[MIPS] Add seccomp bpf support

content/common/sandbox_linux/bpf_gpu_policy_linux.cc

Index: content/common/sandbox_linux/bpf_gpu_policy_linux.cc
diff --git a/content/common/sandbox_linux/bpf_gpu_policy_linux.cc b/content/common/sandbox_linux/bpf_gpu_policy_linux.cc
index 1570114c012ac4dc5ddd563c6a4286ba5e6b1f82..5bc202a35d320dd82501562fc04a3d136da30d99 100644
--- a/content/common/sandbox_linux/bpf_gpu_policy_linux.cc
+++ b/content/common/sandbox_linux/bpf_gpu_policy_linux.cc
@@ -96,11 +96,21 @@ intptr_t GpuSIGSYS_Handler(const struct arch_seccomp_data& args,
             broker_process->Open(reinterpret_cast<const char*>(args.args[1]),
                                  static_cast<int>(args.args[2]));
       } else {
+#if defined(__mips__)
+        // On MIPS, kernel returns errno (instead of -errno)
+        return EPERM;

[jln (very slow on Chromium), 2014/05/02 20:42:04]

Ohh, this is very unfortunate :(

Let's add a helper in sandbox/linux/services/kernel_to_errno.h

With:

inline int KernelRetToErrno(int kernel_ret) {}

inline int ErrnoToKernelRet(int errno) {}

That does what's required on each platform  and let's wrap all of these.

[nedeljko, 2014/05/07 15:40:05]

Helper added.

I created RetValToKernel instead of ErrnoToKernel because MIPS is different from
other architectures (x86 and ARM) in the way in which it distinguishes correct
return value from error.
On MIPS, kernel returns two values. One is regular ret val or errno and second
is value that can be checked to see if syscall was executed successfully. 

+#else
         return -EPERM;
+#endif
       }
     default:
       RAW_CHECK(false);
+#if defined(__mips__)
+        // On MIPS, kernel returns errno (instead of -errno)
+      return ENOSYS;
+#else
       return -ENOSYS;
+#endif
   }
 }
 
@@ -167,7 +177,7 @@ ErrorCode GpuProcessPolicy::EvaluateSyscall(SandboxBPF* sandbox,
                                             int sysno) const {
   switch (sysno) {
     case __NR_ioctl:
-#if defined(__i386__) || defined(__x86_64__)
+#if defined(__i386__) || defined(__x86_64__) || defined(__mips__)
     // The Nvidia driver uses flags not in the baseline policy
     // (MAP_LOCKED | MAP_EXECUTABLE | MAP_32BIT)
     case __NR_mmap: