Complete project

src/user.c

@@ -2,17 +2,41 @@
 
 extern char __stack_top[];
 
+int syscall(int sysno, int arg0, int arg1, int arg2) {
+    register int a0 __asm__("a0") = arg0;
+    register int a1 __asm__("a1") = arg1;
+    register int a2 __asm__("a2") = arg2;
+    register int a3 __asm__("a3") = sysno;
+
+    __asm__ __volatile__("ecall"
+                         : "=r"(a0)
+                         : "r"(a0), "r"(a1), "r"(a2), "r"(a3)
+                         : "memory");
+
+    return a0;
+}
+
+void putchar(char ch) { syscall(SYS_PUTCHAR, ch, 0, 0); }
+
+int getchar(void) { return syscall(SYS_GETCHAR, 0, 0, 0); }
+
+int readfile(const char *filename, char *buf, int len) {
+    return syscall(SYS_READFILE, (int)filename, (int)buf, len);
+}
+
+int writefile(const char *filename, const char *buf, int len) {
+    return syscall(SYS_WRITEFILE, (int)filename, (int)buf, len);
+}
+
 __attribute__((noreturn)) void exit(void) {
+    syscall(SYS_EXIT, 0, 0, 0);
     for (;;)
         ;
 }
 
-void putchar(char c) { /* Доделать*/ }
-
 __attribute__((section(".text.start"))) __attribute__((naked)) void
 start(void) {
-    __asm__ __volatile__(
-        "mv sp, %[stack_top] \n"
-        "call main           \n"
-        "call exit           \n" ::[stack_top] "r"(__stack_top));
+    __asm__ __volatile__("mv sp, %[stack_top]\n"
+                         "call main\n"
+                         "call exit\n" ::[stack_top] "r"(__stack_top));
 }