On Thu, Nov 9, 2017 at 10:31 PM, Dave Hansen <dave.han...@linux.intel.com> wrote: > On 11/09/2017 06:25 PM, Andy Lutomirski wrote: >> Here are two proposals to address this without breaking vsyscalls. >> >> 1. Set NX on low mappings that are _PAGE_USER. Don't set NX on high >> mappings but, optionally, warn if you see _PAGE_USER on any address >> that isn't the vsyscall page. >> >> 2. Ignore _PAGE_USER entirely and just mark the EFI mm as special so >> KAISER doesn't muck with it. > > These are totally doable. But, what's the big deal with breaking native > vsyscall? We can still do the emulation so nothing breaks: it is just slow.
I have nothing against disabling native. I object to breaking the weird binary tracing behavior in the emulation mode, especially if it's tangled up with KAISER. I got all kinds of flak in an earlier version of the vsyscall emulation patches when I broke that use case. KAISER may get very widely backported -- let's not make changes that are already known to break things.
