[systemd-devel] [PATCH] Fix broken syscall(__NR_fanotify_mark... on 32bit mips.

[Lennart Poettering]

On Wed, 20.04.11 11:19, David Daney (ddaney at caviumnetworks.com) wrote:

> 
> On 04/20/2011 11:09 AM, Lennart Poettering wrote:
> >On Wed, 20.04.11 10:36, David Daney (ddaney at caviumnetworks.com) wrote:
> >
> >>You would have to do something like this (untested):
> >>
> >>int foo_fanotify_mark(int fanotify_fd, unsigned int flags, u64 mask,
> >>int dfd, const char  __user * pathname)
> >>{
> >>	u32 mask_low = (u32)mask;
> >>	u32 mask_high = (u32)(mask>>  32);
> >>
> >>	return syscall(4337, fanotify_fd, flags, mask_low, mask_high, dfd,
> >>pathname);
> >>
> >>}
> >>
> >>The order of mask_low, mask_high in the syscall argument list
> >>depends on the endianness.  Figuring out the correct order is left
> >>as an exercise for the reader.
> >
> >That's basically the same patch as this one, right?
> >
> >http://lists.freedesktop.org/archives/systemd-devel/attachments/20110420/be2d393b/attachment.obj
> >
> 
> It looks like it might do the same thing.  Someone should try it on
> an o32 MIPS userland running on a mips64 kernel.
> 
> I think the behavior of the union thing is undefined, but should
> work on GCC.

Hmm, but unions is the official C99 way to do these things, isn't it?
Instead of doing casts here and there which create aliasing probs?

Any comment whether this will break non-MIPS 32bit archs, like x86?

Lennart

-- 
Lennart Poettering - Red Hat, Inc.