On Wed, 2017-03-08 at 19:53 +0300, Stas Sergeev wrote:I don't think someone will want to completely disable
08.03.2017 19:46, Andy Lutomirski ÐÐÑÐÑ:I guess that the _UMIP_FIXUP part makes it clear that emulation, not
But then I am confused with the word "compat" inNo no, since I meant prot mode, this is not what I need.That's what I meant. Turning off FIXUP_UMIP would leave UMIP on but
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.
turn off the fixup, so you'd get a SIGSEGV indicating #GP (or a vm86
GP exit).
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.
UMIP is disabled, allowing the SIGSEGV be delivered to the user space
program.
Would having a COMPAT_MASK0_X86_UMIP_FIXUP to disable emulation and a
COMPAT_MASK0_X86_UMIP to disable UMIP make sense?
Also, wouldn't having a COMPAT_MASK0_X86_UMIP to disable UMIP defeat its
purpose? Applications could simply use this compat mask to bypass UMIP
and gain access to the instructions it protects.