Hi all,
I'm trying to learn x86-64 assembly on OpenBSD starting with a little
"Hello OpenBSD!" to the console. I'm also not using libc because I
want to understand what writing assembly is like at the syscall level.
My main issue is with pinsyscalls and I'm not sure how
to implement it with handwritten assembly and I could not find any
examples of it online.
My current assembly looks like this:
.section ".note.openbsd.ident", "a"
.p2align 2
.long 8
.long 4
.long 1
.ascii "OpenBSD\0"
.long 0
.p2align 2
.section .data
msg: .ascii "Hello OpenBSD!"
.byte 10
.section .text
.globl _start
_start:
movq $4, %rax # write opcode
movq $1, %rdi # stdout
movq $msg, %rsi # msg buffer
movq $15, %rdx # msg length
syscall
movq $1, %rax # exit opcode
movq $0, %rdi # error code 0
syscall
I assemble and link it with these commands (main.s is the src file):
OpenBSD-is-king$ as main.s -o main.o
OpenBSD-is-king$ ld --no-pie main.o -o main
Once I ran the final executable, that's where I got the error:
OpenBSD-is-king$ ./main
main[28033]: pinsyscalls addr 2011c4 code 4, pinoff 0xffffffff
(pin 0 0-0 0) (libcpin 0 0-0 0) error 78
Abort trap (core dumped)
Reading the pinsyscalls man page (man pinsyscalls) says that the
syscalls all need to be in some certain memory block or program will
abort. I dont know how to implement this in assembly, perhaps a
separate section or something like that??
Any help, explanations, docs, or source code solutions would be
appreciated.
Thanks in advance for the time 'n help
