linux-kernel - Re: [RFC][PATCH 00/16] objtool: vmlinux.o and noinstr validation

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Message-Id: <20200317232003.b24aa5575ad9d5fd02978a92@kernel.org>
Date:   Tue, 17 Mar 2020 23:20:03 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Peter Zijlstra <peterz@...radead.org>, jpoimboe@...hat.com,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [RFC][PATCH 00/16] objtool: vmlinux.o and noinstr validation

On Tue, 17 Mar 2020 10:26:49 +0100
Thomas Gleixner <tglx@...utronix.de> wrote:

> Masami Hiramatsu <mhiramat@...nel.org> writes:
> > BTW, out of curiously, if BUG*() or WARN*() cases happens in the noinstr
> > section, do we also need to move them (register dump, stack unwinding,
> > printk, console output, etc.) all into noinstr section?
> 
> The current plan is to declare BUG()/WARN() "safe". On x86 it is kinda
> safe as it uses UD2. That raises an exception which handles the bug/warn
> after establishing the correct state.

OK, so at least the entry of BUG()/WARN() is in noinstr, but the
register/stack dump routines are out of noinstr.

> 
> Of course it's debatable, but moving all of this into the noinstr
> section might be just a too wide scope.

Agreed.

Thank you,

-- 
Masami Hiramatsu <mhiramat@...nel.org>