Add support for openat on mips

arch/mips.c

@@ -56,4 +56,35 @@ uint32_t fork(){
   );
   return (uint32_t)rtn;
 }
+
+int32_t openat(int32_t fd, const char* filename, uint32_t flags, uint32_t mode) {
+  int32_t file = 0;
+  asm volatile (
+    "move $a0, %1\n"
+    "move $a1, %2\n"
+    "move $a2, %3\n"
+    "move $a3, %4\n"
+    "li $v0, 4288\n"
+    "syscall\n"
+    "move %0, $v0\n"
+    : "=r"(file)
+    : "r"(fd), "r"(filename), "r"(flags), "r"(mode)
+    : "a0", "a1", "a2", "a3", "v0"
+  );
+  /*
+  asm volatile (
+    "move $a0, %1\n"
+    "move $a1, %2\n"
+    "move $a2, %3\n"
+    "li $v0, 4005\n"
+    "syscall\n"
+    "move %0, $v0\n"
+    : "=r"(file)
+    : "r"(filename), "r"(flags), "r"(mode)
+    : "a0", "a1", "a2", "a3", "v0"
+  );
+  */
+  return file;
+}
+
 #endif

buildtest.c

@@ -33,7 +33,7 @@ int main() {
   write(STDIO, input_buffer, n_read);
 
   // Test the open syscall
-  #if defined(__x86_64__)
+  #if defined(__x86_64__) || defined(__mips__)
   int32_t file = open("/proc/version", O_RDONLY);
   int i = read(file, input_buffer, INPUT_BUFFER_LEN);
   while(i > 0) {