linux-kernel - Re: [PATCH] LSM: Convert security_hook_heads into explicit array of struct list

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Date:   Sun, 28 May 2017 09:38:13 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     casey@...aufler-ca.com, linux-security-module@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
        hch@...radead.org, igor.stoppa@...wei.com,
        james.l.morris@...cle.com, keescook@...omium.org,
        paul@...l-moore.com, sds@...ho.nsa.gov
Subject: Re: [PATCH] LSM: Convert security_hook_heads into explicit array of struct list_head

Casey Schaufler wrote:
> > But currently, LSM_HOOK_INIT() macro depends on the address of
> > security_hook_heads being known at compile time. If we use an enum
> > so that LSM_HOOK_INIT() macro does not need to know absolute address of
> > security_hook_heads, it will help us to use that allocator for LSM hooks.
> >
> > As a result of introducing an enum, security_hook_heads becomes a local
> > variable, making it easier to allocate security_hook_heads at run time.
> 
> You loose the type checking in security.c. This is the same
> objection I had before to this approach. It's why I objected
> to 3dfc9b02864b19f4 and why I didn't adopt the array approach
> in the first place. If it's so important that randstruct not
> complain about the unnatural cast, revert the patch that
> introduced it. I see no net benefit in hiding the symbol over
> loosing the typing. You trade a list of typed function
> pointers for an enumerated list of values. It doesn't even
> make the code look smaller!

I still cannot understand what you are referring by "type checking".
Please explain me what the type checking in security/security.c is.