linux-kernel - Re: [PATCHv7 10/19] x86/mm: Make __PHYSICAL_MASK_SHIFT and __VIRTUAL_MASK

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Message-ID: <20170928102254.t34en42ruek6d3lu@node.shutemov.name>
Date:   Thu, 28 Sep 2017 13:22:54 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        Borislav Petkov <bp@...e.de>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv7 10/19] x86/mm: Make __PHYSICAL_MASK_SHIFT and
 __VIRTUAL_MASK_SHIFT dynamic

On Thu, Sep 28, 2017 at 10:28:13AM +0200, Ingo Molnar wrote:
> 
> * Kirill A. Shutemov <kirill.shutemov@...ux.intel.com> wrote:
> 
> > --- a/arch/x86/mm/dump_pagetables.c
> > +++ b/arch/x86/mm/dump_pagetables.c
> > @@ -82,8 +82,8 @@ static struct addr_marker address_markers[] = {
> >  	{ 0/* VMALLOC_START */, "vmalloc() Area" },
> >  	{ 0/* VMEMMAP_START */, "Vmemmap" },
> >  #ifdef CONFIG_KASAN
> > -	{ KASAN_SHADOW_START,	"KASAN shadow" },
> > -	{ KASAN_SHADOW_END,	"KASAN shadow end" },
> > +	{ 0/* KASAN_SHADOW_START */,	"KASAN shadow" },
> > +	{ 0/* KASAN_SHADOW_END */,	"KASAN shadow end" },
> 
> What's this? Looks hacky.

KASAN_SHADOW_START and KASAN_SHADOW_END depend on __VIRTUAL_MASK_SHIFT,
which is dynamic for boot-time switching case. It means we cannot
initialize the corresponding address_markers fields compile-time, so we do
it boot-time.

I used the same approach we use to deal with dynamic VMALLOC_START,
VMEMMAP_START and PAGE_OFFSET.

-- 
 Kirill A. Shutemov