Custom syscall Handling

[Anthony Tranduc]

Hi everyone,

I'm looking for a way to intercept system calls by applications in containers and have my own way of handling them. Would this be possible with gVisor? I was looking around and thought I'd go ahead and ask.

For example, if an application gets the current time using a system timing call, I'd like to have a fake time be returned. 

If this requires modifying gVisor (maybe the Sentry?), where should I start to look?

Thanks!

[Ian Lewis]

Hey Anthony,

You can do that but gVisor doesn't provide a pluggable way to do it. You would need to modify the code directly. You can start by taking a look at the pkg/sentry/syscalls/linux directory. That's where all the syscall entrypoints are defined.

https://cs.opensource.google/gvisor/gvisor/+/master:pkg/sentry/syscalls/linux/

Ian

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