[MIPS] Add seccomp bpf support

sandbox/linux/seccomp-bpf/kernel_return_value_helpers.h

Index: sandbox/linux/seccomp-bpf/kernel_return_value_helpers.h
diff --git a/sandbox/linux/seccomp-bpf/kernel_return_value_helpers.h b/sandbox/linux/seccomp-bpf/kernel_return_value_helpers.h
new file mode 100644
index 0000000000000000000000000000000000000000..8ba03115ba7ba3ef6a11a1aeab09086809fcdd98
--- /dev/null
+++ b/sandbox/linux/seccomp-bpf/kernel_return_value_helpers.h
@@ -0,0 +1,23 @@
+// 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_KERNEL_RETURN_VALUE_HELPERS_H__
+#define SANDBOX_LINUX_SERVICES_KERNEL_RETURN_VALUE_HELPERS_H__
+
+#include <signal.h>
+#include <stdint.h>
+
+namespace sandbox {
+
+// Convert |errno| to the value returned by the kernel when it wants to return
+// |errno| to userland after a system call.
+int ErrnoToKernelRet(int errno_val);

[jln (very slow on Chromium), 2014/06/13 02:47:36]

Let's keep the interface of trap handlers as returning -errno on error, even on
MIPS.

[nedeljko, 2014/06/18 13:41:00]

Done.

+
+// Set the registers in |ctx| to match what they would be after a system call
+// returning |ret_val|.

[jln (very slow on Chromium), 2014/06/13 02:47:36]

Let's add: |ret_val| must must follow the SandboxSyscall() convention of being
-errno on errors.

We should simply add this method to the new Syscall class, once it's available.

[nedeljko, 2014/06/18 13:41:00]

Done.

+void PutValueInUcontext(intptr_t ret_val, ucontext_t* ctx);
+
+} // namespace sandbox
+
+#endif  // SANDBOX_LINUX_SERVICES_KERNEL_RETURN_VALUE_HELPERS_H__