linux-kernel - Re: [PATCH v1 2/2] cleanup.h: Introduce DEFINE_INACTIVE_GUARD and activate

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHk-=whef03dn8OWJ01L08hShVHCieVz7Rrzr1HJQOriVBvaDg@mail.gmail.com>
Date: Mon, 2 Sep 2024 11:10:12 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Ingo Molnar <mingo@...hat.com>, 
	linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>, 
	Greg KH <gregkh@...uxfoundation.org>, Sean Christopherson <seanjc@...gle.com>, 
	Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>, 
	Alexei Starovoitov <ast@...nel.org>, Yonghong Song <yhs@...com>, "Paul E . McKenney" <paulmck@...nel.org>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Namhyung Kim <namhyung@...nel.org>, 
	bpf@...r.kernel.org, Joel Fernandes <joel@...lfernandes.org>, 
	linux-trace-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v1 2/2] cleanup.h: Introduce DEFINE_INACTIVE_GUARD and activate_guard

On Mon, 2 Sept 2024 at 08:43, Peter Zijlstra <peterz@...radead.org> wrote:
>
> and Linus took objection to similar patterns. But perhaps my naming
> wasn't right.

Well, more of a "this stuff is new, let's start very limited and very clear".

I'm not loving the inactive guard, but I did try to think of a better
model for it, and I can't.  I absolutely hate the *example*, though:

  void func(bool a)
  {
        DEFINE_INACTIVE_GUARD(preempt_notrace, myguard);

        [...]
        if (a) {
                might_sleep();
                activate_guard(preempt_notrace, myguard)();
        }
        [ protected code ]
  }

because that "protected code" obviously is *NOT* protected code. It's
conditionally protected only in one situation.

Honestly, I still think the guard macros are new enough that we should
strive to avoid them in complicated cases like this. And this *is*
complicated. It *looks* simple, but when even the example that was
given was pure and utter garbage, it's clearly not *actually* simple.

Once some code is sometimes protected, and sometimes isn't, and you
have magic compiler stuff that *hides* it, I'm not sure we should use
the magic compiler stuff.

                Linus