4 ms·

I'd love to see a version of this done using the linux amd64 syscall abi. I've written similar programs for 32bit linux (I know the syscall instruction by heart

I'd love to see a version of this done using the linux amd64 syscall abi. I've written similar programs for 32bit linux (I know the syscall instruction by heart: int 0x80), but I understand 64bit is more complex.

nitrogen 12y ago
Sounds complicated, if AMD and Intel both use different instructions for system calls: http://wiki.osdev.org/Sysenter http://wiki.osdev.org/Sysenter http://articles.manugarg.com/systemcallinlinux2_6.html http://articles.manugarg.com/systemcallinlinux2_6.html
- oso2k 12y ago
  syscall is the standard ABI for a 64-bit kernel in Long Mode [0]. [0] http://wiki.osdev.org/SYSENTER#Compatibility_across_Intel_and_AMD http://wiki.osdev.org/SYSENTER#Compatibility_across_Intel_an...
oso2k 12y ago
The syscall version isn't much more complex. You can compare the syscall ABIs here [0] [0] http://en.wikibooks.org/wiki/X86_Assembly/Interfacing_with_Linux#Making_a_syscall http://en.wikibooks.org/wiki/X86_Assembly/Interfacing_with_L...
tbirdz 12y ago
I don't know if I would call it harder, it's just a bit different is all. Here you go: ; Hello World, linux x86_64, nasm syntax section .rodata ; Begin read only data section hello: db "Hello, World",0x0a ; String, 0x0a is \n hello_len equ $-hello ; $ is current address, length is address after string - address of start of string section .text ; begin code section global _start ; export _start so the linker can see it _start: ; program entry point mov rax, 1 ; write(2) syscall number mov rdi, 1 ; stdout mov rsi, hello ; string address mov rdx, hello_len ; string length syscall ; execute the write syscall mov rax, 60 ; exit(2) syscall number mov rdi, 0 ; exit status syscall ; execute the exit syscall

nitrogen 12y ago

Sounds complicated, if AMD and Intel both use different instructions for system calls: http://wiki.osdev.org/Sysenter http://wiki.osdev.org/Sysenter http://articles.manugarg.com/systemcallinlinux2_6.html http://articles.manugarg.com/systemcallinlinux2_6.html

oso2k 12y ago
syscall is the standard ABI for a 64-bit kernel in Long Mode [0]. [0] http://wiki.osdev.org/SYSENTER#Compatibility_across_Intel_and_AMD http://wiki.osdev.org/SYSENTER#Compatibility_across_Intel_an...

oso2k 12y ago

The syscall version isn't much more complex. You can compare the syscall ABIs here [0] [0] http://en.wikibooks.org/wiki/X86_Assembly/Interfacing_with_Linux#Making_a_syscall http://en.wikibooks.org/wiki/X86_Assembly/Interfacing_with_L...

tbirdz 12y ago

I don't know if I would call it harder, it's just a bit different is all. Here you go: ; Hello World, linux x86_64, nasm syntax section .rodata ; Begin read only data section hello: db "Hello, World",0x0a ; String, 0x0a is \n hello_len equ $-hello ; $ is current address, length is address after string - address of start of string section .text ; begin code section global _start ; export _start so the linker can see it _start: ; program entry point mov rax, 1 ; write(2) syscall number mov rdi, 1 ; stdout mov rsi, hello ; string address mov rdx, hello_len ; string length syscall ; execute the write syscall mov rax, 60 ; exit(2) syscall number mov rdi, 0 ; exit status syscall ; execute the exit syscall