linux-kernel - Re: linux page table

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Message-ID: <CALKntY3Pi8fxQpG6CzuP-DHGYPjhXNNL7M1nqiMBxUgLMv3frA@mail.gmail.com>
Date:	Sat, 1 Sep 2012 13:12:20 -0700
From:	Xin Tong <xerox.time.tech@...il.com>
To:	Shentino <shentino@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: linux page table

On Sat, Sep 1, 2012 at 1:01 PM, Shentino <shentino@...il.com> wrote:
> On Sat, Sep 1, 2012 at 12:30 PM, Xin Tong <xerox.time.tech@...il.com> wrote:
>> When a process is created in Linux, corresponding page table is
>> implemented. In the current x86 linux, the page table is a multi-level
>> page table and CR3 points to the first level of the page table.  I
>> have 2 questions.
>>
>> 1. is the value in CR3 virtual address or physical address ?
>
> It's a physical address.  It points the CPU to it in physical memory.
>
> More generally, all addresses in page tables, directories, etc are
> physical addresses.
>
>> 2. can the address of the first level of the page table during a
>> process's lifetime change ?
>
> This I don't know.
>
>> 3. can two different processes have their CR3 being the same value
>> even though they have different first level page tables ?
>
> I'm not sure about this, but I think CR3 is actually bound to the
> mm_struct and not the process.
>
> Think about separate processes with the same address space, such as
> multithreaded processes.

Do not all the threads share the same address space in a multithreaded program ?

Xin

>
>>
>> Thanks
>> --
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