Merge "[unit tests] Add '-mbranch-protection=standard' flag to arm64"
diff --git a/libc/bionic/malloc_heapprofd.cpp b/libc/bionic/malloc_heapprofd.cpp
index 198d2f0..b2a9e3e 100644
--- a/libc/bionic/malloc_heapprofd.cpp
+++ b/libc/bionic/malloc_heapprofd.cpp
@@ -173,26 +173,46 @@
// not ever have a conflict modifying the globals.
if (!atomic_exchange(&gGlobalsMutating, true)) {
if (!atomic_exchange(&gHeapprofdInitInProgress, true)) {
- // If the backing dispatch is GWP-ASan, we should use GWP-ASan as the
- // intermediate dispatch table during initialisation. It may be possible
- // at this point in time that heapprofd is *already* the default dispatch,
- // and as such we don't want to use heapprofd as the backing store
- // (otherwise infinite recursion occurs).
- gPreviousDefaultDispatchTable = nullptr;
const MallocDispatch* default_dispatch = GetDefaultDispatchTable();
- if (DispatchIsGwpAsan(default_dispatch)) {
+
+ // Below, we initialize heapprofd lazily by redirecting libc's malloc() to
+ // call MallocInitHeapprofdHook, which spawns off a thread and initializes
+ // heapprofd. During the short period between now and when heapprofd is
+ // initialized, allocations may need to be serviced. There are three
+ // possible configurations:
+
+ if (default_dispatch == nullptr) {
+ // 1. No malloc hooking has been done (heapprofd, GWP-ASan, etc.). In
+ // this case, everything but malloc() should come from the system
+ // allocator.
+ gPreviousDefaultDispatchTable = nullptr;
+ gEphemeralDispatch = *NativeAllocatorDispatch();
+ } else if (DispatchIsGwpAsan(default_dispatch)) {
+ // 2. GWP-ASan was installed. We should use GWP-ASan for everything but
+ // malloc() in the interim period before heapprofd is properly
+ // installed. After heapprofd is finished installing, we will use
+ // GWP-ASan as heapprofd's backing allocator to allow heapprofd and
+ // GWP-ASan to coexist.
gPreviousDefaultDispatchTable = default_dispatch;
+ gEphemeralDispatch = *default_dispatch;
+ } else {
+ // 3. It may be possible at this point in time that heapprofd is
+ // *already* the default dispatch, and as such we don't want to use
+ // heapprofd as the backing store for itself (otherwise infinite
+ // recursion occurs). We will use the system allocator functions. Note:
+ // We've checked that no other malloc interceptors are being used by
+ // validating `gHeapprofdIncompatibleHooks` above, so we don't need to
+ // worry about that case here.
+ gPreviousDefaultDispatchTable = nullptr;
+ gEphemeralDispatch = *NativeAllocatorDispatch();
}
- __libc_globals.mutate([](libc_globals* globals) {
- // Wholesale copy the malloc dispatch table here. If the current/default
- // dispatch table is pointing to the malloc_dispatch_table, we can't
- // modify it as it may be racy. This dispatch table copy is ephemeral,
- // and the dispatch tables will be resolved back to the global
- // malloc_dispatch_table after initialization finishes.
- gEphemeralDispatch = globals->malloc_dispatch_table;
- gEphemeralDispatch.malloc = MallocInitHeapprofdHook;
+ // Now, replace the malloc function so that the next call to malloc() will
+ // initialize heapprofd.
+ gEphemeralDispatch.malloc = MallocInitHeapprofdHook;
+ // And finally, install these new malloc-family interceptors.
+ __libc_globals.mutate([](libc_globals* globals) {
atomic_store(&globals->default_dispatch_table, &gEphemeralDispatch);
if (!MallocLimitInstalled()) {
atomic_store(&globals->current_dispatch_table, &gEphemeralDispatch);
