Disable stack protector for __libc_preinit
__libc_preinit sets up the stack protector global cookie value, and thus
cannot intialize a stack protector cookie for itself in the function
prologue. LTO compilation can inline functions requiring a stack
protector into __libc_preinit. This patch disables stack protection for
__libc_preinit and forces all potentially inlined functions into a
helper that can have a stack protector.
Test: run bionic-unit-tests
Change-Id: I45911611190f216c91eb6feff722967214c5f99f
diff --git a/libc/Android.bp b/libc/Android.bp
index 5a1c287..4f6ff1a 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -123,6 +123,12 @@
cflags: ["-fno-stack-protector"],
}
+cc_library_static {
+ name: "libc_init_dynamic",
+ defaults: ["libc_defaults"],
+ srcs: ["bionic/libc_init_dynamic.cpp"],
+ cflags: ["-fno-stack-protector"],
+}
// ========================================================
// libc_tzcode.a - upstream 'tzcode' code
@@ -1757,10 +1763,10 @@
"arch-common/bionic/crtbrand.S",
"bionic/icu.cpp",
"bionic/malloc_common.cpp",
- "bionic/libc_init_dynamic.cpp",
"bionic/NetdClient.cpp",
"arch-common/bionic/crtend_so.S",
],
+ whole_static_libs: ["libc_init_dynamic"],
},
required: ["tzdata"],
diff --git a/libc/bionic/libc_init_dynamic.cpp b/libc/bionic/libc_init_dynamic.cpp
index 43bca30..7c73950 100644
--- a/libc/bionic/libc_init_dynamic.cpp
+++ b/libc/bionic/libc_init_dynamic.cpp
@@ -61,6 +61,21 @@
extern int __cxa_atexit(void (*)(void *), void *, void *);
};
+// We need a helper function for __libc_preinit because compiling with LTO may
+// inline functions requiring a stack protector check, but __stack_chk_guard is
+// not initialized at the start of __libc_preinit. __libc_preinit_impl will run
+// after __stack_chk_guard is initialized and therefore can safely have a stack
+// protector.
+__attribute__((noinline))
+static void __libc_preinit_impl(KernelArgumentBlock& args) {
+ __libc_init_globals(args);
+ __libc_init_common(args);
+
+ // Hooks for various libraries to let them know that we're starting up.
+ __libc_globals.mutate(__libc_init_malloc);
+ netdClientInit();
+}
+
// 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
@@ -79,12 +94,7 @@
// thread's TLS slot with that value. Initialize the local global stack guard with its value.
__stack_chk_guard = reinterpret_cast<uintptr_t>(tls[TLS_SLOT_STACK_GUARD]);
- __libc_init_globals(*args);
- __libc_init_common(*args);
-
- // Hooks for various libraries to let them know that we're starting up.
- __libc_globals.mutate(__libc_init_malloc);
- netdClientInit();
+ __libc_preinit_impl(*args);
}
// This function is called from the executable's _start entry point