From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
Christophe Leroy <christophe.leroy@c-s.fr>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
the arch/x86 maintainers <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: objtool clac/stac handling change..
Date: Thu, 2 Jul 2020 21:59:02 +0100 [thread overview]
Message-ID: <20200702205902.GP2786714@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAHk-=whW7qYEK-MJMS9gKf-K4cBNGTq0pv-5wo4bqE_QtUfkDw@mail.gmail.com>
On Thu, Jul 02, 2020 at 01:32:34PM -0700, Linus Torvalds wrote:
> Ugh, the above is bad anyway.
>
> It doesn't use _ASM_EXTABLE_UA, so it won't warn about the noncanonical cases.
FWIW, the address is inside a sigframe we decided to build, so noncanonical
addresses shouldn't occur in practice.
> Yeah, it would need to be turned into a "jump out" instead of just "jump over".
>
> Which it damn well should do anyway.,
>
> That code should be taken behind a shed and shot. It does so many
> things wrong that it's not even funny. It shouldn't do stac/clac on
> its own.
>
> At least it could use the "user_insn()" helper, which does it inside
> the asm itself, has the right might_fault() marking (but not the
> address check), and which can be trivially changed to have the fixup
> jump be to after the "ASM_CLAC".
I'm not sure it's the right solution in this case. Look at the call chain
and the stuff done nearby (that __clear_user(), for example)...
I'm not saying that this code is not awful - it certainly is. But it's
not that simple, unfortunately ;-/
next prev parent reply other threads:[~2020-07-02 20:59 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-01 18:22 objtool clac/stac handling change Linus Torvalds
2020-07-01 18:29 ` Andy Lutomirski
2020-07-01 19:35 ` Linus Torvalds
2020-07-01 20:36 ` Andy Lutomirski
2020-07-01 20:51 ` Josh Poimboeuf
2020-07-01 21:02 ` Linus Torvalds
2020-07-02 0:00 ` Josh Poimboeuf
2020-07-02 8:05 ` Peter Zijlstra
2020-07-01 20:51 ` Linus Torvalds
2020-07-02 0:47 ` Andy Lutomirski
2020-07-02 2:30 ` Linus Torvalds
2020-07-02 2:35 ` Linus Torvalds
2020-07-02 3:08 ` Andy Lutomirski
2020-07-01 18:41 ` Al Viro
2020-07-01 19:04 ` Linus Torvalds
2020-07-01 19:59 ` Al Viro
2020-07-01 20:25 ` Linus Torvalds
2020-07-02 13:34 ` Michael Ellerman
2020-07-02 14:01 ` Al Viro
2020-07-02 14:04 ` Al Viro
2020-07-02 15:13 ` Christophe Leroy
2020-07-02 20:13 ` Linus Torvalds
2020-07-03 3:59 ` Michael Ellerman
2020-07-03 3:17 ` Michael Ellerman
2020-07-03 5:27 ` Christophe Leroy
2020-07-03 5:27 ` Christophe Leroy
2020-07-02 19:52 ` Linus Torvalds
2020-07-02 20:17 ` Al Viro
2020-07-02 20:32 ` Linus Torvalds
2020-07-02 20:59 ` Al Viro [this message]
2020-07-02 21:55 ` Linus Torvalds
2020-07-03 1:33 ` Al Viro
2020-07-03 3:32 ` Linus Torvalds
2020-07-03 21:02 ` Al Viro
2020-07-03 21:10 ` Linus Torvalds
2020-07-03 21:41 ` Andy Lutomirski
2020-07-03 22:25 ` Al Viro
2020-07-03 21:59 ` Al Viro
2020-07-03 22:04 ` Al Viro
2020-07-03 22:12 ` Al Viro
2020-07-04 0:49 ` Al Viro
2020-07-04 1:54 ` Linus Torvalds
2020-07-04 2:30 ` Al Viro
2020-07-04 3:06 ` Linus Torvalds
2020-07-04 2:11 ` Al Viro
2020-07-07 12:35 ` David Laight
2020-07-10 22:37 ` Linus Torvalds
2020-07-13 9:32 ` David Laight
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