From: Peter Zijlstra <peterz@infradead.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Randy Dunlap <rdunlap@infradead.org>,
akpm@linux-foundation.org, broonie@kernel.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-next@vger.kernel.org, mhocko@suse.cz,
mm-commits@vger.kernel.org, sfr@canb.auug.org.au,
Josh Poimboeuf <jpoimboe@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>
Subject: Re: mmotm 2019-04-19-14-53 uploaded (objtool)
Date: Tue, 23 Apr 2019 19:39:12 +0200 [thread overview]
Message-ID: <20190423173912.GJ12232@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <D7626BC0-FCE9-4424-A6F5-D4AAB6727ED4@amacapital.net>
On Tue, Apr 23, 2019 at 09:07:01AM -0700, Andy Lutomirski wrote:
> > diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
> > index 22ba683afdc2..c82abd6e4ca3 100644
> > --- a/arch/x86/include/asm/uaccess.h
> > +++ b/arch/x86/include/asm/uaccess.h
> > @@ -427,10 +427,11 @@ do { \
> > ({ \
> > __label__ __pu_label; \
> > int __pu_err = -EFAULT; \
> > - __typeof__(*(ptr)) __pu_val; \
> > - __pu_val = x; \
> > + __typeof__(*(ptr)) __pu_val = (x); \
> > + __typeof__(ptr) __pu_ptr = (ptr); \
>
> Hmm. I wonder if this forces the address calculation to be done
> before STAC, which means that gcc can’t use mov ..., %gs:(fancy
> stuff). It probably depends on how clever the optimizer is. Have you
> looked at the generated code?
I have not; will do before posting the real patch.
next prev parent reply other threads:[~2019-04-23 17:39 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-19 21:53 mmotm 2019-04-19-14-53 uploaded akpm
2019-04-20 4:36 ` mmotm 2019-04-19-14-53 uploaded (objtool) Randy Dunlap
2019-04-23 8:24 ` Peter Zijlstra
2019-04-23 15:45 ` Randy Dunlap
2019-04-23 16:07 ` Andy Lutomirski
2019-04-23 17:39 ` Peter Zijlstra [this message]
2019-04-23 18:57 ` Peter Zijlstra
2019-04-23 16:19 ` Linus Torvalds
2019-04-23 17:35 ` Peter Zijlstra
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