Minimal set of changes required to work with Windows eBPF project

[Alan-Jowett]

Minimal set of changes required to work with Windows eBPF project

Resolves: #61

Signed-off-by: Alan Jowett alanjo@microsoft.com

[coveralls]

Coverage decreased (-0.5%) to 95.541% when pulling d2c7bdc on Alan-Jowett:master into 0014f29 on iovisor:master.

[jpsamaroo]

Is there a public repo for this Windows eBPF effort? It would be nice to have some context on what the downstream user for these changes will be.

[Alan-Jowett]

It was pointed out to me by @dthaler that there is a better way to work around some of the issues, which allowed me to reduce the churn even further.

1. Add ubpf_translate that emits x64 machine code from ebpf byte code (with out changing page protections etc).
2. Removed dependency on printf in ebpf_execute
3. Perform correct register mapping / save / restore for Windows ABI.

[Alan-Jowett]

Added code to suppress generation of call to fprintf on divide by zero.

[dthaler]

Added code to suppress generation of call to fprintf on divide by zero.

Why not just implement fprintf (e.g., as a no-op)?

[Alan-Jowett]

Why not just implement fprintf (e.g., as a no-op)?

The issue is that fprintf would need to be treated like a helper function. We would need to pass in the target address to ubpf during jit compilation so that it could emit code with the correct fprintf address in the target environment.

It seems simpler to just make the jitter emit:
"return -1" on integer overflow.

[Alan-Jowett]

Added an option to override what function is called when divide by zero occurs.

[Alan-Jowett]

@jpsamaroo Our project ebpf-for-windows is now public so you can see how we are using ubpf.

It would be great if you would consider the PR now so we can switch to using your repo.

[jpsamaroo]

Thanks for the link! Interesting project 🙂

It would be great if you would consider the PR now so we can switch to using your repo.

This isn't my repo, and I'm not currently actively maintaining my own fork since ubpf integration isn't one of my top priorities right now. This would be up to @pchaigno to consider for merge.

[jpsamaroo]

FWIW, this LGTM!

[rlane]

Very cool!