linux-kernel - Re: generic page.h problem

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

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 23 Mar 2011 15:19:52 -0400
From:	Mike Frysinger <vapier.adi@...il.com>
To:	Mark Salter <msalter@...hat.com>
Cc:	arnd@...db.de, linux-kernel@...r.kernel.org
Subject: Re: generic page.h problem

On Wed, Mar 23, 2011 at 15:12, Mark Salter wrote:
> I'm working with a new architecture port (nommu) and was wanting to use
> the generic page.h but there is a problem. I'm using CONFIG_FLATMEM with
> a non-zero CONFIG_KERNEL_RAM_BASE_ADDRESS. The hardware uses this same
> address to access RAM from code and for DMA purposes. The generic page.h
> has:
>
> #ifdef CONFIG_KERNEL_RAM_BASE_ADDRESS
> #define PAGE_OFFSET             (CONFIG_KERNEL_RAM_BASE_ADDRESS)
> #else
> #define PAGE_OFFSET             (0)
> #endif
>
> #ifndef __ASSEMBLY__
>
> #define __va(x) ((void *)((unsigned long)(x) + PAGE_OFFSET))
> #define __pa(x) ((unsigned long) (x) - PAGE_OFFSET)
>
> The problem I have is that __va(x) and __pa(x) should do nothing on
> this architecture. If I use the following, then everything seems to
> work as it should.
>
>
> diff --git a/include/asm-generic/page.h b/include/asm-generic/page.h
> index 75fec18..4dc4a81 100644
> --- a/include/asm-generic/page.h
> +++ b/include/asm-generic/page.h
> @@ -73,8 +73,8 @@ extern unsigned long memory_end;
>
>  #ifndef __ASSEMBLY__
>
> -#define __va(x) ((void *)((unsigned long)(x) + PAGE_OFFSET))
> -#define __pa(x) ((unsigned long) (x) - PAGE_OFFSET)
> +#define __va(x) ((void *)((unsigned long) (x)))
> +#define __pa(x) ((unsigned long) (x))
>
>  #define virt_to_pfn(kaddr)     (__pa(kaddr) >> PAGE_SHIFT)
>  #define pfn_to_virt(pfn)       __va((pfn) << PAGE_SHIFT)
>
>
> Am I missing something here? The only other arch using the generic
> page.h is blackfin, but it uses a zero PAGE_OFFSET, so my patch
> would have no effect there.

the only arch that defines CONFIG_KERNEL_RAM_BASE_ADDRESS is mn10300,
and it seems that this generic page.h was designed with it in mind.
fwiw, the va/pa defs for mn10300 also ignore PAGE_OFFSET.
-mike
--
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/