| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <CAGXu5jL7L--apmCSO52ErUMPfXPBUBKCCg2NwYAc8FUNZaAGvg@mail.gmail.com>
Date: Thu, 7 Aug 2014 07:35:30 -0700
From: Kees Cook <keescook@...omium.org>
To: Laura Abbott <lauraa@...eaurora.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
Nicolas Pitre <nicolas.pitre@...aro.org>,
Rob Herring <robh@...nel.org>, Liu hua <sdu.liu@...wei.com>,
Catalin Marinas <catalin.marinas@....com>,
Tomasz Figa <t.figa@...sung.com>,
Will Deacon <will.deacon@....com>,
Leif Lindholm <leif.lindholm@...aro.org>,
Doug Anderson <dianders@...gle.com>,
Rabin Vincent <rabin@....in>,
Nikolay Borisov <Nikolay.Borisov@....com>,
Mark Salter <msalter@...hat.com>,
Russell King - ARM Linux <linux@....linux.org.uk>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/7] arm: use generic fixmap.h
On Wed, Aug 6, 2014 at 7:24 PM, Laura Abbott <lauraa@...eaurora.org> wrote:
> On 8/6/2014 12:32 PM, 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"]
>> Signed-off-by: Kees Cook <keescook@...omium.org>
>> ---
>> arch/arm/include/asm/fixmap.h | 27 +++++++++------------------
>> arch/arm/mm/init.c | 2 +-
>> 2 files changed, 10 insertions(+), 19 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/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
>>
>
> I'm working off of a 3.14 kernel and with this backported
> kmap_atomic does not actually map properly for me. This was
>
> my quick fix (not sure if we should be using __set_fixmap?). Or did
> I fail at backportery?
>
> -----8<-----
> From ea11b54704aa0a311ab3d05fd70072679bfe1a0b Mon Sep 17 00:00:00 2001
> From: Laura Abbott <lauraa@...eaurora.org>
> Date: Wed, 6 Aug 2014 19:20:46 -0700
> Subject: [PATCH] arm: Get proper pte for fixmaps
>
> The generic fixmap.h gets indexes from high to low instead
> of low to high so the fixmap idx does not correspond to
> the array entry in fixmap_page_table. Get the proper pte
> to update.
>
> Signed-off-by: Laura Abbott <lauraa@...eaurora.org>
> ---
> arch/arm/mm/highmem.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
> index bedca3a..7f08e64 100644
> --- a/arch/arm/mm/highmem.c
> +++ b/arch/arm/mm/highmem.c
> @@ -22,14 +22,18 @@
> 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);
> - return *(fixmap_page_table + idx);
> + pte_t *ppte = pte_offset_kernel(pmd_off_k(FIXADDR_START), vaddr);
> +
> + return *ppte;
> }
IIUC, what you have is correct: it matches what I had to do for
__set_fixmap and flips the high/low indexing. Thanks! I'll merge this
with the "use generic fixmap" patch, since it's what flips around the
ordering.
-Kees
--
Kees Cook
Chrome OS Security
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists