linux: use /proc/self/exe when exec'ing ourselves

We don't want to ever go out to disk when looking for data after
startup, since they can be changed by an update.

We *should* just be using the zygote, but the zygote is sandboxed-only
for now, and fixing that has a lengthy dependency graph.  In the
interim, /proc/self/exe is the correct executable and exec'ing it should
work as long as the subprocess doesn't need any other files from the
Chrome directory.

BUG=22703
TEST=Start Chrome.  Move away the entire Chrome directory; plugins
should still work.

Review URL: http://codereview.chromium.org/403018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@32486 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 10 insertions, 6 deletions

diff --git a/chrome/common/child_process_host.cc b/chrome/common/child_process_host.cc
index d4a9eda..2e0f1f6 100644
--- a/chrome/common/child_process_host.cc
+++ b/chrome/common/child_process_host.cc
@@ -93,16 +93,20 @@ FilePath ChildProcessHost::GetChildPath() {
   if (!child_path.empty())
     return child_path;
 
-#if !defined(OS_MACOSX)
-  // On most platforms, the child executable is the same as the current
-  // executable.
-  PathService::Get(base::FILE_EXE, &child_path);
-#else
+#if defined(OS_LINUX)
+  // Use /proc/self/exe rather than our known binary path so updates
+  // can't swap out the binary from underneath us.
+  child_path = FilePath("/proc/self/exe");
+#elif defined(OS_MACOSX)
   // On the Mac, the child executable lives at a predefined location within
   // the app bundle's versioned directory.
   child_path = chrome::GetVersionedDirectory().
       Append(chrome::kHelperProcessExecutablePath);
-#endif  // OS_MACOSX
+#else
+  // On most platforms, the child executable is the same as the current
+  // executable.
+  PathService::Get(base::FILE_EXE, &child_path);
+#endif
 
   return child_path;
 }