From: Peter Zijlstra <peterz@infradead.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux Next Mailing List <linux-next@vger.kernel.org>,
rostedt@goodmis.org, ast@kernel.org, hjl.tools@gmail.com,
rick.p.edgecombe@intel.com, rppt@kernel.org,
linux-toolchains@vger.kernel.org, Andrew.Cooper3@citrix.com,
ndesaulniers@google.com
Subject: Re: linux-next: build warnings after merge of the tip tree
Date: Tue, 22 Mar 2022 13:07:25 +0100 [thread overview]
Message-ID: <Yjm7/YbuUwjEP43r@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20220322181454.659b15269d8c2e2348f19ba1@kernel.org>
On Tue, Mar 22, 2022 at 06:14:54PM +0900, Masami Hiramatsu wrote:
> On Tue, 22 Mar 2022 09:08:22 +0100
> Peter Zijlstra <peterz@infradead.org> wrote:
>
> > On Tue, Mar 22, 2022 at 02:31:36PM +0900, Masami Hiramatsu wrote:
> >
> > > > Also, I think both should fix regs->ss.
> > >
> > > I'm not sure this part. Since the return trampoline should run in the same
> > > context of the called function, isn't ss same there too?
> >
> > It creates pt_regs on the stack, so the trampolines do:
> >
> > push $arch_rethook_trampoline
> > push %rsp
> > pushf
> > sub $24, %rsp /* cs, ip, orig_ax */
> > push %rdi
> > ...
> > push %r15
> >
> > That means that if anybody looks at regs->ss, it'll find
> > $arch_rethook_trampoline, which isn't a valid segment descriptor, or am
> > I just really bad at counting today?
>
> Ah, got it. It seems that the ss was skipped from the beginning, and
> no one argued that.
Yeah, this is a long-standing issue, but I noticed it when looking at
the code yesterday.
> > I'm thinking you want a copy of __KERNEL_DS in that stack slot, not a
> > function pointer.
>
> The function pointer is for unwinding stack which involves the kretprobe.
> Anyway, I can add a slot for ss if it is neeeded. But if it always be
> __KERNEL_DS, is it worth to save it?
Probably, to save someone future head-aches. The insn-eval.c stuff will
actually look at SS when it tries to decode BP/SP fields, and I've got
vague memories of actually using that a while ago. I think I was playing
around with double-fault and the whole espfix64 mess and hit the ESPFIX
segment.
next prev parent reply other threads:[~2022-03-22 12:07 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-21 3:03 linux-next: build warnings after merge of the tip tree Stephen Rothwell
2022-03-21 12:55 ` Peter Zijlstra
2022-03-21 13:04 ` Peter Zijlstra
2022-03-21 13:08 ` Peter Zijlstra
2022-03-21 13:45 ` Peter Zijlstra
2022-03-21 14:19 ` Mark Rutland
2022-03-21 15:28 ` Peter Zijlstra
2022-03-21 15:45 ` Peter Zijlstra
2022-03-21 16:37 ` Linus Torvalds
2022-03-21 16:44 ` Peter Zijlstra
2022-03-21 16:52 ` Linus Torvalds
2022-03-21 22:05 ` Stephen Rothwell
2022-03-21 22:12 ` Alexei Starovoitov
2022-03-21 22:46 ` Stephen Rothwell
2022-03-21 22:50 ` Alexei Starovoitov
2022-03-21 22:55 ` Steven Rostedt
2022-03-22 4:51 ` Masami Hiramatsu
2022-03-22 4:53 ` Alexei Starovoitov
2022-03-22 7:42 ` Peter Zijlstra
2022-03-22 4:38 ` Masami Hiramatsu
2022-03-21 15:28 ` Steven Rostedt
2022-03-21 16:04 ` Peter Zijlstra
