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/reserved_signals.h b/libc/platform/bionic/reserved_signals.h
index e8e517e..dab58af 100644
--- a/libc/platform/bionic/reserved_signals.h
+++ b/libc/platform/bionic/reserved_signals.h
@@ -43,9 +43,7 @@
// 37 (__SIGRTMIN + 5) coverage (libprofile-extras)
// 38 (__SIGRTMIN + 6) heapprofd ART managed heap dumps
// 39 (__SIGRTMIN + 7) fdtrack
-//
-// If you change this, also change __ndk_legacy___libc_current_sigrtmin
-// in <android/legacy_signal_inlines.h> to match.
+// 40 (__SIGRTMIN + 8) android_run_on_all_threads (bionic/pthread_internal.cpp)
#define BIONIC_SIGNAL_POSIX_TIMERS (__SIGRTMIN + 0)
#define BIONIC_SIGNAL_BACKTRACE (__SIGRTMIN + 1)
@@ -53,8 +51,9 @@
#define BIONIC_SIGNAL_PROFILER (__SIGRTMIN + 4)
#define BIONIC_SIGNAL_ART_PROFILER (__SIGRTMIN + 6)
#define BIONIC_SIGNAL_FDTRACK (__SIGRTMIN + 7)
+#define BIONIC_SIGNAL_RUN_ON_ALL_THREADS (__SIGRTMIN + 8)
-#define __SIGRT_RESERVED 8
+#define __SIGRT_RESERVED 9
static inline __always_inline sigset64_t filter_reserved_signals(sigset64_t sigset, int how) {
int (*block)(sigset64_t*, int);
int (*unblock)(sigset64_t*, int);
@@ -83,5 +82,6 @@
unblock(&sigset, __SIGRTMIN + 5);
unblock(&sigset, __SIGRTMIN + 6);
unblock(&sigset, __SIGRTMIN + 7);
+ unblock(&sigset, __SIGRTMIN + 8);
return sigset;
}