WIP: Implement seccomp-bpf sandbox for nacl_helper_nonsfi.

sandbox/linux/services/syscall_wrappers.h

Index: sandbox/linux/services/syscall_wrappers.h
diff --git a/sandbox/linux/services/syscall_wrappers.h b/sandbox/linux/services/syscall_wrappers.h
index 28cc3a7de3f1e320f370e716a4ccb1f3f1fb4d82..1e5f392cbb483c4bb9ec6097449dfedc70be16ae 100644
--- a/sandbox/linux/services/syscall_wrappers.h
+++ b/sandbox/linux/services/syscall_wrappers.h
@@ -8,6 +8,7 @@
 #include <stdint.h>
 #include <sys/types.h>
 
+#include "sandbox/linux/system_headers/linux_signal.h"
 #include "sandbox/sandbox_export.h"
 
 struct sock_fprog;
@@ -56,6 +57,12 @@ SANDBOX_EXPORT int sys_capget(struct cap_hdr* hdrp, struct cap_data* datap);
 SANDBOX_EXPORT int sys_capset(struct cap_hdr* hdrp,
                               const struct cap_data* datap);
 
+// Some libcs do not expose sigprocmask/sigaction wrappers.
+SANDBOX_EXPORT int sys_sigprocmask(int how, const linux_sigset_t* set,
+                                   linux_sigset_t* oldset);
+SANDBOX_EXPORT int sys_sigaction(int signum, const struct linux_sigaction* act,
+                                 struct linux_sigaction* oldact);
+
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_SERVICES_SYSCALL_WRAPPERS_H_