Anatomy of a system call, part 1 [LWN.net]

Anatomy of a system call, part 1

Posted Jul 11, 2014 9:53 UTC (Fri) by sasha (guest, #16070)
In reply to: Anatomy of a system call, part 1 by geuder
Parent article: Anatomy of a system call, part 1

> What is the technical reason to have partially architecture specific syscall number?

For "compatibility" with other, older OSes used on the architecture. No, I do not understand what kind of "compatibility" you can get in such a way, but it is the main reason.

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Anatomy of a system call, part 1

Posted Jul 11, 2014 16:55 UTC (Fri) by alonz (subscriber, #815) [Link] (2 responses)

I believe by now the reason is mainly historical.

Originally (in the days of Linux 1.x / 2.0) Linux attempted to be binary compatible to existing Unices on common hardware (the personality(2) system call is also part of this). As time passed, compatibility with other Unices became mostly a non-issue – but now we do need to maintain binary compatibility with older Linux binaries…

Anatomy of a system call, part 1

Posted Jul 11, 2014 22:12 UTC (Fri) by geuder (subscriber, #62854) [Link] (1 responses)

> Originally (in the days of Linux 1.x / 2.0) Linux attempted to be binary compatible to existing Unices on common hardware

That sounds like a reasonable explanation. Besides that back in those days what Unices were running on x86_64 and ARM? And these 2 differ. Yeah well, maybe the dependencies are not direct, but somehow indirect over other platforms?

Anatomy of a system call, part 1

Posted Jul 11, 2014 22:22 UTC (Fri) by sfeam (subscriber, #2841) [Link]

As I recall, linux binaries for alpha would run under Digital Unix on alpha.