[MIPS] Add seccomp bpf support

sandbox/linux/seccomp-bpf/kernel_return_value_helpers_unittest.cc

+// 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.
+
+
+#include <errno.h>
+#include <asm/unistd.h>
+
+#include "sandbox/linux/seccomp-bpf/bpf_tests.h"
+#include "sandbox/linux/seccomp-bpf/kernel_return_value_helpers.h"
+#include "sandbox/linux/seccomp-bpf/syscall.h"
+#include "sandbox/linux/tests/unit_tests.h"
+
+namespace sandbox {
+
+namespace {
+
+// Check that ErrnoToKernelRet works.
+TEST(KernelReturnValueHelpers, ErrnoToKernelRet) {
+  int expected_kernel_ret = SandboxSyscall(__NR_dup, -1);
+#if defined(__mips__)
+  // SandboxSyscall() for MIPS was written so it returns negation of the value
+  // returned by kernel on error. This was done in order for this function to
+  // behave like other architectures on places where return value from
+  // SandboxSyscall() is used directly (like in the most tests), but for this
+  // test to pass we need to cancel this negation.
+  expected_kernel_ret = - expected_kernel_ret;

[jln (very slow on Chromium), 2014/05/28 00:06:57]

This looks very strange as it doesn't really like we're testing anything.

Is the __SYSCALL() macro available on MIPS? Maybe it could be a way to perform a
raw syscall?

[nedeljko, 2014/05/28 09:33:43]

I could use SandboxSyscallRaw() as you suggested in syscall.cc

[nedeljko, 2014/05/29 14:06:45]

Done.

+#endif
+  ASSERT_EQ(expected_kernel_ret, ErrnoToKernelRet(EBADF));}
+
+}
+} // namespace sandbox