From 06de3cc17d05da7f1a8b604e831eba8ddec800ef Mon Sep 17 00:00:00 2001
From: Lucas Schumacher <technolucas@protonmail.com>
Date: Fri, 11 Apr 2025 23:50:36 -0400
Subject: [PATCH] Add fork support for x86_64

---
 print.c | 38 +++++++++++++++++++++++++++++++++-----
 1 file changed, 33 insertions(+), 5 deletions(-)

diff --git a/print.c b/print.c
index 370b6b6..4f4736a 100644
--- a/print.c
+++ b/print.c
@@ -30,9 +30,9 @@ long print(const void *buf, long count) {
     return 0;
 }
 
-#if defined(__aarch64__)
 #define CLONE_CHILD_SETTID   0x1000000
 #define CLONE_CHILD_CLEARTID 0x200000
+#if defined(__aarch64__)
 long int fork() {
   long int rtn;
   long int flags = CLONE_CHILD_CLEARTID | CLONE_CHILD_SETTID;
@@ -42,8 +42,8 @@ long int fork() {
       "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
+      "mov x3, #0\n"    // tls
+      "mov x4, #0\n"    // child_tidptr
       "svc #0\n"        // Make the syscall
       "mov %0, x0\n"    // save return value
       // Output operands
@@ -55,6 +55,34 @@ long int fork() {
     );
   return rtn;
 }
+#elif defined(__x86_64__)
+long int fork() {
+  long int rtn;
+  /*
+  long int flags = CLONE_CHILD_CLEARTID | CLONE_CHILD_SETTID;
+  asm volatile(
+    "movq %%rax, 56\n"   // syscall number for 'clone' is 56 for x86-64
+    "movq %%rdi, %1\n"    // clone flags
+    "movq %%rsi, 0\n"    // child stack pointer
+    "movq %%rdx, 0\n"    // parent tidptr
+    "movq %%r10, 0\n"    // child tidptr
+    "movq %%r8,  0\n"     // tls
+    "syscall\n"         // syscall
+    "movq %0, %%rax\n"    // save return value
+    : "=r"(rtn)
+    : "r"(flags)
+    : "rax", "rdi", "rsi", "rdx", "r10", "r8", "r9", "r10", "r11"
+  );
+  */
+  asm volatile(
+    "syscall\n"         // syscall
+    "movq %0, %%rax\n"    // save return value
+    : "=r"(rtn)
+    : "a"(57)
+    :
+  );
+  return rtn;
+}
 #endif
 
 void exit(int status) {
@@ -87,7 +115,7 @@ void exit(int status) {
 
 
 int main() {
-#if defined(__aarch64__)
+#if defined(__x86_64__) || defined(__aarch64__)
   long int pid = fork();
   char msg[17] = {' '};
   msg[16] = '\n';
@@ -99,7 +127,7 @@ int main() {
     msg[i] = c;
   }
   print(msg, 17);
-  #elif
+  #else
   char *msg = "Hello World!\n";
   print(msg, 13);
 #endif