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description Description of '!pmc' command in HyperDbg.

!pmc (hook RDPMC instruction execution)

Command

!pmc

Syntax

!pmc [pid (hex value)] [core (hex value)] [imm (yes|no)] [event options]

Description

Triggers when the debugging machine executes RDPMC instruction in any level of execution (kernel-mode or user-mode).

{% hint style="danger" %} Using this command makes HyperDbg vulnerable to timing methods to detect the presence of hypervisor. You should not use this command in transparent-mode. {% endhint %}

Parameters

[pid (hex value)]

      Optional value to trigger the event in just a specific process. Add `pid xx` to your command; thus, the command will be executed if the process id is equal to `xx`. If you don't specify this, option then by default, you receive events on all processes.

[core (hex value)]

      Optional value to trigger the event in just a specific core. Add `core xx` to your command thus command will be executed if core id is equal to `xx`. If you don't specify this option, then by default, you receive events on all cores.

[imm (yes|no)]

      Optional value in which `yes` means the results \(printed texts in scripts\) should be delivered immediately to the debugger. `no` means that the results can be accumulated and delivered as a couple of messages when the buffer is full; thus, it's substantially faster, but it's not real-time. By default, this value is set to  `yes`.

[event options]

      Regular event parameters that are used in HyperDbg events. \(For more information, read [this ](https://docs.hyperdbg.com/using-hyperdbg/prerequisites)topic\)

Context

As the Context (r8 in custom code and rdx in condition code register) to the event trigger, HyperDbg sends NULL.

Debugger

This event supports three debugging mechanisms.

  • Break
  • Script
  • Custom Code

{% hint style="info" %} Please read "How to create a condition?" if you need a conditional event, a conditional event can be used in all "Break", "Script", and "Custom Code". {% endhint %}

Break

We want to break and get control over all RDPMC execution in our system.

HyperDbg> !pmc

Imagine we want to break on all RDPMC executions of a process id 0x490 in core 2.

HyperDbg> !pmc pid 490 core 2

Script

Using the following command, you can use HyperDbg's Script Engine. You should replace the string between braces (HyperDbg Script Here) with your script. You can find script examples here.

HyperDbg> !pmc script { HyperDbg Script Here }

The above command when messages don't need to be delivered immediately.

HyperDbg> !pmc script { HyperDbg Script Here } imm no

Script (From File)

If you saved your script into a file then you can add file: instead of a script and append the file path to it. For example, the following examples show how you can run a script from file:c:\users\sina\desktop\script.txt.

HyperDbg> !pmc script {file:c:\users\sina\desktop\script.txt}

{% hint style="success" %} You can use event forwarding to forward the event monitoring results from this event and other events to an external source, e.g., File, NamedPipe, or TCP Socket. This way, you can use HyperDbg as a monitoring tool and gather your target system's behavior and use it later or analyze it on other systems. {% endhint %}

Custom Code

Please read "How to create an action?" to get an idea about how to run the custom buffer code in HyperDbg.

{% hint style="warning" %} Your custom code will be executed in vmx-root mode. Take a look at this topic for more information. Running code in vmx-root is considered "unsafe". {% endhint %}

Run Custom Code (Unconditional)

Monitoring process id 0x490 for RDPMC instruction execution ****and run 3 nops whenever the event is triggered. Take a look at Run Custom Code for more information.

HyperDbg> !pmc pid 490 code {90 90 90}

Run Custom Code (Conditional)

Monitoring process id 0x490 for RDPMC instruction execution and runs 3 nops whenever the event condition is triggered and runs 3 nops whenever the event is triggered. Take a look at Run Custom Code and how to create a condition for more information.

HyperDbg> !pmc pid 490 code {90 90 90} condition {90 90 90}

{% hint style="success" %} Keep in mind that a conditional event can be used in Breaking to Debugger and Running Script too. {% endhint %}

IOCTL

This command uses the same method to send IOCTL for regular events.

As EventType use PMC_INSTRUCTION_EXECUTION in DEBUGGER_GENERAL_EVENT_DETAIL.

Design

This command uses RDPMC (EXIT_REASON_RDPMC - 15) vm-exit to implement RDPMC hooks.

Remarks

This is an event command, but in the current version of HyperDbg (in Debugger Mode), this command will continue the debuggee for some time; however, you can use this trick to make sure you won't lose any event.

Requirements

None

Related

!tsc (hook RDTSC/RDTSCP instruction execution)