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Hi,<br>
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<div>If you have your file data in a user space buffer, "get_user_pages" and "kmap" can be used to get it mapped to a kernel virtual address. <span style="font-size:10pt">But I still doubt that this would solve the problem of mapping the disk file data to kernel
space.</span></div>
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<div style="margin:0 0 2pt 0"><font color="#7F7F7F" face="Tahoma,sans-serif" size="1"><span style="font-size:8pt">Regards,</span></font></div>
<div style="margin:0 0 2pt 0"><font color="#404040" face="Tahoma,sans-serif" size="1"><span style="font-size:8pt"><b>Binoy Jayan</b></span></font></div>
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<div id="divRpF552557" style="direction:ltr"><font face="Tahoma" size="2" color="#000000"><b>From:</b> kernelnewbies-bounces@kernelnewbies.org [kernelnewbies-bounces@kernelnewbies.org] on behalf of Yu Bi [lazysmartegg@gmail.com]<br>
<b>Sent:</b> Tuesday, December 31, 2013 8:05 AM<br>
<b>To:</b> kernelnewbies@kernelnewbies.org<br>
<b>Subject:</b> Re: how to use mmap() on a disk file to get a kernel address?<br>
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<div dir="ltr">Thanks for your idea.<br>
Because I implement a kernel storage service based on a disk file through VFS layer.
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To simplify the implementation, I prefer to read/write the mapped kernel space address instead of the file data access api(such as page cache API / VFS API).<br>
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In FreeBSD, I can use <span>vm_map_find</span><span></span> to map a file into kernel space address( vnode pager)<br>
But in linux, I don't know how to implement this(map disk file into kernel space)?
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<div class="gmail_quote">On Thu, Dec 26, 2013 at 3:42 PM, Yu Bi <span dir="ltr"><<a href="mailto:lazysmartegg@gmail.com" target="_blank">lazysmartegg@gmail.com</a>></span> wrote:<br>
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<div>Hi,</div>
<div> <span style="line-height:16.666667938232422px; font-size:13.333333969116211px; font-family:Arial,'Liberation Sans','DejaVu Sans',sans-serif">I try to mmap a file in a linux kernel module. I have tried to use the function do_mmap_pgoff</span><span style="line-height:16.666667938232422px; font-size:13.333333969116211px; font-family:Arial,'Liberation Sans','DejaVu Sans',sans-serif">.
But the address returned is memory virtual address in current process' user space, i.e., below the kernel boundary. Instead, I want to map the file in the kernel space and get the kernel virtual address of the mapped region. Is there any kernel API in Linux
support this operation? Or I have to reimplement a kernel mmap version ? </span></div>
<div> But reimplement a kernel version mmap() is not easy I guess. Do you have any idea? </div>
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