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

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Date:   Thu, 12 Mar 2020 12:44:20 -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,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [RFC][PATCH 00/16] objtool: vmlinux.o and noinstr validation

On Thu, Mar 12, 2020 at 05:23:37PM +0100, Peter Zijlstra wrote:
> So one of the problem i've ran into while playing with this and Thomas'
> patches is that it is 'difficult' to deal with indirect function calls.
> 
> objtool basically gives up instantly.
> 
> I know smatch has passes were it looks for function pointer assignments
> and carries that forward into it's callchain generation. Doing something
> like that for objtool is going to be 'fun'...

Yeah, it would have to keep track of register and memory values, even
across function calls.  Which is basically crossing over into emulation
territory.  Which objtool wasn't really built for.

-- 
Josh