linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Peter Zijlstra <peterz@infradead.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org, x86@kernel.org,
	mhiramat@kernel.org, mbenes@suse.cz
Subject: Re: [PATCH v4 01/13] objtool: Remove CFI save/restore special case
Date: Thu, 26 Mar 2020 16:49:38 +0100	[thread overview]
Message-ID: <20200326154938.GO20713@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200326135620.tlmof5fa7p5wct62@treble>

On Thu, Mar 26, 2020 at 08:56:20AM -0500, Josh Poimboeuf wrote:
> On Thu, Mar 26, 2020 at 12:30:49PM +0100, Peter Zijlstra wrote:
> > This isn't ideal either; stuffing code with NOPs just to make
> > annotations work is certainly sub-optimal, but given that sync_core()
> > is stupid expensive in any case, one extra nop isn't going to be a
> > problem here.
> 
> /me puts his hardened objtool maintainer's glasses on...
> 
> The problem is, when you do this kind of change to somebody else's code
> -- like adding a NOP to driver code -- there's a 90% chance they'll NACK
> it and tell you to fix your shit.  Because they'll be happy to tell you
> the code itself should never be changed just to "make objtool happy".

So the only objtool annotation drivers tend to run into is that uaccess
crud. Drivers really had better not need the CFI annotations, otherwise
they doing massively dodgy things.

And the nice thing with the uaccess crud is that they're anchored to
actual instructions, as opposed to this.

> And honestly, they'd be right, and there's not much you can say in
> reply.  And then we end up having to fix it in objtool again anyway.

Well, I agree. I just haven't managed to come up with anything sensible.

> The 'insn == first' check isn't ideal, but at least it works (I think?).

It works, yes, for exactly this one case.



  reply	other threads:[~2020-03-26 15:49 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-25 17:45 [PATCH v4 00/13] objtool: vmlinux.o and moinstr validation Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 01/13] objtool: Remove CFI save/restore special case Peter Zijlstra
2020-03-26 11:30   ` Peter Zijlstra
2020-03-26 12:58     ` Peter Zijlstra
2020-03-26 13:44       ` Josh Poimboeuf
2020-03-26 15:38         ` Peter Zijlstra
2020-03-27  4:19           ` Josh Poimboeuf
2020-03-26 14:44       ` Miroslav Benes
2020-03-26 15:04         ` Miroslav Benes
2020-03-26 13:00     ` Peter Zijlstra
2020-03-26 13:56     ` Josh Poimboeuf
2020-03-26 15:49       ` Peter Zijlstra [this message]
2020-03-26 19:57         ` Peter Zijlstra
2020-03-27  1:00           ` Josh Poimboeuf
2020-03-30 17:02             ` Peter Zijlstra
2020-03-30 19:02               ` Josh Poimboeuf
2020-03-30 20:02                 ` Peter Zijlstra
2020-03-30 20:29                   ` Peter Zijlstra
2020-03-31 11:16                   ` [RFC][PATCH] objtool,ftrace: Implement UNWIND_HINT_RET_OFFSET Peter Zijlstra
2020-03-31 15:31                     ` Steven Rostedt
2020-03-31 16:06                       ` [RFC][PATCH] x86,ftrace: Shrink ftrace_regs_caller() by one byte Peter Zijlstra
2020-03-31 19:58                       ` [RFC][PATCH] objtool,ftrace: Implement UNWIND_HINT_RET_OFFSET Peter Zijlstra
2020-03-31 20:26                         ` Josh Poimboeuf
2020-03-31 20:23                     ` Josh Poimboeuf
2020-03-31 20:40                       ` Peter Zijlstra
2020-03-31 21:07                         ` Peter Zijlstra
2020-03-31 21:17                         ` Josh Poimboeuf
2020-03-31 21:20                           ` Josh Poimboeuf
2020-03-31 22:27                             ` [PATCH v2] " Peter Zijlstra
2020-04-01 14:14                               ` Josh Poimboeuf
2020-04-01 14:22                                 ` Peter Zijlstra
2020-04-01 14:39                                   ` Josh Poimboeuf
2020-04-01 15:38                                     ` Peter Zijlstra
2020-04-01 15:39                                     ` Steven Rostedt
2020-04-01 15:43                               ` Julien Thierry
2020-04-01 17:09                                 ` Peter Zijlstra
2020-04-01 17:33                                   ` Steven Rostedt
2020-04-01 17:45                                     ` Peter Zijlstra
2020-04-01 18:20                                       ` Steven Rostedt
2020-04-01 20:20                                         ` Peter Zijlstra
2020-04-01 17:37                                   ` Josh Poimboeuf
2020-04-02  6:41                                   ` Julien Thierry
2020-04-02  6:56                                     ` Julien Thierry
2020-04-02  7:50                                     ` Peter Zijlstra
2020-04-02  8:16                                       ` Julien Thierry
2020-04-02  8:17                                       ` Peter Zijlstra
2020-04-02  8:29                                         ` Julien Thierry
2020-04-02  8:58                                           ` Miroslav Benes
2020-03-25 17:45 ` [PATCH v4 02/13] objtool: Factor out CFI hints Peter Zijlstra
2020-03-25 18:26   ` Miroslav Benes
2020-03-25 19:41     ` Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 03/13] objtool: Rename struct cfi_state Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 04/13] objtool: Fix !CFI insn_state propagation Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 05/13] objtool: Implement noinstr validation Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 06/13] objtool: Optimize !vmlinux.o again Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 07/13] objtool: Use sec_offset_hash() for insn_hash Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 08/13] objtool: Detect loading function pointers across noinstr Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 09/13] kbuild/objtool: Add objtool-vmlinux.o pass Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 10/13] objtool: Avoid iterating !text section symbols Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 11/13] objtool: Rearrange validate_section() Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 12/13] objtool: Add STT_NOTYPE noinstr validation Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 13/13] objtool: Also consider .entry.text as noinstr Peter Zijlstra
2020-03-25 19:03 ` [PATCH v4 00/13] objtool: vmlinux.o and moinstr validation Miroslav Benes

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=20200326154938.GO20713@hirez.programming.kicks-ass.net \
    --to=peterz@infradead.org \
    --cc=jpoimboe@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mbenes@suse.cz \
    --cc=mhiramat@kernel.org \
    --cc=tglx@linutronix.de \
    --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 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).