From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>, Peter Anvin <hpa@zytor.com>,
Julien Thierry <julien.thierry@arm.com>,
Will Deacon <will.deacon@arm.com>,
Andy Lutomirski <luto@amacapital.net>,
Ingo Molnar <mingo@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
James Morse <james.morse@arm.com>,
valentin.schneider@arm.com, Brian Gerst <brgerst@gmail.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Andrew Lutomirski <luto@kernel.org>,
Borislav Petkov <bp@alien8.de>,
Denys Vlasenko <dvlasenk@redhat.com>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
Chris Wilson <chris@chris-wilson.co.uk>
Subject: Re: [PATCH 6/8] i915,uaccess: Fix redundant CLAC
Date: Fri, 1 Mar 2019 15:38:00 +0100 [thread overview]
Message-ID: <20190301143800.GT32534@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190301125718.GS32534@hirez.programming.kicks-ass.net>
On Fri, Mar 01, 2019 at 01:57:18PM +0100, Peter Zijlstra wrote:
> On Fri, Mar 01, 2019 at 01:27:45PM +0100, Peter Zijlstra wrote:
> > arch/x86/lib/usercopy_64.o: warning: objtool: .altinstr_replacement+0x30: redundant UACCESS disable
>
> > The usercopy one is difficult, that's copy_user_handle_tail(), it is
> > buggered though, because that lacks notrace and thus has a __fentry__
> > call in.
> >
> > Also, afaict all exception jumps into copy_user_handle_tail() will have
> > AC=1, but the __{get,put}_user_nocheck() things do STAC/CLAC all over
> > again.
> >
> > So what do we do? Annotate that we start with AC=1 and then immediately
> > do the clac, and then let __{get,put}_user_nocheck() do their own thing?
> > or make it use the unsafe stuff?
>
> Or.. we move the thing to assembly. Of course, I suck at (writing) asm,
> so the below is probably broken in various ways.
The advantage is that it now all lives in the same .o file and objtool
can actually follow and find the complete control flow.
I've made it ENDPROC() such that it becomes STT_FUNC and objtool does
all the normal things. I've also moved the ALIGN_DESTINATION macro into
the .S file.
Andy, do we have a sensible self-test for this path?
next prev parent reply other threads:[~2019-03-01 14:38 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-28 14:54 [PATCH 0/8] objtool: UACCESS validation v2 Peter Zijlstra
2019-02-28 14:54 ` [PATCH 1/8] kasan,x86: Frob kasan_report() in an exception Peter Zijlstra
2019-02-28 15:22 ` Dmitry Vyukov
2019-02-28 15:45 ` Peter Zijlstra
2019-02-28 15:52 ` Dmitry Vyukov
2019-02-28 16:01 ` Andrey Ryabinin
2019-02-28 16:03 ` Dmitry Vyukov
2019-02-28 17:46 ` Peter Zijlstra
2019-02-28 18:18 ` Dmitry Vyukov
2019-03-01 14:45 ` Peter Zijlstra
2019-03-01 15:06 ` Dmitry Vyukov
2019-03-01 15:23 ` Peter Zijlstra
2019-03-06 13:13 ` Peter Zijlstra
2019-03-06 13:39 ` Dmitry Vyukov
2019-03-06 13:57 ` Peter Zijlstra
2019-03-06 14:01 ` Dmitry Vyukov
2019-03-06 14:12 ` Peter Zijlstra
2019-03-06 14:34 ` Peter Zijlstra
2019-03-06 14:40 ` Dmitry Vyukov
2019-03-06 14:41 ` Dmitry Vyukov
2019-03-06 14:55 ` Peter Zijlstra
2019-03-06 15:01 ` Dmitry Vyukov
2019-03-06 17:14 ` Peter Zijlstra
2019-03-06 17:27 ` Linus Torvalds
2019-03-06 17:37 ` Peter Zijlstra
2019-03-06 17:59 ` Linus Torvalds
2019-03-07 13:49 ` Peter Zijlstra
2019-02-28 14:54 ` [PATCH 2/8] x86/ia32: Fix ia32_restore_sigcontext AC leak Peter Zijlstra
2019-02-28 14:54 ` [PATCH 3/8] objtool: Set insn->func for alternatives Peter Zijlstra
2019-02-28 14:54 ` [PATCH 4/8] objtool: Hande function aliases Peter Zijlstra
2019-02-28 14:54 ` [PATCH 5/8] objtool: Rewrite add_ignores() Peter Zijlstra
2019-02-28 14:54 ` [PATCH 6/8] i915,uaccess: Fix redundant CLAC Peter Zijlstra
2019-02-28 15:10 ` Chris Wilson
2019-02-28 15:24 ` Peter Zijlstra
2019-02-28 16:49 ` Linus Torvalds
2019-02-28 17:51 ` Peter Zijlstra
2019-02-28 18:01 ` Peter Zijlstra
2019-02-28 18:29 ` Linus Torvalds
2019-02-28 19:01 ` Peter Zijlstra
2019-03-01 10:34 ` Peter Zijlstra
2019-03-01 12:27 ` Peter Zijlstra
2019-03-01 12:57 ` Peter Zijlstra
2019-03-01 14:38 ` Peter Zijlstra [this message]
2019-03-01 15:27 ` Andy Lutomirski
2019-03-01 16:15 ` Linus Torvalds
2019-03-01 16:17 ` Linus Torvalds
2019-02-28 14:54 ` [PATCH 7/8] objtool: Add UACCESS validation Peter Zijlstra
2019-02-28 14:54 ` [PATCH 8/8] objtool: Add Direction Flag validation Peter Zijlstra
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