Initialize TLS before any application code is run.
Since e19d702b8e33, dlsym and friends use recursive mutexes that
require the current thread id, which is not available before the libc
constructor. This prevents us from using dlsym() in .preinit_array.
This change moves TLS initialization from libc constructor to the earliest
possible point - immediately after linker itself is relocated. As a result,
pthread_internal_t for the initial thread is available from the start.
As a bonus, values stored in TLS in .preinit_array are not lost when libc is
initialized.
Change-Id: Iee5a710ee000173bff63e924adeb4a4c600c1e2d
diff --git a/libc/bionic/libc_init_common.c b/libc/bionic/libc_init_common.c
index b6a6379..7fb1246 100644
--- a/libc/bionic/libc_init_common.c
+++ b/libc/bionic/libc_init_common.c
@@ -52,12 +52,19 @@
int __system_properties_init(void);
-void __libc_init_common(uintptr_t *elfdata)
+/* 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.
+ *
+ * Note: this function creates a pthread_internal_t for the initial thread and
+ * 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 elfdata argument in a specific TLS slot to be later
+ * picked up by the libc constructor.
+ */
+void __libc_init_tls(unsigned** elfdata)
{
- int argc = *elfdata;
- char** argv = (char**)(elfdata + 1);
- char** envp = argv + argc + 1;
-
pthread_attr_t thread_attr;
static pthread_internal_t thread;
static void* tls_area[BIONIC_TLS_SLOTS];
@@ -72,7 +79,19 @@
_init_thread(&thread, gettid(), &thread_attr, (void*)stackbottom);
__init_tls(tls_area, &thread);
- /* clear errno - requires TLS area */
+ tls_area[TLS_SLOT_BIONIC_PREINIT] = elfdata;
+}
+
+void __libc_init_common(uintptr_t *elfdata)
+{
+ int argc = *elfdata;
+ char** argv = (char**)(elfdata + 1);
+ char** envp = argv + argc + 1;
+
+ /* get the initial thread from TLS and add it to gThreadList */
+ _pthread_internal_add(__get_thread());
+
+ /* clear errno */
errno = 0;
/* set program name */
diff --git a/libc/bionic/libc_init_static.c b/libc/bionic/libc_init_static.c
index a2c11a9..f97961d 100644
--- a/libc/bionic/libc_init_static.c
+++ b/libc/bionic/libc_init_static.c
@@ -65,6 +65,11 @@
int argc;
char **argv, **envp;
+ __libc_init_tls(NULL);
+
+ /* get the initial thread from TLS and add it to gThreadList */
+ _pthread_internal_add(__get_thread());
+
/* Initialize the C runtime environment */
__libc_init_common(elfdata);
diff --git a/libc/bionic/pthread.c b/libc/bionic/pthread.c
index fdfe508..5cad167 100644
--- a/libc/bionic/pthread.c
+++ b/libc/bionic/pthread.c
@@ -145,7 +145,7 @@
pthread_mutex_unlock(&gThreadListLock);
}
-static void
+__LIBC_ABI_PRIVATE__ void
_pthread_internal_add( pthread_internal_t* thread )
{
pthread_mutex_lock(&gThreadListLock);
@@ -157,7 +157,7 @@
pthread_mutex_unlock(&gThreadListLock);
}
-pthread_internal_t*
+__LIBC_ABI_PRIVATE__ pthread_internal_t*
__get_thread(void)
{
void** tls = (void**)__get_tls();
@@ -217,6 +217,7 @@
pthread_exit( (void*)func(arg) );
}
+__LIBC_ABI_PRIVATE__
void _init_thread(pthread_internal_t * thread, pid_t kernel_id, pthread_attr_t * attr, void * stack_base)
{
if (attr == NULL) {
@@ -238,8 +239,6 @@
thread->join_count = 0;
thread->cleanup_stack = NULL;
-
- _pthread_internal_add(thread);
}
@@ -371,6 +370,8 @@
_init_thread(thread, tid, (pthread_attr_t*)attr, stack);
+ _pthread_internal_add(thread);
+
if (!madestack)
thread->attr.flags |= PTHREAD_ATTR_FLAG_USER_STACK;
diff --git a/libc/bionic/pthread_internal.h b/libc/bionic/pthread_internal.h
index 655b8f3..268cacf 100644
--- a/libc/bionic/pthread_internal.h
+++ b/libc/bionic/pthread_internal.h
@@ -47,6 +47,8 @@
} pthread_internal_t;
extern void _init_thread(pthread_internal_t * thread, pid_t kernel_id, pthread_attr_t * attr, void * stack_base);
+void _pthread_internal_add( pthread_internal_t* thread );
+pthread_internal_t* __get_thread(void);
/* needed by posix-timers.c */
diff --git a/libc/private/bionic_tls.h b/libc/private/bionic_tls.h
index 008fd2f..af19554 100644
--- a/libc/private/bionic_tls.h
+++ b/libc/private/bionic_tls.h
@@ -134,6 +134,9 @@
/* return the stack base and size, used by our malloc debugger */
extern void* __get_stack_base(int *p_stack_size);
+/* Initialize the TLS. */
+extern void __libc_init_tls(unsigned** elfdata);
+
__END_DECLS
#endif /* _SYS_TLS_H */
diff --git a/linker/linker.c b/linker/linker.c
index 9805b35..6b6282d 100644
--- a/linker/linker.c
+++ b/linker/linker.c
@@ -2054,10 +2054,6 @@
}
}
-#define ANDROID_TLS_SLOTS BIONIC_TLS_SLOTS
-
-static void * __tls_area[ANDROID_TLS_SLOTS];
-
/*
* This code is called after the linker has linked itself and
* fixed it's own GOT. It is safe to make references to externs
@@ -2076,18 +2072,6 @@
const char *ldpath_env = NULL;
const char *ldpreload_env = NULL;
- /* Setup a temporary TLS area that is used to get a working
- * errno for system calls.
- */
- __set_tls(__tls_area);
-
- pid = getpid();
-
-#if TIMING
- struct timeval t0, t1;
- gettimeofday(&t0, 0);
-#endif
-
/* NOTE: we store the elfdata pointer on a special location
* of the temporary TLS area in order to pass it to
* the C Library's runtime initializer.
@@ -2096,7 +2080,14 @@
* to point to a different location to ensure that no other
* shared library constructor can access it.
*/
- __tls_area[TLS_SLOT_BIONIC_PREINIT] = elfdata;
+ __libc_init_tls(elfdata);
+
+ pid = getpid();
+
+#if TIMING
+ struct timeval t0, t1;
+ gettimeofday(&t0, 0);
+#endif
/* Initialize environment functions, and get to the ELF aux vectors table */
vecs = linker_env_init(vecs);