From: Al Viro <viro@zeniv.linux.org.uk>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
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Subject: Re: [PATCH v3 12/26] compat_ioctl: move more drivers to compat_ptr_ioctl
Date: Thu, 25 Apr 2019 17:42:35 +0100 [thread overview]
Message-ID: <20190425164235.GT2217@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAK8P3a2HmiYQJ2FV2FgLiFsD8M9UKteC9Jetx7ja06PQVZWYfA@mail.gmail.com>
On Thu, Apr 25, 2019 at 05:55:23PM +0200, Arnd Bergmann wrote:
> On Thu, Apr 25, 2019 at 5:35 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> >
> > On Thu, Apr 25, 2019 at 12:21:53PM -0300, Mauro Carvalho Chehab wrote:
> >
> > > If I understand your patch description well, using compat_ptr_ioctl
> > > only works if the driver is not for s390, right?
> >
> > No; s390 is where "oh, just set ->compat_ioctl same as ->unlocked_ioctl
> > and be done with that; compat_ptr() is a no-op anyway" breaks. IOW,
> > s390 is the reason for having compat_ptr_ioctl() in the first place;
> > that thing works on all biarch architectures, as long as all stuff
> > handled by ->ioctl() takes pointer to arch-independent object as
> > argument. IOW,
> > argument ignored => OK
> > any arithmetical type => no go, compat_ptr() would bugger it
> > pointer to int => OK
> > pointer to string => OK
> > pointer to u64 => OK
> > pointer to struct {u64 addr; char s[11];} => OK
>
> To be extra pedantic, the 'struct {u64 addr; char s[11];} '
> case is also broken on x86, because sizeof (obj) is smaller
> on i386, even though the location of the members are
> the same. i.e. you can copy_from_user() this, but not
> copy_to_user(), which overwrites 4 bytes after the end of
> the 20-byte user structure.
D'oh! FWIW, it might be worth putting into Documentation/ somewhere;
basically, what is and what isn't biarch-neutral.
Or arch-neutral, for that matter - it's very close. The only real
exception, IIRC, is an extra twist on m68k, where int behaves
like x86 long long - its alignment is only half its size, so
sizeof(struct {char c; int x;}) is 6, not 8 as everywhere
else. Irrelevant for biarch, thankfully (until somebody gets insane
enough to implement 64bit coldfire, kernel port for it *and* biarch
support for m68k binaries on that thing, that is)...
next prev parent reply other threads:[~2019-04-25 16:43 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-16 20:19 [PATCH v3 00/26] compat_ioctl: cleanups Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 01/26] compat_ioctl: pppoe: fix PPPOEIOCSFWD handling Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 02/26] compat_ioctl: move simple ppp command handling into driver Arnd Bergmann
2019-04-17 21:13 ` Al Viro
2019-04-17 22:03 ` Arnd Bergmann
2019-04-17 23:53 ` Al Viro
2019-04-18 5:57 ` Al Viro
2019-04-18 15:14 ` Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 03/26] compat_ioctl: avoid unused function warning for do_ioctl Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 04/26] compat_ioctl: move PPPIOCSCOMPRESS32 to ppp-generic.c Arnd Bergmann
2019-04-17 21:16 ` Al Viro
2019-04-17 21:44 ` Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 05/26] compat_ioctl: move PPPIOCSPASS32/PPPIOCSACTIVE32 to ppp_generic.c Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 06/26] compat_ioctl: handle PPPIOCGIDLE for 64-bit time_t Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 07/26] compat_ioctl: move rtc handling into rtc-dev.c Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 08/26] compat_ioctl: add compat_ptr_ioctl() Arnd Bergmann
2019-04-17 21:19 ` Al Viro
2019-04-17 21:34 ` Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 09/26] compat_ioctl: move drivers to compat_ptr_ioctl Arnd Bergmann
2019-04-16 20:31 ` Jiri Kosina
2019-04-18 11:10 ` Stefan Hajnoczi
2019-04-19 23:16 ` Michael S. Tsirkin
2019-04-16 20:19 ` [PATCH v3 10/26] compat_ioctl: use correct compat_ptr() translation in drivers Arnd Bergmann
2019-04-17 21:21 ` Al Viro
2019-04-16 20:19 ` [PATCH v3 11/26] ceph: fix compat_ioctl for ceph_dir_operations Arnd Bergmann
2019-04-17 21:23 ` Al Viro
2019-04-17 21:31 ` Arnd Bergmann
2019-04-16 20:25 ` [PATCH v3 12/26] compat_ioctl: move more drivers to compat_ptr_ioctl Arnd Bergmann
2019-04-16 20:25 ` [PATCH v3 13/26] compat_ioctl: move tape handling into drivers Arnd Bergmann
2019-04-16 20:25 ` [PATCH v3 14/26] compat_ioctl: move ATYFB_CLK handling to atyfb driver Arnd Bergmann
2019-04-17 21:27 ` Al Viro
2019-04-17 21:28 ` Al Viro
2019-05-06 13:37 ` Bartlomiej Zolnierkiewicz
2019-04-16 20:25 ` [PATCH v3 15/26] compat_ioctl: move isdn/capi ioctl translation into driver Arnd Bergmann
2019-04-16 20:25 ` [PATCH v3 16/26] compat_ioctl: move rfcomm handlers " Arnd Bergmann
2019-04-16 20:25 ` [PATCH v3 17/26] compat_ioctl: move hci_sock " Arnd Bergmann
2019-04-16 20:25 ` [PATCH v3 18/26] compat_ioctl: remove HCIUART handling Arnd Bergmann
2019-04-16 20:25 ` [PATCH v3 19/26] compat_ioctl: remove HIDIO translation Arnd Bergmann
2019-04-25 15:21 ` [PATCH v3 12/26] compat_ioctl: move more drivers to compat_ptr_ioctl Mauro Carvalho Chehab
2019-04-25 15:32 ` Arnd Bergmann
2019-04-25 15:35 ` Al Viro
2019-04-25 15:53 ` Mauro Carvalho Chehab
2019-04-25 15:55 ` Arnd Bergmann
2019-04-25 16:42 ` Al Viro [this message]
2019-04-25 21:25 ` Johannes Berg
2019-04-26 7:46 ` Arnd Bergmann
2019-04-16 20:28 ` [PATCH v3 20/26] compat_ioctl: remove translation for sound ioctls Arnd Bergmann
2019-04-16 20:28 ` [PATCH v3 21/26] compat_ioctl: remove IGNORE_IOCTL() Arnd Bergmann
2019-04-16 20:28 ` [PATCH v3 22/26] compat_ioctl: remove /dev/random commands Arnd Bergmann
2019-04-16 20:28 ` [PATCH v3 23/26] compat_ioctl: remove joystick ioctl translation Arnd Bergmann
2019-04-16 20:28 ` [PATCH v3 24/26] compat_ioctl: remove PCI " Arnd Bergmann
2019-04-16 20:28 ` [PATCH v3 25/26] compat_ioctl: remove /dev/raw " Arnd Bergmann
2019-04-16 20:28 ` [PATCH v3 26/26] compat_ioctl: remove last RAID handling code Arnd Bergmann
2019-04-17 8:05 ` [PATCH v3 20/26] compat_ioctl: remove translation for sound ioctls Takashi Iwai
2019-04-29 7:05 ` Takashi Iwai
2019-04-29 12:43 ` Arnd Bergmann
2019-04-16 22:33 ` [PATCH v3 00/26] compat_ioctl: cleanups Douglas Gilbert
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