Messages in this thread | | | Date | Mon, 8 Jan 2018 22:03:55 +0100 | From | Willy Tarreau <> | Subject | Re: [PATCH RFC 2/4] x86/arch_prctl: add ARCH_GET_NOPTI and ARCH_SET_NOPTI to enable/disable PTI |
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On Mon, Jan 08, 2018 at 09:49:23PM +0100, Thomas Gleixner wrote: > On Mon, 8 Jan 2018, Willy Tarreau wrote: > > On Mon, Jan 08, 2018 at 09:54:05AM -0800, Linus Torvalds wrote: > > > > > So make the thing per-mm, and then at task switch time as you switch > > > mms, you set the bit in a percpu variable for testing at kernel entry. > > > > I'll see how to do that, this is not yet 100% clear to me, I'm still > > discovering (this code has immensely changed since last time I *really* > > dug into it). So I suspect I'll have to set this variable in > > __switch_to() based on this other MM flag. > > The right thing is probably the cpu entry area because that's what you can > access before switching CR3 if PTI is enabled for the task
In fact I didn't need any such thing, because when coming from user space I can simply check CR3.12 : if 0, we had PTI disabled for the task, otherwise it's enabled.
I'll repost the cleaned up series ASAP, unfortunately I need to go now.
Thanks, Willy
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