linux-kernel - Re: [PATCH] retpoline/module: Taint kernel for missing retpoline in module

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Date:   Sat, 13 Jan 2018 06:53:00 -0800
From:   Andi Kleen <andi@...stfloor.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Andi Kleen <andi@...stfloor.org>, tglx@...utronix.de,
        dwmw@...zon.co.uk, torvalds@...ux-foundation.org,
        linux-kernel@...r.kernel.org, arjan.van.de.ven@...el.com,
        peterz@...radead.org, Andi Kleen <ak@...ux.intel.com>,
        jeyu@...nel.org
Subject: Re: [PATCH] retpoline/module: Taint kernel for missing retpoline in
 module

> > When the a module hasn't been compiled with a retpoline
> > aware compiler, print a warning and set a taint flag.
> 
> Isn't that caught by the "build with a different compiler/version" check
> that we have?  Or used to have?  If not, can't we just make it into that

- the compiler version number may not change if a distribution backports
the gcc changes for the new flag
- the module might be using a custom make file that does not correctly
set the flag, even if the compiler supports it

> type of check to catch this type of problem no matter what type of
> feature/option it is trying to catch?

I suspect that would be far more complicated. Also what's the point
of putting this information into every symbol? Once per module 
is good enough.

We already have similar checks for staging etc.

-Andi