On 22 August 2014 14:27, Andreas Färber <afaer...@suse.de> wrote: > Am 22.08.2014 14:09, schrieb Laurent Vivier: >> as in the kernel timer_t is an "int" (as said PMM), you should cast to >> "int" to remove garbage on 64bit hosts and check sign ... > > So maybe that's the bug Alex was trying to fix downstream with the use > of unsigned types?
I imagine the reason the SuSE tree switches to abi_ulong for the arg* is that it fixes a bunch of bugs we have where we're incorrectly casting a (probably 32 bit) abi_long to a 64 bit signed host type and getting a sign-extension, when the semantics of those particular syscalls require unsigned values. But conversely the change probably means that places which wanted the sign-extension are no longer getting it. If we were writing this code from scratch then there's probably a good argument for making the arg* be the unsigned type rather than signed. Unfortunately at this point it's basically impossible to change over, because we'd have to audit every use of them in a 10,000 line file to determine whether we needed to put a cast back in to get sign extension or not. I'd rather we just fixed the places that don't want sign-extension, because presumably we at least have examples of failing guest programs we can use to tell us what the problematic syscalls are... -- PMM
