Messages in this thread | | | From | Linus Torvalds <> | Date | Thu, 1 Mar 2018 10:38:21 -0800 | Subject | Re: [PATCH 12/31] x86/entry/32: Add PTI cr3 switch to non-NMI entry/exit points |
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On Thu, Mar 1, 2018 at 10:24 AM, Brian Gerst <brgerst@gmail.com> wrote: > > The IF flag only affects external maskable interrupts, not traps or > faults. You do need to check CR3 because SYSENTER does not clear TF > and will immediately cause a debug trap on kernel entry (with user > CR3) if set. That is why the code existed before to check for the > entry stack for debug/NMI.
Note that debug traps can happen regardless of TF, Think kgdb etc. Arguably kgdb users get what they deserve, but still.. I think root can set kernel breakpoints too.
Linus
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