Add read support for mips

arch/mips.c

@@ -28,7 +28,21 @@ intptr_t write(int32_t fd, const void* buf, intptr_t size){
   );
   return n_written;
 }
-//intptr_t read(int32_t fd, const void* buf, intptr_t size);
+intptr_t read(int32_t fd, const void* buf, intptr_t size){
+  intptr_t n_read = 0;
+  asm volatile ( 
+    "move $a0, %1\n"
+    "move $a1, %2\n"
+    "move $a2, %3\n"
+    "li $v0, 4004\n"
+    "syscall\n"
+    "move %0, $v0\n"
+    : "=r"(n_read)
+    : "r"(fd), "r"(buf), "r"(size)
+    : "a0", "a1", "a2", "v0" //TODO: temp registers clobbered by syscall should probably also be listed but this fn returns right away so it should be fine?
+  );
+  return n_read;
+}
 
 uint32_t fork(){
   int rtn;