linux-kernel - Re: [Patch BUGFIX] kcore: fix its wrong size on x86

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Date:	Fri, 12 Jun 2009 21:20:50 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Amerigo Wang <xiyou.wangcong@...il.com>
Cc:	Tao Ma <tao.ma@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Alexey Dobriyan <adobriyan@...il.com>
Subject: Re: [Patch BUGFIX] kcore: fix its wrong size on x86_64

Amerigo Wang <xiyou.wangcong@...il.com> writes:

> Fix wrong /proc/kcore size on x86_64.

How does that change anything?

> x86_64 uses __va() macro to caculate the virtual address passed to kclist_add()
> but decodes it with its own macro kc_vadd_to_offset(). This is wrong.
>
> Also, according to Documentation/x86/x86_64/mm.txt, kc_vaddr_to_offset()
> is wrong too.
>
> So just remove them, use the generic macro.
>
> BTW, the man page for /proc/kcore is wrong, its size can be more than
> the physical memory size, because it also contains memory area of
> vmalloc(), vsyscall etc...

The set of offsets that are usable sure.

However the size from stat is:
          proc_root_kcore->size = (size_t)high_memory - PAGE_OFFSET + PAGE_SIZE;

Which can not be different than the physical memory size.

> Reported-by: Tao Ma <tao.ma@...cle.com>
> Signed-off-by: WANG Cong <amwang@...hat.com>
> Cc: Eric W. Biederman <ebiederm@...ssion.com>
>
> ---
> diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
> index abde308..cdbfd1d 100644
> --- a/arch/x86/include/asm/pgtable_64.h
> +++ b/arch/x86/include/asm/pgtable_64.h
> @@ -163,12 +163,6 @@ extern void cleanup_highmap(void);
>  #define PAGE_AGP    PAGE_KERNEL_NOCACHE
>  #define HAVE_PAGE_AGP 1
>  
> -/* fs/proc/kcore.c */
> -#define	kc_vaddr_to_offset(v) ((v) & __VIRTUAL_MASK)
> -#define	kc_offset_to_vaddr(o)				\
> -	(((o) & (1UL << (__VIRTUAL_MASK_SHIFT - 1)))	\
> -	 ? ((o) | ~__VIRTUAL_MASK)			\
> -	 : (o))
>  
>  #define __HAVE_ARCH_PTE_SAME
>  #endif /* !__ASSEMBLY__ */
--
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