From c2d03d048a494d1eb78b9b74abf9bddcf86c045a Mon Sep 17 00:00:00 2001
From: Lucas Schumacher <technolucas@protonmail.com>
Date: Mon, 14 Apr 2025 14:01:25 -0400
Subject: [PATCH] Fix AArch64 write return value

---
 arch/aarch64.c | 22 ++++++++++++++--------
 buildtest.c    |  6 +++++-
 2 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/arch/aarch64.c b/arch/aarch64.c
index 5d0e2f0..21f4b0a 100644
--- a/arch/aarch64.c
+++ b/arch/aarch64.c
@@ -14,15 +14,21 @@ void exit(int8_t status){
 
 intptr_t write(int32_t fd, const void* buf, intptr_t size){
   intptr_t n_written = 0;
+  //register int32_t fd_w asm("w0") = fd;
   asm volatile( 
-    "mov x0, %2\n"
-    "mov x1, %0\n"
-    "mov x2, %1\n"
-    "mov x8, #64\n"
-    "svc #0\n"
-    : //TODO: n_written
-    : "r" (buf), "r"(size), "r"(fd)
-    : "x0", "x8"           // Clobbered registers
+    // Assembly Instructions
+    "mov x0, %1\n"  // Set x0 to value of fd
+    "mov x1, %2\n"  // Set x1 to value of buf
+    "mov x2, %3\n"  // Set x2 to value of size
+    "mov x8, #64\n" // Syscall number for 'write' is 64 in AArch64
+    "svc #0\n"      // Make syscall
+    "mov %0, x0\n"  // Store return value in n_written
+    // Output operands
+    : "=r"(n_written)
+    // Input operands
+    : "r"((int64_t)fd), "r" (buf), "r"(size)
+    // Clobbered registers
+    : "x0", "x1", "x2", "x8"
   );
   return n_written;
 }
diff --git a/buildtest.c b/buildtest.c
index 1f277e8..595be89 100644
--- a/buildtest.c
+++ b/buildtest.c
@@ -3,8 +3,12 @@
 
 
 int main() {
-  uint64_t pid = fork();
+  // Test the write syscall
+  intptr_t n = write(STDIO, "Hello\n", 6);
+  if(n != 6) return n;
 
+  // Test the fork syscall
+  uint64_t pid = fork();
   // Print the pid in hex
   char msg[17] = {' '};
   msg[16] = '\n';