From: Linus Torvalds <[email protected]>
Date: Wed, 1 Feb 2006 21:36:40 -0800 (PST)
> Wouldn't it be _much_ better to declare the argument as a "long", since
> some architectures (alpha, for example) may assume that 32-bit arguments
> have been _sign_extended, not zero-extended.
>
> Then, when the "compat_sys_xxxx()" function passes the "long" down to the
> _real_ function (which takes an "int"), those architectures (and only
> those architectures) that actually have assumptions about high bits will
> have the compiler automatically do the right zero- or sign-extensions at
> that call-site.
There is the convention that for the compat system calls all the args
will be 32-bit zero extended by the platform syscall entry code before
the C code is invoked. This topic used to come up a lot and finally
we all decided that was the thing to do.
It's important (at least I think so :-) for all of this generic compat
code to be able to have a well defined argument environment.
Anyways, I think that's how Stephen arrived at his patch.
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