Re: [PATCH] sendfile compat functions on x86_64 and ia64
From: Alexey Toptygin
Date: Fri May 05 2006 - 16:44:07 EST
On Fri, 5 May 2006, Andi Kleen wrote:
With your change there wouldn't be any sign extension and rw_verify_area
couldn't reject negative values them anymore.
I think it would be a wrong change because it would differ from a native
32bit kernel.
No...
On a 32 bit kernel (and on a 64 bit kernel using the native interface),
count is passed to sendfile as unsigned. rw_verify_area explicitly casts
to signed before checking for negativeness. The only place anywhere in the
kernel that count is signed (other than where rw_verify area explicitly
casts it for one test) is in the declaration of sys32_sendfile in the
x86_64 compat code. I'm pretty sure it's supposed to be unsigned there
too, and the current code is a typo.
Alexey
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