Re: [RFC PATCH v4 19/27] x86/cet/shstk: Introduce WRUSS instruction

2018-10-02 Thread Eugene Syromiatnikov
On Fri, Sep 21, 2018 at 08:03:43AM -0700, Yu-cheng Yu wrote: > WRUSS is a new kernel-mode instruction but writes directly > to user shadow stack memory. This is used to construct > a return address on the shadow stack for the signal > handler. > > This instruction can fault if the user shadow sta

[RFC PATCH v4 19/27] x86/cet/shstk: Introduce WRUSS instruction

2018-09-21 Thread Yu-cheng Yu
WRUSS is a new kernel-mode instruction but writes directly to user shadow stack memory. This is used to construct a return address on the shadow stack for the signal handler. This instruction can fault if the user shadow stack is invalid shadow stack memory. In that case, the kernel does fixup.