1 files changed, 65 insertions, 3 deletions

diff --git a/js/src/jsnativestack.cpp b/js/src/jsnativestack.cpp
index 05928ea3d..166a5a4f7 100644
--- a/js/src/jsnativestack.cpp
+++ b/js/src/jsnativestack.cpp
@@ -21,6 +21,18 @@
 #  include <unistd.h>
 # endif
 
+# if defined(XP_LINUX) && !defined(ANDROID) && defined(__GLIBC__)
+#  include <dlfcn.h>
+#  include <sys/syscall.h>
+#  include <sys/types.h>
+#  include <unistd.h>
+static pid_t
+gettid()
+{
+    return syscall(__NR_gettid);
+}
+# endif
+
 #else
 # error "Unsupported platform"
 
@@ -88,6 +100,52 @@ js::GetNativeStackBaseImpl()
         context.uc_stack.ss_size;
 }
 
+#elif defined(XP_LINUX) && !defined(ANDROID) && defined(__GLIBC__)
+void*
+js::GetNativeStackBaseImpl()
+{
+    // On the main thread, get stack base from glibc's __libc_stack_end rather than pthread APIs
+    // to avoid filesystem calls /proc/self/maps.  Non-main threads spawned with pthreads can read
+    // this information directly from their pthread struct, but when using the pthreads API, the
+    // main thread must go parse /proc/self/maps to figure the mapped stack address space ranges.
+    // We want to avoid reading from /proc/ so that the application can run in restricted
+    // environments where /proc may not be mounted (e.g. chroot).
+    if (gettid() == getpid()) {
+        void** pLibcStackEnd = (void**)dlsym(RTLD_DEFAULT, "__libc_stack_end");
+
+        // If __libc_stack_end is not found, architecture specific frame pointer hopping will need
+        // to be implemented.
+        MOZ_RELEASE_ASSERT(pLibcStackEnd, "__libc_stack_end unavailable, unable to setup stack range for JS.");
+        void* stackBase = *pLibcStackEnd;
+        MOZ_RELEASE_ASSERT(stackBase, "Invalid stack base, unable to setup stack range for JS.");
+
+        // We don't need to fix stackBase, as it already roughly points to beginning of the stack.
+        return stackBase;
+    }
+
+    // Non-main threads have the required info stored in memory, so no filesystem calls are made.
+    pthread_t thread = pthread_self();
+    pthread_attr_t sattr;
+    pthread_attr_init(&sattr);
+    pthread_getattr_np(thread, &sattr);
+
+    // stackBase will be the *lowest* address on all architectures.
+    void* stackBase = nullptr;
+    size_t stackSize = 0;
+    int rc = pthread_attr_getstack(&sattr, &stackBase, &stackSize);
+    if (rc) {
+        MOZ_CRASH("Call to pthread_attr_getstack failed, unable to setup stack range for JS.");
+    }
+    MOZ_RELEASE_ASSERT(stackBase, "Invalid stack base, unable to setup stack range for JS.");
+    pthread_attr_destroy(&sattr);
+
+# if JS_STACK_GROWTH_DIRECTION > 0
+    return stackBase;
+# else
+    return static_cast<char*>(stackBase) + stackSize;
+# endif
+}
+
 #else /* XP_UNIX */
 
 void*
@@ -156,11 +214,15 @@ js::GetNativeStackBaseImpl()
         // the truth.
         rc = pthread_attr_getstack(&sattr, &stackBase, &stackSize);
 # else
+    // Use the default pthread_attr_getstack() call. Note that this function
+    // differs between libc implementations and could imply /proc access etc.
+    // which may not work in restricted environments.
     rc = pthread_attr_getstack(&sattr, &stackBase, &stackSize);
 # endif
-    if (rc)
-        MOZ_CRASH();
-    MOZ_ASSERT(stackBase);
+    if (rc) {
+        MOZ_CRASH("Call to pthread_attr_getstack failed, unable to setup stack range for JS.");
+    }
+    MOZ_RELEASE_ASSERT(stackBase, "Invalid stack base, unable to setup stack range for JS.");
     pthread_attr_destroy(&sattr);
 
 #  if JS_STACK_GROWTH_DIRECTION > 0