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Subject: Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention
To: Andy Lutomirski <luto@amacapital.net>
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Cc: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Andy Lutomirski <luto@kernel.org>,
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08.03.2017 19:46, Andy Lutomirski пишет:
>> No no, since I meant prot mode, this is not what I need.
>> I would never need to disable UMIP as to allow the
>> prot mode apps to do SLDT. Instead it would be good
>> to have an ability to provide a replacement for the dummy
>> emulation that is currently being proposed for kernel.
>> All is needed for this, is just to deliver a SIGSEGV.
> That's what I meant.  Turning off FIXUP_UMIP would leave UMIP on but
> turn off the fixup, so you'd get a SIGSEGV indicating #GP (or a vm86
> GP exit).
But then I am confused with the word "compat" in
your "COMPAT_MASK0_X86_UMIP_FIXUP" and
"sys_adjust_compat_mask(int op, int word, u32 mask);"

Leaving UMIP on and only disabling a fixup doesn't
sound like a compat option to me. I would expect
compat to disable it completely.