is called
* from arch-$ARCH/bionic/crtbegin_dynamic.S which is itself called
* by the dynamic linker after all libraries have been loaded and
* initialized.
*/
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <elf.h>
#include "atexit.h"
#include "libc_init_common.h"
#include <bionic_tls.h>
/* We flag the __libc_preinit function as a constructor to ensure
* that its address is listed in libc.so's .init_array section.
* This ensures that the function is called by the dynamic linker
* as soon as the shared library is loaded.
*/
void __attribute__((constructor)) __libc_preinit(void);
void __libc_preinit(void)
{
/* Read the ELF data pointer from a special slot of the
* TLS area, then call __libc_init_common with it.
*
* Note that:
* - we clear the slot so no other initializer sees its value.
* - __libc_init_common() will change the TLS area so the old one
* won't be accessible anyway.
*/
void** tls_area = (void**)__get_tls();
unsigned* elfdata = tls_area[TLS_SLOT_BIONIC_PREINIT];
tls_area[TLS_SLOT_BIONIC_PREINIT] = NULL;
__libc_init_common(elfdata);
/* Setup pthread routines accordingly to the environment.
* Requires system properties
*/
extern void pthread_debug_init(void);
pthread_debug_init();
/* Setup malloc routines accordingly to the environment.
* Requires system properties
*/
extern void malloc_debug_init(void);
malloc_debug_init();
}
void __libc_postfini(void)
{
extern void malloc_debug_fini(void);
malloc_debug_fini();
}
/* This function is called from the executable's _start entry point
* (see arch-$ARCH/bionic/crtbegin_dynamic.S), which is itself
* called by the dynamic linker after it has loaded all shared
* libraries the executable depends on.
*
* Note that the dynamic linker has also run all constructors in the
* executable at this point.
*/
__noreturn void __libc_init(uintptr_t *elfdata,
void (*onexit)(void),
int (*slingshot)(int, char**, char**),
structors_array_t const * const structors)
{
int argc = (int)*elfdata;
char** argv = (char**)(elfdata + 1);
char** envp = argv + argc + 1;
/* Several Linux ABIs don't pass the onexit pointer, and the ones that
* do never use it. Therefore, we ignore it.
*/
/* The executable may have its own destructors listed in its .fini_array
* so we need to ensure that these are called when the program exits
* normally.
*/
if (structors->fini_array)
__cxa_atexit(__libc_fini,structors->fini_array,NULL);
exit(slingshot(argc, argv, envp));
}

115
libc/bionic/libc_init_dynamic.cpp Normal file
View File

@ -0,0 +1,115 @@
/*
* Copyright (C) 2008 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.
*/
/*
* libc_init_dynamic.c
*
* This source files provides two important functions for dynamic
* executables:
*
* - a C runtime initializer (__libc_preinit), which is called by
* the dynamic linker when libc.so is loaded. This happens before
* any other initializer (e.g. static C++ constructors in other
* shared libraries the program depends on).
*
* - a program launch function (__libc_init), which is called after
* all dynamic linking has been performed. Technically, it is called
* from arch-$ARCH/bionic/crtbegin_dynamic.S which is itself called
* by the dynamic linker after all libraries have been loaded and
* initialized.
*/
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <elf.h>
#include "atexit.h"
#include "KernelArgumentBlock.h"
#include "libc_init_common.h"
#include <bionic_tls.h>
extern "C" {
extern void pthread_debug_init(void);
extern void malloc_debug_init(void);
extern void malloc_debug_fini(void);
};
// We flag the __libc_preinit function as a constructor to ensure
// that its address is listed in libc.so's .init_array section.
// This ensures that the function is called by the dynamic linker
// as soon as the shared library is loaded.
void __attribute__((constructor)) __libc_preinit(void);
void __libc_preinit() {
// Read the kernel argument block pointer from TLS.
void* tls = const_cast<void*>(__get_tls());
KernelArgumentBlock** args_slot = &reinterpret_cast<KernelArgumentBlock**>(tls)[TLS_SLOT_BIONIC_PREINIT];
KernelArgumentBlock* args = *args_slot;
// Clear the slot so no other initializer sees its value.
// __libc_init_common() will change the TLS area so the old one won't be accessible anyway.
*args_slot = NULL;
__libc_init_common(*args);
// Hooks for the debug malloc and pthread libraries to let them know that we're starting up.
pthread_debug_init();
malloc_debug_init();
}
void __libc_postfini() {
// A hook for the debug malloc library to let it know that we're shutting down.
malloc_debug_fini();
}
// This function is called from the executable's _start entry point
// (see arch-$ARCH/bionic/crtbegin_dynamic.S), which is itself
// called by the dynamic linker after it has loaded all shared
// libraries the executable depends on.
//
// Note that the dynamic linker has also run all constructors in the
// executable at this point.
__noreturn void __libc_init(void* raw_args,
void (*onexit)(void),
int (*slingshot)(int, char**, char**),
structors_array_t const * const structors) {
KernelArgumentBlock args(raw_args);
// Several Linux ABIs don't pass the onexit pointer, and the ones that
// do never use it. Therefore, we ignore it.
// The executable may have its own destructors listed in its .fini_array
// so we need to ensure that these are called when the program exits
// normally.
if (structors->fini_array) {
__cxa_atexit(__libc_fini,structors->fini_array,NULL);
}
exit(slingshot(args.argc, args.argv, args.envp));
}

