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/platform/bionic/malloc.h b/libc/platform/bionic/malloc.h
index f9eb03f..16ef3a0 100644
--- a/libc/platform/bionic/malloc.h
+++ b/libc/platform/bionic/malloc.h
@@ -105,6 +105,13 @@
// arg_size = sizeof(bool)
M_INITIALIZE_GWP_ASAN = 10,
#define M_INITIALIZE_GWP_ASAN M_INITIALIZE_GWP_ASAN
+ // Disable heap initialization across the whole process. If the hardware supports memory
+ // tagging, it also disables memory tagging. May be called at any time including
+ // when multiple threads are running. arg and arg_size are unused and must be set to 0.
+ // Note that the memory mitigations are only implemented in scudo and therefore this API call will
+ // have no effect when using another allocator.
+ M_DISABLE_MEMORY_MITIGATIONS = 11,
+#define M_DISABLE_MEMORY_MITIGATIONS M_DISABLE_MEMORY_MITIGATIONS
};
enum HeapTaggingLevel {