On 19/11/15 17:34, Andrew Cooper wrote: > A sample Gentoo compliation of Xen contains > > lea -0x1058(%rsp),%rsp > orq $0x0,(%rsp) > lea 0x1020(%rsp),%rsp > > Whatever the reason for silly code like this, it fools the current stack > overflow detection logic in the #DF handler (which triggers reliably on the > 'orq' instruction). > > Update the overflow condition to declare an overflow if %esp is anywhere > within the guard page, rather than just within the upper 8th of the page. > > Additionally, check %esp against the expected stack base in all builds. > > Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com> > --- > CC: Jan Beulich <jbeul...@suse.com> > CC: Atom2 <ariel.at...@web2web.at> > > Currently untested, therefore RFC > > Atom2: If you have a free moment, would you mind giving this patch a spin on a > debug hypervisor? I would expect it to top erroniously informing you that no > overflow was detected > ---
Another question is whether, given that the sample above moves the stack by more than 4k, it would be wise to also guard the 4th currently-spare page between the primary stack and IST stacks. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
