Date: Mon, 18 May 2015 15:32:12 +0200 From: Arnd Bergmann <arnd@...db.de> To: y2038@...ts.linaro.org Cc: Thorsten Glaser <tg@...bsd.de>, klibc@...or.com, libc-alpha@...rceware.org, linux-api@...r.kernel.org, musl@...ts.openwall.com, linux-kernel@...r.kernel.org, Rich Felker <dalias@...c.org>, cferris@...gle.com, enh@...gle.com, "Joseph S. Myers" <joseph@...esourcery.com> Subject: Re: [Y2038] [klibc] kernel/libc uapi changes for y2038 On Monday 18 May 2015 12:16:48 Thorsten Glaser wrote: > Arnd Bergmann dixit: > > >In the patch series I posted recently , I introduce new system calls to deal > >with modified data structures, but left the question open on how these should > >be best accessed from libc. The patches introduce a new __kernel_time64_t type > > Can we please have ioctls fixed for mixed 32/64-bit systems > such as MIPS (o32/n32/n64) and x86 (i386/x32/amd64) first, > before even more such chance for breakage is introduced? It's hard because we don't even know what ioctls are affected at this point, and I was hoping to get this part merged as a stepping stone in the process of finding out. The problem is that there are so many different cases we have to worry about just for time_t: a) ioctls that pass a data structure from include/uapi/ with time_t and have a properly defined (using _IOW()/_IOR()/_IORW()) command number: these are easy enough to find and fix. b) ioctls that have a data structure as before but define their ioctl commands differently (e.g. using a literal number). I don't think we can fix them before we introduce the __KERNEL_TIME_BITS macro from my patch, because user space needs to see a different command number here, and we have a lot of these. c) ioctls that are defined ad-hoc, without any uapi header containing the structure, but using a proper _IOW()/_IOR()/_IORW() macro. These are much harder to find than a), but just as easy to fix d) ioctls that are defined ad-hoc based on a time_t value and with a wrong command number. These will be broken no matter what we do, and our only hope is to find all applications using them so we can fix the user space sources. e) ioctls that pass a time value as a 'long' or '__u32' instead of 'time_t'. Fixing them requires adding new ioctl commands to let them work beyond 2038, independent of what we do here. f) ioctls that use structures with pointers to other structures that are not defined in the uapi headers. (this might not be a problem, I haven't been able to figure out of these are real) All of the above are currently broken for x32, but fixing them will likely take a few years and leave x32 still broken because of other uses of __kernel_long_t in ioctl. MIPS on the other hand is no more broken than any of the other 32-bit ABIs, because it does not use 64-bit __kernel_long_t in its n32 ABI. > I still need to use an amd64 chroot on my x32 system to do > things such as set up iptables, because those ioctls break, > because they contain data structures that contain, well, > time types. Your proposal has a non-zero chance to bring > these issues to i386 (and other architectures). We should indeed not start widely deploying user space with 64-bit time_t on 32-bit architectures until we found and fixed a good part of the ioctls. My plan at this point is to eliminate all uses of time_t in the kernel and replace them with time64_t or other safe types. This way, we will eventually find all code that passes 32-bit time types to user space and can fix it. This will take care of the time_t related problems on x32 as well. Arnd
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