linux-kernel - Re: [PATCH 14/21] x86/xen: Support objtool vmlinux.o validation in xen-head.S

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Date:   Thu, 14 Jan 2021 19:32:32 -0500
From:   boris.ostrovsky@...cle.com
To:     Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux@...glegroups.com,
        Miroslav Benes <mbenes@...e.cz>,
        Juergen Gross <jgross@...e.com>
Subject: Re: [PATCH 14/21] x86/xen: Support objtool vmlinux.o validation in
 xen-head.S


On 1/14/21 2:40 PM, Josh Poimboeuf wrote:
> The Xen hypercall page is filled with zeros, causing objtool to fall
> through all the empty hypercall functions until it reaches a real
> function, resulting in a stack state mismatch.
>
> The build-time contents of the hypercall page don't matter, since it
> gets mapped to the hypervisor.  Make it more palatable to objtool by
> making each hypervisor function a true empty function, with nops and a
> return.
>
> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Cc: Juergen Gross <jgross@...e.com>
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>


Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>