Why doesn’t the ‘syscall’ instruction work under Linux?

I have a very basic assembly program that runs in Linux userland:

section .text
global _start

_start:
    mov edx, 14
    mov ecx, msg
    mov ebx, 1
    mov eax, 4
    syscall

    mov eax, 1
    syscall

section .data
msg db "Hello, World!", 0xA

However, this doesn’t work as it is, but only if I replace the syscalls with int 0x80. Don’t these do the same thing? I know that syscall was designed to be lower-latency, but other than that, I didn’t think there was a difference. Why doesn’t it work?

Answer

syscall works only in x86-64 operating systems and you should put the system call number in rax register instead of eax. See this website for more information.