* Linus Torvalds <torva...@linux-foundation.org> wrote:
> On Tue, Oct 6, 2015 at 8:56 AM, Ingo Molnar <mi...@kernel.org> wrote:
> >
> > Yes, but note that those interfaces are x86 only at the moment, so they'd
> > have
> > to be factored out and generalized before we can use it in generic code.
>
> ARM64 these days (as a part of ARM8.1) has "Privileged Access Never", which
> is
> their name for SMAP. They do it somewhat similarly with an instruction to
> clear/set the PAN bit in the pstate register.
>
> So we really should strive to make this support generic, because by now it's
> not
> x86-specific, and x86 and ARM64 together aren't exactly some odd special
> case..
Absolutely.
> I do in fact wonder if we should aim (eventually) for the rule that the "__"
> versions of the user access functions should not do the SMAP/PAN thing, since
> they have to be explicitly checked for pointer being valid anyway. And just
> make
> the rule be that since you have to check for the pointer being valid, you
> might
> as well also have to do the SMAP/PAN thing too.
>
> We really should try get rid of _all_ uses of the "__" versions unless they
> are
> very locally and obviously checked with access_ok(). We've had way too many
> cases where people thought they were clever, and weren't really.
That's a good idea.
The logistics worries me a bit: it looks like a major undertaking, considering
the
widespread use of these APIs in 1400+ call sites:
triton:~/tip> git grep -E '__get_user|__put_user' | grep -vE '\.h:|arch/' |
wc -l
1086
triton:~/tip> git grep -E '__get_user|__put_user' arch/x86/ arch/arm64/ | wc
-l
354
... affecting 93 files:
triton:~/tip> git grep -lE '__get_user|__put_user' | grep -vE '\.h:|arch/' |
wc -l
70
triton:~/tip> git grep -lE '__get_user|__put_user' arch/x86/ arch/arm64/ | wc
-l
23
(Assuming my grep-fu is strong enough.)
Which is probably more than a hundred commits until we get rid of all
double-underscore uses?
Thanks,
Ingo
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