Fixed read loop glitch

helper.s

@@ -64,6 +64,7 @@ read:
 # rsi = char*
 write:
   push r15
+  push r11
   mov r15, rdi
   mov rdi, rsi # no need to touch rsi
   call count
@@ -73,6 +74,7 @@ write:
   mov rdi, r15
 
   syscall
+  pop r11
   pop r15
   ret
 
@@ -80,9 +82,9 @@ write:
 count:
   mov rax, rdi
 count_loop:
-  mov r8b, [rax]
+  mov r9b, [rax]
   inc rax
-  cmp r8b, 0
+  cmp r9b, 0
   jnz count_loop
   dec rax
   sub rax, rdi