[MIPS] Add seccomp bpf support

sandbox/linux/seccomp-bpf/syscall.h

Index: sandbox/linux/seccomp-bpf/syscall.h
diff --git a/sandbox/linux/seccomp-bpf/syscall.h b/sandbox/linux/seccomp-bpf/syscall.h
index f444d3a36303e52dd1e6498dcded12633b764c90..4f29776f775dbef6a4acea8118be31c839840621 100644
--- a/sandbox/linux/seccomp-bpf/syscall.h
+++ b/sandbox/linux/seccomp-bpf/syscall.h
@@ -11,6 +11,8 @@
 
 namespace sandbox {
 
+// This function will return the  kernel return value on success and -errno on
+// error on all architectures.
 // We have to make sure that we have a single "magic" return address for
 // our system calls, which we can check from within a BPF filter. This
 // works by writing a little bit of asm() code that a) enters the kernel, and
@@ -25,6 +27,21 @@ SANDBOX_EXPORT intptr_t SandboxSyscall(int nr,
                                        intptr_t p4,
                                        intptr_t p5);
 
+#if defined(__mips__)
+// This function basically does on MIPS what SandboxSyscall() is doing on
+// othere architectures. However, because of specificity of MIPS regarding
+// handelling syscall errors, SandboxSyscall() is made as a wrapper for this
+// function in order for SandboxSyscall() to behave more like on othere

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

nit: othere -> other

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

Done.

+// architectures on places where return value from SandboxSyscall() is used
+// directly (like in most tests).
+// The syscall "nr" is called with arguments that are set in an array on which
+// pointer "args" points to and an information weather there is an error or no
+// is returned to SandboxSyscall() by err_stat.
+intptr_t SandboxSyscallRaw(int nr,
+                        const intptr_t *args,

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

Nit: indent (simply use "git cl format").

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

Done.

+                        intptr_t* err_stat);
+#endif  // defined(__mips__)
+
 // System calls can take up to six parameters. Traditionally, glibc
 // implements this property by using variadic argument lists. This works, but
 // confuses modern tools such as valgrind, because we are nominally passing