I don't really think so. They're OSs that, when they added support for x86-64 CPUs, all opted to use the externally-defined ELF executable file format with the

I don't really think so. They're OSs that, when they added support for x86-64 CPUs, all opted to use the externally-defined ELF executable file format with the x86-64-sysv ABI. Note also that the architecture/ABI already includes a dedicated `syscall` assembly instruction. On top of that, 3 of the OSs (FreeBSD, NetBSD, OpenBSD) share a common source code ancestry, meaning that the oldest and most fundamental Unix system calls (like `write(2)`) had an excellent chance of remaining compatible. Yes, calling write(2) on Linux is different, but only in the syscall number. That's also not a coincidence, as the behaviour of write() is highly constrained by POSIX which Linux and the BSDs both adhere to, and the way to pass parameters to the call is specified by the `syscall` instruction. That there are enough differences in the environment to be able to figure out which of Linux or *BSD the program is running on is a bit of luck, but probably not that much.