diff options
| -rw-r--r-- | libc/arch-arm/bionic/crtbegin_dynamic.S | 26 | ||||
| -rw-r--r-- | libc/arch-arm/bionic/crtbegin_static.S | 33 | ||||
| -rw-r--r-- | libc/arch-x86/bionic/crtbegin_dynamic.S | 24 | ||||
| -rw-r--r-- | libc/arch-x86/bionic/crtbegin_static.S | 24 | ||||
| -rw-r--r-- | libc/bionic/libc_init_common.c | 58 | ||||
| -rw-r--r-- | libc/bionic/libc_init_dynamic.c | 40 | ||||
| -rw-r--r-- | libc/bionic/libc_init_static.c | 37 | ||||
| -rw-r--r-- | libc/private/bionic_preinit.h | 76 | ||||
| -rw-r--r-- | libc/private/pthread_internal.h (renamed from libc/bionic/pthread_internal.h) | 0 | ||||
| -rw-r--r-- | linker/README.TXT | 43 | ||||
| -rw-r--r-- | linker/linker.c | 6 |
11 files changed, 273 insertions, 94 deletions
diff --git a/libc/arch-arm/bionic/crtbegin_dynamic.S b/libc/arch-arm/bionic/crtbegin_dynamic.S index e265923..624d611 100644 --- a/libc/arch-arm/bionic/crtbegin_dynamic.S +++ b/libc/arch-arm/bionic/crtbegin_dynamic.S @@ -30,25 +30,35 @@ .type _start,#function .globl _start -# this is the small startup code that is first run when -# any executable that is statically-linked with Bionic -# runs. +# This is the small startup code that is called from +# the dynamic linker to execute an executable once all +# dependent shared libraries have been loaded and +# initialized. # -# it's purpose is to call __libc_init with appropriate +# It's purpose is to call __libc_init as defined in +# bionic/libc_init_dynamic.c with appropriate # arguments, which are: # # - the address of the raw data block setup by the Linux # kernel ELF loader # -# - address of an "onexit" function, not used on any -# platform supported by Bionic +# - address of an "onexit" function (not used on any +# platform supported by Bionic) # # - address of the "main" function of the program. We # can't hard-code it in the adr pseudo instruction # so we use a tiny trampoline that will get relocated # by the dynamic linker before this code runs # -# - address of the constructor list +# - address of the constructors table, i.e. a table +# that points to various initialization and +# finalization sections for the program. +# +# NOTE: This code is currently placed in shared libraries +# by the build system, but will be ignored. +# +# On the other hand, the arrays defined below are +# required and will be parsed by the dynamic linker. # _start: mov r0, sp @@ -63,7 +73,7 @@ _start: .long __INIT_ARRAY__ .long __FINI_ARRAY__ .long __CTOR_LIST__ - + # the .ctors section contains a list of pointers to "constructor" # functions that need to be called in order during C library initialization, # just before the program is being run. This is a C++ requirement diff --git a/libc/arch-arm/bionic/crtbegin_static.S b/libc/arch-arm/bionic/crtbegin_static.S index e265923..69d8df6 100644 --- a/libc/arch-arm/bionic/crtbegin_static.S +++ b/libc/arch-arm/bionic/crtbegin_static.S @@ -30,25 +30,27 @@ .type _start,#function .globl _start -# this is the small startup code that is first run when -# any executable that is statically-linked with Bionic -# runs. +# This is the small startup code that is first run when +# any static executable runs. A static executable is one +# that is started directly by the Linux kernel, not from +# the dynamic linker, it thus cannot depend on any shared +# library. # -# it's purpose is to call __libc_init with appropriate +# It's purpose is to call __libc_init as defined in +# bionic/libc_init_static.c with appropriate # arguments, which are: # # - the address of the raw data block setup by the Linux # kernel ELF loader # -# - address of an "onexit" function, not used on any -# platform supported by Bionic +# - address of an "onexit" function (not used on any +# platform supported by Bionic). # -# - address of the "main" function of the program. We -# can't hard-code it in the adr pseudo instruction -# so we use a tiny trampoline that will get relocated -# by the dynamic linker before this code runs +# - address of the "main" function of the program. # -# - address of the constructor list +# - address