I am messing around with my new raspberry pi and I am fairly new to assembly. I have scoured Google and SO for a solution to this, and this was the closest I got to having a running program.
main.s (comments are from explanations I've found on the internet)
.section .text
.global _start
_start:
mov x0, #0 // return value 0 for success
mov x7, #1 // 1 is exit in the vector table
svc 0 // execute the system call to exit the program
I then assemble with as main.s -o main.o and link with ld main.o -o main. Running with ./main outputs "Illegal instruction (core dumped)".
It's a Raspberry Pi Model B running ARM Arch Linux on a 64-bit quad-core ARM Cortex-A53.
Goal: Have an ARM assembly program compiled and linked with only as and ld that will exit successfully
In the man page for syscall, it states that the arm64 architecture calling convention for syscalls is: "argument: x8" and "instruction: svc #0". On this github project, the syscall argument for 'exit' is defined as '93'. Therefore, this is a working, exiting, and succeeding arm program compiled using only as and ld...
.section .text
.global _start
_start:
mov x0, #0 // exit with status 0
mov x8, #93 // svc argument goes in x8, and the argument for 'exit' is 93
svc #0 // executes a syscall in arm64
Another answer on SO with useful info on system calls