From 8db222397eebaececbb1adff41404a65fb474e45 Mon Sep 17 00:00:00 2001
From: dwrz <dwrz@dwrz.net>
Date: Thu, 16 Mar 2023 00:54:00 +0000
Subject: [PATCH] Add exit

---
 exit/exit.s | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 exit/exit.s

diff --git a/exit/exit.s b/exit/exit.s
new file mode 100644
index 0000000..e89cddf
--- /dev/null
+++ b/exit/exit.s
@@ -0,0 +1,37 @@
+#PURPOSE:   Simple program that exits and returns a
+#           status code back to the Linux kernel
+#
+
+#INPUT:     none
+#
+
+#OUTPUT:    returns a status code  This can be viewed
+#           by typing
+#
+#           echo $?
+#
+#           after running the program
+#
+
+#VARIABLES:
+#           %rax holds the system call number
+#           %rbx holds the return status
+#
+.section .data
+
+.section .text
+.globl _start
+
+_start:
+mov $1, %rax       # this is the linux kernel command
+                    # number (system call) for exiting
+                    # $ means immediate mode addressing,
+                    # without $ it defaults to direct
+                    # mode, looking up a number in
+                    # address 1
+
+mov $0, %rbx       # this is the status number we will
+                    # return to the OS
+
+int $0x80           # this wakes up the kernel to run the
+                    # exit command