of the constructors table, i.e. a table +# that points to various initialization and +# finalization sections for the program. # _start: mov r0, sp @@ -59,11 +61,18 @@ _start: 0: b main +# The "C++ ABI for ARM" document that static C++ constructors +# shall only be called from the .init_array section. +# +# Do we really need a .ctors section on ARM platforms ? +# It looks like it will always be empty. +# + 1: .long __PREINIT_ARRAY__ .long __INIT_ARRAY__ .long __FINI_ARRAY__ .long __CTOR_LIST__ - + # the .ctors section contains a list of pointers to "constructor" # functions that need to be called in order during C library initialization, # just before the program is being run. This is a C++ requirement diff --git a/libc/arch-x86/bionic/crtbegin_dynamic.S b/libc/arch-x86/bionic/crtbegin_dynamic.S index 3b47b18..b013641 100644 --- a/libc/arch-x86/bionic/crtbegin_dynamic.S +++ b/libc/arch-x86/bionic/crtbegin_dynamic.S @@ -29,25 +29,35 @@ .type _start, @function .globl _start -# this is the small startup code that is first run when -# any executable that is statically-linked with Bionic -# runs. +# This is the small startup code that is called from +# the dynamic linker to execute an executable once all +# dependent shared libraries have been loaded and +# initialized. # -# it's purpose is to call __libc_init with appropriate +# It's purpose is to call __libc_init as defined in +# bionic/libc_init_dynamic.c with appropriate # arguments, which are: # # - the address of the raw data block setup by the Linux # kernel ELF loader # -# - address of an "onexit" function, not used on any -# platform supported by Bionic +# - address of an "onexit" function (not used on any +# platform supported by Bionic) # # - address of the "main" function of the program. We # can't hard-code it in the adr pseudo instruction # so we use a tiny trampoline that will get relocated # by the dynamic linker before this code runs # -# - address of the constructor list +# - address of the constructors table, i.e. a table +# that points to various initialization and +# finalization sections for the program. +# +# NOTE: This code is currently placed in shared libraries +# by the build system, but will be ignored. +# +# On the other hand, the arrays defined below are +# required and will be parsed by the dynamic linker. # _start: mov %esp, %eax diff --git a/libc/arch-x86/bionic/crtbegin_static.S b/libc/arch-x86/bionic/crtbegin_static.S index eb4acee..a6c9ebf 100644 --- a/libc/arch-x86/bionic/crtbegin_static.S +++ b/libc/arch-x86/bionic/crtbegin_static.S @@ -29,25 +29,27 @@ .type _start, @function .globl _start -# this is the small startup code that is first run when -# any executable that is statically-linked with Bionic -# runs. +# This is the small startup code that is first run when +# any static executable runs. A static executable is one +# that is started directly by the Linux kernel, not from +# the dynamic linker, it thus cannot depend on any shared +# library. # -# it's purpose is to call __libc_init with appropriate +# It's purpose is to call __libc_init as defined in +# bionic/libc_init_static.c with appropriate # arguments, which are: # # - the address of the raw data block setup by the Linux # kernel ELF loader # -# - address of an "onexit" function, not used on any -# platform supported by Bionic +# - address of an "onexit" function (not used on any +# platform supported by Bionic). # -# - address of the "main" function of the program. We -# can't hard-code it in the adr pseudo instruction -# so we use a tiny trampoline that will get relocated -# by the dynamic linker before this code runs +# - address of the "main" function of the program. # -# - address of the constructor list +# - address of the constructors table, i.e. a table +# that points to various initialization and +# finalization sections for the program. # _start: mov %esp, %eax diff --git a/libc/bionic/libc_init_common.c b/libc/bionic/libc_init_common.c index de4919d..523afcf 100644 --- a/libc/bionic/libc_init_common.c +++ b/libc/bionic/libc_init_common.c @@ -39,8 +39,11 @@ #include <bionic_tls.h> #include <errno.h> -extern void _init(void); -extern void _fini(void); +/* This contains the common C library initialization code. + * To understand what happens here, you should read the + * "Initialization and Finalization" section of the file + * named bionic/linker/README.TXT + */ static void call_array(void(**list)()) { @@ -50,15 +53,6 @@ static void call_array(void(**list)()) } } -static void __bionic_do_global_dtors(structors_array_t const * const p) -{ - call_array(p->fini_array); - //_fini(); -} - -extern unsigned __get_sp(void); -extern pid_t gettid(void); - char* __progname; char **environ; @@ -69,30 +63,28 @@ unsigned int __page_shift = PAGE_SHIFT; int __system_properties_init(void); +/* This function can be run under two different contexts: + * + * - for statically linked executables (i.e. those who do + * not depend on shared libraries at all), it will be + * called from the __libc_init() function defined in + * bionic/libc_init_static.c + * + * - for dynamic executables, it will be called from the + * __libc_init() function defined in bionic/libc_init_dynamic.c + * + */ void __libc_init_common(uintptr_t *elfdata, void (*onexit)(void), int (*slingshot)(int, char**, char**), structors_array_t const * const structors, void (*pre_ctor_hook)()) { - pthread_internal_t thread; - pthread_attr_t thread_attr; - void *tls_area[BIONIC_TLS_SLOTS]; int argc; char **argv, **envp, **envend; struct auxentry *auxentry; unsigned int page_size = 0, page_shift = 0; - /* The main thread's stack has empirically shown to be 84k */ - unsigned stacktop = (__get_sp() & ~(PAGE_SIZE - 1)) + PAGE_SIZE; - unsigned stacksize = 128 * 1024; //84 * 1024; - unsigned stackbottom = stacktop - stacksize; - - pthread_attr_init(&thread_attr); - pthread_attr_setstack(&thread_attr, (void*)stackbottom, stacksize); - _init_thread(&thread, gettid(), &thread_attr, (void*)stackbottom); - __init_tls(tls_area, &thread); - argc = (int) *elfdata++; argv = (char**) elfdata; envp = argv+(argc+1); @@ -106,17 +98,17 @@ void __libc_init_common(uintptr_t *elfdata, if (pre_ctor_hook) pre_ctor_hook(); - // XXX: we should execute the .fini_array upon exit - - // pre-init array. - // XXX: I'm not sure what's the different with the init array. - call_array(structors->preinit_array); + if (structors != NULL) { + // pre-init array. + call_array(structors->preinit_array); - // for compatibility with non-eabi binary, call the .ctors section - call_array(structors->ctors_array); + // for compatibility with non-eabi binary, call the .ctors section + // this is only useful for static non-ARM (e.g. x86) executables. + call_array(structors->ctors_array); - // call static constructors - call_array(structors->init_array); + // call static constructors + call_array(structors->init_array); + } exit(slingshot(argc, argv, envp)); } diff --git a/libc/bionic/libc_init_dynamic.c b/libc/bionic/libc_init_dynamic.c index 8cf24b4..e1ff13d 100644 --- a/libc/bionic/libc_init_dynamic.c +++ b/libc/bionic/libc_init_dynamic.c @@ -25,18 +25,29 @@ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ + /* * libc_init_static.c * - * This function takes the raw data block set up by the ELF loader - * in the kernel and parses it. It is invoked by crt0.S which makes - * any necessary adjustments and passes calls this function using - * the standard C calling convention. + * This function is called for dynamic executables after the dynamic + * linker has loaded and initialized all dependent shared libraries. + * + * It takes the raw data block set up by the ELF loader + * in the kernel and parses it. * * The arguments are: - * uintptr_t *elfdata -- The ELF loader data block; usually from the stack. - * Basically a pointer to argc. - * void (*onexit)(void) -- Function to install into onexit + * elfdata -- The ELF loader data block; usually from the stack. + * Basically a pointer to argc. + * + * onexit -- Function to call on exit, can be NULL. + * + * slingshot -- Address of the program's main function + * + * structors -- Table