On Tue, 2011-12-27 at 21:33 +0100, Ben Hutchings wrote:
> This allows uswsusp built for i386 to run on an x86_64 kernel (tested
> with Debian package version 1.0+20110509-2).
Now I wonder whether all this code was necessary.
[...]
> +#ifdef CONFIG_COMPAT
> +
> +struct compat_resume_swap_area {
> + compat_loff_t offset;
> + u32 dev;
> +} __packed;
[...]
Is there actually any case where this doesn't have compatible layout
with struct resume_swap_area? It may have lower alignment, but
misalignment is dealt with automatically when copying in/out of
userland.
If the structure size was variable then the ioctl number would be as
well, and commit cf007e3526a785a95a738d5a8fba44f1f4fe33e0 is supposed to
have removed the last ioctls that had that problem.
So maybe the compat function can be as simple as:
static long
snapshot_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
BUILD_BUG_ON(sizeof(loff_t) != sizeof(compat_loff_t));
BUILD_BUG_ON(sizeof(struct resume_swap_area) !=
sizeof(struct compat_resume_swap_area));
switch (cmd) {
case SNAPSHOT_SET_SWAP_AREA:
case SNAPSHOT_GET_IMAGE_SIZE:
case SNAPSHOT_CREATE_IMAGE:
case SNAPSHOT_AVAIL_SWAP_SIZE:
case SNAPSHOT_ALLOC_SWAP_PAGE:
return snapshot_ioctl(file, cmd,
(unsigned long) compat_ptr(arg));
default:
return snapshot_ioctl(file, cmd, arg);
}
}
Ben.
--
Ben Hutchings
Design a system any fool can use, and only a fool will want to use it.
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