Make nacl_helper easily debuggable

This makes it so that attaching gdb to a nacl_helper process, or using gdb
on a core dump from such a process, automatically finds the symbols of the
nacl_helper executable and all the shared libraries it uses.  The theory of
operation and the details are explained in comments in the code.

BUG= http://code.google.com/p/chromium/issues/detail?id=103436
TEST= nacl still works, gdb attach on nacl_helper process, or gdb on core file from one, find symbols

R=mseaborn@chromium.org,bradchen@google.com

Review URL: http://codereview.chromium.org/8491060

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@110120 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 6 insertions, 0 deletions

diff --git a/chrome/app/nacl_fork_delegate_linux.cc b/chrome/app/nacl_fork_delegate_linux.cc
index a3723a3..372a5b7 100644
--- a/chrome/app/nacl_fork_delegate_linux.cc
+++ b/chrome/app/nacl_fork_delegate_linux.cc
@@ -26,7 +26,12 @@ NaClForkDelegate::NaClForkDelegate()
       sandboxed_(false),
       fd_(-1) {}
 
+/*
+ * Note these need to match up with their counterparts in nacl_helper_linux.c
+ * and nacl_helper_bootstrap_linux.c.
+ */
 const char kNaClHelperAtZero[] = "--at-zero";
+const char kNaClHelperRDebug[] = "--r_debug=0xXXXXXXXXXXXXXXXX";
 
 void NaClForkDelegate::Init(const bool sandboxed,
                             const int browserdesc,
@@ -59,6 +64,7 @@ void NaClForkDelegate::Init(const bool sandboxed,
     CommandLine cmd_line(helper_bootstrap_exe);
     cmd_line.AppendArgPath(helper_exe);
     cmd_line.AppendArgNative(kNaClHelperAtZero);
+    cmd_line.AppendArgNative(kNaClHelperRDebug);
     base::LaunchOptions options;
     options.fds_to_remap = &fds_to_map;
     options.clone_flags = CLONE_FS | SIGCHLD;