of constructor functions arrays that must + * be called before the slingshot. + * + * It is called from the assembly fragment found in + * arch-$ARCH/bionic/crtbegin_dynamic.S */ /* @@ -62,5 +73,18 @@ __noreturn void __libc_init(uintptr_t *elfdata, int (*slingshot)(int, char**, char**), structors_array_t const * const structors) { - __libc_init_common(elfdata, onexit, slingshot, structors, malloc_debug_init); + /* NOTE: At this point, the dynamic linker has *already* called + * all initializers properly, so we ignore 'structors' to + * avoid calling them twice. + */ + + /* NOTE2: Is it worthwhile to use malloc_debug_init() in the case of + * of the non-debug shared C library ? + * + * The implementation in bionic/malloc_leak.c contains a lot + * of code which will turn to be unused, and we add a dispatch + * overhead to malloc() et al. that proved to be significant + * in the past (e.g. making boot sequence 5% slower) + */ + __libc_init_common(elfdata, onexit, slingshot, NULL, malloc_debug_init); } diff --git a/libc/bionic/libc_init_static.c b/libc/bionic/libc_init_static.c index ec463f7..d7af640 100644 --- a/libc/bionic/libc_init_static.c +++ b/libc/bionic/libc_init_static.c @@ -25,18 +25,30 @@ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ + /* * libc_init_static.c * - * This function takes the raw data block set up by the ELF loader - * in the kernel and parses it. It is invoked by crt0.S which makes - * any necessary adjustments and passes calls this function using - * the standard C calling convention. + * This function is called for static executables, i.e. those that + * dont depend on shared libraries and are directly started by the + * Linux kernel. + * + * It takes the raw data block set up by the ELF loader + * in the kernel and parses it. * * The arguments are: - * uintptr_t *elfdata -- The ELF loader data block; usually from the stack. - * Basically a pointer to argc. - * void (*onexit)(void) -- Function to install into onexit + * elfdata -- The ELF loader data block; usually from the stack. + * Basically a pointer to argc. + * + * onexit -- Function to call on exit, can be NULL. + * + * slingshot -- Address of the program's main function + * + * structors -- Table of constructor functions arrays that must + * be called before the slingshot. + * + * It is called from the assembly fragment found in + * arch-$ARCH/bionic/crtbegin_static.S */ /* @@ -51,18 +63,19 @@ #include <stdlib.h> #include <stdint.h> #include <elf.h> -#include "pthread_internal.h" -#include "atexit.h" +#include "bionic_preinit.h" #include "libc_init_common.h" -#include <bionic_tls.h> -#include <errno.h> - __noreturn void __libc_init(uintptr_t *elfdata, void (*onexit)(void), int (*slingshot)(int, char**, char**), structors_array_t const * const structors) { + pthread_internal_t thread; + void *tls_area[BIONIC_TLS_SLOTS]; + + __libc_preinit( &thread, tls_area ); + /* * To enable malloc checks for statically linked programs, add * "WITH_MALLOC_CHECK_LIBC_A := true" in device/buildspec.mk diff --git a/libc/private/bionic_preinit.h b/libc/private/bionic_preinit.h new file mode 100644 index 0000000..b74a8b4 --- /dev/null +++ b/libc/private/bionic_preinit.h @@ -0,0 +1,76 @@ +/* + * Copyright (C) 2009 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. + */ + +#ifndef _BIONIC_PREINIT_H +#define _BIONIC_PREINIT_H + +#include "pthread_internal.h" +#include "bionic_tls.h" +#include <asm/page.h> + +/* this function is used to perform a minimal initialization of the + * the C library. This must be performed before any other call to + * other functions, in either the dynamic linker's startup code + * or libc_init_static.c + * + * 'main_thread' and 'tls_area' must be persistent variables, + * which means they must be either global, or allocated in the + * main thread's stack frame and never, ever, freed before + * program exit. + * + * VERY IMPORTANT NOTE: + * + * THIS IMPLEMENTATION SHOULD NOT USE GLOBAL VARIABLES. + * + * The reason is the dynamic linker's tricky usage of C library + * functions and later renaming