Bug 1925181 - Properly set small alloc randomization on Android content processes as well r=jld

Differential Revision: https://phabricator.services.mozilla.com/D226135

dom/ipc/ContentChild.cpp

@@ -805,9 +805,7 @@ void ContentChild::Init(mozilla::ipc::UntypedEndpoint&& aEndpoint,
       }));
 #endif
 
-// Bug 1925181: Unrelated to forkserver, the android content processes are
-// created in a way that makes them not follow this option correctly
-#if defined(MOZ_MEMORY) && defined(DEBUG) && !defined(ANDROID)
+#if defined(MOZ_MEMORY) && defined(DEBUG)
   jemalloc_stats_t stats;
   jemalloc_stats(&stats);
   MOZ_ASSERT(!stats.opt_randomize_small,

memory/build/malloc_decls.h

@@ -114,12 +114,9 @@ MALLOC_DECL(jemalloc_free_dirty_pages, void)
 // after lowering the max dirty pages threshold to get RSS back to normal.
 MALLOC_DECL(jemalloc_free_excess_dirty_pages, void)
 
-// Only used by ForkServer after forking new child processes.
 // Change the value of opt_randomize_small to control small allocation
 // randomization and maybe perform a reinitialization of the arena's PRNG.
-#    if defined(MOZ_ENABLE_FORKSERVER)
 MALLOC_DECL(jemalloc_reset_small_alloc_randomization, void, bool)
-#    endif
 
 // Opt in or out of a thread local arena (bool argument is whether to opt-in
 // (true) or out (false)).

memory/build/mozjemalloc.cpp

@@ -5188,7 +5188,6 @@ inline void MozJemalloc::moz_set_max_dirty_page_modifier(int32_t aModifier) {
   gArenas.SetDefaultMaxDirtyPageModifier(aModifier);
 }
 
-#if defined(MOZ_ENABLE_FORKSERVER)
 inline void MozJemalloc::jemalloc_reset_small_alloc_randomization(
     bool aRandomizeSmall) {
   // When this process got forked by ForkServer then it inherited the existing
@@ -5196,6 +5195,9 @@ inline void MozJemalloc::jemalloc_reset_small_alloc_randomization(
   // been done but it may not reflect anymore the current set of options after
   // the fork().
   //
+  // Similar behavior is also present on Android where it is also required to
+  // perform this step.
+  //
   // Content process will have randomization on small malloc disabled via the
   // MALLOC_OPTIONS environment variable set by parent process, missing this
   // will lead to serious performance regressions because CPU prefetch will
@@ -5203,11 +5205,11 @@ inline void MozJemalloc::jemalloc_reset_small_alloc_randomization(
   // environment is not yet reset when the postfork child handler is being
   // called.
   //
-  // This API is here to allow those forkserver-forked Content processes to
-  // notify jemalloc to turn off the randomization on small allocations and
-  // perform the required reinitialization of already existing arena's PRNG.
-  // It is important to make sure that the PRNG state is properly re-initialized
-  // otherwise child processes would share all the same state.
+  // This API is here to allow those Content processes (spawned by ForkServer or
+  // Android service) to notify jemalloc to turn off the randomization on small
+  // allocations and perform the required reinitialization of already existing
+  // arena's PRNG.  It is important to make sure that the PRNG state is properly
+  // re-initialized otherwise child processes would share all the same state.
 
   {
     AutoLock<StaticMutex> lock(gInitLock);
@@ -5219,7 +5221,6 @@ inline void MozJemalloc::jemalloc_reset_small_alloc_randomization(
     arena->ResetSmallAllocRandomization();
   }
 }
-#endif
 
 #define MALLOC_DECL(name, return_type, ...)                          \
   inline return_type MozJemalloc::moz_arena_##name(                  \

mozglue/android/APKOpen.cpp

@@ -402,6 +402,12 @@ Java_org_mozilla_gecko_mozglue_GeckoLoader_nativeRun(JNIEnv* jenv, jclass jc,
 
     SetGeckoProcessType(argv[--argc]);
     SetGeckoChildID(argv[--argc]);
+#if defined(MOZ_MEMORY)
+    // XRE_IsContentProcess is not accessible here
+    jemalloc_reset_small_alloc_randomization(
+        /* aRandomizeSmall */ GetGeckoProcessType() !=
+        GeckoProcessType_Content);
+#endif
 
     gBootstrap->XRE_SetAndroidChildFds(jenv, jfds);
 
@@ -425,8 +431,14 @@ extern "C" APKOPEN_EXPORT mozglueresult ChildProcessInit(int argc,
   if (argc < 2) {
     return FAILURE;
   }
+
   SetGeckoProcessType(argv[--argc]);
   SetGeckoChildID(argv[--argc]);
+#if defined(MOZ_MEMORY)
+  // XRE_IsContentProcess is not accessible here
+  jemalloc_reset_small_alloc_randomization(
+      /* aRandomizeSmall */ GetGeckoProcessType() != GeckoProcessType_Content);
+#endif
 
   if (loadNSSLibs() != SUCCESS) {
     return FAILURE;