Re: [PATCH v4 2/3] x86, mpx: hook #BR exception handler to allocate bound tables

[Ren Qiaowei]

On 02/13/2014 04:19 AM, Andy Lutomirski wrote:
> On 02/12/2014 10:36 AM, Qiaowei Ren wrote:
> > An access to an invalid bound directory entry will cause a #BR
> > exception. This patch hook #BR exception handler to allocate
> > one bound table and bind it with that buond directory entry.
> >
> > This will avoid the need of forwarding the #BR exception
> > to the user space when bound directory has invalid entry.
> >
> > Signed-off-by: Qiaowei Ren <qiaowei.ren@xxxxxxxxx>
> > ---
> > +void do_mpx_bt_fault(struct xsave_struct *xsave_buf)
> > +{
> > +	unsigned long status;
> > +	unsigned long bd_entry, bd_base;
> > +	unsigned long bd_size = 1UL << (MPX_L1_BITS+MPX_L1_SHIFT);
> > +
> > +	bd_base = xsave_buf->bndcsr.cfg_reg_u & MPX_BNDCFG_ADDR_MASK;
> > +	status = xsave_buf->bndcsr.status_reg;
> > +
> > +	bd_entry = status & MPX_BNDSTA_ADDR_MASK;
> > +	if ((bd_entry >= bd_base) && (bd_entry < bd_base + bd_size))
> > +		allocate_bt(bd_entry);
> > +}
>
> This still just loops on failure, right?
Seems like that SIGBUS should be raised if the allocation fail.

	if (!do_mpx_bt_fault(xsave_buf))
		force_sig(SIGBUS, tsk);

Thanks,
Qiaowei

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