Added arm directory to exercise 3

Signed-off-by: ummthespruce <[email protected]>

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 *~

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