Bug 1752703 - Move the pthread_thread_create() interposer under mozglue and prepare for having a single place where we place interposer functions r=glandium

Differential Revision: https://phabricator.services.mozilla.com/D164470

browser/app/moz.build

@@ -53,11 +53,6 @@ LOCAL_INCLUDES += [
     "/xpcom/build",
 ]
 
-# The pthred_create() interposer needs to be linked as early as possible so
-# that it will appear before libpthread when resolving symbols.
-if CONFIG["OS_ARCH"] == "Linux" and CONFIG["MOZ_CRASHREPORTER"]:
-    USE_LIBS += ["pthread_create_interposer"]
-
 if CONFIG["LIBFUZZER"]:
     USE_LIBS += ["fuzzer"]
     LOCAL_INCLUDES += [

ipc/app/moz.build

@@ -16,11 +16,6 @@ else:
         "MozillaRuntimeMain.cpp",
     ]
 
-# The pthred_create() interposer needs to be linked as early as possible so
-# that it will appear before libpthread when resolving symbols.
-if CONFIG["OS_ARCH"] == "Linux" and CONFIG["MOZ_CRASHREPORTER"]:
-    USE_LIBS += ["pthread_create_interposer"]
-
 include("/ipc/chromium/chromium-config.mozbuild")
 
 LOCAL_INCLUDES += [

js/src/make-source-package.py

@@ -155,6 +155,7 @@ rsync_filter_list = """
 
 + /mozglue/baseprofiler/**
 + /mozglue/build/**
++ /mozglue/interposers/**
 + /mozglue/misc/**
 + /mozglue/moz.build
 + /mozglue/static/**

js/xpconnect/shell/moz.build

@@ -10,11 +10,6 @@ SOURCES += [
     "xpcshell.cpp",
 ]
 
-# The pthred_create() interposer needs to be linked as early as possible so
-# that it will appear before libpthread when resolving symbols.
-if CONFIG["OS_ARCH"] == "Linux" and CONFIG["MOZ_CRASHREPORTER"]:
-    USE_LIBS += ["pthread_create_interposer"]
-
 if CONFIG["LIBFUZZER"]:
     USE_LIBS += ["fuzzer"]
 

mozglue/interposers/InterposerHelper.h

@@ -0,0 +1,66 @@
+/* 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/. */
+
+#ifndef InterposerHelper_h
+#define InterposerHelper_h
+
+#include <type_traits>
+
+#ifdef MOZ_LINKER
+#  include "Linker.h"
+#else
+#  include <dlfcn.h>
+#endif
+
+#include "mozilla/Assertions.h"
+
+template <typename T>
+static inline T dlsym_wrapper(void* aHandle, const char* aName) {
+#ifdef MOZ_LINKER
+  return reinterpret_cast<T>(__wrap_dlsym(aHandle, aName));
+#else
+  return reinterpret_cast<T>(dlsym(aHandle, aName));
+#endif  // MOZ_LINKER
+}
+
+template <typename T>
+static T get_real_symbol(const char* aName, T aReplacementSymbol) {
+  // T can only be a function pointer
+  static_assert(std::is_function<typename std::remove_pointer<T>::type>::value);
+
+  // Find the corresponding function in the linked libraries
+  T real_symbol = dlsym_wrapper<T>(RTLD_NEXT, aName);
+
+#if defined(ANDROID)
+  if (real_symbol == nullptr) {
+    // On old versions of Android the application runtime links in libc before
+    // we get a chance to link libmozglue, so its symbols don't appear when
+    // resolving them with RTLD_NEXT but rather with RTLD_DEFAULT. If RTLD_NEXT
+    // failed to find a symbol we try again with RTLD_DEFAULT. The checks below
+    // make sure that we crash in case the symbol we get matches the
+    // replacement one so this is safe albeit a bit weird.
+    real_symbol = dlsym_wrapper<T>(RTLD_DEFAULT, aName);
+  }
+#endif
+
+  if (real_symbol == nullptr) {
+    MOZ_CRASH_UNSAFE_PRINTF(
+        "%s() interposition failed but the interposer function is "
+        "still being called, this won't work!",
+        aName);
+  }
+
+  if (real_symbol == aReplacementSymbol) {
+    MOZ_CRASH_UNSAFE_PRINTF(
+        "We could not obtain the real %s(). Calling the symbol we "
+        "got would make us enter an infinite loop so stop here instead.",
+        aName);
+  }
+
+  return real_symbol;
+}
+
+#define GET_REAL_SYMBOL(name) get_real_symbol(#name, name)
+
+#endif  // InterposerHelper_h

