Messages in this thread | | | Date | Fri, 8 Jan 2010 16:34:43 +0100 | From | Christoph Hellwig <> | Subject | Re: [PATCH v3 3/3] generic sys_ipc wrapper |
| |
On Fri, Jan 08, 2010 at 11:57:17AM +0100, Arnd Bergmann wrote: > > Add a generic implementation of the ipc demultiplexer syscall. Except for > > s390 and sparc64 all implementations of the sys_ipc are nearly identical. > > I think the s390 version is trivial to add as well, like > > SYSCALL_DEFINE5(s390_ipc, uint, call, int, first, unsigned long, second, > unsigned long, third, void __user *, ptr) > { > if (call == SEMTIMEDOP) > return sys_semtimedop(first, (struct sembuf __user *)ptr, > (unsigned) second, > (const struct timespec __user *)third); > > return sys_ipc(call & 0xffff, first, second, third, ptr, 0); > }
Possiblly. Not sure if it's worth it, though. If the s390 maintainers want it I'd say do it as a separate patch.
> But while going over the code again, I noticed that you broke sign extension > at least on powerpc and s390, possibly on all 64 bit machines:
> > + return -EINVAL; > > + if (get_user(fourth.__pad, (void __user * __user *) ptr)) > > + return -EFAULT; > > + return sys_semctl(first, second, third, fourth); > > return sys_semctl(first, (int)second, third, fourth);
What does the explicit case buy us in terms of sign-extension over the implicit one given that the second argument to sys_semctl already is types as int?
> This is needed to make sure the upper half of the register is filled with > zero-extended or sign-extended correctly and does not contain random garbage > in the native 64 bit case. IIRC, x86_64 does not have this problem and mips64 > may have the wrong code already. Alpha, parisc and ia64 don't have a native > sys_ipc and the rest are 32 bit, so they don't care.
I can fix it up, but I don't quite understand the need.
| |