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Date:	Thu, 7 Aug 2014 18:38:32 +0100
From:	Leif Lindholm <leif.lindholm@...aro.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	linux-kernel@...r.kernel.org, Mark Salter <msalter@...hat.com>,
	Laura Abbott <lauraa@...eaurora.org>,
	Liu hua <sdu.liu@...wei.com>, Rabin Vincent <rabin@....in>,
	Nikolay Borisov <Nikolay.Borisov@....com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Tomasz Figa <t.figa@...sung.com>,
	Rob Herring <robh@...nel.org>,
	Doug Anderson <dianders@...gle.com>,
	Jason Wessel <jason.wessel@...driver.com>,
	Will Deacon <will.deacon@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/8] arm: use generic fixmap.h

On Thu, Aug 07, 2014 at 08:01:46AM -0700, Kees Cook wrote:
> From: Mark Salter <msalter@...hat.com>
> 
> ARM is different from other architectures in that fixmap pages are indexed
> with a positive offset from FIXADDR_START.  Other architectures index with
> a negative offset from FIXADDR_TOP.  In order to use the generic fixmap.h
> definitions, this patch redefines FIXADDR_TOP to be inclusive of the
> useable range.  That is, FIXADDR_TOP is the virtual address of the topmost
> fixed page.  The newly defined FIXADDR_END is the first virtual address
> past the fixed mappings.
> 
> Signed-off-by: Mark Salter <msalter@...hat.com>
> Reviewed-by: Doug Anderson <dianders@...omium.org>
> [update for "ARM: 8031/2: change fixmap mapping region to support 32 CPUs"]
> [flipped highmem order, thanks to Laura Abbott]
> Signed-off-by: Kees Cook <keescook@...omium.org>
> Cc: Laura Abbott <lauraa@...eaurora.org>
> ---
>  arch/arm/include/asm/fixmap.h | 27 +++++++++------------------
>  arch/arm/mm/highmem.c         |  8 ++++++--
>  arch/arm/mm/init.c            |  2 +-
>  3 files changed, 16 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
> index 74124b0d0d79..190142d174ee 100644
> --- a/arch/arm/include/asm/fixmap.h
> +++ b/arch/arm/include/asm/fixmap.h
> @@ -2,27 +2,18 @@
>  #define _ASM_FIXMAP_H
>  
>  #define FIXADDR_START		0xffc00000UL
> -#define FIXADDR_TOP		0xffe00000UL
> -#define FIXADDR_SIZE		(FIXADDR_TOP - FIXADDR_START)
> +#define FIXADDR_END		0xffe00000UL
> +#define FIXADDR_TOP		(FIXADDR_END - PAGE_SIZE)
> +#define FIXADDR_SIZE		(FIXADDR_END - FIXADDR_START)
>  
>  #define FIX_KMAP_NR_PTES	(FIXADDR_SIZE >> PAGE_SHIFT)
>  
> -#define __fix_to_virt(x)	(FIXADDR_START + ((x) << PAGE_SHIFT))
> -#define __virt_to_fix(x)	(((x) - FIXADDR_START) >> PAGE_SHIFT)
> +enum fixed_addresses {
> +	FIX_KMAP_BEGIN,
> +	FIX_KMAP_END = FIX_KMAP_NR_PTES - 1,
> +	__end_of_fixed_addresses
> +};
>  
> -extern void __this_fixmap_does_not_exist(void);
> -
> -static inline unsigned long fix_to_virt(const unsigned int idx)
> -{
> -	if (idx >= FIX_KMAP_NR_PTES)
> -		__this_fixmap_does_not_exist();
> -	return __fix_to_virt(idx);
> -}
> -
> -static inline unsigned int virt_to_fix(const unsigned long vaddr)
> -{
> -	BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
> -	return __virt_to_fix(vaddr);
> -}
> +#include <asm-generic/fixmap.h>
>  
>  #endif
> diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
> index 45aeaaca9052..a1241ee8425e 100644
> --- a/arch/arm/mm/highmem.c
> +++ b/arch/arm/mm/highmem.c
> @@ -23,14 +23,18 @@ pte_t *fixmap_page_table;
>  static inline void set_fixmap_pte(int idx, pte_t pte)
>  {
>  	unsigned long vaddr = __fix_to_virt(idx);
> -	set_pte_ext(fixmap_page_table + idx, pte, 0);
> +	pte_t *ppte = pte_offset_kernel(pmd_off_k(FIXADDR_START), vaddr);
> +
> +	set_pte_ext(ppte, pte, 0);
>  	local_flush_tlb_kernel_page(vaddr);
>  }
>  
>  static inline pte_t get_fixmap_pte(unsigned long vaddr)
>  {
>  	unsigned long idx = __virt_to_fix(vaddr);

idx is now "unused variable".

> -	return *(fixmap_page_table + idx);
> +	pte_t *ppte = pte_offset_kernel(pmd_off_k(FIXADDR_START), vaddr);
> +
> +	return *ppte;
>  }
>  
>  void *kmap(struct page *page)
> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
> index 659c75d808dc..ad82c05bfc3a 100644
> --- a/arch/arm/mm/init.c
> +++ b/arch/arm/mm/init.c
> @@ -570,7 +570,7 @@ void __init mem_init(void)
>  			MLK(DTCM_OFFSET, (unsigned long) dtcm_end),
>  			MLK(ITCM_OFFSET, (unsigned long) itcm_end),
>  #endif
> -			MLK(FIXADDR_START, FIXADDR_TOP),
> +			MLK(FIXADDR_START, FIXADDR_END),
>  			MLM(VMALLOC_START, VMALLOC_END),
>  			MLM(PAGE_OFFSET, (unsigned long)high_memory),
>  #ifdef CONFIG_HIGHMEM
> -- 
> 1.9.1

Apart from that, verified with early_ioremap/UEFI patches on TC2.

Tested-by: Leif Lindholm <leif.lindholm@...aro.org>
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