commit a3125fd1396a09a7fc4872dc4653f342150a3deb
author Elliott Hughes <enh@google.com> Tue Mar 31 02:42:39 2015 +0000
committer Elliott Hughes <enh@google.com> Tue Mar 31 02:42:39 2015 +0000
tree 5042f453214b2d176c601710c87350c30c7f3944
parent 595752f623ae88f7e4193a6e531a0805f1c6c4dc

Revert "add guard pages to the internal signal stacks"

This reverts commit 595752f623ae88f7e4193a6e531a0805f1c6c4dc.

Change-Id: Iefa66e9049ca0424e53cd5fc320d161b93556dcb

libc/bionic/pthread_create.cpp

diff --git a/libc/bionic/pthread_create.cpp b/libc/bionic/pthread_create.cpp
index 179ae95..66632c4 100644
--- a/libc/bionic/pthread_create.cpp
+++ b/libc/bionic/pthread_create.cpp
@@ -69,23 +69,17 @@
 
 void __init_alternate_signal_stack(pthread_internal_t* thread) {
   // Create and set an alternate signal stack.
-  void* stack_base = mmap(NULL, SIGNAL_STACK_SIZE, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
-  if (stack_base != MAP_FAILED) {
-    // Create a guard page to catch stack overflows in signal handlers.
-    if (mprotect(stack_base, PAGE_SIZE, PROT_NONE) == -1) {
-      munmap(stack_base, SIGNAL_STACK_SIZE);
-      return;
-    }
-    stack_t ss;
-    ss.ss_sp = stack_base + PAGE_SIZE;
-    ss.ss_size = SIGNAL_STACK_SIZE - PAGE_SIZE;
+  stack_t ss;
+  ss.ss_sp = mmap(NULL, SIGSTKSZ, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+  if (ss.ss_sp != MAP_FAILED) {
+    ss.ss_size = SIGSTKSZ;
     ss.ss_flags = 0;
     sigaltstack(&ss, NULL);
-    thread->alternate_signal_stack = stack_base;
+    thread->alternate_signal_stack = ss.ss_sp;
 
     // We can only use const static allocated string for mapped region name, as Android kernel
     // uses the string pointer directly when dumping /proc/pid/maps.
-    prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, stack_base, SIGNAL_STACK_SIZE, "thread signal stack");
+    prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, ss.ss_sp, ss.ss_size, "thread signal stack");
   }
 }