WIP: Implement seccomp-bpf sandbox for nacl_helper_nonsfi.

sandbox/linux/services/syscall_wrappers.cc

Index: sandbox/linux/services/syscall_wrappers.cc
diff --git a/sandbox/linux/services/syscall_wrappers.cc b/sandbox/linux/services/syscall_wrappers.cc
index 5a4045b4d2c4b786c882bd09c1bee885d9446f0d..365664392acc5b053834c1911059f38859ac14e5 100644
--- a/sandbox/linux/services/syscall_wrappers.cc
+++ b/sandbox/linux/services/syscall_wrappers.cc
@@ -17,6 +17,7 @@
 #include "base/logging.h"
 #include "base/third_party/valgrind/valgrind.h"
 #include "build/build_config.h"
+#include "sandbox/linux/system_headers/linux_signal.h"
 #include "sandbox/linux/system_headers/linux_syscalls.h"
 
 namespace sandbox {
@@ -85,4 +86,15 @@ int sys_capset(cap_hdr* hdrp, const cap_data* datap) {
   return syscall(__NR_capset, hdrp, datap);
 }
 
+int sys_sigprocmask(
+    int how, const linux_sigset_t* set, linux_sigset_t* oldset) {
+  return syscall(__NR_rt_sigprocmask, how, set, oldset, sizeof(*set));
+}
+
+int sys_sigaction(int signum, const struct linux_sigaction* act,
+                  struct linux_sigaction* oldact) {
+  // TODO: Do we need to return an error if act has SA_RESTORE?
+  return syscall(__NR_rt_sigaction, signum, act, oldact, sizeof(act->sa_mask));
+}
+
 }  // namespace sandbox