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Date: Tue, 1 Mar 2005 17:17:36 +0000 (GMT)
From: Hugh Dickins <hugh@veritas.com>
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To: Prakash Bhurke <prakash_bhurke@yahoo.com>
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Subject: Re: memory mapping of vmalloc
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On Tue, 1 Mar 2005, Prakash Bhurke wrote:
>   I am trying to map a vmalloc kernel buffer to user
> space using remap_page_range(). In my module, this
> function returns success if we call mmap() from user
> space, but i can not access content of vmalloc buffer
> from user space. Pointer returned by mmap() syscall
> seems pointing to other memory page which contains
> zeros. I am using linux 2.6.10 kernel on Pentium 4
> system.

Look for "rvmalloc" in various drivers in the kernel source tree:
you must SetPageReserved before remap_pfn_range (or remap_page_range)
agrees to map the page, and ClearPageReserved before freeing after.

Hugh