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

12 files changed, 301 insertions, 282 deletions

diff --git a/libc/Android.mk b/libc/Android.mk
index 301be37..c7828cf 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -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
diff --git a/libc/arch-arm/bionic/crtbegin.c b/libc/arch-arm/bionic/crtbegin.c
index 0e2d31e..cc58797 100644
--- a/libc/arch-arm/bionic/crtbegin.c
+++ b/libc/arch-arm/bionic/crtbegin.c
@@ -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"
diff --git a/libc/arch-x86/bionic/crtbegin.c b/libc/arch-x86/bionic/crtbegin.c
index 5106d9e..63e58a6 100755
--- a/libc/arch-x86/bionic/crtbegin.c
+++ b/libc/arch-x86/bionic/crtbegin.c
@@ -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"
diff --git a/libc/bionic/getauxval.cpp b/libc/bionic/getauxval.cpp
index 38a05fc..fd225e0 100644
--- a/libc/bionic/getauxval.cpp
+++ b/libc/bionic/getauxval.cpp
@@ -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;
 }
diff --git a/libc/bionic/libc_init_common.c b/libc/bionic/libc_init_common.cpp
index 86e1eb5..6b4ae2c 100644
--- a/libc/bionic/libc_init_common.c
+++ b/libc/bionic/libc_init_common.cpp
@@ -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) {
diff --git a/libc/bionic/libc_init_common.h b/libc/bionic/libc_init_common.h
index c55594b..23ac305 100644
--- a/libc/bionic/libc_init_common.h
+++ b/libc/bionic/libc_init_common.h
@@ -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
diff --git a/libc/bionic/libc_init_dynamic.c b/libc/bionic/libc_init_dynamic.c
deleted file mode 100644
index 3a7e8e2..0000000
--- a/libc/bionic/libc_init_dynamic.c
+++ /dev/null
@@ -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));
-}
diff --git a/libc/bionic/libc_init_dynamic.cpp b/libc/bionic/libc_init_dynamic.cpp
new file mode 100644
index 0000000..af03fb0
--- /dev/null
+++ b/libc/bionic/libc_init_dynamic.cpp
@@ -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));
+}
diff --git a/libc/bionic/libc_init_static.c b/libc/bionic/libc_init_static.cpp
index 24a4397..e5506d1 100644
--- a/libc/bionic/libc_init_static.c
+++ b/libc/bionic/libc_init_static.cpp
@@ -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 <sys/auxv.h>
+#include <sys/mman.h>
+
 #include "atexit.h"
+#include "bionic_tls.h"
+#include "KernelArgumentBlock.h"
 #include "libc_init_common.h"
-
-#include <bionic_tls.h>
-#include <errno.h>
-#include <sys/mman.h>
-#include <sys/auxv.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;
-
-    phdr_start = (Elf32_Phdr *) getauxval(AT_PHDR);
-    phdr_ct    = getauxval(AT_PHNUM);
+  Elf32_Phdr* phdr_start = reinterpret_cast<Elf32_Phdr*>(getauxval(AT_PHDR));
+  unsigned long int 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;
     }
-}
 
-__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;
+    Elf32_Addr seg_page_start = PAGE_START(phdr->p_vaddr);
+    Elf32_Addr seg_page_end = PAGE_END(phdr->p_vaddr + phdr->p_memsz);
 
-    __libc_init_tls(NULL);
-
-    /* Initialize the C runtime environment */
-    __libc_init_common(elfdata);
+    // 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);
+  }
+}
 
-    apply_gnu_relro();
+__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);
 
-    /* Several Linux ABIs don't pass the onexit pointer, and the ones that
-     * do never use it.  Therefore, we ignore it.
-     */
+  KernelArgumentBlock args(raw_args);
+  __libc_init_common(args);
 
-    /* pre-init array. */
-    call_array(structors->preinit_array);
+  apply_gnu_relro();
 
-    // call static constructors
-    call_array(structors->init_array);
+  // Several Linux ABIs don't pass the onexit pointer, and the ones that
+  // do never use it.  Therefore, we ignore it.
 
-    argc = (int) *elfdata;
-    argv = (char**)(elfdata + 1);
-    envp = argv + argc + 1;
+  call_array(structors->preinit_array);
+  call_array(structors->init_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)
-        __cxa_atexit(__libc_fini,structors->fini_array,NULL);
+  // 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);
+  }
 
-    exit(slingshot(argc, argv, envp));
+  exit(slingshot(args.argc, args.argv, args.envp));
 }
diff --git a/libc/private/KernelArgumentBlock.h b/libc/private/KernelArgumentBlock.h
new file mode 100644
index 0000000..d777267
--- /dev/null
+++ b/libc/private/KernelArgumentBlock.h
@@ -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
diff --git a/libc/private/bionic_tls.h b/libc/private/bionic_tls.h
index f661ccf..920f506 100644
--- a/libc/private/bionic_tls.h
+++ b/libc/private/bionic_tls.h
@@ -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
 
diff --git a/libc/stdlib/atexit.h b/libc/stdlib/atexit.h
index 1b23565..39df2e1 100644
--- a/libc/stdlib/atexit.h
+++ b/libc/stdlib/atexit.h
@@ -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