linux-kernel - Re: [PATCH v3 1/7] x86/sgx: Provide indication of life-cycle of EPC pages

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Date:   Fri, 30 Jul 2021 03:34:35 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     "Hansen, Dave" <dave.hansen@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/7] x86/sgx: Provide indication of life-cycle of EPC
 pages

On Wed, Jul 28, 2021 at 10:57:07PM +0000, Luck, Tony wrote:
> > Wouldn't it be safer to do something like:
> >
> >	page->owner = owner ? owner : (void *)-1;
> >
> > -1 is non-NULL, but also invalid, which makes it harder for us to poke
> > ourselves in the eye.
> 
> Does Linux have some #define INVALID_POINTER thing that
> provides a guaranteed bad (e.g. non-canonical) value?
> 
> (void *)-1 seems hacky.
> 
> -Tony

MAP_FAILED?

/Jarkko