!ioout (hook OUT instruction execution)
Description of the '!ioout' command in HyperDbg.
!ioout
!ioout [Port (hex)] [pid ProcessId (hex)] [core CoreId (hex)] [imm IsImmediate (yesno)] [buffer PreAllocatedBuffer (hex)] [script { Script (string) }] [condition { Condition (hex) }] [code { Code (hex) }]
Triggers when the debugging machine executes OUT or OUT* instructions or, in other words, when Windows or a driver tries to use I/O ports.
When you enable this event, only your specific I/O port will be hooked, so this command won't trigger on all I/O ports, thus won't make your computer slow.
[Port (hex)]
Trigger in the case of using a special I/O port. If you don't specify this parameter, then it will be triggered for all I/O ports.
[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.[buffer PreAllocatedBuffer (hex)] (optional)
[script { Script (string) }] (optional)
[condition { Condition (hex) }] (optional)
[code { Code (hex) }] (optional)
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 the port number that the target tries to access.This event supports three debugging mechanisms.
- Break
- Script
- Custom Code
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".
Imagine we want to break on all accesses (OUT/OUT* instructions) to I/O ports.
HyperDbg> !ioout
If we want to break on I/O port 0x3f8.
HyperDbg> !ioout 0x3f8
Note that default ports for serial connections are: 0x03f8, 0x02f8, 0x03e8, 0x02e8.
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> !ioout 0x3f8 script { HyperDbg Script Here }
The above command when messages don't need to be delivered immediately.
HyperDbg> !ioout 0x3f8 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> !ioout 0x3f8 script {file:c:\users\sina\desktop\script.txt}
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.
Please read "How to create an action?" 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 this topic for more information. Running code in vmx-root is considered "unsafe".
Run Custom Code (Unconditional)
Monitoring execution of OUT/OUT* instructions for I/O port 0x3f8 and run 3 nops whenever the event is triggered. Take a look at Run Custom Code for more information.
HyperDbg> !ioout 0x3f8 code {90 90 90}
Run Custom Code (Conditional)
Monitoring execution of OUT/OUT* instructions for I/O port 0x3f8 and run 3 nops whenever the event condition is triggered and run 3 nops whenever the event is triggered. Take a look at Run Custom Code and how to create a condition for more information.
HyperDbg> !ioout 0x3f8 code {90 90 90} condition {90 90 90}
Keep in mind that a conditional event can be used in Breaking to Debugger and Running Script too.
As EventType use
OUT_INSTRUCTION_EXECUTION and send the special I/O port (if any) if you want to monitor just an I/O port in OptionalParam1 in DEBUGGER_GENERAL_EVENT_DETAIL.Both !ioin and !ioout use the vm-exits caused by setting bits in the I/O Bitmap (I/O Bitmap A, I/O Bitmap B) field of the hypervisor VMCS.
For emulating I/O ports, vm-exit with (EXIT_REASON_IO_INSTRUCTION) or exit-reason 30 is used.
You can also modify the content of I/O ports for both IN and OUT instructions.
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.
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Last modified 1mo ago