Add an API for per-process disabling memory initialization.
Introduce an android_mallopt(M_DISABLE_MEMORY_MITIGATIONS) API call
that may be used to disable zero- or pattern-init on non-MTE hardware,
or memory tagging on MTE hardware. The intent is that this function
may be called at any time, including when there are multiple threads
running.
Disabling zero- or pattern-init is quite trivial, we just need to set
a global variable to 0 via a Scudo API call (although there will be
some separate work required on the Scudo side to make this operation
thread-safe).
It is a bit more tricky to disable MTE across a process, because
the kernel does not provide an API for disabling tag checking in all
threads in a process, only per-thread. We need to send a signal to each
of the process's threads with a handler that issues the required prctl
call, and lock thread creation for the duration of the API call to
avoid races between thread enumeration and calls to pthread_create().
Bug: 135772972
Change-Id: I81ece86ace916eb6b435ab516cd431ec4b48a3bf
diff --git a/libc/bionic/pthread_internal.h b/libc/bionic/pthread_internal.h
index 1f055f5..071a5bc 100644
--- a/libc/bionic/pthread_internal.h
+++ b/libc/bionic/pthread_internal.h
@@ -132,6 +132,11 @@
// top of the stack quickly, which would otherwise require special logic for the main thread.
uintptr_t stack_top;
+ // Whether the thread is in the process of terminating (has blocked signals), or has already
+ // terminated. This is used by android_run_on_all_threads() to avoid sending a signal to a thread
+ // that will never receive it.
+ _Atomic(bool) terminating;
+
Lock startup_handshake_lock;
void* mmap_base;
@@ -242,3 +247,7 @@
__LIBC_HIDDEN__ extern void __bionic_atfork_run_prepare();
__LIBC_HIDDEN__ extern void __bionic_atfork_run_child();
__LIBC_HIDDEN__ extern void __bionic_atfork_run_parent();
+
+extern "C" bool android_run_on_all_threads(bool (*func)(void*), void* arg);
+
+extern pthread_rwlock_t g_thread_creation_lock;