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

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Date:   Thu, 1 Feb 2018 18:14:27 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     David Woodhouse <dwmw2@...radead.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        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, Feb 01, 2018 at 04:51:35PM +0000, David Woodhouse wrote:
> > Ideally we'd have a way to mark the module 'unsafe' or something.
> 
> No, we just need to set IBRS before doing it. 

That would work, assuming IBRS is available to begin with of course. Do
we WARN if we hit this code and don't have IBRS available?

> The same applies to any
> EFI runtime calls, APM and all kinds of other random crap that calls
> into firmware. I'm not sure why those aren't showing up.

arch/x86/platform/efi/Makefile:OBJECT_FILES_NON_STANDARD_efi_thunk_$(BITS).o := y
arch/x86/platform/efi/Makefile:OBJECT_FILES_NON_STANDARD_efi_stub_$(BITS).o := y

And similar things tell objtool to please not look..