How do I retrieve CPU information using the \'cpuid\' instruction in Linux with GCC?

How to Use the "cpuid" Instruction in Linux

In Linux environments, where GCC is commonly used, developers can access CPU information through the "cpuid" instruction. While assembly language can be employed, there is a more efficient approach.

Using __get_cpuid_max and __get_cpuid

GCC includes the cpuid.h header file, which provides the following functions:

• __get_cpuid_max: Determines the highest supported CPUID level.
• __get_cpuid: Retrieves CPUID data at a specific level.

Example Usage:

<code class="cpp">#include <cpuid.h>

int main() {
  unsigned int eax, ebx, ecx, edx;

  // Determine the highest supported CPUID level.
  unsigned int max_level = __get_cpuid_max(0, NULL);

  // Fetch CPUID information for each supported level.
  for (unsigned int level = 0; level <= max_level; level++) {
    if (__get_cpuid(level, &eax, &ebx, &ecx, &edx)) {
      printf("CPUID Level %u: EAX=%08X, EBX=%08X, ECX=%08X, EDX=%08X\n",
             level, eax, ebx, ecx, edx);
    }
  }

  return 0;
}</code>

Benefits of Using GCC Functions:

Reliance on GCC-provided functions offers several advantages:

• Guaranteed compatibility with different processors.
• Simplified code implementation, eliminating the need for assembly language.
• Enhanced portability across various Linux platforms.

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