From 61927b3f2960105d888c4fec7a6f5caed38d6be9 Mon Sep 17 00:00:00 2001
From: ummthespruce <130300985+ummthespruce@users.noreply.github.com>
Date: Tue, 31 Oct 2023 11:10:40 +0200
Subject: [PATCH] software-stack/lab: Add arm implementation for basic-syscall
 exercise

Add arm skeleton from basic-syscall exercise

Signed-off-by: Andrei Lipan <andreivlipan2003@gmail.com>
---
 .../lab/support/basic-syscall/arm/Makefile    | 18 +++++++
 .../lab/support/basic-syscall/arm/hello.s     | 54 +++++++++++++++++++
 2 files changed, 72 insertions(+)
 create mode 100644 content/chapters/software-stack/lab/support/basic-syscall/arm/Makefile
 create mode 100644 content/chapters/software-stack/lab/support/basic-syscall/arm/hello.s

diff --git a/content/chapters/software-stack/lab/support/basic-syscall/arm/Makefile b/content/chapters/software-stack/lab/support/basic-syscall/arm/Makefile
new file mode 100644
index 0000000000..ba8fab91af
--- /dev/null
+++ b/content/chapters/software-stack/lab/support/basic-syscall/arm/Makefile
@@ -0,0 +1,18 @@
+CC = aarch64-linux-gnu-gcc
+AS = aarch64-linux-gnu-as
+QEMU = qemu-aarch64
+
+.PHONY: all clean
+
+all: hello
+
+hello: hello.o
+
+hello.o: hello.s
+
+run: hello
+	$(QEMU) ./hello
+
+clean:
+	-rm -f hello.o hello
+	-rm -f *~
diff --git a/content/chapters/software-stack/lab/support/basic-syscall/arm/hello.s b/content/chapters/software-stack/lab/support/basic-syscall/arm/hello.s
new file mode 100644
index 0000000000..10390a57b3
--- /dev/null
+++ b/content/chapters/software-stack/lab/support/basic-syscall/arm/hello.s
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+
+.section .bss
+
+    .lcomm buffer, 128
+
+    /*
+     * We need to add some padding due to a QEMU bug, present
+     * on the 4.2.1 version, that produces a SEGFAULT;
+     * the program works perfectly fine otherwise
+     */
+    .p2align 12
+
+.equ len, 128
+
+.section .rodata
+
+hello:
+    .ascii "Hello, world!\n\0"
+
+bye:
+    .ascii "Bye, world!\n\0"
+
+.section .text
+
+.global main
+
+
+
+main:
+    /* syscall calling in arm found at */
+    /* https://arm64.syscall.sh/ */
+
+    /* needed instructions: */
+
+    /* mov <register>, #<value> , moves an 8 bit value*/
+    /* ldr <register>, =<value>,loads a value, usually an address */
+    /* svc #<value>, syscall (use value 0 for syscall) */
+    /* ret , return*/
+
+
+    /* Call write(1, "Hello, world!\n", 14). */
+    /* x8 <- __NR_write (index of write syscall: 64) */
+    /* x0 <- first syscall argument (fd: 1) */
+    /* x1 <- second syscall argument (buffer: hello) */
+    /* x2 <- third syscall argument (length: 14) */
+
+
+    /* Call exit(0). */
+    /* x8 <- __NR_exit (index of exit syscall: 93) */
+    /* x0 <- first syscall argument (error_code: 0) */
+
+
+    ret