linux-kernel - Re: [PATCH 0/7] objtool: retpoline validation

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Message-ID: <1517499131.18619.317.camel@infradead.org>
Date:   Thu, 01 Feb 2018 15:32:11 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>
Subject: Re: [PATCH 0/7] objtool: retpoline validation

On Thu, 2018-02-01 at 09:28 -0600, Josh Poimboeuf wrote:
> On Thu, Feb 01, 2018 at 03:34:21PM +0100, Peter Zijlstra wrote:
> > 
> > There are the retpoline validation patches; they work with the
> > __noretpoline
> > thing from David.
> Have you run this through 0-day bot yet?  A manual awk/sed found
> another
> one, which objtool confirms:
> 
>   drivers/watchdog/.tmp_hpwdt.o: warning: objtool: .text+0x24:
> indirect call found in RETPOLINE build
> 
> And my search wasn't exhaustive so it would be good to sic 0-day bot on
> it.

We discussed that one. It's correct; we're calling into firmware so
there's *no* point in retpolining that one. We need to set IBRS before
any runtime calls into firmware, if we want to be safe.
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