linux-kernel - Re: Fwd: Problem with set_memory

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Message-ID: <20100204091250.GD13318@laptop>
Date:	Thu, 4 Feb 2010 20:12:50 +1100
From:	Nick Piggin <npiggin@...e.de>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Oleg Kutkov <elenbert@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: Fwd: Problem with set_memory_rw

On Thu, Feb 04, 2010 at 05:51:33PM +0900, KAMEZAWA Hiroyuki wrote:
> On Thu, 4 Feb 2010 10:09:57 +0200
> Oleg Kutkov <elenbert@...il.com> wrote:
> > Thank for answer!
> > But this is a very strange, because 0x0509940 - 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. 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.
> > 
> 
> Below is only about virt_to_page() etc... (not about set_memory_rw())
> Maybe my answer for set_memory_rw() was pointless.
> 
> I think system call table is on .rodata section and set_memory_rw() doesn't
> allow change attributes on .rodata sections(not .text)
> ..I'm sorry if I'm wrong.

You are right. static_protections() forbids rodata from being marked RW.

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