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        • basics
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        • beginning
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        • events
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  • Commands
    • Debugging Commands
      • ? (evaluate and execute expressions and scripts in debuggee)
      • ~ (display and change the current operating core)
      • a (assemble virtual address)
      • load (load the kernel modules)
      • unload (unload the kernel modules)
      • status (show the debuggee status)
      • events (show and modify active/disabled events)
      • p (step-over)
      • t (step-in)
      • i (instrumentation step-in)
      • gu (step-out or go up)
      • r (read or modify registers)
      • bp (set breakpoint)
      • bl (list breakpoints)
      • be (enable breakpoints)
      • bd (disable breakpoints)
      • bc (clear and remove breakpoints)
      • g (continue debuggee or processing kernel packets)
      • x (examine symbols and find functions and variables address)
      • db, dc, dd, dq (read virtual memory)
      • eb, ed, eq (edit virtual memory)
      • sb, sd, sq (search virtual memory)
      • u, u64, u2, u32 (disassemble virtual address)
      • k, kd, kq (display stack backtrace)
      • dt (display and map virtual memory to structures)
      • struct (make structures, enums, data types from symbols)
      • sleep (wait for specific time in the .script command)
      • pause (break to the debugger and pause processing kernel packets)
      • print (evaluate and print expression in debuggee)
      • lm (view loaded modules)
      • cpu (check cpu supported technologies)
      • rdmsr (read model-specific register)
      • wrmsr (write model-specific register)
      • flush (remove pending kernel buffers and messages)
      • prealloc (reserve pre-allocated pools)
      • preactivate (pre-activate special functionalities)
      • output (create output source for event forwarding)
      • test (test functionalities)
      • settings (configures different options and preferences)
      • exit (exit from the debugger)
    • Meta Commands
      • .help (show the help of commands)
      • .debug (prepare and connect to debugger)
      • .connect (connect to a session)
      • .disconnect (disconnect from a session)
      • .listen (listen on a port and wait for the debugger to connect)
      • .status (show the debugger status)
      • .start (start a new process)
      • .restart (restart the process)
      • .attach (attach to a process)
      • .detach (detach from the process)
      • .switch (show the list and switch between active debugging processes)
      • .kill (terminate the process)
      • .process, .process2 (show the current process and switch to another process)
      • .thread, .thread2 (show the current thread and switch to another thread)
      • .pagein (bring the page into the RAM)
      • .dump (save the virtual memory into a file)
      • .formats (show number formats)
      • .script (run batch script commands)
      • .sympath (set the symbol server)
      • .sym (load pdb symbols)
      • .pe (parse PE file)
      • .logopen (open log file)
      • .logclose (close log file)
      • .cls (clear the screen)
    • Extension Commands
      • !a (assemble physical address)
      • !pte (display page-level address and entries)
      • !db, !dc, !dd, !dq (read physical memory)
      • !eb, !ed, !eq (edit physical memory)
      • !sb, !sd, !sq (search physical memory)
      • !u, !u64, !u2, !u32 (disassemble physical address)
      • !dt (display and map physical memory to structures)
      • !track (track and map function calls and returns to the symbols)
      • !epthook (hidden hook with EPT - stealth breakpoints)
      • !epthook2 (hidden hook with EPT - detours)
      • !monitor (monitor read/write/execute to a range of memory)
      • !syscall, !syscall2 (hook system-calls)
      • !sysret, !sysret2 (hook SYSRET instruction execution)
      • !mode (detect kernel-to-user and user-to-kernel transitions)
      • !cpuid (hook CPUID instruction execution)
      • !msrread (hook RDMSR instruction execution)
      • !msrwrite (hook WRMSR instruction execution)
      • !tsc (hook RDTSC/RDTSCP instruction execution)
      • !pmc (hook RDPMC instruction execution)
      • !vmcall (hook hypercalls)
      • !exception (hook first 32 entries of IDT)
      • !interrupt (hook external device interrupts)
      • !dr (hook access to debug registers)
      • !ioin (hook IN instruction execution)
      • !ioout (hook OUT instruction execution)
      • !hide (enable transparent-mode)
      • !unhide (disable transparent-mode)
      • !measure (measuring and providing details for transparent-mode)
      • !va2pa (convert a virtual address to physical address)
      • !pa2va (convert physical address to virtual address)
      • !dump (save the physical memory into a file)
      • !pcitree (show PCI/PCIe device tree)
      • !pcicam (dump the PCI/PCIe configuration space)
      • !idt (show Interrupt Descriptor Table entries)
      • !apic (dump local APIC entries in XAPIC and X2APIC modes)
      • !ioapic (dump I/O APIC)
    • Scripting Language
      • Assumptions & Evaluations
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      • Casting & Type-awareness
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      • Constants & Functions
      • Debugger Script (DS)
      • Examples
        • view system state (registers, memory, variables)
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          • eb, ed, eq
          • eb_pa, ed_pa, eq_pa
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          • disassemble_len
          • disassemble_len32
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          • spinlock_lock_custom_wait
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        • strings
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    • Commands Map
  • Tips & Tricks
    • Considerations
      • Basic concepts in Intel VT-x
      • VMX root-mode vs VMX non-root mode
      • The "unsafe" behavior
      • Script engine in VMX non-root mode
      • Difference between process and thread switching commands
      • Accessing Invalid Address
      • Transparent Mode
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      • Customize build
        • Increase Communication Buffer Size
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  • Contribution
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  • Design
    • Features
      • VMM (Module)
        • Control over NMIs
        • VMX root-mode compatible message tracing
        • Design of !epthook
        • Design of !epthook2
        • Design of !monitor
        • Design of !syscall & !sysret
        • Design of !exception & !interrupt
    • Debugger Internals
      • Events
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  • Command
  • Syntax
  • Description
  • Parameters
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  • Calling Stages
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  • Design
  • Remarks
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Edit on GitHub
  1. Commands
  2. Extension Commands

!dr (hook access to debug registers)

Description of the '!dr' command in HyperDbg.

