Segmentation fault when switching system call the "int" to "syscall" in Assembly x86 linux

Question

When I change the system call of int $0x80 for syscall or sysenter in this code:

    mov $4, %rax
    mov $1, %rbx
    mov $String1, %rcx
    mov $16, %rdx
    int $0x80

the program ends up in Segmentation fault. In GDB it shows:

Program Received Signal SIGSEGV, Segmentation fault. 0x0000f7ffdbe9 in ?? ()

Why is this change making this impact? Thank you

Answer 1

• syscall is for x86_64
• sysenter is for 32 bits
• int 0x80 works for both

This is a summary of the same question in:
https://stackoverflow.com/questions/12806584/what-is-better-int-0x80-or-syscall