Add cpuinfo module

[Hannibal404]

No description provided.

[brenns10]

I'm sorry I haven't gotten the chance to do a detailed review of the PR yet, but I did get started on it. Here's some comments for the first few functions. I'll send more feedback tomorrow!

[brenns10]

Let's use .read_() here (docs).

The reasoning here is that the cpuinfo struct is a large-ish structure, and we're going to be reading parts of it very frequently. The way drgn handles this (in the live case) is by calling read(/proc/kcore) for each time we access a value. And reading from /proc/kcore has a quite high overhead for each call (but the overhead for each additional byte of data read is much lower). Thus, it makes sense to read chunks of data at a time, rather than small reads. If we call .read_() like shown, then the whole structure gets read at once, and the result is saved as the value of the object.

This means that the value won't be updated to reflect changes over time. But that also is good, because the chances are much better that your read would be atomic, in the live case.

Suggested change

	if "cpu_data" in prog:
	cpuinfo_struct = prog["cpu_data"]
	elif "boot_cpu_data" in prog:
	cpuinfo_struct = prog["boot_cpu_data"]
	if "cpu_data" in prog:
	cpuinfo_struct = prog["cpu_data"].read_()
	elif "boot_cpu_data" in prog:
	cpuinfo_struct = prog["boot_cpu_data"].read_()

[brenns10]

Ok, finished reviewing this. Thanks for doing all of the logic for these different CPU mitigations. I know there's a lot of it here.

[brenns10]

One last thing here, then I think we'll be good, assuming tests pass.

[brenns10]

Looking good, but there's an internal CI failure:

    def get_retbleed_mitigation(prog: Program, cpuinfo: Object) -> str:
        """
        Extracts Mitigation for Retbleed
        """
        if "retbleed_state" in prog:
            if prog["retbleed_state"] == prog.constant(
                "RETBLEED_MITIGATION_UNRET"
            ):
                if (
>                   cpuinfo.x86_vendor != X86_VENDOR_AMD
                    and cpuinfo.x86_vendor != X86_VENDOR_HYGON
                ):
E               AttributeError: '_drgn.Object' object has no attribute 'x86_vendor'

Looks like get_retbleed_mitigation() expects the cpuinfo object, not the feature/bug flags bitfield. You could add that as another parameter or just look it up from prog.

[brenns10]

This is looking good, thanks!