Command

!dr

Syntax

!dr [pid ProcessId (hex)] [core CoreId (hex)] [imm IsImmediate (yesno)] [sc EnableShortCircuiting (onoff)] [stage CallingStage (prepostall)] [buffer PreAllocatedBuffer (hex)] [script { Script (string) }] [asm condition { Condition (assembly/hex) }] [asm code { Code (assembly/hex) }] [output {OutputName (string)}]

Description

Triggers, when the debugging machine accesses one of the hardware debug registers.

Parameters

[pid ProcessId (hex)] (optional)

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.

Still, in the case of user-mode debugging, HyperDbg will apply it only to the current active debugging process (not all the processes). In that case, you can specify pid all to intercept events from the entire system.

[core CoreId (hex)] (optional)

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 IsImmediate (yesno)] (optional)

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.

[sc EnableShortCircuiting (onoff)] (optional)

[stage CallingStage (prepostall)] (optional)

[buffer PreAllocatedBuffer (hex)] (optional)

[script { Script (string) }] (optional)

[asm condition { Condition (assembly/hex) }] (optional)

[asm code { Code (assembly/hex) }] (optional)

[output {OutputName (string)}] (optional)

Context

As the Context ($context pseudo-register in the event's script, r8 in custom code, and rdx in condition code register) to the event trigger, HyperDbg sends NULL.

Short-circuiting

Calling Stages

Debugger

This event supports three debugging mechanisms.

  • Break

  • Script

  • Custom Code

Break

We want to break and get control over each access to hardware debug registers in our system.

HyperDbg> !dr

Imagine we want to break on all accesses to hardware debug registers of a process id 0x490.

HyperDbg> !dr pid 490

Imagine we want to break on all accesses to hardware debug registers of a process id 0x490 and only on core 3.

HyperDbg> !dr pid 490 core 3

Script

HyperDbg> !dr script { HyperDbg Script Here }

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

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

Custom Code

Run Custom Code (Unconditional)

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

Or if you want to use assembly codes directly, you can add an asm before the code.

HyperDbg> !dr pid 490 asm code {nop; nop; nop}

Run Custom Code (Conditional)

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

Or if you want to use assembly codes directly, you can add an asm before the condition and also before the code.

HyperDbg> !dr pid 490 asm code {nop; nop; nop} asm condition {nop; nop; nop}

Keep in mind that a conditional event can be used in Breaking to Debugger and Running Script too.

IOCTL

As EventType use DEBUG_REGISTERS_ACCESSED in DEBUGGER_GENERAL_EVENT_DETAIL.

Design

This command uses Debug Register Access (EXIT_REASON_DR_ACCESS) vm-exits (29) to implement hardware debug registers hooks.

Remarks

None

Requirements

None

Related

None

Previous!interrupt (hook external device interrupts)Next!ioin (hook IN instruction execution)

Last updated 9 months ago

Optional value to ignore the emulation (skip execution) of the event. Add sc on to your command thus whenever the event is triggered, the effects and the execution of the actual event will be ignored. For more information, please read article. If you don't specify this option, then by default, all the events will be emulated (executed). By default, this value is set to off.

Optional value to configure the of the event. To trigger the event before the emulation, include stage pre in your command. Conversely, using stage post will cause the event to be triggered after the emulation. Additionally, using stage all will trigger the event both before and after the emulation. For more information, please read article. By default, this value is set to pre.

Optional value which reserves a safe to be accessed within the event codes.

A HyperDbg will be executed each time the event is triggered.

Optional assembly codes which check for in assembly.

Optional will be executed each time the event is triggered.

Optional output resource name for .

This event supports '', which means that you can configure HyperDbg to ignore its execution and its effects. For additional details, please refer to the article provided .

This event supports different . The 'pre' calling stage is triggered prior to modifying the hardware debug registers, whereas the 'post' calling stage is triggered subsequent to the modification of the hardware debug registers; thus, you can read/modify the memory or registers or the event in the 'pre' stage, and view/modify the results in the 'post' stage. In addition, the 'all' calling stage will trigger the event in both cases. For more information, please refer to the article provided .

Please read "" if you need a conditional event, a conditional event can be used in all "Break", "Script", and "Custom Code".

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 .

You can use 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.

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

Your custom code will be executed in vmx-root mode. Take a look at for more information. Running code in vmx-root is considered "".

Monitoring process ID 0x490 for any access to hardware debug registers and run 3 nops whenever the event is triggered. Take a look at for more information.

Monitoring process ID 0x490 for any access to hardware debug registers and run 3 nops whenever the event condition is triggered and run 3 nops whenever the event is triggered. Take a look at and for more information.

This command uses the same method to .

This command creates an . Starting from HyperDbg v0.7, events are guaranteed to keep the debuggee in a halt state (in the ); thus, nothing will change during its execution and the context (registers and memory) remain untouched. You can visit for more information.

this
calling stage
this
pre-allocated buffer
script
conditions
assembly codes
forwarding events
event short-circuiting
here
calling stages
ignore
here
How to create a condition?
here
event forwarding
How to create an action?
this topic
unsafe
Run Custom Code
Run Custom Code
how to create a condition
send IOCTL for regular events
event
Debugger Mode
instant events