2022-03-21 16:12 ` Steven Rostedt
2022-03-21 16:15 ` Steven Rostedt
2022-03-21 16:22 ` Steven Rostedt
2022-03-21 16:39 ` Steven Rostedt
2022-03-21 16:40 ` Peter Zijlstra
2022-03-21 16:45 ` Steven Rostedt
2022-03-21 16:50 ` Peter Zijlstra
2022-03-21 16:54 ` Steven Rostedt
2022-03-22 7:54 ` Peter Zijlstra
2022-03-22 13:12 ` Steven Rostedt
2022-03-22 14:35 ` Peter Zijlstra
2022-03-22 15:04 ` Steven Rostedt
2022-03-22 15:19 ` Peter Zijlstra
2022-03-22 15:48 ` Peter Zijlstra
2022-03-22 16:17 ` Steven Rostedt
2022-03-23 2:23 ` Masami Hiramatsu
2022-03-23 2:42 ` Steven Rostedt
2022-03-23 6:28 ` Masami Hiramatsu
2022-03-22 14:25 ` Masami Hiramatsu
2022-03-21 16:48 ` Peter Zijlstra
2022-03-22 5:31 ` Masami Hiramatsu
2022-03-22 8:08 ` Peter Zijlstra
2022-03-22 9:14 ` Masami Hiramatsu
2022-03-22 12:07 ` Peter Zijlstra [this message]
2022-03-22 12:17 ` Peter Zijlstra
2022-03-22 12:46 ` Masami Hiramatsu
2022-03-22 13:22 ` Steven Rostedt
2022-03-22 13:15 ` Mark Rutland
2022-03-22 13:51 ` Masami Hiramatsu
2022-03-22 10:46 ` Peter Zijlstra
2022-03-22 10:59 ` Peter Zijlstra
-- strict thread matches above, loose matches on Subject: below --
2024-02-02 3:59 Stephen Rothwell
2023-12-01 0:29 Stephen Rothwell
2023-12-01 12:09 ` Uros Bizjak
2023-12-04 4:08 ` Stephen Rothwell
2023-12-04 7:02 ` Uros Bizjak
2023-12-11 5:19 ` Stephen Rothwell
2023-12-11 7:06 ` Uros Bizjak
2023-06-02 3:12 Stephen Rothwell
2022-11-21 7:41 Stephen Rothwell
2022-05-20 7:49 Stephen Rothwell
2022-04-27 0:10 Stephen Rothwell
2022-04-27 11:31 ` Borislav Petkov
2022-04-27 13:43 ` Tom Lendacky
2022-03-22 3:51 Stephen Rothwell
2022-03-22 21:52 ` Peter Zijlstra
2022-03-22 23:11 ` Stephen Rothwell
2021-12-17 3:40 Stephen Rothwell
2022-01-21 23:58 ` Stephen Rothwell
2022-03-15 2:32 ` Stephen Rothwell
2022-04-04 3:26 ` Stephen Rothwell
2021-10-12 10:20 Stephen Rothwell
2021-10-12 13:58 ` André Almeida
2020-11-30 7:05 Stephen Rothwell
2020-11-30 10:17 ` Borislav Petkov
2020-11-30 21:56 ` Ernst, Justin
2020-11-30 22:18 ` Borislav Petkov
2020-11-23 7:19 Stephen Rothwell
2020-11-23 23:03 ` Jarkko Sakkinen
2017-11-02 2:53 Stephen Rothwell
2017-11-03 21:00 ` Masami Hiramatsu
2017-11-04 8:01 ` Ingo Molnar
2017-11-04 12:16 ` Masami Hiramatsu
2017-11-13 11:31 ` Stephen Rothwell
2017-06-23 4:19 Stephen Rothwell
2016-07-14 3:49 Stephen Rothwell
2016-07-14 3:37 Stephen Rothwell
2016-07-14 4:18 ` Stephen Rothwell
2012-10-12 5:11 Stephen Rothwell
2011-01-31 4:27 Stephen Rothwell
2011-01-31 5:08 ` Jaswinder Singh
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=Yjm7/YbuUwjEP43r@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=Andrew.Cooper3@citrix.com \
--cc=ast@kernel.org \
--cc=hjl.tools@gmail.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-next@vger.kernel.org \
--cc=linux-toolchains@vger.kernel.org \
--cc=mhiramat@kernel.org \
--cc=mingo@redhat.com \
--cc=ndesaulniers@google.com \
--cc=rick.p.edgecombe@intel.com \
--cc=rostedt@goodmis.org \
--cc=rppt@kernel.org \
--cc=sfr@canb.auug.org.au \
--cc=tglx@linutronix.de \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).