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Re: GNU Mach: disabling all network device drivers


From: Da Zheng
Subject: Re: GNU Mach: disabling all network device drivers
Date: Fri, 03 Sep 2010 10:01:48 -0400
User-agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1.11) Gecko/20100711 Thunderbird/3.0.6

Hello,

It's strange. I thought the problem doesn't exist any more after I made some
changes in the kernel. Are you using the latest gnumach in the
master-user_level_drivers branch?

Best,
Zheng Da

On 8/30/10 12:15 AM, Diego Nieto Cid wrote:
> Hello,
> 
> Short story: something is clearing kernel_page_dir.
> 
> Long story follows. :)
> 
> On Wed, Jun 09, 2010 at 08:24:55AM +0200, Samuel Thibault wrote:
>>
>> These are correct. So that must the the pagetable that is incorrect.
>> Check out cr3 and such.
>>
>  
> While trying DDE I came across this problem too. I run a few tests and
> your guess is apparently correct:
> 
>  +-------+--------+--------+---------+------+-----+---------+
>  | Test# |   eip  |  *esp  |   kpd   | kpd' | CR3 |   CR3'  |
>  + ------+--------+--------+---------+------+-----+---------+
>  |   1   | 107e92 | 1436c7 |   ---   | ---  | --- |   ---   |
>  +-------+--------+--------+---------+------+-----+---------+
>  |   2   | 1051f9 |   ---  | 1371000 | ---  | kpd | 2e8f000 |
>  +-------+--------+--------+---------+------+-----+---------+
>  |   3   | 107e92 | 1436c7 | 1371000 |   0  | kpd | 219a000 |
>  +-------+--------+--------+---------+------+-----+---------+
>  |   4   | 107e92 | 1436c7 | 1371000 |   0  | kpd | 2d18000 |
>  +-------+--------+--------+---------+------+-----+---------+
> 
> Where kpd is the contraction of kernel_page_dir, ' means after the
> trap and --- that there is no available information.
> 
> Meaning of some addresses:
> 
>   # addr2line -e /boot/gnumach 0x107392 0x1436c7 0x1051f9
>   ...gnumach/i386/i386/spl.S:217
>   ...gnumach/i386/i386at/interrupt.S:40
>   ...gnumach/i386/i386at/kdasm.S:113
> 
> CR3 value was taken from qemu's monitor console:
> 
>   (qemu) info registers
> 
> And this is where kpd was read from:
> 
>   # nm /boot/gnumach | grep kernel_page_dir
>   001aa2b0 B kernel_page_dir
> 
> All the test were done by running the following commands:
> 
>   # settrans -acfgp /servers/drivers/eth0 /hurd/dde/dde_ne2k_pci
>   ...
>   # settrans -acfgp /dev/eth0 /hurd/dde/devnode eth0 \
>   > -M /servers/drivers/eth0
>   ...
>   # settrans -acfgp /servers/socket/2 /hurd/dde/pfinet -i /dev/eth0 \
>   > -a 10.0.2.16 -g 10.0.2.2 -m 255.255.255.0
>   ...
>   # wget www.google.com
>   --2010-08-30 02:18:19-- http://www.google.com/
>   Resolving www.google.com... <<<<<trap point
> 
> During the first test I collected the values of the registers.
> They are similar to what Zheng Da showed before.
> ---------
> Kernel General protection trap, eip 0x107e92
> kernel: General protection (13), code=25a
> Stopped at 0x107e92:   ret
> db> trace
> 0x107e92(646565,656b6f70,6761705f,66007365,5f656572)
> 
> no memory is assigned to address 6c610077
> db> show registers
> cs        0x8
> ds       0x10
> es       0x10
> fs       0x10
> gs       0x10
> ss       0x10
> eax       0x5
> ecx      0x1c
> edx       0x5
> ebx   0x44520
> esp  0x1a9f20
> ebp 0x12dbd1c
> esi   0x44560
> edi      0x3c
> eip  0x107e92
> efl     0x297
> db> examine 0x1a9f20
>        1436c7
> db>
> ---------
> 
> The second test went really wrong for some reason and I couldn't get
> all the information.
> -----------
>   Kernel General protection trap, eip 0x1051f9rotection trap, eip 0x107e92
>   kernel: General protection (13), code=202
>   Stopped at 0x1051f9:   repe movsw  (%esi),%es:(%edi)
>   db> trace
>   Bad character ']'
>   ?
>   db> show registers
>   Bad character ']'
>   ?
>   db>
> ---------
> 




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