109
libc/bionic/libc_init_static.c → libc/bionic/libc_init_static.cpp
View File

@ -37,19 +37,20 @@
* arrays that must be run before the program's 'main' routine is launched.
*/
#include <elf.h>
#include <errno.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <elf.h>
#include "pthread_internal.h"
#include "atexit.h"
#include "libc_init_common.h"
#include <bionic_tls.h>
#include <errno.h>
#include <sys/mman.h>
#include <sys/auxv.h>
#include <sys/mman.h>
#include "atexit.h"
#include "bionic_tls.h"
#include "KernelArgumentBlock.h"
#include "libc_init_common.h"
#include "pthread_internal.h"
// Returns the address of the page containing address 'x'.
#define PAGE_START(x) ((x) & PAGE_MASK)
@ -58,71 +59,53 @@
// itself at the start of a page.
#define PAGE_END(x) PAGE_START((x) + (PAGE_SIZE-1))
static void call_array(void(**list)())
{
// First element is -1, list is null-terminated
while (*++list) {
(*list)();
}
static void call_array(void(**list)()) {
// First element is -1, list is null-terminated
while (*++list) {
(*list)();
}
}
static void apply_gnu_relro() {
Elf32_Phdr *phdr_start;
unsigned long int phdr_ct;
Elf32_Phdr *phdr;
Elf32_Phdr* phdr_start = reinterpret_cast<Elf32_Phdr*>(getauxval(AT_PHDR));
unsigned long int phdr_ct = getauxval(AT_PHNUM);
phdr_start = (Elf32_Phdr *) getauxval(AT_PHDR);
phdr_ct = getauxval(AT_PHNUM);
for (phdr = phdr_start; phdr < (phdr_start + phdr_ct); phdr++) {
if (phdr->p_type != PT_GNU_RELRO)
continue;
Elf32_Addr seg_page_start = PAGE_START(phdr->p_vaddr);
Elf32_Addr seg_page_end = PAGE_END(phdr->p_vaddr + phdr->p_memsz);
// Check return value here? What do we do if we fail?
mprotect((void *) seg_page_start,
seg_page_end - seg_page_start,
PROT_READ);
for (Elf32_Phdr* phdr = phdr_start; phdr < (phdr_start + phdr_ct); phdr++) {
if (phdr->p_type != PT_GNU_RELRO) {
continue;
}
Elf32_Addr seg_page_start = PAGE_START(phdr->p_vaddr);
Elf32_Addr seg_page_end = PAGE_END(phdr->p_vaddr + phdr->p_memsz);
// Check return value here? What do we do if we fail?
mprotect(reinterpret_cast<void*>(seg_page_start), seg_page_end - seg_page_start, PROT_READ);
}
}
__noreturn void __libc_init(uintptr_t *elfdata,
void (*onexit)(void),
int (*slingshot)(int, char**, char**),
structors_array_t const * const structors)
{
int argc;
char **argv, **envp;
__noreturn void __libc_init(void* raw_args,
void (*onexit)(void),
int (*slingshot)(int, char**, char**),
structors_array_t const * const structors) {
__libc_init_tls(NULL);
__libc_init_tls(NULL);
KernelArgumentBlock args(raw_args);
__libc_init_common(args);
/* Initialize the C runtime environment */
__libc_init_common(elfdata);
apply_gnu_relro();
apply_gnu_relro();
// Several Linux ABIs don't pass the onexit pointer, and the ones that
// do never use it. Therefore, we ignore it.
/* Several Linux ABIs don't pass the onexit pointer, and the ones that
* do never use it. Therefore, we ignore it.
*/
call_array(structors->preinit_array);
call_array(structors->init_array);
/* pre-init array. */
call_array(structors->preinit_array);
// The executable may have its own destructors listed in its .fini_array
// so we need to ensure that these are called when the program exits
// normally.
if (structors->fini_array != NULL) {
__cxa_atexit(__libc_fini,structors->fini_array,NULL);
}
// call static constructors
call_array(structors->init_array);
argc = (int) *elfdata;
argv = (char**)(elfdata + 1);
envp = argv + argc + 1;
/* The executable may have its own destructors listed in its .fini_array
* so we need to ensure that these are called when the program exits
* normally.
*/
if (structors->fini_array)
__cxa_atexit(__libc_fini,structors->fini_array,NULL);
exit(slingshot(argc, argv, envp));
exit(slingshot(args.argc, args.argv, args.envp));
}

