[PATCH for 4.18 2/6] rseq: use get_user/put_user rather than __get_user/__put_user

----- On Jul 9, 2018, at 2:04 PM, Linus Torvalds torvalds at linux-foundation.org wrote:

On Mon, Jul 9, 2018 at 10:28 AM Mathieu Desnoyers
[off-list ref] wrote:

quoted

So, another twist to this story: ppc32 does not implement u64 get_user().

I was going to say that "that's not possible", since we actually have
64-bit arguments at least in the form of "loff_t __user *".

But when I started looking, it turns out that yeah, we do
"copy_from_user()" on them, and instead made the x86 copy_from_user()
have special cases for constant sizes.

So a 8-byte copy_from_user() is fine. It ends up being a "get_user()"
on x86 anyway.

Given that this memory area has already been checked with access_ok()
on rseq registration, are you fine with leaving
__get_user/__put_user/__copy_{from,to}_user in place so we do the
minimal change at this stage of rc, or should I go ahead and replace
the lot with get_user/put_user/copy_{from,to}_user ?

Thanks,

Mathieu


-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com