CODEWITHSUNDEEP
macosassemblyarm64mach-o
Mmakabaka1880
Mmakabaka1880

Reputation: 43

How do I put label definitions in the `.bss` section and get the symbol address into a register in AArch64 Mach-O Assembly?

Entry Info
Computer MacBook 2022 M2 13 inch 24GB
OS MacOS 15.1 Beta 2405055e
Compiling Command as as -g hello.s -o hello.o && ld -o hello.exec hello.o -lSystem -syslibroot `xcrun -sdk macosx --show-sdk-path` -e _start -arch arm64

Hi nice people at SO

I'm new to assembly, and I'm learning Mach-O AArch64 asm. I'm trying to create a simple print(input()) program, by allocating a buffer, reading it through STDIN, and then output it through STDOUT.

I had the problem of not able to write to the buffer section, but some nice people told me to put the declaration(or definition?) of the label in the .bss section. This worked just fine on my raspi 4B

.section .bss
buffer: .skip 128

How can I do it on a mach-o system? If I used the same code, the compiler complains about “unknown AArch64 fixup kind”

Here's my code:

.global _start
.align 8

_start: mov X0, #0
        adr X1, buffer
        mov X2, #128
        mov X8, #63
        svc #0

        mov X0, #1
        mov X2, #5
        mov X8, #64
        svc #0

        mov X0, #0
        mov X8, #93
        svc #0

.section .bss
buffer: .skip 128

Upvotes: 1

Views: 25

Answers (0)

Related Questions