76
libc/private/KernelArgumentBlock.h Normal file
View File

@ -0,0 +1,76 @@
/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef KERNEL_ARGUMENT_BLOCK_H
#define KERNEL_ARGUMENT_BLOCK_H
#include <elf.h>
#include <stdint.h>
#include <sys/auxv.h>
// When the kernel starts the dynamic linker, it passes a pointer to a block
// of memory containing argc, the argv array, the environment variable array,
// and the array of ELF aux vectors. This class breaks that block up into its
// constituents for easy access.
class KernelArgumentBlock {
public:
KernelArgumentBlock(void* raw_args) {
uint32_t* args = reinterpret_cast<uint32_t*>(raw_args);
argc = static_cast<int>(*args);
argv = reinterpret_cast<char**>(args + 1);
envp = argv + argc + 1;
// Skip over all environment variable definitions to find aux vector.
// The end of the environment block is marked by two NULL pointers.
char** p = envp;
while (*p != NULL) {
++p;
}
++p; // Skip second NULL;
auxv = reinterpret_cast<Elf32_auxv_t*>(p);
}
// Similar to ::getauxval but doesn't require the libc global variables to be set up,
// so it's safe to call this really early on. This function also lets you distinguish
// between the inability to find the given type and its value just happening to be 0.
unsigned long getauxval(unsigned long type, bool* found_match = NULL) {
for (Elf32_auxv_t* v = auxv; v->a_type != AT_NULL; ++v) {
if (v->a_type == type) {
if (found_match != NULL) {
*found_match = true;
}
return v->a_un.a_val;
}
}
if (found_match != NULL) {
*found_match = false;
}
return 0;
}
int argc;
char** argv;
char** envp;
Elf32_auxv_t* auxv;
private:
// Disallow copy and assignment.
KernelArgumentBlock(const KernelArgumentBlock&);
void operator=(const KernelArgumentBlock&);
};
#endif // KERNEL_ARGUMENT_BLOCK_H

2
libc/private/bionic_tls.h
View File

@ -134,7 +134,7 @@ extern void* __get_tls( void );
extern void* __get_stack_base(int *p_stack_size);
/* Initialize the TLS. */
extern void __libc_init_tls(unsigned** elfdata);
extern void __libc_init_tls(void* kernel_argument_block);
__END_DECLS

4
libc/stdlib/atexit.h
View File

@ -44,8 +44,12 @@ struct atexit {
} fns[1]; /* the table itself */
};
__BEGIN_DECLS
extern int __atexit_invalid;
extern struct atexit *__atexit; /* points to head of LIFO stack */
int __cxa_atexit(void (*)(void *), void *, void *);
void __cxa_finalize(void *);
__END_DECLS

15
linker/arch/x86/begin.c
View File

@ -26,24 +26,23 @@
* SUCH DAMAGE.
*/
#include <stdint.h>
#include <sys/cdefs.h>
extern unsigned __linker_init(unsigned int *elfdata);
extern unsigned __linker_init(void* raw_args);
__attribute__((visibility("hidden")))
void _start() {
__LIBC_HIDDEN__ void _start() {
void (*start)(void);
void* elfdata = (void*) ((uintptr_t) __builtin_frame_address(0) + sizeof(void*));
start = (void(*)(void))__linker_init(elfdata);
void* raw_args = (void*) ((uintptr_t) __builtin_frame_address(0) + sizeof(void*));
start = (void(*)(void))__linker_init(raw_args);
/* linker init returns (%eax) the _entry address in the main image */
/* entry point expects sp to point to elfdata */
/* entry point expects sp to point to raw_args */
__asm__ (
"mov %0, %%esp\n\t"
"jmp *%1\n\t"
: : "r"(elfdata), "r"(start) :
: : "r"(raw_args), "r"(start) :
);
/* Unreachable */

