linux-kernel - Re: Problem with set_memory

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Message-ID: <4B6A8889.4070407@gmail.com>
Date:	Thu, 04 Feb 2010 10:42:49 +0200
From:	Oleg Kutkov <elenbert@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: Problem with set_memory_rw

"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com 
<mailto:kamezawa.hiroyu@...fujitsu.com>> wrote:
> set_memory_rw()'s 1st argument requires virtual address.
> So, you need virtual address of the page you want.
>
>  - phys_to_virt() ... convert physical address to virtual address.
>  - virt_to_phys() ... convert virtual address to physical.
>
> Anyway, RW is vitual address mapping's attribute and not for physical.
>
> Thanks,
> -Kame   
>

Thank for answer!
But this is a very strange, because 0x0509940, i passed, - it a virtual 
memory address (i got it from System.map, this is a system call table, 
on my machine). set_memory_rw return zero, anyway. So i can't continue 
writing to memory. Maybe, system call table is much write protected, so 
i can't change attribute of memory page?
One more interesting thing:

struct page *pg;
pg = virt_to_page(addr);
unsigned long page_addr;
page_addr = (unsigned long) page_address(pg);

addr - this is my virtual address (provided by System.map)
But page_addr got another value!
What wrong?
Sorry, if my questions is to stupid.

P.S. I know, that overwriting system call table is very bad, i just 
experimenting with my own network drivers and i need to replace some 
network system calls..

Best regard,
Oleg.

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