Linux: Add support for chrooted renderers.

http://code.google.com/p/chromium/wiki/LinuxSandboxIPC

Without filesystem access from the renderers, we need another way of
dealing with fontconfig and font loading.

This add support for:
  * An "SBX_D" environment variable in the renderers which is used to
    signal the end of dynamic linking so that the chroot can be
    enforced.
  * A sandbox_host process, running outside the sandbox, to deal with
    fontconfig requests from the renderers. See the wiki page for
    the reasoning behind making it a separate process.
  * A new, custom SkFontHost for Skia. Because this is Chrome
    specific, it will live outside the upstream Skia tree. This
    FontHost can be configured either to drive fontconfig directly
    (for the browser process and for any unsandboxed renderers) or to
    use an IPC system. Since the same SkFontHost has to be linked into
    both the browser and renderer (they are the same binary), this
    switch has to be made at run time.

Sandbox IPC calls are rare (a couple of dozen at page load time) and
add about 50us of overhead for each call.

(Reland of r17575 which was reverted in r17577)

http://codereview.chromium.org/112074
BUG=8081


git-svn-id: svn://svn.chromium.org/chrome/trunk/src@18405 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 5 insertions, 0 deletions

diff --git a/base/process_util_linux.cc b/base/process_util_linux.cc
index 7560257..a5337b4 100644
--- a/base/process_util_linux.cc
+++ b/base/process_util_linux.cc
@@ -102,6 +102,11 @@ bool LaunchApp(const std::vector<std::string>& argv,
     if (!ShuffleFileDescriptors(fd_shuffle))
       exit(127);
 
+    // If we are using the SUID sandbox, it sets a magic environment variable
+    // ("SBX_D"), so we remove that variable from the environment here on the
+    // off chance that it's already set.
+    unsetenv("SBX_D");
+
     CloseSuperfluousFds(fd_shuffle);
 
     scoped_array<char*> argv_cstr(new char*[argv.size() + 1]);