From: Michael Ellerman <mpe@ellerman.id.au>
To: Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>
Cc: Guenter Roeck <linux@roeck-us.net>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH] Convert filldir[64]() from __put_user() to unsafe_put_user()
Date: Tue, 15 Oct 2019 14:46:41 +1100 [thread overview]
Message-ID: <87h84avffi.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <CAHk-=wgO1EW5qVuy7=sc9Kua98-afMx75gaeX4FHKf3+wPLmkw@mail.gmail.com>
Linus Torvalds <torvalds@linux-foundation.org> writes:
> On Sun, Oct 13, 2019 at 12:59 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>> Re plotting: how strongly would you object against passing the range to
>> user_access_end()? Powerpc folks have a very close analogue of stac/clac,
>> currently buried inside their __get_user()/__put_user()/etc. - the same
>> places where x86 does, including futex.h and friends.
>>
>> And there it's even costlier than on x86. It would obviously be nice
>> to lift it at least out of unsafe_get_user()/unsafe_put_user() and
>> move into user_access_begin()/user_access_end(); unfortunately, in
>> one subarchitecture they really want it the range on the user_access_end()
>> side as well.
>
> Hmm. I'm ok with that.
>
> Do they want the actual range, or would it prefer some kind of opaque
> cookie that user_access_begin() returns (where 0 would mean "failure"
> of course)?
The code does want the actual range, or at least the range rounded to a
segment boundary (256MB).
But it can get that already from a value it stashes in current->thread,
it was just more natural to pass the addr/size with the way the code is
currently structured.
It seems to generate slightly better code to pass addr/size vs loading
it from current->thread, but it's probably in the noise vs everything
else that's going on.
So a cookie would work fine, we could return the encoded addr/size in
the cookie and that might generate better code than loading it back from
current->thread. Equally we could just use the value in current->thread
and not have any cookie at all.
cheers
next prev parent reply other threads:[~2019-10-15 3:46 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-06 22:20 [PATCH] Convert filldir[64]() from __put_user() to unsafe_put_user() Guenter Roeck
2019-10-06 23:06 ` Linus Torvalds
2019-10-06 23:35 ` Linus Torvalds
2019-10-07 0:04 ` Guenter Roeck
2019-10-07 1:17 ` Linus Torvalds
2019-10-07 1:24 ` Al Viro
2019-10-07 2:06 ` Linus Torvalds
2019-10-07 2:50 ` Al Viro
2019-10-07 3:11 ` Linus Torvalds
2019-10-07 15:40 ` David Laight
2019-10-07 18:11 ` Linus Torvalds
2019-10-08 9:58 ` David Laight
2019-10-07 17:34 ` Al Viro
2019-10-07 18:13 ` Linus Torvalds
2019-10-07 18:22 ` Al Viro
2019-10-07 18:26 ` Linus Torvalds
2019-10-07 18:36 ` Tony Luck
2019-10-07 19:08 ` Linus Torvalds
2019-10-07 19:49 ` Tony Luck
2019-10-07 20:04 ` Linus Torvalds
2019-10-08 3:29 ` Al Viro
2019-10-08 4:09 ` Linus Torvalds
2019-10-08 4:14 ` Linus Torvalds
2019-10-08 5:02 ` Al Viro
2019-10-08 4:24 ` Linus Torvalds
2019-10-10 19:55 ` Al Viro
2019-10-10 22:12 ` Linus Torvalds
2019-10-11 0:11 ` Al Viro
2019-10-11 0:31 ` Linus Torvalds
2019-10-13 18:13 ` Al Viro
2019-10-13 18:43 ` Linus Torvalds
2019-10-13 19:10 ` Al Viro
2019-10-13 19:22 ` Linus Torvalds
2019-10-13 19:59 ` Al Viro
2019-10-13 20:20 ` Linus Torvalds
2019-10-15 3:46 ` Michael Ellerman [this message]
2019-10-15 18:08 ` Al Viro
2019-10-15 19:00 ` Linus Torvalds
2019-10-15 19:40 ` Al Viro
2019-10-15 20:18 ` Al Viro
2019-10-16 12:12 ` [RFC] change of calling conventions for arch_futex_atomic_op_inuser() Al Viro
2019-10-16 12:24 ` Thomas Gleixner
2019-10-16 20:25 ` [PATCH] Convert filldir[64]() from __put_user() to unsafe_put_user() Al Viro
2019-10-17 19:36 ` [RFC][PATCHES] drivers/scsi/sg.c uaccess cleanups/fixes Al Viro
2019-10-17 19:39 ` [RFC PATCH 1/8] sg_ioctl(): fix copyout handling Al Viro
2019-10-17 19:39 ` [RFC PATCH 2/8] sg_new_write(): replace access_ok() + __copy_from_user() with copy_from_user() Al Viro
2019-10-17 19:39 ` [RFC PATCH 3/8] sg_write(): __get_user() can fail Al Viro
2019-10-17 19:39 ` [RFC PATCH 4/8] sg_read(): simplify reading ->pack_id of userland sg_io_hdr_t Al Viro
2019-10-17 19:39 ` [RFC PATCH 5/8] sg_new_write(): don't bother with access_ok Al Viro
2019-10-17 19:39 ` [RFC PATCH 6/8] sg_read(): get rid of access_ok()/__copy_..._user() Al Viro
2019-10-17 19:39 ` [RFC PATCH 7/8] sg_write(): get rid of access_ok()/__copy_from_user()/__get_user() Al Viro
2019-10-17 19:39 ` [RFC PATCH 8/8] SG_IO: get rid of access_ok() Al Viro
2019-10-17 21:44 ` [RFC][PATCHES] drivers/scsi/sg.c uaccess cleanups/fixes Douglas Gilbert
2019-11-05 4:54 ` Martin K. Petersen
2019-11-05 5:25 ` Al Viro
2019-11-06 4:29 ` Martin K. Petersen
2019-10-18 0:27 ` [RFC] csum_and_copy_from_user() semantics Al Viro
2019-10-25 14:01 ` [PATCH] Convert filldir[64]() from __put_user() to unsafe_put_user() Thomas Gleixner
2019-10-08 4:57 ` Al Viro
2019-10-08 13:14 ` Greg KH
2019-10-08 15:29 ` Al Viro
2019-10-08 15:38 ` Greg KH
2019-10-08 17:06 ` Al Viro
2019-10-08 19:58 ` Al Viro
2019-10-08 20:16 ` Al Viro
2019-10-08 20:34 ` Al Viro
2019-10-07 2:30 ` Guenter Roeck
2019-10-07 3:12 ` Linus Torvalds
2019-10-07 0:23 ` Guenter Roeck
2019-10-07 4:04 ` Max Filippov
2019-10-07 12:16 ` Guenter Roeck
2019-10-07 19:21 ` Linus Torvalds
2019-10-07 20:29 ` Guenter Roeck
2019-10-07 23:27 ` Guenter Roeck
2019-10-08 6:28 ` Geert Uytterhoeven
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