freebsd32_ioctl.c

Kostik Belousov kostikbel at gmail.com
Thu Oct 7 16:13:44 UTC 2010


On Thu, Oct 07, 2010 at 09:05:49AM -0700, mdf at freebsd.org wrote:
> I added some more ioctls to those translated by freebsd32_ioctl in my
> local tree, and then I started thinking.  If we support all the
> various drivers as loadable modules, but the ioctl translation is in
> the base kernel, that's a lot of code to have for COMPAT_IA32 that may
> never get run.  It would be nice to keep the ioctl argument munging in
> the driver, but while it's not hard to check in the driver's ioctl
> function if p_sysent is freebsd32_sysent, the code isn't as clean as a
> passthrough function like freebsd32_ioctl().
> 
> So I was wondering if that would be considered an issue.  Should we
> just be adding ioctl argument munging as we go along and not worry
> about the size?  Or is there simple way to keep the munging inside the
> driver?  Perhaps my making the driver's ioctl look something like:
I think that in-driver variant is the best.

> 
> #ifdef COMPAT_IA32
> static int
> xxx_ioctl32(struct cdev *dev, u_long com32, caddr_t arg, int flag,
>     struct thread *td)
> {
> 	struct xxx_32 *cmd32 = (void *)arg;
> 	struct xxx cmd;
> 	u_long com;
> 	int error;
> 
> 	CP(*cmd32, cmd, field1);
> 	/* ... */
> 	error = xxx_ioctl(dev, com, &cmd, flag, td);
> 	if (error == 0 && (com & IOC_OUT) != 0) {
> 		CP(cmd, *cmd32, field1);
> 		/* ... */
> 	}
> 	return (error);
> }
> #endif /* COMPAT_IA32 */
> 
> static int
> xxx_ioctl_devsw(struct cdev *dev, u_long com, caddr_t arg, int flag,
>     struct thread *td)
> {
> #ifdef COMPAT_IA32
> 	if (td->td_proc->p_sysent == &ia32_freebsd_sysvec)
> 		return (xxx_ioctl32(dev, com, arg, flag, td));
> #endif
> 	return (xxx_ioctl(dev, com, arg, flag, td);
> }
> 
> ... and the check for p_sysent == &ia32_freebsd_sysvec should probably
> be a more-correct macro.
	if (SV_CURPROC_FLAG(SV_ILP32))
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