Bug 1908630 - Override LLVM Profiling for manual handling r=firefox-build-system-reviewers,glandium

Differential Revision: https://phabricator.services.mozilla.com/D218428

build/templates.mozbuild

@@ -15,11 +15,24 @@ def Binary():
         OS_LIBS += ["log"]
 
 
+@template
+def MaybeAddProfiling(name):
+    if (
+        CONFIG["MOZ_ENABLE_FORKSERVER"]
+        and CONFIG["NIGHTLY_BUILD"]
+        and CONFIG["OS_TARGET"] == "Linux"
+        and CONFIG["MOZ_PROFILE_GENERATE"] == "1"
+    ):
+        USE_LIBS += ["profiling"]
+
+
 @template
 def Program(name):
     """Template for program executables."""
     PROGRAM = name
 
+    MaybeAddProfiling(name)
+
     Binary()
 
 
@@ -126,6 +139,8 @@ def SharedLibrary(name, output_category=None):
     if output_category:
         SHARED_LIBRARY_OUTPUT_CATEGORY = output_category
 
+    MaybeAddProfiling(name)
+
     Binary()
 
 

build/unix/moz.build

@@ -6,3 +6,11 @@
 
 if CONFIG["USE_ELF_HACK"] or CONFIG["RELRHACK"]:
     DIRS += ["elfhack"]
+
+if (
+    CONFIG["MOZ_ENABLE_FORKSERVER"]
+    and CONFIG["NIGHTLY_BUILD"]
+    and CONFIG["OS_TARGET"] == "Linux"
+    and CONFIG["MOZ_PROFILE_GENERATE"] == "1"
+):
+    DIRS += ["profiling"]

build/unix/profiling/moz.build

@@ -0,0 +1,9 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+Library("profiling")
+
+SOURCES += ["profiling.cpp"]

build/unix/profiling/profiling.cpp

@@ -0,0 +1,45 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#if defined(MOZ_PROFILE_GENERATE) && defined(XP_LINUX) && !defined(ANDROID)
+
+#  include <pthread.h>
+#  include <stdio.h>
+#  include <stdlib.h>
+#  include <unistd.h>
+#  include <errno.h>
+
+#  if defined(__cplusplus)
+extern "C" {
+#  endif
+void __llvm_profile_initialize(void);
+void __llvm_profile_initialize_file(void);
+void __llvm_profile_set_filename(const char*);
+
+// Use the API to force a different filename, then set back the original one.
+// This will make sure the pattern is re-parsed and thus the PID properly
+// updated within the lprofCurFilename struct.
+static void updateFilenameAfterFork(void) {
+  __llvm_profile_set_filename("default.profraw");
+  __llvm_profile_initialize_file();
+  __llvm_profile_set_filename(getenv("LLVM_PROFILE_FILE"));
+  __llvm_profile_initialize_file();
+}
+
+static int CustomRegisterRuntime(void) {
+  __llvm_profile_initialize();
+
+  if (pthread_atfork(NULL, NULL, updateFilenameAfterFork) < 0) {
+    fprintf(stderr, "[%d] [%s] pthread_atfork()=%d\n", getpid(),
+            __PRETTY_FUNCTION__, errno);
+  }
+  return 0;
+}
+
+MOZ_RUNINIT int __llvm_profile_runtime = CustomRegisterRuntime();
+#  if defined(__cplusplus)
+}
+#  endif
+#endif  //  defined(MOZ_PROFILE_GENERATE) && defined(XP_LINUX) &&
+        //  !defined(ANDROID)

modules/libpref/init/StaticPrefList.yaml

@@ -3013,7 +3013,7 @@
 #ifdef MOZ_ENABLE_FORKSERVER
 - name: dom.ipc.forkserver.enable
   type: bool
-#if defined(MOZ_CODE_COVERAGE) || defined(MOZ_ASAN) || defined(MOZ_TSAN) || defined(MOZ_MSAN) || defined(MOZ_UBSAN) || defined(MOZ_PROFILE_GENERATE)
+#if defined(MOZ_CODE_COVERAGE) || defined(MOZ_ASAN) || defined(MOZ_TSAN) || defined(MOZ_MSAN) || defined(MOZ_UBSAN)
   value: false
 #else
   value: @IS_NIGHTLY_BUILD@

mozglue/interposers/pthread_atfork_interposer.cpp

@@ -17,7 +17,7 @@ using mozilla::DebugOnly;
 #if defined(MOZ_ENABLE_FORKSERVER) && !defined(MOZ_TSAN)
 #  include "mozilla/pthread_atfork.h"
 
-static constexpr const int maxHandlers = 16;
+static constexpr const int maxHandlers = 32;
 static constexpr const int idxPreFork = 0;
 static constexpr const int idxPostForkParent = 1;
 static constexpr const int idxPostForkChild = 2;