How to get CPU brand information in ARM64?

问题

In Windows X86, the CPU brand can be queried with cpuid intrinsic function. Here is a sample of the code:

#include <stdio.h>
#include <intrin.h>

int main(void)
{
    int cpubrand[4 * 3];

    __cpuid(&cpubrand[0], 0x80000002);
    __cpuid(&cpubrand[4], 0x80000003);
    __cpuid(&cpubrand[8], 0x80000004);

    char str[48];
    memset(str, 0, sizeof str);
    memcpy(str, cpubrand, sizeof cpubrand);
    printf("%s\n", str);
}

What is the alternative of this in Windows ARM64?

回答1:

Not a way to get name directly from the CPU either, but you can get processor name from the WMI Win32_Processor class

It can be obtained by running wmic cpu get name in cmd or (Get-WmiObject Win32_Processor).Name in PowerShell. Getting it from C# is also easy, something like

ManagementObjectSearcher mos = new ManagementObjectSearcher("SELECT Name FROM Win32_Processor")
foreach (ManagementObject mo in mos.Get())
{
    Console.WriteLine(mo["Name"]);
}

However doing that from C is a lot trickier. Luckily there's already a similar example in this answer. The main part should be like this

BSTR query    = SysAllocString(L"SELECT Name FROM Win32_Processor");
hr = services->lpVtbl->ExecQuery(services, language, query, WBEM_FLAG_BIDIRECTIONAL, NULL, &results);
...
hr = result->lpVtbl->Get(result, L"Name", 0, &name, 0, 0);
SysFreeString(query);

回答2:

Although probably not the answer you're looking for (i.e. directly interrogating the CPU), you can fetch the "ProcessorNameString" value from the Windows Registry using code like the following:

#define BUFSIZ 64 // For easy adjustment of limits, if required

char answer[BUFSIZ] = "Error Reading CPU Name from Registry!", inBuffer[BUFSIZ] = "";
const char *csName = "HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0";
HKEY hKey;  DWORD gotType, gotSize = BUFSIZ;
if (RegOpenKeyExA(HKEY_LOCAL_MACHINE, csName, 0, KEY_READ, &hKey) == ERROR_SUCCESS) {
    if (!RegQueryValueExA(hKey, "ProcessorNameString", nullptr, &gotType, (PBYTE)(inBuffer), &gotSize)) {
        if ((gotType == REG_SZ) && strlen(inBuffer)) strcpy(answer, inBuffer);
    }
    RegCloseKey(hKey);
}

This will (or should) give you the processor's 'name' that the Windows system sees! I don't have access to an ARM64 system, so I can't properly test it but, on my x64 system, I get the following (correct) string: Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz (which is exactly that returned by using __cpuid() calls to get the "Brand String").

However, like you, I would be very interested to know of a way to do this directly - i.e., how would the Windows O/S get this info on an ARM64 system?

回答3:

The direct way to get this information would be to read the Main ID Register MIDR_EL1. This could be done via the mrs instruction in (inline) assembly or via the _ReadStatusReg instrinct.

Unfortunately this register cannot be accessed from user mode (i.e. EL0) and every attempt throws an exception. At Linux the behavior is then emulated so that MIDR_EL1 can still be accessed. However, I do not know or have the opportunity to test whether Windows also offers this feature.

References:

ARM64 CPU Feature Registers at kernel.org (how Linux made MIDR_EL1 accessible)
Main ID Register at developer.arm.com (from the Cortex-A53 docs)
ARM64 Instrincts at Microsoft Docs

来源：https://stackoverflow.com/questions/60588765/how-to-get-cpu-brand-information-in-arm64

标签

windows

intrinsics

arm64