151
linker/linker.cpp
View File

@ -42,6 +42,7 @@
// Private C library headers.
#include <private/bionic_tls.h>
#include <private/debug_format.h>
#include <private/KernelArgumentBlock.h>
#include <private/logd.h>
#include <private/ScopedPthreadMutexLocker.h>
@ -1771,15 +1772,8 @@ static bool soinfo_link_image(soinfo* si) {
* fixed it's own GOT. It is safe to make references to externs
* and other non-local data at this point.
*/
static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linker_base)
{
static soinfo linker_soinfo;
int argc = (int) *elfdata;
char **argv = (char**) (elfdata + 1);
unsigned *vecs = (unsigned*) (argv + argc + 1);
/* NOTE: we store the elfdata pointer on a special location
static unsigned __linker_init_post_relocation(KernelArgumentBlock& args, unsigned linker_base) {
/* NOTE: we store the args pointer on a special location
* of the temporary TLS area in order to pass it to
* the C Library's runtime initializer.
*
@ -1787,7 +1781,7 @@ static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linke
* to point to a different location to ensure that no other
* shared library constructor can access it.
*/
__libc_init_tls(elfdata);
__libc_init_tls(&args);
#if TIMING
struct timeval t0, t1;
@ -1795,7 +1789,7 @@ static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linke
#endif
// Initialize environment functions, and get to the ELF aux vectors table.
vecs = linker_env_init(vecs);
linker_env_init(args);
debugger_init();
@ -1815,9 +1809,8 @@ static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linke
}
INFO("[ android linker & debugger ]\n");
DEBUG("elfdata @ 0x%08x\n", (unsigned)elfdata);
soinfo* si = soinfo_alloc(argv[0]);
soinfo* si = soinfo_alloc(args.argv[0]);
if (si == NULL) {
exit(EXIT_FAILURE);
}
@ -1827,7 +1820,7 @@ static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linke
link_map* map = &(si->linkmap);
map->l_addr = 0;
map->l_name = argv[0];
map->l_name = args.argv[0];
map->l_prev = NULL;
map->l_next = NULL;
@ -1841,9 +1834,11 @@ static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linke
* Don't use soinfo_alloc(), because the linker shouldn't
* be on the soinfo list.
*/
strlcpy((char*) linker_soinfo.name, "/system/bin/linker", sizeof linker_soinfo.name);
static soinfo linker_soinfo;
strlcpy(linker_soinfo.name, "/system/bin/linker", sizeof(linker_soinfo.name));
linker_soinfo.flags = 0;
linker_soinfo.base = linker_base;
/*
* Set the dynamic field in the link map otherwise gdb will complain with
* the following:
@ -1851,42 +1846,29 @@ static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linke
* expected address (wrong library or version mismatch?)
*/
Elf32_Ehdr *elf_hdr = (Elf32_Ehdr *) linker_base;
Elf32_Phdr *phdr =
(Elf32_Phdr *)((unsigned char *) linker_base + elf_hdr->e_phoff);
Elf32_Phdr *phdr = (Elf32_Phdr*)((unsigned char*) linker_base + elf_hdr->e_phoff);
phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base,
&linker_soinfo.dynamic, NULL, NULL);
insert_soinfo_into_debug_map(&linker_soinfo);
/* extract information passed from the kernel */
while (vecs[0] != 0){
switch(vecs[0]){
case AT_PHDR:
si->phdr = (Elf32_Phdr*) vecs[1];
break;
case AT_PHNUM:
si->phnum = (int) vecs[1];
break;
case AT_ENTRY:
si->entry = vecs[1];
break;
}
vecs += 2;
}
// Extract information passed from the kernel.
si->phdr = reinterpret_cast<Elf32_Phdr*>(args.getauxval(AT_PHDR));
si->phnum = args.getauxval(AT_PHNUM);
si->entry = args.getauxval(AT_ENTRY);
/* Compute the value of si->base. We can't rely on the fact that
* the first entry is the PHDR because this will not be true
* for certain executables (e.g. some in the NDK unit test suite)
*/
int nn;
si->base = 0;
si->size = phdr_table_get_load_size(si->phdr, si->phnum);
si->load_bias = 0;
for ( nn = 0; nn < si->phnum; nn++ ) {
if (si->phdr[nn].p_type == PT_PHDR) {
si->load_bias = (Elf32_Addr)si->phdr - si->phdr[nn].p_vaddr;
si->base = (Elf32_Addr) si->phdr - si->phdr[nn].p_offset;
break;
}
for (int i = 0; i < si->phnum; ++i) {
if (si->phdr[i].p_type == PT_PHDR) {
si->load_bias = reinterpret_cast<Elf32_Addr>(si->phdr) - si->phdr[i].p_vaddr;
si->base = reinterpret_cast<Elf32_Addr>(si->phdr) - si->phdr[i].p_offset;
break;
}
}
si->dynamic = (unsigned *)-1;
si->refcount = 1;
