用windbg寻找设备树根节点

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    用ReactOS上明确说过，Pnp管理器对每种设备都会创建一个虚拟root device用于构建设备树；同时这个新创建的root device又作为一个设备栈的栈底，往上形成完整的设备栈。用windbg调试时，可以看到这个虚拟设备属于/driver/pnpmanager驱动。

    昨天出于好奇想看下设备树，结果发现只有虚拟设备attach在/driver/pnpmanger创建的设备上，而类似pci/usb设备的设备栈栈底根本不是/driver/pnpmanager设备，这让我很是怀疑，M$到底怎样形成以root为根节点的设备树。

如mssmbios.sys位于设备管理器system设备类下，注册表路径为:HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\SYSTEM\0002

用windbg查看设备堆栈，可以看到这个设备attach在/driver/pnpmanger根节点上:

kd> !drvobj mssmbios
Driver object (81f81da0) is for:
 \Driver\mssmbios
Driver Extension List: (id , addr)

Device Object list:
81c8e408  
kd> !devstack 81c8e408  
  !DevObj   !DrvObj            !DevExt   ObjectName
> 81c8e408  \Driver\mssmbios   81c8e4c0  
  821e73d0  \Driver\PnpManager 821e7488  00000034 
!DevNode 821e7288 :
  DeviceInst is "Root\SYSTEM\0002"
  ServiceName is "mssmbios"

其设备栈为:,亦可看到栈底pnpmanager设备

kd> !drvobj busenum
Driver object (81f81030) is for:
 \Driver\busenum
Driver Extension List: (id , addr)

Device Object list:
81ff3030  
kd> !devstack 81ff3030  
  !DevObj   !DrvObj            !DevExt   ObjectName
> 81ff3030  \Driver\busenum    81ff30e8  
  821e7190  \Driver\PnpManager 821e7248  00000035
!DevNode 821a0008 :
  DeviceInst is "Root\SYSTEM\0003"
  ServiceName is "busenum"

kd> !drvobj pci
Driver object (82189218) is for:
 \Driver\PCI
Driver Extension List: (id , addr)

Device Object list:
82127c70  82127e50  82127030  821e03a0
...
8219cb98  821e5370  821ba160  
kd> !devstack 82127c70  
  !DevObj   !DrvObj            !DevExt   ObjectName
  81d34028  \Driver\usbehci    81d340e0  USBFDO-1
  82127790  \Driver\ACPI       82187810  00000064
> 82127c70  \Driver\PCI        82127d28  NTPNP_PCI0043
!DevNode 821272e8 :
  DeviceInst is "PCI\VEN_15AD&DEV_0770&SUBSYS_077015AD&REV_00\4&47b7341&0&1888"
  ServiceName is "usbehci"

kd> !drvobj usbhub
Driver object (820de2c0) is for:
 \Driver\usbhub
Driver Extension List: (id , addr)

Device Object list:
81c74c98  81d542f0  820f1b70  81fcac98
81c7ac98  
kd> !devstack  81c74c98  
  !DevObj   !DrvObj            !DevExt   ObjectName
> 81c74c98  \Driver\usbhub     81c74d50  00000079
  81d542f0  \Driver\usbhub     81d543a8  USBPDO-3
!DevNode 81c82c48 :
  DeviceInst is "USB\Vid_0e0f&Pid_0002\6&2edefd9b&0&2"
  ServiceName is "usbhub"

    顺着周AM的思路，我重新调试了一遍，的确找到了PCI总线所在的Pnpmanager，以上面的环境为例，

kd> !drvobj pci
Driver object (82189218) is for:
 \Driver\PCI
Driver Extension List: (id , addr)

Device Object list:
82127c70  82127e50  82127030  821e03a0
...
8219cb98  821e5370  821ba160 

kd> !devstack 821ba160
  !DevObj   !DrvObj            !DevExt   ObjectName
> 821ba160  \Driver\PCI        821ba218  
  821731a8  \Driver\ACPI       821e2940  00000038
!DevNode 821de178 :
  DeviceInst is "ACPI\PNP0A03\2&daba3ff&0"
  ServiceName is "pci"

kd> !drvobj ACPI
Driver object (8219ca10) is for:
 \Driver\ACPI
Driver Extension List: (id , addr)

Device Object list:
8212c628  8212c740  8212c858  82126538
...
821731a8  8219c8f8  
kd> !devstack 8219c8f8  
  !DevObj   !DrvObj            !DevExt   ObjectName
> 8219c8f8  \Driver\ACPI       821e2ea0  
  821a0aa8  \Driver\ACPI_HAL   821a0b60  00000037
!DevNode 8219cd50 :
  DeviceInst is "ACPI_HAL\PNP0C08\0"
  ServiceName is "ACPI"

kd> !drvobj ACPI_HAL
Driver object (821a0f38) is for:
 \Driver\ACPI_HAL
Driver Extension List: (id , addr)

Device Object list:
821a0aa8  821a0bc8  
kd> !devstack 821a0bc8  
  !DevObj   !DrvObj            !DevExt   ObjectName
> 821a0bc8  \Driver\ACPI_HAL   821a0c80  
  821a4c68  \Driver\PnpManager 821a4d20  00000001
!DevNode 821a4b20 :
  DeviceInst is "Root\ACPI_HAL\0000"

    如果此时再深究一下PnpManager驱动创建的设备对象，会发现系统中果真只有一个根设备节点，而其他的PnpManager设备对象都是为了扩展设备树一点一点生长出来的:

kd> !drvobj PnpManager
Driver object (821eb2e8) is for:
 \Driver\PnpManager
Driver Extension List: (id , addr)

Device Object list:
821e7190  821e73d0  821e7610  821e7850
...
821a4c68  821a4020  
kd> !devstack  821a4020  
  !DevObj   !DrvObj            !DevExt   ObjectName
> 821a4020  \Driver\PnpManager 821a40d8  
!DevNode 821a4ee8 :
  DeviceInst is "HTREE\ROOT\0" <----从名字能感觉出这是根设备节点
kd> !devstack 821a4c68  
  !DevObj   !DrvObj            !DevExt   ObjectName
  821a0bc8  \Driver\ACPI_HAL   821a0c80  
> 821a4c68  \Driver\PnpManager 821a4d20  00000001  <----<span style="font-family: Arial, Helvetica, sans-serif;">名字看着这么没个性，肯定不是根设备节点了</span>
!DevNode 821a4b20 :
  DeviceInst is "Root\ACPI_HAL\0000" 

用windbg寻找设备树根节点

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原文地址：http://blog.csdn.net/lixiangminghate/article/details/51729945