Clean up TLS_SLOT_BIONIC_PREINIT usage a bit
- It is only needed for dynamic executables, so move the initialization
out of __libc_init_main_thread and just before the solib constructor
calls. For static executables, the slot was initialized, then never
used or cleared. Instead, leave it clear.
- For static executables, __libc_init_main_thread already initialized the
stack guard, so remove the redundant __init_thread_stack_guard call.
- Simplify the slot access/clearing a bit in __libc_preinit.
- Remove the "__libc_init_common() will change the TLS area so the old one
won't be accessible anyway." comment. AFAICT, it's incorrect -- the
main thread's TLS area in a dynamic executable is initialized to a
static pthread_internal_t object in the linker, then reused by libc.so.
Test: adb shell /data/nativetest/bionic-unit-tests/bionic-unit-tests
Test: adb shell /data/nativetest/bionic-unit-tests-static/bionic-unit-tests-static
Change-Id: Ie2da6f5be3ad563fa65b38eaadf8ba6ecc6a64b6
diff --git a/libc/bionic/libc_init_dynamic.cpp b/libc/bionic/libc_init_dynamic.cpp
index 0b68280..fb086c8 100644
--- a/libc/bionic/libc_init_dynamic.cpp
+++ b/libc/bionic/libc_init_dynamic.cpp
@@ -85,14 +85,11 @@
// to run before any others (such as the jemalloc constructor), and lower
// is better (http://b/68046352).
__attribute__((constructor(1))) static void __libc_preinit() {
- // Read the kernel argument block pointer from TLS.
+ // Read the kernel argument block pointer from TLS, then clear the slot so no
+ // other initializer sees its value.
void** tls = __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;
+ KernelArgumentBlock* args = static_cast<KernelArgumentBlock*>(tls[TLS_SLOT_BIONIC_PREINIT]);
+ tls[TLS_SLOT_BIONIC_PREINIT] = nullptr;
// The linker has initialized its copy of the global stack_chk_guard, and filled in the main
// thread's TLS slot with that value. Initialize the local global stack guard with its value.
@@ -102,9 +99,8 @@
}
// This function is called from the executable's _start entry point
-// (see arch-$ARCH/bionic/crtbegin_dynamic.S), which is itself
-// called by the dynamic linker after it has loaded all shared
-// libraries the executable depends on.
+// (see arch-$ARCH/bionic/crtbegin.c), 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.