@ -1920,13 +1902,13 @@ static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linke
#if TIMING
gettimeofday(&t1,NULL);
PRINT("LINKER TIME: %s: %d microseconds\n", argv[0], (int) (
PRINT("LINKER TIME: %s: %d microseconds\n", e.argv[0], (int) (
(((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) -
(((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec)
));
#endif
#if STATS
PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol\n", argv[0],
PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol\n", e.argv[0],
linker_stats.count[kRelocAbsolute],
linker_stats.count[kRelocRelative],
linker_stats.count[kRelocCopy],
@ -1946,7 +1928,7 @@ static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linke
}
}
}
PRINT("PAGES MODIFIED: %s: %d (%dKB)\n", argv[0], count, count * 4);
PRINT("PAGES MODIFIED: %s: %d (%dKB)\n", e.argv[0], count, count * 4);
}
#endif
@ -1958,31 +1940,6 @@ static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linke
return si->entry;
}
/*
* Find the value of AT_BASE passed to us by the kernel. This is the load
* location of the linker.
*/
static unsigned find_linker_base(unsigned **elfdata) {
int argc = (int) *elfdata;
char **argv = (char**) (elfdata + 1);
unsigned *vecs = (unsigned*) (argv + argc + 1);
while (vecs[0] != 0) {
vecs++;
}
/* The end of the environment block is marked by two NULL pointers */
vecs++;
while(vecs[0]) {
if (vecs[0] == AT_BASE) {
return vecs[1];
}
vecs += 2;
}
return 0; // should never happen
}
/* Compute the load-bias of an existing executable. This shall only
* be used to compute the load bias of an executable or shared library
* that was loaded by the kernel itself.
@ -2018,39 +1975,41 @@ get_elf_exec_load_bias(const Elf32_Ehdr* elf)
* relocations, any attempt to reference an extern variable, extern
* function, or other GOT reference will generate a segfault.
*/
extern "C" unsigned __linker_init(unsigned **elfdata) {
unsigned linker_addr = find_linker_base(elfdata);
Elf32_Ehdr *elf_hdr = (Elf32_Ehdr *) linker_addr;
Elf32_Phdr *phdr =
(Elf32_Phdr *)((unsigned char *) linker_addr + elf_hdr->e_phoff);
extern "C" unsigned __linker_init(void* raw_args) {
KernelArgumentBlock args(raw_args);
soinfo linker_so;
memset(&linker_so, 0, sizeof(soinfo));
unsigned linker_addr = args.getauxval(AT_BASE);
linker_so.base = linker_addr;
linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum);
linker_so.load_bias = get_elf_exec_load_bias(elf_hdr);
linker_so.dynamic = (unsigned *) -1;
linker_so.phdr = phdr;
linker_so.phnum = elf_hdr->e_phnum;
linker_so.flags |= FLAG_LINKER;
Elf32_Ehdr *elf_hdr = (Elf32_Ehdr*) linker_addr;
Elf32_Phdr *phdr = (Elf32_Phdr*)((unsigned char*) linker_addr + elf_hdr->e_phoff);
if (!soinfo_link_image(&linker_so)) {
// It would be nice to print an error message, but if the linker
// can't link itself, there's no guarantee that we'll be able to
// call write() (because it involves a GOT reference).
//
// This situation should never occur unless the linker itself
// is corrupt.
exit(EXIT_FAILURE);
}
soinfo linker_so;
memset(&linker_so, 0, sizeof(soinfo));
// We have successfully fixed our own relocations. It's safe to run
// the main part of the linker now.
unsigned start_address = __linker_init_post_relocation(elfdata, linker_addr);
linker_so.base = linker_addr;
linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum);
linker_so.load_bias = get_elf_exec_load_bias(elf_hdr);
linker_so.dynamic = (unsigned*) -1;
linker_so.phdr = phdr;
linker_so.phnum = elf_hdr->e_phnum;
linker_so.flags |= FLAG_LINKER;
set_soinfo_pool_protection(PROT_READ);
if (!soinfo_link_image(&linker_so)) {
// It would be nice to print an error message, but if the linker
// can't link itself, there's no guarantee that we'll be able to
// call write() (because it involves a GOT reference).
//
// This situation should never occur unless the linker itself
// is corrupt.
exit(EXIT_FAILURE);
}
// Return the address that the calling assembly stub should jump to.
return start_address;
// We have successfully fixed our own relocations. It's safe to run
// the main part of the linker now.
unsigned start_address = __linker_init_post_relocation(args, linker_addr);
set_soinfo_pool_protection(PROT_READ);
// Return the address that the calling assembly stub should jump to.
return start_address;
}

