.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
.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
.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
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
.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
.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
#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)())
{
}
}
-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;
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);
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));
}
* 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-$ARCH/bionic/crtbegin_dynamic.S
*/
/*
int (*slingshot)(int, char**, char**),
structors_array_t const * const structors)
{
- __libc_init_common(elfdata, onexit, slingshot, structors, malloc_debug_init);
+ /* NOTE: At this point, the dynamic linker has *already* called
+ * all initializers properly, so we ignore 'structors' to
+ * avoid calling them twice.
+ */
+
+ /* NOTE2: Is it worthwhile to use malloc_debug_init() in the case of
+ * of the non-debug shared C library ?
+ *
+ * The implementation in bionic/malloc_leak.c contains a lot
+ * of code which will turn to be unused, and we add a dispatch
+ * overhead to malloc() et al. that proved to be significant
+ * in the past (e.g. making boot sequence 5% slower)
+ */
+ __libc_init_common(elfdata, onexit, slingshot, NULL, malloc_debug_init);
}
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
+
/*
* libc_init_static.c
*
- * This function takes the raw data block set up by the ELF loader
- * in the kernel and parses it. It is invoked by crt0.S which makes
- * any necessary adjustments and passes calls this function using
- * the standard C calling convention.
+ * This function is called for static executables, i.e. those that
+ * dont depend on shared libraries and are directly started by the
+ * Linux kernel.
+ *
+ * It takes the raw data block set up by the ELF loader
+ * in the kernel and parses it.
*
* The arguments are:
- * uintptr_t *elfdata -- The ELF loader data block; usually from the stack.
- * Basically a pointer to argc.
- * void (*onexit)(void) -- Function to install into onexit
+ * elfdata -- The ELF loader data block; usually from the stack.
+ * Basically a pointer to argc.
+ *
+ * onexit -- Function to call on exit, can be NULL.
+ *
+ * slingshot -- Address of the program's main function
+ *
+ * structors -- Table of constructor functions arrays that must
+ * be called before the slingshot.
+ *
+ * It is called from the assembly fragment found in
+ * arch-$ARCH/bionic/crtbegin_static.S
*/
/*
#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
--- /dev/null
+/*
+ * 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 */
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.
#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"
#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)
{
gettimeofday(&t0, 0);
#endif
- __set_tls(__tls_area);
- ((unsigned *)__get_tls())[TLS_SLOT_THREAD_ID] = gettid();
+ __libc_preinit(&__main_thread, __tls_area);
debugger_init();
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