lscpu: Read CPU information from sysfs

[alxndrv]

Adding a sysfs module to lscpu, to facilitate reading and parsing CPU information out from various files under /sys/.

As part of this, implemented the following sections:

• Various CPU topology related fields (online cores, core count, threads per core, sockets etc.)
• CPU cache levels and sizes
• CPU vulnerability mitigation states

Output on my machine after these changes:

Architecture:             x86_64
  Address sizes:          48 bits physical, 48 bits virtual
  Byte Order:             Little Endian
CPU(s):                   16
  On-line CPU(s) list:    0-15
Vendor ID:                AuthenticAMD
  Model name:             AMD Ryzen 7 7700X 8-Core Processor
    CPU Family:           25
    Model:                97
    Thread(s) per core:   2
    Core(s) per socket:   8
    Socket(s):            1
    Frequency boost:      enabled
Caches (sum of all):      
  L1d:                    256 KiB (8 instances)
  L1i:                    256 KiB (8 instances)
  L2:                     8 MiB (8 instances)
  L3:                     32 MiB (1 instances)
Vulnerabilities:          
  Gather data sampling:   Not affected
  Itlb multihit:          Not affected
  L1tf:                   Not affected
  Mds:                    Not affected
  Meltdown:               Not affected
  Mmio stale data:        Not affected
  Reg file data sampling: Not affected
  Retbleed:               Not affected
  Spec rstack overflow:   Mitigation: Safe RET
  Spec store bypass:      Mitigation: Speculative Store Bypass disabled via prctl
  Spectre v1:             Mitigation: usercopy/swapgs barriers and __user pointer sanitization
  Spectre v2:             Mitigation: Enhanced / Automatic IBRS; IBPB: conditional; STIBP: always-on; RSB filling; PBRSB-eIBRS: Not affected; BHI: Not affected
  Srbds:                  Not affected
  Tsx async abort:        Not affected

[alxndrv]

@cakebaker Since you mentioned in my previous PR that relying on sysinfo might be a good idea long-term, these changes might warrant some additional explanation on my part.

I took a look at sysinfo and it looks like the information it exposes is quite limited in the grand scheme of things. As far as I can tell, things like CPU vulnerability mitigations and topology are completely absent, so we would have to read those from /sys/ in any case. From what I gather, the original lscpu is also tightly coupled to Linux specifically and wouldn't work on anything else, so I'm not sure if we should restrict ourselves to cross-platform support either (at least not yet).

I realize that these changes are pretty much the exact opposite of what you suggested but hopefully the reasoning makes sense 😅 Let me know what you think...

[cakebaker]

@alxndrv Your approach using /proc and /sys is fine :)

I made my comment with regard to the long-term goal of making our version of lscpu work on other platforms. And for that we probably have to rely on external crates.

[cakebaker]

Well done :)

[cakebaker]

Thanks!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 0.00%. Comparing base (95d57eb) to head (748bbf8).
Report is 43 commits behind head on main.

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