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Cake day: August 18th, 2025
  • Mttw_@lemmy.dbzer0.comtoPiracy: ꜱᴀɪʟ ᴛʜᴇ ʜɪɢʜ ꜱᴇᴀꜱ@lemmy.dbzer0.com•DenuvOwO is coming to LinuxEnglish
    5·
    1 month ago

    No, 5800x3d is zen3 sadly.

    But you can actually test it with a small python script:

    # docs: https://man.archlinux.org/man/arch_prctl.2
import ctypes
import errno
import mmap
import os
import signal
import subprocess
import sys

SYS_arch_prctl = 158
ARCH_SET_CPUID = 0x1012

libc = ctypes.CDLL(None, use_errno=True)
libc.syscall.restype = ctypes.c_long

def arch_set_cpuid(enabled: bool) -> None:
    rc = libc.syscall(SYS_arch_prctl, ARCH_SET_CPUID, 1 if enabled else 0)
    if rc != 0:
        e = ctypes.get_errno()
        raise OSError(e, os.strerror(e))

def make_cpuid_stub():
    # push rbx
    # xor eax, eax
    # cpuid
    # pop rbx
    # ret
    code = b"\x53\x31\xc0\x0f\xa2\x5b\xc3"
    mm = mmap.mmap(
        -1,
        len(code),
        flags=mmap.MAP_PRIVATE | mmap.MAP_ANONYMOUS,
        prot=mmap.PROT_READ | mmap.PROT_WRITE | mmap.PROT_EXEC,
    )
    mm.write(code)
    addr = ctypes.addressof(ctypes.c_char.from_buffer(mm))
    func = ctypes.CFUNCTYPE(None)(addr)
    func._mm = mm
    return func

def child():
    cpuid = make_cpuid_stub()

    print("Trying normal CPUID...")
    cpuid()
    print("Normal CPUID worked.")

    try:
        arch_set_cpuid(False)
    except OSError as e:
        if e.errno == errno.ENODEV:
            print("CPU does not support CPUID faulting.")
            return 2
        raise

    print("CPUID disabled for this thread. Calling CPUID again...")
    cpuid()  # should SIGSEGV -11 if faulting is supported
    print("Unexpected: CPUID did not fault.")
    return 0

if __name__ == "__main__":
    if len(sys.argv) > 1 and sys.argv[1] == "child":
        raise SystemExit(child())

    p = subprocess.run([sys.executable, __file__, "child"], text=True)
    print(f"child exit code: {p.returncode}")

    if p.returncode == -signal.SIGSEGV:
        print("Result: CPUID faulting is supported and worked.")
    elif p.returncode == 2:
        print("Result: CPUID faulting is not supported by the hardware.")
    else:
        print("Result: test did not complete cleanly.")