linux-kernel - unable to mmap /dev/kmem

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Date:	Thu, 18 Jan 2007 17:47:12 +0100
From:	Nadia Derbey <Nadia.Derbey@...l.net>
To:	LKML <linux-kernel@...r.kernel.org>
Subject: unable to mmap /dev/kmem

Hi there,

Trying to mmap /dev/kmem with an offset I take from /boot/System.map, I 
get an EIO error on a 2.6.20-rc4.
This is something that used to work on older kernels.

Had a look at mmap_kmem() in drivers/char/mem.c, and I'm wondering 
whether pfn is correctly computed there: shouldn't we have something like

pfn = PFN_DOWN(virt_to_phys((void *)PAGE_OFFSET)) +
       __pa(vma->vm_pgoff << PAGE_SHIFT);

instead of

pfn = PFN_DOWN(virt_to_phys((void *)PAGE_OFFSET)) + vma->vm_pgoff;

Or may be should I substract PAGE_OFFSET from the value I get from 
System.map before mmapping /dev/kmem?

Thanks for your help

Regards,
Nadia




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