first C hello world!

05/main.c

@@ -1,49 +1,50 @@
-typedef unsigned long va_list;
-#define va_start(list, arg) ((list) = (unsigned long)&arg)
-#define va_arg(list, type) (*((type *)(list += ((sizeof(type) + 7) & 0xfffffffffffffff8))))
-#define va_end(list)
+static unsigned char __syscall_data[] = {
+	// mov rax, [rsp+24]
+	0x48, 0x8b, 0x84, 0x24, 24, 0, 0, 0,
+	// mov rdi, rax
+	0x48, 0x89, 0xc7,
+	// mov rax, [rsp+32]
+	0x48, 0x8b, 0x84, 0x24, 32, 0, 0, 0,
+	// mov rsi, rax
+	0x48, 0x89, 0xc6,
+	// mov rax, [rsp+40]
+	0x48, 0x8b, 0x84, 0x24, 40, 0, 0, 0,
+	// mov rdx, rax
+	0x48, 0x89, 0xc2,
+	// mov rax, [rsp+48]
+	0x48, 0x8b, 0x84, 0x24, 48, 0, 0, 0,
+	// mov r10, rax
+	0x49, 0x89, 0xc2,
+	// mov rax, [rsp+56]
+	0x48, 0x8b, 0x84, 0x24, 56, 0, 0, 0,
+	// mov r8, rax
+	0x49, 0x89, 0xc0,
+	// mov rax, [rsp+64]
+	0x48, 0x8b, 0x84, 0x24, 64, 0, 0, 0,
+	// mov r9, rax
+	0x49, 0x89, 0xc1,
+	// mov rax, [rsp+16]
+	0x48, 0x8b, 0x84, 0x24, 16, 0, 0, 0,
+	// syscall
+	0x0f, 0x05,
+	// mov [rsp+8], rax
+	0x48, 0x89, 0x84, 0x24, 8, 0, 0, 0,
+	// ret
+	0xc3
+};
 
-int sum(int n, ...) {
-	va_list args;
-	int i;
-	int total = 0;
-	va_start(args, n);
-	for (i = 0; i < n; ++i) {
-		total += va_arg(args, int);
-	}
-	return total;
+#define __syscall(no, arg1, arg2, arg3, arg4, arg5, arg6)\
+	(((unsigned long (*)(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long))__syscall_data)\
+		(no, arg1, arg2, arg3, arg4, arg5, arg6))
+
+typedef unsigned long size_t;
+
+long write(int fd, void *buf, size_t count) {
+	__syscall(1, fd, buf, count, 0, 0, 0);
 }
 
-long factorial(long x) {
-	if (x == 0) {
-		return 1;
-	} else {
-		return x * factorial(x-1);
-	}
-}
-
-long fibonacci(long x) {
-	return x > 0 ?
-		x > 1 ?
-			fibonacci(x-1) + fibonacci(x-2)
-		: 1
-		: 0;
-}
-
-long gcd(long a, long b) {
-	while (a != 0) {
-		long temp = a;
-		a = b % a;
-		b = temp;
-	}
-	return b;
-}
-
-int f() {
-	lb: goto lb;
-}
-
-int main(int argc, char **argv) {	
-	return sum(3, -100, 200, -300);
+int main(int argc, char **argv) {
+	write(1, "Hello, world!\n", 14);
+	return 0;
 }