of their symbols. See the + * "C Library Usage Restriction" section in bionic/linker/README.TXT + * for details. + */ + +extern unsigned __get_sp(void); +extern pid_t gettid(void); + +static __inline__ void +__libc_preinit( pthread_internal_t* main_thread, + void* tls_area[BIONIC_TLS_SLOTS] ) +{ + pthread_attr_t thread_attr; + + /* Setup the main thread's information */ + unsigned stacktop = (__get_sp() & ~(PAGE_SIZE - 1)) + PAGE_SIZE; + unsigned stacksize = 128 * 1024; + unsigned stackbottom = stacktop - stacksize; + + pthread_attr_init(&thread_attr); + pthread_attr_setstack(&thread_attr, (void*)stackbottom, stacksize); + _init_thread(main_thread, gettid(), &thread_attr, (void*)stackbottom); + __init_tls(tls_area, main_thread); +} + +#endif /* _BIONIC_INIT_H */ diff --git a/libc/bionic/pthread_internal.h b/libc/private/pthread_internal.h index eb4e80c..eb4e80c 100644 --- a/libc/bionic/pthread_internal.h +++ b/libc/private/pthread_internal.h diff --git a/linker/README.TXT b/linker/README.TXT index 4fff14e..0be9be4 100644 --- a/linker/README.TXT +++ b/linker/README.TXT @@ -112,3 +112,46 @@ On x86, the lists of constructors and destructors are placed in special sections named ".ctors" and ".dtors", and the DT_INIT / DT_FINI functions are in charge of calling them explicitely. + +C Library Usage Restrictions: +----------------------------- + +The dynamic linker executable (/system/bin/linker) is built using the +static version of the C library (libc.a), in order to use various functions +and system calls provided by it. + +However, it will normally, at runtime, map the shared library version +of the C library (/system/lib/libc.so) as well in the process' address +space. This means that: + +- any global variable defined by the C library will appear twice in + the process address space, at different addresses. + +- some functions will be duplicated too, though those that refer to + global variables will refer to distinct addresses. + +This can lead to subtle conflicts, typically for process-specific data that +is managed through the kernel. A good example is the handling of the +end of the data segment, which is normally done through the 'sbrk' or +'brk' system call by the malloc implementation. + +If two similar, but distinct, malloc implementations run at the same time, +and if each one thinks it exclusively manages some process settings, hideous +corruption or crashes may occur. + +For this very reason, THE DYNAMIC LINKER CANNOT USE malloc()/free() ! +That's why it is linked to a special version of the C library that will +abort when any of these functions (or calloc()/realloc()) is called. + +Moreover, it cannot use any C library feature that could use these +indirectly. Experience as shown that this meant: + +- avoiding any FILE* - related stdio function (fopen, fread, fprintf, etc...) +- avoiding snprintf() with any floating-point formatter ("%f", "%g") + +There are probably other cases that haven't been discovered yet, so the +code needs to be very frugal in its use of the C library. + +This also explains why the linker's tracing macros are all disabled by +default. Enabling them sometimes creates problems, depending on the process +being loaded, so they should be considered an experimental feature for now. diff --git a/linker/linker.c b/linker/linker.c index e398f82..e7d5ab4 100644 --- a/linker/linker.c +++ b/linker/linker.c @@ -44,7 +44,7 @@ #include <sys/atomics.h> /* special private C library header - see Android.mk */ -#include <bionic_tls.h> +#include <bionic_preinit.h> #include "linker.h" #include "linker_debug.h" @@ -1691,6 +1691,7 @@ int main(int argc, char **argv) #define ANDROID_TLS_SLOTS BIONIC_TLS_SLOTS static void * __tls_area[ANDROID_TLS_SLOTS]; +static pthread_internal_t __main_thread; unsigned __linker_init(unsigned **elfdata) { @@ -1709,8 +1710,7 @@ unsigned __linker_init(unsigned **elfdata) gettimeofday(&t0, 0); #endif - __set_tls(__tls_area); - ((unsigned *)__get_tls())[TLS_SLOT_THREAD_ID] = gettid(); + __libc_preinit(&__main_thread, __tls_area); debugger_init(); |