From: Linus Torvalds <torvalds@linux-foundation.org>
To: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Jani Nikula <jani.nikula@linux.intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
"the arch/x86 maintainers" <x86@kernel.org>
Subject: Re: [PATCH v3 2/7] uaccess: Tell user_access_begin() if it's for a write or not
Date: Thu, 23 Jan 2020 10:02:33 -0800 [thread overview]
Message-ID: <CAHk-=wg4HEABOZdjxMzbembNmxs1zYfrNAEc2L+JS9FBSnM8JA@mail.gmail.com> (raw)
In-Reply-To: <e11a8f0670251267f87e3114e0bdbacb1eb72980.1579783936.git.christophe.leroy@c-s.fr>
On Thu, Jan 23, 2020 at 4:59 AM Christophe Leroy
<christophe.leroy@c-s.fr> wrote:
>
> On 32 bits powerPC (book3s/32), only write accesses to user are
> protected and there is no point spending time on unlocking for reads.
Honestly, I'm starting to think that 32-bit ppc just needs to look
more like everybody else, than make these changes.
We used to have a read/write argument to the old "verify_area()" and
"access_ok()" model, and it was a mistake. It was due to odd i386 user
access issues. We got rid of it. I'm not convinced this is any better
- it looks very similar and for odd ppc access issues.
But if we really do want to do this, then:
> Add an argument to user_access_begin() to tell when it's for write and
> return an opaque key that will be used by user_access_end() to know
> what was done by user_access_begin().
You should make it more opaque than "unsigned long".
Also, it shouldn't be a "is this a write". What if it's a read _and_ a
write? Only a write? Only a read?
Linus
next prev parent reply other threads:[~2020-01-23 18:02 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-23 12:59 [PATCH v3 1/7] fs/readdir: Fix filldir() and filldir64() use of user_access_begin() Christophe Leroy
2020-01-23 12:59 ` [PATCH v3 2/7] uaccess: Tell user_access_begin() if it's for a write or not Christophe Leroy
2020-01-23 13:11 ` Jani Nikula
2020-01-23 18:02 ` Linus Torvalds [this message]
2020-01-23 19:47 ` christophe leroy
2020-01-23 19:57 ` Linus Torvalds
2020-01-24 2:03 ` hpa
2020-01-25 6:17 ` Tony Luck
2020-01-25 14:40 ` kbuild test robot
2020-01-23 12:59 ` [PATCH v3 3/7] powerpc/32s: Fix bad_kuap_fault() Christophe Leroy
2020-01-23 12:59 ` [PATCH v3 4/7] powerpc/kuap: Fix set direction in allow/prevent_user_access() Christophe Leroy
2020-01-23 12:59 ` [PATCH v3 5/7] powerpc/32s: Drop NULL addr verification Christophe Leroy
2020-01-23 12:59 ` [PATCH v3 6/7] powerpc/32s: Prepare allow_user_access() for user_access_begin() Christophe Leroy
2020-01-23 12:59 ` [PATCH v3 7/7] powerpc: Implement user_access_begin and friends Christophe Leroy
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