Introduce sys_sigprocmask and sys_sigaction.

sandbox/linux/services/syscall_wrappers.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SANDBOX_LINUX_SERVICES_SYSCALL_WRAPPERS_H_
 #define SANDBOX_LINUX_SERVICES_SYSCALL_WRAPPERS_H_
 
+#include <signal.h>
 #include <stdint.h>
 #include <sys/types.h>
 
 #include "sandbox/sandbox_export.h"
 
 struct sock_fprog;
 struct rlimit64;
 struct cap_hdr;
 struct cap_data;
 
@@ skipping 41 matching lines @@
 // Some libcs do not expose getresuid/getresgid wrappers.
 SANDBOX_EXPORT int sys_getresuid(uid_t* ruid, uid_t* euid, uid_t* suid);
 SANDBOX_EXPORT int sys_getresgid(gid_t* rgid, gid_t* egid, gid_t* sgid);
 
 // Some libcs do not expose a chroot wrapper.
 SANDBOX_EXPORT int sys_chroot(const char* path);
 
 // Some libcs do not expose a unshare wrapper.
 SANDBOX_EXPORT int sys_unshare(int flags);
 
+// Some libcs do not expose a sigprocmask. Note that oldset must be a nullptr,
+// because of some ABI gap between toolchain's and Linux's.
+SANDBOX_EXPORT int sys_sigprocmask(
+    int how, const sigset_t* set, decltype(nullptr) oldset);
+
+// Some libcs do not expose a sigaction().
+SANDBOX_EXPORT int sys_sigaction(int signum, const struct sigaction* act,
+                                 struct sigaction* oldact);
+
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_SERVICES_SYSCALL_WRAPPERS_H_