In Linux Breakpad, point the child stack at the top-most address rather than the bottom-most address before calling clone().

BUG=none
TEST=Official builds on Linux should be able to dump/upload reliably when running with --crash-test.
Review URL: http://codereview.chromium.org/115955

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@17354 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 8 insertions, 1 deletions

diff --git a/breakpad/linux/exception_handler.cc b/breakpad/linux/exception_handler.cc
index fe72f2f..ad7a11d 100644
--- a/breakpad/linux/exception_handler.cc
+++ b/breakpad/linux/exception_handler.cc
@@ -79,6 +79,7 @@
 #include <sys/wait.h>
 #include <unistd.h>
 
+#include "breakpad/linux/linux_libc_support.h"
 #include "breakpad/linux/linux_syscall_support.h"
 #include "breakpad/linux/memory.h"
 #include "breakpad/linux/minidump_writer.h"
@@ -266,8 +267,14 @@ bool ExceptionHandler::HandleSignal(int sig, siginfo_t* info, void* uc) {
                                        callback_context_))
     return true;
 
+  static const unsigned kChildStackSize = 8000;
   PageAllocator allocator;
-  void* const stack = allocator.Alloc(8000);
+  uint8_t* stack = (uint8_t*) allocator.Alloc(kChildStackSize);
+  if (!stack)
+    return false;
+  // clone() needs the top-most address. (scrub just to be safe)
+  stack += kChildStackSize;
+  my_memset(stack - 16, 0, 16);
 
   ThreadArgument thread_arg;
   thread_arg.handler = this;