From 495c13b6993d5e7efdf5180a9e3de07c1f0c7fe8 Mon Sep 17 00:00:00 2001
From: FreeArtMan <dos21h@gmail.com>
Date: Mon, 21 Jun 2021 22:32:16 +0100
Subject: Initial arm64 hello world

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+title:ARM64 assembly hello world
+keywords:assembly,m1,arm64,macos,linux
+
+# ARM64 assembly hello world
+
+## Intro
+
+Hello world in ARM64 assembly for Linux and Macos. First example
+is how to compile hello world for raspberry pi 4, as its supports
+ARMv8 instruction set. Second example is how to run assembly on 
+Apple M1 chip that also supports ARMv8 instruction set
+
+Two assembly examples are equivalent to C code
+
+```c
+int main() {
+    char *s="Hello ARM64";
+    write(1,s,strlen(s));
+    exit(0);
+}
+```
+
+## Raspberry Pi 4
+
+Running 64bit linux. To detect with architecture and what bitness of 
+os run command
+
+```
+uname
+```
+
+Architecture shown as aarch64 good enoughs to indicate that os ir 64bit
+```
+Linux raspberrypi 5.4.42-v8+ #1319 SMP PREEMPT Wed May 20 14:18:56 BST 2020 aarch64 GNU/Linux
+```
+
+
+```asm
+.data
+
+/* Data segment: define our message string and calculate its length. */
+msg:
+    .ascii        "Hello, ARM64!\n"
+len = . - msg
+
+.text
+
+/* Our application's entry point. */
+.globl _start
+_start:
+    /* syscall write(int fd, const void *buf, size_t count) */
+    mov     x0, #1      /* fd := STDOUT_FILENO */
+    ldr     x1, =msg    /* buf := msg */
+    ldr     x2, =len    /* count := len */
+    mov     w8, #64     /* write is syscall #64 */
+    svc     #0          /* invoke syscall */
+
+    /* syscall exit(int status) */
+    mov     x0, #0      /* status := 0 */
+    mov     w8, #93     /* exit is syscall #1 */
+    svc     #0          /* invoke syscall */
+```
+
+### Compile
+
+Too compile check if there is installed gnu gcc, other compilers such as clang also 
+should work perfectly fine.
+
+```makefile
+    as hello.s -o hello.o
+    gcc hello.o -o hello
+```
+
+
+
+## Apple M1
+
+
+```asm
+.global _start            // Provide program starting address to linker
+.align 2            // Make sure everything is aligned properly
+
+// Setup the parameters to print hello world
+// and then call the Kernel to do it.
+_start: 
+    mov    X0, #1        // 1 = StdOut
+    adr    X1, helloworld     // string to print
+    mov    X2, #13            // length of our string
+    mov    X16, #4        // Unix write system call
+    svc    #0x80        // Call kernel to output the string
+
+// Setup the parameters to exit the program
+// and then call the kernel to do it.
+    mov     X0, #0        // Use 0 return code
+    mov     X16, #1        // System call number 1 terminates this program
+    svc     #0x80        // Call kernel to terminate the program
+
+helloworld:      .ascii  "Hello World!\n"
+```
+
+### Compile
+
+Install xcode tools before compilation
+
+```makefile
+    as -o hello.o hello.s
+	ld -macosx_version_min 11.0.0 -o hello hello.o -lSystem -syslibroot `xcrun -sdk macosx --show-sdk-path` -e _start -arch arm64
+```
+
+## Links
+
+[https://en.wikipedia.org/wiki/ARM_architecture#ARMv8](https://en.wikipedia.org/wiki/ARM_architecture#ARMv8)   
+[https://smist08.wordpress.com/2021/01/08/apple-m1-assembly-language-hello-world/](https://smist08.wordpress.com/2021/01/08/apple-m1-assembly-language-hello-world/)  
+[https://github.com/below/HelloSilicon](https://github.com/below/HelloSilicon)  
+[https://thinkingeek.com/2013/01/09/arm-assembler-raspberry-pi-chapter-1/](https://thinkingeek.com/2013/01/09/arm-assembler-raspberry-pi-chapter-1/  
+[https://s-matyukevich.github.io/raspberry-pi-os/docs/lesson01/rpi-os.html](https://s-matyukevich.github.io/raspberry-pi-os/docs/lesson01/rpi-os.html)  
+[https://peterdn.com/post/2020/08/22/hello-world-in-arm64-assembly/](https://peterdn.com/post/2020/08/22/hello-world-in-arm64-assembly/)  
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