From: Peter Zijlstra <peterz@infradead.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Julien Thierry <julien.thierry@arm.com>,
Will Deacon <will.deacon@arm.com>, 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>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 5/6] objtool: Add UACCESS validation
Date: Mon, 25 Feb 2019 18:15:31 +0100 [thread overview]
Message-ID: <20190225171531.GD32534@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190225161234.GM32477@hirez.programming.kicks-ass.net>
On Mon, Feb 25, 2019 at 05:12:34PM +0100, Peter Zijlstra wrote:
> On Mon, Feb 25, 2019 at 07:53:01AM -0800, Andy Lutomirski wrote:
> > On Mon, Feb 25, 2019 at 4:53 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> > > +#define UACCESS_SAFE(func) \
> > > + asm (".pushsection .discard.uaccess_safe_strtab, \"S\", @3\n\t" \
> > > + "999: .ascii \"" #func "\"\n\t" \
> > > + " .byte 0\n\t" \
> > > + ".popsection\n\t" \
> > > + ".pushsection .discard.uaccess_safe\n\t" \
> > > + ".long 999b - .\n\t" \
> > > + ".popsection")
> >
> > Minor nit: using big numbers like 999: like this always bugs me. It
> > relies on there not being a macro nested inside or outside this that
> > uses the same number. My general preference is to do something like
> > .Ldescription_\@ instead.
> >
> > Otherwise this looks conceptually good :)
>
> I seem to remember here being an issue with the \@ thing. Notably we're
> not using it in nospsec-branch.h.
>
> I'll see if I can dig up why we decided not to use it there.
Ah, so the thing we need for inline-asm is %=, but Linus didn't like it:
https://lkml.kernel.org/r/20180111175626.GJ6176@hirez.programming.kicks-ass.net
Also, I think at the time we didn't use it because backporting efforts.
I can't really find what happened between:
https://lkml.kernel.org/r/1515508997-6154-2-git-send-email-dwmw@amazon.co.uk
and
https://lkml.kernel.org/r/1515707194-20531-4-git-send-email-dwmw@amazon.co.uk
But the %= thing went away.
next prev parent reply other threads:[~2019-02-25 17:15 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-25 12:43 [PATCH 0/6] objtool: UACCESS validation Peter Zijlstra
2019-02-25 12:43 ` [PATCH 1/6] x86/uaccess: Dont evaluate argument inside AC region Peter Zijlstra
2019-02-25 15:43 ` Andy Lutomirski
2019-02-25 16:02 ` Peter Zijlstra
2019-02-25 16:36 ` Borislav Petkov
2019-02-25 16:50 ` Andy Lutomirski
2019-02-25 19:09 ` Linus Torvalds
2019-02-25 19:18 ` Borislav Petkov
2019-02-25 18:10 ` [tip:x86/urgent] x86/uaccess: Don't leak the AC flag into __put_user() value evaluation tip-bot for Andy Lutomirski
2019-02-25 19:46 ` tip-bot for Andy Lutomirski
2019-02-25 12:43 ` [PATCH 2/6] x86/ia32: Fix ia32_restore_sigcontext AC leak Peter Zijlstra
2019-02-25 15:41 ` Andy Lutomirski
2019-02-25 16:10 ` Peter Zijlstra
2019-02-25 16:29 ` Andy Lutomirski
2019-02-25 16:37 ` Peter Zijlstra
2019-02-25 16:41 ` Peter Zijlstra
2019-02-25 16:49 ` Andy Lutomirski
2019-02-25 12:43 ` [PATCH 3/6] objtool: Set insn->func for alternatives Peter Zijlstra
2019-02-25 12:43 ` [PATCH 4/6] objtool: Replace STACK_FRAME_NON_STANDARD annotation Peter Zijlstra
2019-02-25 16:11 ` Josh Poimboeuf
2019-02-25 16:17 ` Peter Zijlstra
2019-02-25 16:23 ` Josh Poimboeuf
2019-02-27 12:20 ` Peter Zijlstra
2019-02-28 0:30 ` Andy Lutomirski
2019-02-25 12:43 ` [PATCH 5/6] objtool: Add UACCESS validation Peter Zijlstra
2019-02-25 15:53 ` Andy Lutomirski
2019-02-25 16:12 ` Peter Zijlstra
2019-02-25 17:15 ` Peter Zijlstra [this message]
2019-02-25 17:34 ` Linus Torvalds
2019-02-25 17:38 ` Josh Poimboeuf
2019-02-27 14:08 ` Peter Zijlstra
2019-02-27 14:17 ` Andrey Ryabinin
2019-02-27 14:26 ` Peter Zijlstra
2019-02-27 14:33 ` Peter Zijlstra
2019-02-27 15:40 ` Dmitry Vyukov
2019-02-27 17:28 ` Peter Zijlstra
2019-02-28 9:40 ` Peter Zijlstra
2019-02-28 9:59 ` Dmitry Vyukov
2019-02-28 10:05 ` Dmitry Vyukov
2019-02-28 10:52 ` Peter Zijlstra
2019-02-27 16:18 ` Linus Torvalds
2019-02-27 17:30 ` Peter Zijlstra
2019-02-27 17:36 ` Linus Torvalds
2019-02-25 12:43 ` [PATCH 6/6] objtool: Add Direction Flag validation Peter Zijlstra
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