From 307091dc306c34ce9e4ee6cc3b467807b3a3bd12 Mon Sep 17 00:00:00 2001
From: Elliott Hughes <enh@google.com>
Date: Wed, 27 Aug 2014 11:47:01 -0700
Subject: [PATCH] Actually ask the pthread implementation for the stack guard
 size.

Bug: 17111575
Change-Id: I23919b1e8aeff627a65daf57f1109bec60b196cc
---
 runtime/thread.cc | 32 ++++++++++----------------------
 runtime/utils.cc  |  9 ++++++++-
 runtime/utils.h   |  2 +-
 3 files changed, 19 insertions(+), 24 deletions(-)

diff --git a/runtime/thread.cc b/runtime/thread.cc
index e6521006c..e58e8641e 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -487,11 +487,14 @@ void Thread::SetThreadName(const char* name) {
 void Thread::InitStackHwm() {
   void* read_stack_base;
   size_t read_stack_size;
-  GetThreadStack(tlsPtr_.pthread_self, &read_stack_base, &read_stack_size);
+  size_t read_guard_size;
+  GetThreadStack(tlsPtr_.pthread_self, &read_stack_base, &read_stack_size, &read_guard_size);
 
-  // TODO: include this in the thread dumps; potentially useful in SIGQUIT output?
-  VLOG(threads) << StringPrintf("Native stack is at %p (%s)", read_stack_base,
-                                PrettySize(read_stack_size).c_str());
+  // This is included in the SIGQUIT output, but it's useful here for thread debugging.
+  VLOG(threads) << StringPrintf("Native stack is at %p (%s with %s guard)",
+                                read_stack_base,
+                                PrettySize(read_stack_size).c_str(),
+                                PrettySize(read_guard_size).c_str());
 
   tlsPtr_.stack_begin = reinterpret_cast<byte*>(read_stack_base);
   tlsPtr_.stack_size = read_stack_size;
@@ -544,28 +547,13 @@ void Thread::InitStackHwm() {
 
   // Install the protected region if we are doing implicit overflow checks.
   if (implicit_stack_check) {
-    size_t guardsize;
-    pthread_attr_t attributes;
-    CHECK_PTHREAD_CALL(pthread_attr_init, (&attributes), "guard size query");
-    CHECK_PTHREAD_CALL(pthread_attr_getguardsize, (&attributes, &guardsize), "guard size query");
-    CHECK_PTHREAD_CALL(pthread_attr_destroy, (&attributes), "guard size query");
     // The thread might have protected region at the bottom.  We need
     // to install our own region so we need to move the limits
     // of the stack to make room for it.
 
-#if defined(__i386__) || defined(__x86_64__)
-    // Work around issue trying to read last page of stack on Intel.
-    // The bug for this is b/17111575.  The problem is that we are
-    // unable to read the page just above the guard page on the
-    // main stack on an intel target.  When the bug is fixed
-    // this can be removed.
-    if (::art::GetTid() == getpid()) {
-      guardsize += 4 * KB;
-    }
-#endif
-    tlsPtr_.stack_begin += guardsize + kStackOverflowProtectedSize;
-    tlsPtr_.stack_end += guardsize + kStackOverflowProtectedSize;
-    tlsPtr_.stack_size -= guardsize;
+    tlsPtr_.stack_begin += read_guard_size + kStackOverflowProtectedSize;
+    tlsPtr_.stack_end += read_guard_size + kStackOverflowProtectedSize;
+    tlsPtr_.stack_size -= read_guard_size;
 
     InstallImplicitProtection();
   }
diff --git a/runtime/utils.cc b/runtime/utils.cc
index 4f73e6975..d704eec9a 100644
--- a/runtime/utils.cc
+++ b/runtime/utils.cc
@@ -82,7 +82,7 @@ std::string GetThreadName(pid_t tid) {
   return result;
 }
 
-void GetThreadStack(pthread_t thread, void** stack_base, size_t* stack_size) {
+void GetThreadStack(pthread_t thread, void** stack_base, size_t* stack_size, size_t* guard_size) {
 #if defined(__APPLE__)
   *stack_size = pthread_get_stacksize_np(thread);
   void* stack_addr = pthread_get_stackaddr_np(thread);
@@ -95,10 +95,17 @@ void GetThreadStack(pthread_t thread, void** stack_base, size_t* stack_size) {
   } else {
     *stack_base = stack_addr;
   }
+
+  // This is wrong, but there doesn't seem to be a way to get the actual value on the Mac.
+  pthread_attr_t attributes;
+  CHECK_PTHREAD_CALL(pthread_attr_init, (&attributes), __FUNCTION__);
+  CHECK_PTHREAD_CALL(pthread_attr_getguardsize, (&attributes, guard_size), __FUNCTION__);
+  CHECK_PTHREAD_CALL(pthread_attr_destroy, (&attributes), __FUNCTION__);
 #else
   pthread_attr_t attributes;
   CHECK_PTHREAD_CALL(pthread_getattr_np, (thread, &attributes), __FUNCTION__);
   CHECK_PTHREAD_CALL(pthread_attr_getstack, (&attributes, stack_base, stack_size), __FUNCTION__);
+  CHECK_PTHREAD_CALL(pthread_attr_getguardsize, (&attributes, guard_size), __FUNCTION__);
   CHECK_PTHREAD_CALL(pthread_attr_destroy, (&attributes), __FUNCTION__);
 #endif
 }
diff --git a/runtime/utils.h b/runtime/utils.h
index d821ae199..c4a58950c 100644
--- a/runtime/utils.h
+++ b/runtime/utils.h
@@ -416,7 +416,7 @@ pid_t GetTid();
 std::string GetThreadName(pid_t tid);
 
 // Returns details of the given thread's stack.
-void GetThreadStack(pthread_t thread, void** stack_base, size_t* stack_size);
+void GetThreadStack(pthread_t thread, void** stack_base, size_t* stack_size, size_t* guard_size);
 
 // Reads data from "/proc/self/task/${tid}/stat".
 void GetTaskStats(pid_t tid, char* state, int* utime, int* stime, int* task_cpu);
-- 
2.11.0