From mboxrd@z Thu Jan 1 00:00:00 1970 From: machi1271 Subject: Re: Modify cr0 at dom0 Date: Fri, 17 Oct 2014 15:14:34 +0800 Message-ID: <201410171514301630964@gmail.com> References: <201410170947517919470@gmail.com>, <5440B647.2000502@bitdefender.com> <201410171434447719581@gmail.com>, <5440BBBD.4040709@bitdefender.com> Reply-To: machi1271 Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0130163055619504797==" Return-path: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Razvan Cojocaru , xen-devel List-Id: xen-devel@lists.xenproject.org This is a multi-part message in MIME format. --===============0130163055619504797== Content-Type: multipart/alternative; boundary="----=_001_NextPart581547053873_=----" This is a multi-part message in MIME format. ------=_001_NextPart581547053873_=---- Content-Type: text/plain; charset="gb2312" Content-Transfer-Encoding: base64 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I'v tried the way to modify CR0 by writing to it directly. But I got = the=20 following error:
=02(XEN) traps.c:1768:d0 Attempt to change unmodifiable CR0=20 flags.
general protection fault: 0000 [1] SMP
last sysfs fi= le:=20 /devices/pci0000:00/0000:00:00.0/resource
CPU 0
Modules linked = in:=20 fsp(U) autofs4 hidp rfcomm l2cap bluetooth lockd sunrpc=20 ip_conntrack_netbios_ns ip_conntrack nfnetlink xt_tcpudp iptable_filte= r=20 ip_tables x_tables acpiphp loop dm_multipath scsi_dh video backlight s= bs=20 power_meter hwmon i2c_ec dell_wmi wmi button battery asus_acpi ac ipv6= =20 xfrm_nalgo crypto_api lp joydev floppy sg snd_ens1371 gameport i2c_pii= x4=20 snd_rawmidi snd_ac97_codec ac97_bus snd_seq_dummy snd_seq_oss=20 snd_seq_midi_event snd_seq i2c_core pcspkr snd_seq_device snd_pcm_oss=20 snd_mixer_oss snd_pcm e1000 snd_timer snd soundcore snd_page_alloc shp= chp=20 serio_raw ide_cd parport_pc parport cdrom serial_core dm_raid45 dm_mes= sage=20 dm_region_hash dm_mem_cache dm_snapshot dm_zero dm_mirror dm_log dm_mo= d=20 ata_piix libata mptspi mptscsih mptbase scsi_transport_spi sd_mod scsi= _mod=20 ext3 jbd uhci_hcd ohci_hcd ehci_hcd
Pid: 4103, comm: insmod Tainted= :=20 G      2.6.18-194.el5xen #1
RIP:=20 e030:[<ffffffff88218020>]  [<ffffffff88218020>]=20 :fsp:init_fsp+0x20/0x2d
RSP: e02b:ffff880025145f50  EFLAGS:=20 00010202
RAX: 000000008004003b RBX: ffffffff88680600 RCX:=20 0000000000000000
RDX: 000000008005003b RSI: 0000000000000000 RDI:=20 0000000000000000
RBP: 000000001fc65060 R08: 000000001fc65060 R09:=20 0000000000000000
R10: ffff880024967360 R11: ffff880032c42100 R12:=20 0000000000094ee5
R13: 00002b3383dc6010 R14: 0000000000100000 R15:=20 0000000000100000
FS:  00002b3383dc5750(0000)=20 GS:ffffffff805d2000(0000) knlGS:0000000000000000
CS:  e033 DS:= 0000=20 ES: 0000
Process insmod (pid: 4103, threadinfo ffff880025144000, ta= sk=20 ffff880032c42100)
Stack:  ffffffff802a28e8 =20 0000000000100000  00002b3383dc6010  0000000000000003
=20 00007fff5237dbdc  0000000000094ee5  ffffffff802602f9 =20 0000000000000206
0000000000000000  0000000000001007
Call= =20 Trace:
[<ffffffff802a28e8>] sys_init_module+0xaf/0x1f2
=20 [<ffffffff802602f9>] tracesys+0xab/0xb6


Code: 0f 22 c= 0 31=20 c0 48 89 15 3c 09 47 00 c3 00 00 00 00 00 00 00
RIP =20 [<ffffffff88218020>] :fsp:init_fsp+0x20/0x2d
RSP=20 <ffff880025145f50>
<0>Kernel panic - not syncing: Fata= l=20 exception
(XEN) Domain 0 crashed: rebooting machine in 5 seconds.<= /DIV>
 
Directly modifying CR0 by assembly language seems to m= odify=20 the real physical register on the  real CPU,
but I just want to modify dom's virtual CR0 in the vcpu str= ucture,=20 since I want to modify some memory area
in dom0's kernel which is protected by dom0's vcpu's CR0.WP= =20 bit.
Regards~
 
machi1271
 
Date: 2014-10-17 14:48
To: machi1271;= xen-devel
Subject: Re: [Xen-devel] Modify cr0 at dom0
On 10/17/14 09:34, machi1271 wrote:
> Thanks Razvan~
>  
> I'm new to Xen and Linux.
> Could you please tell me is t= here any Xen-independent manner to modify
> CR0, or the memory area protected&= nbsp;by CR0.WP bit?
 
Sure, there's an example here:
 
https://stackoverflow.com/questions/3962950/how-to-set-control-regist= er-0-cr0-bits-in-x86-64-using-gcc-assembly-on-linux
 
 
Razvan
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