bdump

A windbg-js plugin to dump the cpu state.

Usage

You'll probably want the VM to have 1 vCPU. Sometimes kd gets confused about which CPU scripts run on. Additionally, once you hit your bp you should verify that GSBASE and KERNEL_GSBASE are different:

kd> rdmsr c0000101
msr[c0000101] = 0x41414141
kd> rdmsr c0000102
msr[c0000102] = 0x42424242

If they are the same, youll need to hit the bp again. I have no idea why this happens.

kd> .scriptload c:\path\to\bdump.js
kd> !bdump "c:\\path\\to\\dump"

This will create two files:

• dump\mem.dmp is a standard windows dumpfile. Note that this is not a minidump!
• dump\regs.json is a JSON object containing all the register values encoded as hex strings. E.g

{"rax": "0x41414141", "rbx": "0x42424242", ... }

There is also a cpu-jtoy.py script which converts the registers from JSON to YAML. This file is vanilla YAML and is used to allow hex encoding of integers and avoid the 53-bit limitation in some JSON implementations. Hopefully with BigInt support in more JS engines soon I can drop this...

This script will also add in the AVX register state with all values zeroed.

Caveats

• doesn't currently capture xmm/ymm/zmm register states
• doesn't currently capture mxcsr_mask
• capturing segments (especially tr and es) is kinda sketchy