linux-kernel - Re: [PATCH] arm64: add kc_offset_to_vaddr and kc_vaddr_to

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Message-ID: <20150904165102.GA25257@e104818-lin.cambridge.arm.com>
Date:	Fri, 4 Sep 2015 17:51:02 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Will Deacon <will.deacon@....com>
Cc:	yalin wang <yalin.wang2010@...il.com>,
	"fkan@....com" <fkan@....com>,
	"steve.capper@...aro.org" <steve.capper@...aro.org>,
	"ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"minchan@...nel.org" <minchan@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"lauraa@...eaurora.org" <lauraa@...eaurora.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH] arm64: add kc_offset_to_vaddr and kc_vaddr_to_offset
 macro

On Wed, Sep 02, 2015 at 11:24:54AM +0100, Will Deacon wrote:
> On Sun, Aug 30, 2015 at 07:19:59AM +0100, yalin wang wrote:
> > This patch add kc_offset_to_vaddr() and kc_vaddr_to_offset(),
> > the default version doesn't work on arm64, because arm64 kernel address
> > is below the PAGE_OFFSET, like module address and vmemmap address are
> > all below PAGE_OFFSET address.
> > 
> > Signed-off-by: yalin wang <yalin.wang2010@...il.com>
> > ---
> >  arch/arm64/include/asm/pgtable.h | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> > index d374191..ef1ed5c 100644
> > --- a/arch/arm64/include/asm/pgtable.h
> > +++ b/arch/arm64/include/asm/pgtable.h
> > @@ -660,6 +660,8 @@ static inline void update_mmu_cache(struct vm_area_struct *vma,
> >  
> >  #define update_mmu_cache_pmd(vma, address, pmd) do { } while (0)
> >  
> > +#define	kc_vaddr_to_offset(v) ((v) & ((1UL << VA_BITS) - 1))
> > +#define	kc_offset_to_vaddr(o) ((o) | ~((1UL << VA_BITS) - 1))
> 
> I think it would be cleaner to define something like VIRTUAL_BASE, and
> then define the vmalloc area in terms of that as well as these kcore
> macros.

The KASan patches were doing this, defining VA_START and defining
VMALLOC_START in terms of it. But they missed the merging window.

-- 
Catalin
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