From: "H. Peter Anvin" <hpa@zytor.com>
To: Borislav Petkov <bp@alien8.de>,
Denys Vlasenko <vda.linux@googlemail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>,
Andy Lutomirski <luto@amacapital.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>, 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 Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/4] x86: entry.S: tidy up several suboptimal insns
Date: Tue, 24 Feb 2015 14:51:10 -0800 [thread overview]
Message-ID: <54ED005E.4070603@zytor.com> (raw)
In-Reply-To: <20150224203635.GN3420@pd.tnic>
On 02/24/2015 12:36 PM, Borislav Petkov wrote:
> On Tue, Feb 24, 2015 at 09:13:03PM +0100, Denys Vlasenko wrote:
>> They aren't equal. $1 and $2 in two lowest bits will also
>> be interpreted as "userspace" here. "Equal to $3" sends
>> a wrong message here to a human reading the code,
>> the code doesn't test for CPL=3, it tests for any nonzero CPL.
>
> Doh, of course.
>
> I was going to propose to make it even more explicit:
>
> andb $3, CS(%rsp)...
>
> but that's destructive.
>
> So yours makes it less misleading, actually. To me at least and
> obviously.
>
Yes, please use JZ/JNZ with TEST.
-hpa
next prev parent reply other threads:[~2015-02-24 22:51 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
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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=54ED005E.4070603@zytor.com \
--to=hpa@zytor.com \
--cc=ast@plumgrid.com \
--cc=bp@alien8.de \
--cc=dvlasenk@redhat.com \
--cc=fweisbec@gmail.com \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=rostedt@goodmis.org \
--cc=torvalds@linux-foundation.org \
--cc=vda.linux@googlemail.com \
--cc=wad@chromium.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.