On Tue, 13 Feb 2007, Stephen Rothwell wrote:
> A better way here might be to have each 64 bit architecture define
> compat_epoll_event in its asm/compat.h and then you can just use:
>
> if (copy_from_user(&user, event, sizeof(user)))
> return -EFAULT;
> kernel = compat_alloc_user_space(sizeof(struct epoll_event));
> err |= __put_user(user.events, &kernel->events);
> err |= __put_user(user.data, &kernel->data);
>
> And you shouldn't need the compat routine if
> offsetof(struct compat_epoll_event, data) == offsetof(struct epoll_event, data).
That is *definitely* better, because at that point you can make them also
define a NEED_COMPAT_EPOLL_{CTL,WAIT}, and that code can be excluded
altogether if not needed. I simply wanted to reduce work for arch
maintainers, but I'm all for something like the above.
> OK, I have thought about this some more and I *think* the only
> architecture that needs compat_sys_epoll_ctl or compat_sys_epoll_wait is
> ia64 where the 64 bit version of struct epoll_event is different from the
> 32 bit version. On x86_64, the struct is explictly packed (so it is the
> same as the 32 bit version) and on all the other 64 bit architectures the
> alignment of the u64 is the same as the equivalent 32 bit version.
>
> Since ia64 already has its own version of these two, we only have to
> worry about epoll_pwait and then the struct epoll_event is only a problem
> for ia64.
>
> Am I right? (I have cc'd linux-arch for guidance.)
ARM-OABI also defines them, dunno why. Rmk?
- Davide
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