Add fork support for AARCH64

print.c

@@ -30,6 +30,33 @@ long print(const void *buf, long count) {
     return 0;
 }
 
+#if defined(__aarch64__)
+#define CLONE_CHILD_SETTID   0x1000000
+#define CLONE_CHILD_CLEARTID 0x200000
+long int fork() {
+  long int rtn;
+  long int flags = CLONE_CHILD_CLEARTID | CLONE_CHILD_SETTID;
+    asm volatile (
+      // Assembly Instructions
+      "mov x8, #220\n"  // Syscall number for 'clone' is 220 in AArch64
+      "mov x0, %1\n"    // clone flags
+      "mov x1, #0\n"    // child stack pointer
+      "mov x2, #0\n"    // parent_tidptr
+      "mov x3, #0\n"    // child_tidptr
+      "mov x4, #0\n"    // tls
+      "svc #0\n"        // Make the syscall
+      "mov %0, x0\n"    // save return value
+      // Output operands
+      : "=r" (rtn)
+      // Input operand
+      : "r" (flags)
+      // Clobbered registers
+      : "x0", "x1", "x2", "x3", "x4", "x8"
+    );
+  return rtn;
+}
+#endif
+
 void exit(int status) {
 #if defined(__x86_64__)
   asm volatile(
@@ -60,9 +87,22 @@ void exit(int status) {
 
 
 int main() {
-//void _start() {
+#if defined(__aarch64__)
+  long int pid = fork();
+  char msg[17] = {' '};
+  msg[16] = '\n';
+  for(int i = 0; i < 16; ++i) {
+    char nibble = (pid >> ((15 - i) * 4)) & 0xf;
+    char c;
+    if (nibble > 9) {c = nibble + '7';}
+    else {c = nibble + '0';}
+    msg[i] = c;
+  }
+  print(msg, 17);
+  #elif
   char *msg = "Hello World!\n";
   print(msg, 13);
+#endif
   return 69;
 }
 void __libc_start_main() {exit(main());}