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Diffstat (limited to 'src/arch')
| -rw-r--r-- | src/arch/README.md | 1 | ||||
| -rw-r--r-- | src/arch/arm64.md | 65 |
2 files changed, 66 insertions, 0 deletions
diff --git a/src/arch/README.md b/src/arch/README.md index 48f0332..b14cd98 100644 --- a/src/arch/README.md +++ b/src/arch/README.md @@ -1,3 +1,4 @@ # Arch - [x86_64](./x86_64.md) +- [arm64](./arm64.md) diff --git a/src/arch/arm64.md b/src/arch/arm64.md new file mode 100644 index 0000000..2286bd8 --- /dev/null +++ b/src/arch/arm64.md @@ -0,0 +1,65 @@ +# arm64 +keywords: arm64, aarch64, abi + +- 64bit synonyms: `arm64`, `aarch64` +- ISA type: `RISC` +- Endianness: `little`, `big` + + +## ASM skeleton +Small assembler skeleton, ready to use with following properties: +- use raw Linux syscalls (`man 2 syscall` for ABI) +- no `C runtime (crt)` +- gnu assembler [`gas`][gas_doc] +```armasm +// file: greet.S + +#include <asm/unistd.h> // syscall NRs + + .arch armv8-a + + .section .text, "ax", @progbits + .align 2 + .global _start +_start: + mov x0, 2 // fd + ldr x1, =greeting // buf + ldr x2, =greeting_len // &len + ldr x2, [x2] // len + mov w8, __NR_write // write(2) syscall + svc 0 + + mov x0, 0 // exit code + mov w8, __NR_exit // exit(2) syscall + svc 0 + + .align 3 + .section .rodata, "a", @progbits +greeting: + .asciz "Hi ASM-World!\n" +greeting_len: + .int .-greeting +``` +> man gcc: `file.S` assembler code that must be preprocessed. + +To cross-compile and run: +```bash +> aarch64-linux-gnu-g++ -o greet greet.S -nostartfiles -nostdlib \ + -Wl,--dynamic-linker=/usr/aarch64-linux-gnu/lib/ld-linux-aarch64.so.1 \ + && qemu-aarch64 ./greet +Hi ASM-World! +``` +> Cross-compiling on `Ubuntu 20.04`, paths might differ on other distributions. +> Compiling natively on arm64, specifying the dynamic linker should not be required. + +## References +- [Procedure Call Standard ARM64][aapcs64] +- [ARMv8 Programmer's Guide][armv8a_prog_guide] +- [GNU Assembler][gas_doc] +- [GNU Assembler Directives][gas_directives] + + +[aapcs64]: https://github.com/ARM-software/abi-aa/blob/master/aapcs64/aapcs64.rst +[armv8a_prog_guide]: https://developer.arm.com/documentation/den0024/a +[gas_doc]: https://sourceware.org/binutils/docs/as +[gas_directives]: https://sourceware.org/binutils/docs/as/Pseudo-Ops.html#Pseudo-Ops |