linux-kernel - Re: [RFC PATCH] text_poke/ftrace/x86: Allow text

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Message-ID: <20221024210535.61174928@gandalf.local.home>
Date:   Mon, 24 Oct 2022 21:05:35 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-arch@...r.kernel.org
Subject: Re: [RFC PATCH] text_poke/ftrace/x86: Allow text_poke() to be
 called in early boot

On Mon, 24 Oct 2022 18:02:32 -0700
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Mon, Oct 24, 2022 at 5:21 PM Steven Rostedt <rostedt@...dmis.org> wrote:
> >
> > It's all about updating read only pages that are executable with a shadow mm.  
> 
> Right. And it doesn't actually need the mm at all, all it wants is the
> kernel page tables. Which is why all the "dup_mmap()" stuff seems so
> wrong.
> 
> I suspect mm_alloc() does everything that VM actually needs.
> 
> IOW, it shouldn't have used the fork() helper, it should have used the
> execve() helper that actually starts out from a clean slate. Because a
> clean slate is exactly what that code wants.
> 
> No?
> 

Something to look into. But I'm guessing that's best for the next merge
window, and not for the -rc releases?

-- Steve