Linux sandbox: change API to start the sandbox

components/nacl/loader/sandbox_linux/nacl_sandbox_linux.cc

Index: components/nacl/loader/sandbox_linux/nacl_sandbox_linux.cc
diff --git a/components/nacl/loader/sandbox_linux/nacl_sandbox_linux.cc b/components/nacl/loader/sandbox_linux/nacl_sandbox_linux.cc
index 1914116c4b3dd7f3e569e26b103428429741960f..95c02a05e8275b4b3736583a9f34c3e45180cb43 100644
--- a/components/nacl/loader/sandbox_linux/nacl_sandbox_linux.cc
+++ b/components/nacl/loader/sandbox_linux/nacl_sandbox_linux.cc
@@ -14,6 +14,7 @@
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
+#include "base/files/scoped_file.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/posix/eintr_wrapper.h"
@@ -21,6 +22,7 @@
 #include "components/nacl/common/nacl_switches.h"
 #include "components/nacl/loader/nonsfi/nonsfi_sandbox.h"
 #include "components/nacl/loader/sandbox_linux/nacl_bpf_sandbox_linux.h"
+#include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
 #include "sandbox/linux/services/credentials.h"
 #include "sandbox/linux/services/thread_helpers.h"
 #include "sandbox/linux/suid/client/setuid_sandbox_client.h"
@@ -39,6 +41,15 @@ bool IsSandboxed() {
   return true;
 }
 
+// Open a new file descriptor to /proc/self/task/ by using
+// |proc_fd|.
+base::ScopedFD GetProcSelfTask(int proc_fd) {
+  base::ScopedFD proc_self_task(HANDLE_EINTR(
+      openat(proc_fd, "self/task/", O_RDONLY | O_DIRECTORY | O_CLOEXEC)));
+  PCHECK(proc_self_task.is_valid());
+  return proc_self_task.Pass();
+}
+
 }  // namespace
 
 NaClSandbox::NaClSandbox()
@@ -51,6 +62,9 @@ NaClSandbox::NaClSandbox()
   proc_fd_.reset(
       HANDLE_EINTR(open("/proc", O_DIRECTORY | O_RDONLY | O_CLOEXEC)));
   PCHECK(proc_fd_.is_valid());
+  // Determine if the kernel supports seccomp-bpf and let it cache the
+  // result. This must be done before any sandbox is engaged.
+  sandbox::SandboxBPF::SupportsSeccompSandbox();
 }
 
 NaClSandbox::~NaClSandbox() {
@@ -58,9 +72,7 @@ NaClSandbox::~NaClSandbox() {
 
 bool NaClSandbox::IsSingleThreaded() {
   CHECK(proc_fd_.is_valid());
-  base::ScopedFD proc_self_task(HANDLE_EINTR(openat(
-      proc_fd_.get(), "self/task/", O_RDONLY | O_DIRECTORY | O_CLOEXEC)));
-  PCHECK(proc_self_task.is_valid());
+  base::ScopedFD proc_self_task(GetProcSelfTask(proc_fd_.get()));
   return sandbox::ThreadHelpers::IsSingleThreaded(proc_self_task.get());
 }
 
@@ -114,11 +126,14 @@ void NaClSandbox::InitializeLayerTwoSandbox(bool uses_nonsfi_mode) {
   CHECK(IsSingleThreaded());
   CheckForExpectedNumberOfOpenFds();
 
+  base::ScopedFD proc_self_task(GetProcSelfTask(proc_fd_.get()));
+
   if (uses_nonsfi_mode) {
-    layer_two_enabled_ = nacl::nonsfi::InitializeBPFSandbox();
+    layer_two_enabled_ =
+        nacl::nonsfi::InitializeBPFSandbox(proc_self_task.Pass());
     layer_two_is_nonsfi_ = true;
   } else {
-    layer_two_enabled_ = nacl::InitializeBPFSandbox();
+    layer_two_enabled_ = nacl::InitializeBPFSandbox(proc_self_task.Pass());
   }
 }