* Andy Lutomirski <[email protected]> wrote:
> On Mon, Dec 11, 2017 at 5:39 AM, Ingo Molnar <[email protected]> wrote:
> >
> > * Andy Lutomirski <[email protected]> wrote:
> >
> >> The kernel is very erratic as to which pagetables have _PAGE_USER
> >> set. The vsyscall page gets lucky: it seems that all of the
> >> relevant pagetables are among the apparently arbitrary ones that set
> >> _PAGE_USER. Rather than relying on chance, just explicitly set
> >> _PAGE_USER.
> >>
> >> This will let us clean up pagetable setup to stop setting
> >> _PAGE_USER. The added code can also be reused by pagetable
> >> isolation to manage the _PAGE_USER bit in the usermode tables.
> >>
> >> Signed-off-by: Andy Lutomirski <[email protected]>
> >> ---
> >> arch/x86/entry/vsyscall/vsyscall_64.c | 33
> >> ++++++++++++++++++++++++++++++++-
> >> 1 file changed, 32 insertions(+), 1 deletion(-)
> >
> > Btw., would it make sense to clean up all this confusion?
> >
> > In particular a 'KERNEL' pre of post fix is ambiguous in this context I
> > think, and
> > the PAGE_KERNEL_ prefix is actively harmful I think and is at the root of
> > the
> > confusion.
> >
> > So if renamed it and used this nomenclature consistently instead:
> >
> > PAGE_USER_
> > PAGE_SYSTEM_
>
> Like _PAGE_USER_VSYSCALL?
>
> Anyway, that's not the confusion I'm talking about. I'm talking about
> _KERNPG_TABLE vs _PAGE_TABLE. The latter should be called
> _USERPG_TABLE, and a whole bunch of its users should be switched to
> _KERNPG_TABLE.
Yeah.
> But, since PTI is intended for backporting, I think these types of big
> cleanups should wait.
Absolutely.
Thanks,
Ingo