37
linker/linker_environ.cpp
View File

@ -33,6 +33,8 @@
#include <stdlib.h>
#include <unistd.h>
#include <private/KernelArgumentBlock.h>
static char** _envp;
static bool _AT_SECURE_value = true;
@ -40,21 +42,18 @@ bool get_AT_SECURE() {
return _AT_SECURE_value;
}
static void __init_AT_SECURE(unsigned* auxv) {
static void __init_AT_SECURE(KernelArgumentBlock& args) {
// Check auxv for AT_SECURE first to see if program is setuid, setgid,
// has file caps, or caused a SELinux/AppArmor domain transition.
for (unsigned* v = auxv; v[0]; v += 2) {
if (v[0] == AT_SECURE) {
// Kernel told us whether to enable secure mode.
_AT_SECURE_value = v[1];
return;
}
}
bool kernel_supplied_AT_SECURE;
_AT_SECURE_value = args.getauxval(AT_SECURE, &kernel_supplied_AT_SECURE);
// We don't support ancient kernels.
const char* msg = "FATAL: kernel did not supply AT_SECURE\n";
write(2, msg, strlen(msg));
exit(EXIT_FAILURE);
if (!kernel_supplied_AT_SECURE) {
const char* msg = "FATAL: kernel did not supply AT_SECURE\n";
write(2, msg, strlen(msg));
exit(EXIT_FAILURE);
}
}
// Check if the environment variable definition at 'envstr'
@ -164,22 +163,12 @@ static void __sanitize_environment_variables() {
dst[0] = NULL;
}
unsigned* linker_env_init(unsigned* environment_and_aux_vectors) {
void linker_env_init(KernelArgumentBlock& args) {
// Store environment pointer - can't be NULL.
_envp = reinterpret_cast<char**>(environment_and_aux_vectors);
_envp = args.envp;
// Skip over all environment variable definitions.
// The end of the environment block is marked by two NULL pointers.
unsigned* aux_vectors = environment_and_aux_vectors;
while (aux_vectors[0] != 0) {
++aux_vectors;
}
++aux_vectors;
__init_AT_SECURE(aux_vectors);
__init_AT_SECURE(args);
__sanitize_environment_variables();
return aux_vectors;
}
const char* linker_env_get(const char* name) {

10
linker/linker_environ.h
View File

@ -29,10 +29,10 @@
#ifndef LINKER_ENVIRON_H
#define LINKER_ENVIRON_H
// Call this function before anything else. 'environment_and_aux_vectors'
// must point to the environment block in the ELF data block. The function
// returns the start of the aux vectors after the environment block.
extern unsigned* linker_env_init(unsigned* environment_and_aux_vectors);
struct KernelArgumentBlock;
// Call this function before any of the other functions in this header file.
extern void linker_env_init(KernelArgumentBlock& args);
// Returns the value of environment variable 'name' if defined and not
// empty, or NULL otherwise.
@ -41,4 +41,4 @@ extern const char* linker_env_get(const char* name);
// Returns the value of this program's AT_SECURE variable.
extern bool get_AT_SECURE();
#endif /* LINKER_ENVIRON_H */
#endif // LINKER_ENVIRON_H