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From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
	Oleg Nesterov <oleg@redhat.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Alexei Starovoitov <ast@plumgrid.com>,
	Will Drewry <wad@chromium.org>, Kees Cook <keescook@chromium.org>,
	X86 ML <x86@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Tony Luck <tony.luck@intel.com>
Subject: Re: [PATCH 2/4] x86: get rid of KERNEL_STACK_OFFSET
Date: Thu, 26 Feb 2015 12:42:52 +0100	[thread overview]
Message-ID: <20150226114252.GA4593@gmail.com> (raw)
In-Reply-To: <CALCETrUvoRUGS9O0baofq-HG-RWpfRXbw3YsEmTX7jSruVFU7Q@mail.gmail.com>


* Andy Lutomirski <luto@amacapital.net> wrote:

> >> I added that in and applied this patch.
> >
> > So this is not just slightly buggy, it's fundamentally 
> > wrong as well as it removes the possibility of an RSP 
> > value optimization from the 64-bit path, see my 
> > previous mail.
> 
> This is just trying to check that the function is 
> executing on the per-thread stack.  It was correct (and 
> fairly heavily tested by Tony) wither KERNEL_STACK_OFFSET 
> being nonzero, but we're checking the wrong page if 
> KERNEL_STACK_OFFSET becomes zero.
> 
> I don't think I understand your objection to this bit.

I object to the KERNEL_STACK_OFFSET removal patch you fixed 
here, not to the add-on fix in particular (which is correct 
in the context of that patch).

Thanks,

	Ingo

  reply	other threads:[~2015-02-26 11:43 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-24 18:51 [PATCH 1/4] x86: entry.S: tidy up several suboptimal insns Denys Vlasenko
2015-02-24 18:51 ` [PATCH 2/4] x86: get rid of KERNEL_STACK_OFFSET Denys Vlasenko
2015-02-24 19:30   ` Steven Rostedt
2015-02-24 20:02     ` Denys Vlasenko
2015-02-24 22:37   ` Andy Lutomirski
2015-02-25  9:45     ` Ingo Molnar
2015-02-25 16:14       ` Andy Lutomirski
2015-02-26 11:42         ` Ingo Molnar [this message]
2015-02-26 15:21           ` Andy Lutomirski
2015-02-26 15:29             ` Andy Lutomirski
2015-02-25  8:53   ` Ingo Molnar
2015-02-25 12:48     ` Denys Vlasenko
2015-02-25 13:25       ` Denys Vlasenko
2015-02-25 13:53         ` Ingo Molnar
2015-02-24 18:51 ` [PATCH 3/4] x86: save r11 into pt_regs->eflags on SYSCALL64 fastpath Denys Vlasenko
2015-02-24 22:44   ` Andy Lutomirski
2015-02-24 18:51 ` [PATCH 4/4] x86: save user %rsp in pt_regs->sp Denys Vlasenko
2015-02-24 22:55   ` Andy Lutomirski
2015-02-24 19:58 ` [PATCH 1/4] x86: entry.S: tidy up several suboptimal insns Borislav Petkov
2015-02-24 20:13   ` Denys Vlasenko
2015-02-24 20:36     ` Borislav Petkov
2015-02-24 22:51       ` H. Peter Anvin
2015-02-24 22:25 ` Andy Lutomirski
2015-02-24 22:52   ` H. Peter Anvin
2015-02-24 22:56     ` Andy Lutomirski
2015-02-24 23:01       ` H. Peter Anvin
2015-02-24 23:03         ` Andy Lutomirski
2015-02-24 23:26           ` Denys Vlasenko
2015-02-25  9:20     ` Ingo Molnar
2015-02-25  9:27       ` H. Peter Anvin
2015-02-25  9:39         ` Ingo Molnar
2015-02-25 14:43       ` Steven Rostedt
2015-02-25 15:40         ` Denys Vlasenko
2015-02-25 16:01           ` Steven Rostedt
2015-02-25 16:06             ` Borislav Petkov
2015-02-26 11:47             ` Ingo Molnar
2015-02-26 12:47               ` Steven Rostedt
2015-02-26 12:50               ` Steven Rostedt

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