Re: [PATCH 1/8] arm: use generic fixmap.h

Kees Cook
2014-08-07T17:47:32Z

On Thu, Aug 7, 2014 at 10:38 AM, Leif Lindholm <leif.lindholm@linaro.org> wrote:
> On Thu, Aug 07, 2014 at 08:01:46AM -0700, Kees Cook wrote:
>> From: Mark Salter <msalter@redhat.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@redhat.com>
>> Reviewed-by: Doug Anderson <dianders@chromium.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@chromium.org>
>> Cc: Laura Abbott <lauraa@codeaurora.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".

Ah! Yes, thanks. I'll add HIGHMEM to my build cycles.

>
>> - 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@linaro.org>

Thanks! I've added this and fixed idx above for the future v3 of this series.

-Kees

--
Kees Cook
Chrome OS Security