fix syscalls YET AGAIN

user/libc/syscall.h

@@ -1,21 +1,79 @@
-#pragma once
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   System call wrappers for userspace
+ * @license GPL-3.0-only
+ */
 
-// 3 because 3 arguments to the call, get it??
+#pragma once
+// TODO: replace all ifndef/define/endif by pragma once..
+
+#include <stddef.h>
+#include <stdint.h>
+
+// 3-args syscall
 static inline long syscall3(long n, long a, long b, long c) {
     long ret;
 
     __asm__ volatile (
         "int $0x80"
         : "=a"(ret)
-        : "a"(n), "D"(a), "S"(b), "d"(c)
+        : "a"(n), "D"(a), "S"(b), "d"(c) // a = rax, D = rdi, S = rsi, d = rdx
         : "memory"
     );
 
     return ret;
 }
 
-static inline void write(int fd, const char* buf, long len) {
-    syscall3(1, fd, (long)buf, len);
+// 4-args syscall
+static inline long syscall4(long n, long a, long b, long c, long d) {
+    long ret;
+    register long r10 __asm__("r10") = d;
+
+    __asm__ volatile (
+        "int $0x80"
+        : "=a"(ret)
+        : "a"(n), "D"(a), "S"(b), "d"(c), "r"(r10)
+        : "memory"
+    );
+
+    return ret;
+}
+
+// Single-arg syscall
+static inline long syscall1(long n, long a) {
+    return syscall3(n, a, 0, 0);
+}
+
+static inline int write(int fd, const char* buf, long len) {
+    return (int)syscall3(1, fd, (long)buf, len);
+}
+
+static inline int read(int fd, char* buf, long len) {
+    return (int)syscall3(0, fd, (long)buf, len);
+}
+
+static inline int open(const char* path, int flags) {
+    return (int)syscall3(2, (long)path, flags, 0);
+}
+
+static inline int close(unsigned int fd) {
+    return (int)syscall3(3, fd, 0, 0);
+}
+
+static inline int seek(int fd, int offset, int whence) {
+    return (int)syscall3(8, fd, offset, whence);
+}
+
+static inline int tell(unsigned int fd) {
+    return (int)syscall1(9, fd);
+}
+
+static inline int eof(unsigned int fd) {
+    return (int)syscall1(10, fd);
+}
+
+static inline int draw(const unsigned char* buf, int width, int height, int channels) {
+    return (int)syscall4(11, (long)buf, width, height, channels);
 }
 
 static inline void exit(int code) {