Re: [PATCH] compat: fix compat_sys_openat and friends

[Linus Torvalds <torvalds@osdl.org>]

On Thu, 2 Feb 2006, Stephen Rothwell wrote:
>
> Most of the 64 bit architectures will zero extend the first argument to
> compat_sys_{openat,newfstatat,futimesat} which will fail if the 32 bit
> syscall was passed AT_FDCWD (which is a small negative number).  Declare
> the first argument to be an unsigned int which will force the correct
> sign extension when the internal functions are called in each case.

Umm.

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.

		Linus