mozglue/interposers/moz.build

@@ -0,0 +1,20 @@
+# -*- 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("interposers")
+
+DEFINES["IMPL_MFBT"] = True
+
+if CONFIG["MOZ_CRASHREPORTER"]:
+    UNIFIED_SOURCES += [
+        "pthread_create_interposer.cpp",
+    ]
+
+if CONFIG["MOZ_LINKER"] and CONFIG["MOZ_WIDGET_TOOLKIT"] == "android":
+    LOCAL_INCLUDES += [
+        "/mozglue/linker",
+    ]
+
+FINAL_LIBRARY = "mozglue"

mozglue/interposers/pthread_create_interposer.cpp

@@ -4,7 +4,6 @@
 
 #include <algorithm>
 
-#include <dlfcn.h>
 #include <pthread.h>
 #include <signal.h>
 #include <stdlib.h>
@@ -13,6 +12,8 @@
 #include "mozilla/Assertions.h"
 #include "mozilla/DebugOnly.h"
 
+#include "InterposerHelper.h"
+
 using mozilla::DebugOnly;
 
 struct SigAltStack {
@@ -83,30 +84,12 @@ void* set_alt_signal_stack_and_start(PthreadCreateParams* params) {
   return thread_rv;
 }
 
-using pthread_create_func_t = int (*)(pthread_t*, const pthread_attr_t*,
-                                      void* (*)(void*), void*);
-
 extern "C" {
 // This interposer replaces libpthread's pthread_create() so that we can
 // inject an alternate signal stack in every new thread.
-__attribute__((visibility("default"))) int pthread_create(
+MFBT_API int pthread_create(pthread_t* thread, const pthread_attr_t* attr,
-    pthread_t* thread, const pthread_attr_t* attr,
                             void* (*start_routine)(void*), void* arg) {
-  // static const pthread_create_func_t real_pthread_create =
+  static const auto real_pthread_create = GET_REAL_SYMBOL(pthread_create);
-  static const pthread_create_func_t real_pthread_create =
-      (pthread_create_func_t)dlsym(RTLD_NEXT, "pthread_create");
-
-  if (real_pthread_create == nullptr) {
-    MOZ_CRASH(
-        "pthread_create() interposition failed but the interposer function is "
-        "still being called, this won't work!");
-  }
-
-  if (real_pthread_create == pthread_create) {
-    MOZ_CRASH(
-        "We could not obtain the real pthread_create(). Calling the symbol we "
-        "got would make us enter an infinte loop so stop here instead.");
-  }
 
   PthreadCreateParams* params =
       (PthreadCreateParams*)malloc(sizeof(PthreadCreateParams));

mozglue/moz.build

@@ -13,6 +13,9 @@ if CONFIG["MOZ_LINKER"] or CONFIG["MOZ_WIDGET_TOOLKIT"] == "android":
 if CONFIG["MOZ_WIDGET_TOOLKIT"] == "android":
     DIRS += ["android"]
 
+if CONFIG["OS_ARCH"] == "Linux":
+    DIRS += ["interposers"]
+
 DIRS += [
     "baseprofiler",
     "build",

toolkit/crashreporter/moz.build

@@ -53,7 +53,6 @@ if CONFIG["MOZ_CRASHREPORTER"]:
             "google-breakpad/src/common",
             "google-breakpad/src/common/linux",
             "google-breakpad/src/processor",
-            "pthread_create_interposer",
         ]
 
         if CONFIG["MOZ_OXIDIZED_BREAKPAD"]:

toolkit/crashreporter/pthread_create_interposer/moz.build

@@ -1,12 +0,0 @@
-# -*- 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("pthread_create_interposer")
-
-NoVisibilityFlags()
-
-UNIFIED_SOURCES += [
-    "pthread_create_interposer.cpp",
-]