linux-kernel - Re: [PATCH v2 5/7] x86/mm, tracing: Fix CR2 corruption

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Message-ID: <48e29640-fedc-3e72-535c-27ef07b73938@etsukata.com>
Date:   Mon, 8 Jul 2019 17:58:49 +0900
From:   Eiichi Tsukata <devel@...ukata.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Andrew Lutomirski <luto@...nel.org>,
        Peter Anvin <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Juergen Gross <jgross@...e.com>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        He Zhe <zhe.he@...driver.com>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH v2 5/7] x86/mm, tracing: Fix CR2 corruption



On 2019/07/08 16:48, Peter Zijlstra wrote:
...

> 
> Or are we going to put the CR2 save/restore on every single tracepoint?
> But then we also need it on the mcount/fentry stubs and we again have
> multiple places.
> 
> Whereas if we stick it in the entry path, like I proposed, we fix it in
> one location and we're done.
> 

Thanks to your detailed comments and the discussion, I've come to realize
that your solution "save CR2 early in the entry" is the simplest and reasonable.

By the way, is there possibility that the WARNING(#GP in execve(2)) which Steven
previously hit? : https://lore.kernel.org/lkml/20190321095502.47b51356@gandalf.local.home/

Even if there were, it will *Not* be the bug introduced by this patch series,
but the bug revealed by this series.

Thanks,

Eiichi