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Re: RFD: x32 ABI system call numbers

Aug 31, 2011, 17:20 (0 Talkback[s])


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"From Linus Torvalds <>
Subject Re: RFD: x32 ABI system call numbers

On Mon, Aug 29, 2011 at 12:01 PM, Geert Uytterhoeven
> Which will break all this non-portable 32-bit-only source code x32 was invented
> for in the first place?


Guys, get a f&*king grip already!

There are absolutely ZERO compatibility issues.

If you want compatibility, you run traditional 32-bit x86.

If you want full 64-bit, you run standard x86-64 binaries.

x32 is *not* about compatibility. It's about pure performance, and perhaps smaller binaries. Nothing else. If you start blathering about "compatibility", you're so on the wrong track that it isn't even funny!

I would seriously suggest that if you want compatible ioctl's, don't use x32. There's no point. It's not why x32 exists. If this turns into a "let's add a new compat layer", or "let's just re-do x86-32 all over again just using "syscall", I think the whole thing is totally pointless.

If something isn't performance-sensitive, why do it in x32 at all? It involves new libraries, new compiler support, new calling conventions, and it will be *less well supported* than the traditional compat mode.

The *only* reason to use x32 is:

- you get all the new x86-64 registers, and the improved calling convention (big registers, more of them)

- you get a faster system call.

- smaller memory footprint (32-bit pointers and long).

But no, "compatibility" isn't one of those reasons. You won't be able to use old libraries, you won't even be able to use an old compiler,and I would seriously suggest that maybe we shouldn't care about the more esoteric ioctl's if they end up being a pain.


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