linux-kernel - Re: [PATCH v3 23/26] kbuild/objtool: Add objtool-vmlinux.o pass

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Message-ID: <20200324220321.ivoh47j4tkbcwotr@treble>
Date:   Tue, 24 Mar 2020 17:03:21 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org, x86@...nel.org,
        mhiramat@...nel.org, mbenes@...e.cz, brgerst@...il.com
Subject: Re: [PATCH v3 23/26] kbuild/objtool: Add objtool-vmlinux.o pass

On Tue, Mar 24, 2020 at 04:31:36PM +0100, Peter Zijlstra wrote:
> Now that objtool is capable of processing vmlinux.o and actually has
> something useful to do there, (conditionally) add it to the final link
> pass.
> 
> This will increase build time by a few seconds.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  lib/Kconfig.debug       |    5 +++++
>  scripts/link-vmlinux.sh |   24 ++++++++++++++++++++++++
>  2 files changed, 29 insertions(+)
> 
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -379,6 +379,11 @@ config STACK_VALIDATION
>  	  For more information, see
>  	  tools/objtool/Documentation/stack-validation.txt.
>  
> +config VMLINUX_VALIDATION
> +	bool
> +	depends on STACK_VALIDATION && DEBUG_ENTRY && !PARAVIRT
> +	default y
> +

So I'm assuming this is incompatible with PARAVIRT because of all the
indirect pvops calls?

I'm thinking it should be easy to detect those and whitelist them
because they always have a pv_ops relocation associated with the call
instruction.

-- 
Josh