Re: [EXTERNAL] QEMU plugin system

[Robert Henry]

Our approach to this problem was to make the plugin sensitive to the execution of well-chosen instructions to turn on/turn off the actions of the plugin. The plugin will still be called (don't unregister it) but should return immediately if the on/off state is off.  This will still slow the emulation down.

My guest ISA is arm64.  For that ISA, we made these choices; perhaps something else is better:

  asm("hint 0b0010001");  // arm64 PSB Profile Sync Buffer (turn on)

  asm("hint 0b0010010");  // arm64 TSB Trace Sync Buffer (turn off)

Put these instructions in a library and arrange to have your application call the library functions as appropriate for the application's programming language.

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From: Qemu-discuss <qemu-discuss-bounces+robhenry=microsoft.com@nongnu.org> on behalf of Kamil Garifullin <kgariful@gmail.com>
Sent: Wednesday, July 29, 2020 1:35 AM
To: qemu-discuss@nongnu.org <qemu-discuss@nongnu.org>
Subject: [EXTERNAL] QEMU plugin system

 

Hi,

I'm trying to create a plugin which will track an activity during a particular period of time. 

Can I somehow send a signal from the guest to the instrumentation plugin?

For example, I want to boot linux, do some preparations, then start a targeted application and start my tracking. It can be both: do not inject instrumentation until special indication or just a special plugin event to set up some flags.

My thoughts were to have an event which will indicate that pmon was touched. It allows you to do all the preparations in the guest machine, then dump pmons as an indicator to start tracking and then run the target application.