Fix read input from user program

programs/keyboard/src/main.cpp

@@ -11,9 +11,12 @@
 const char* source = "Hello world";
 
 int main(){
+    char buffer[16];
+
     for(int i = 0; i < 10; ++i){
-        auto c = read_char();
-        print(c);
+        auto c = read_input(buffer, 15);
+        buffer[c] = '\0';
+        print(buffer);
     }
 
     exit(0);

userlib/include/print.hpp

@@ -47,12 +47,12 @@ void print_line(size_t v){
     print_line();
 }
 
-char read_char(){
+size_t read_input(char* buffer, size_t max){
     size_t value;
     asm volatile("mov rax, 3; int 50; mov %0, rax"
         : "=m" (value)
-        : //No inputs
-        : "rax", "rbx");
+        : "b" (buffer), "c" (max)
+        : "rax");
     return value;
 }