Forcing a System Crash from the Keyboard
Most of the following keyboards can cause a system crash directly:
PS/2 keyboards connected on i8042prt ports
You must ensure the following three settings before the keyboard can cause a system crash:
- If you wish a crash dump file to be written, you must enable such dump files, choose the path and file name, and select the size of the dump file. For more information, see Enabling a Kernel-Mode Dump File.
- With PS/2 keyboards, you must enable the keyboard-initiated crash in the registry. In the registry key
Code:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\i8042prt\Parameters
create a value named CrashOnCtrlScroll, and set it equal to a REG_DWORD value of 0x01.
- With USB keyboards, you must enable the keyboard-initiated crash in the registry. In the registry key
Code:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\kbdhid\Parameters
create a value named CrashOnCtrlScroll, and set it equal to a REG_DWORD value of 0x01.
You must restart the system for these settings to take effect.
After this is completed, the keyboard crash can be initiated by using the following hotkey sequence: Hold down the
rightmost CTRL key, and press the SCROLL LOCK key twice.
The system then calls
KeBugCheck and issues
bug check 0xE2 (MANUALLY_INITIATED_CRASH). Unless crash dumps have been disabled, a crash dump file is written at this point.
If a kernel debugger is attached to the crashed machine, the machine will break into the kernel debugger after the crash dump file has been written.
For more information on using this feature, refer to the article
Generate a memory dump file by using the keyboard (KB 244139).
Defining Alternate Keyboard Shortcuts to Force a System Crash from the Keyboard
You can configure values under the following registry subkeys for different keyboard shortcut sequences to generate the memory dump file:
For PS/2 keyboards:
Code:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i8042prt\crashdump
For USB keyboards:
Code:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\kbdhid\crashdump
You must create the following registry REG_DWORD values under these subkeys: Dump1Keys
The Dump1Keys registry value is a bit map of the first hot key to use. For example, instead of using the rightmost CTRL key to initiate the hot key sequence, you can set the first hot key to be the leftmost SHIFT key.
The values for the first hot key are described in the following table.
Code:
Value | First key used in the keyboard shortcut sequence
==== | =====================================
0x01 Rightmost SHIFT key
0x02 Rightmost CTRL key
0x04 Rightmost ALT key
0x10 Leftmost SHIFT key
0x20 Leftmost CTRL key
0x40 Leftmost ALT key
Note: You can assign Dump1Keys a value that enables one or more keys as the first key used in the keyboard shortcut sequence. For example, assign Dump1Keys a value of 0x11 to define both the rightmost and leftmost SHIFT keys as the first key in the keyboard shortcut sequence.
Dump2Key
The
Dump2Key registry value is the index into the scancode table for the keyboard layout of the target computer. The following is the actual table in the driver.
const UCHAR keyToScanTbl[134] = { 0x00,0x29,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09, 0x0A,0x0B,0x0C,0x0D,0x7D,0x0E,0x0F,0x10,0x11,0x12, 0x13,0x14,0x15,0x16,0x17,0x18,0x19,0x1A,0x1B,0x00, 0x3A,0x1E,0x1F,0x20,0x21,0x22,0x23,0x24,0x25,0x26, 0x27,0x28,0x2B,0x1C,0x2A,0x00,0x2C,0x2D,0x2E,0x2F, 0x30,0x31,0x32,0x33,0x34,0x35,0x73,0x36,0x1D,0x00, 0x38,0x39,0xB8,0x00,0x9D,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0xD2,0xD3,0x00,0x00,0xCB, 0xC7,0xCF,0x00,0xC8,0xD0,0xC9,0xD1,0x00,0x00,0xCD, 0x45,0x47,0x4B,0x4F,0x00,0xB5,0x48,0x4C,0x50,0x52, 0x37,0x49,0x4D,0x51,0x53,0x4A,0x4E,0x00,0x9C,0x00, 0x01,0x00,0x3B,0x3C,0x3D,0x3E,0x3F,0x40,0x41,0x42, 0x43,0x44,0x57,0x58,0x00,0x46,0x00,0x00,0x00,0x00, 0x00,0x7B,0x79,0x70 };
Note Index 124 (sysreq) is a special case because an 84-key keyboard has a different scan code.
If you define alternate keyboard shortcuts to force a system crash from a USB or PS/2 keyboard, you must either set the
CrashOnCtrlScroll registry value to 0 or remove it from the registry.
Limitations
It is possible for a system to freeze in such a way that the keyboard shortcut sequence will not work. However, this should be a very rare occurrence. Using the keyboard shortcut sequence to initiate a crash will work even in many instances where CTRL+ALT+DELETE does not work.
Forcing a system crash from the keyboard does not work if the computer stops responding at a high interrupt request level (IRQL). This limitation exists because the
Kbdhid.sys driver, which allows the memory dump process to run, operates at a lower IRQL than the
i8042prt.sys driver.
Source: Forcing a System Crash from the Keyboard
