CPUID - Intel SGX Capabilities Detection

cpuid_sgx.c

/* 
 * For more information about the availability of SGX for your system check: https://github.com/ayeks/SGX-hardware
 * Example output from a SGX enabled CPU is provided at the end of the Readme in that repo.
 * This GIST won't be updated, however it will stay because it is linked in Stackoverflow.
 */
#include <stdio.h>

static inline void native_cpuid(unsigned int *eax, unsigned int *ebx,
                                unsigned int *ecx, unsigned int *edx)
{
        /* ecx is often an input as well as an output. */
        asm volatile("cpuid"
            : "=a" (*eax),
              "=b" (*ebx),
              "=c" (*ecx),
              "=d" (*edx)
            : "0" (*eax), "2" (*ecx));
}

int main(int argc, char **argv)
{
  /* This programm prints some CPUID information and tests the SGX support of the CPU */

  unsigned eax, ebx, ecx, edx;
  eax = 1; /* processor info and feature bits */

  native_cpuid(&eax, &ebx, &ecx, &edx);
  printf("eax: %x ebx: %x ecx: %x edx: %x\n", eax, ebx, ecx, edx);

  printf("stepping %d\n", eax & 0xF); // Bit 3-0
  printf("model %d\n", (eax >> 4) & 0xF); // Bit 7-4
  printf("family %d\n", (eax >> 8) & 0xF); // Bit 11-8
  printf("processor type %d\n", (eax >> 12) & 0x3); // Bit 13-12
  printf("extended model %d\n", (eax >> 16) & 0xF); // Bit 19-16
  printf("extended family %d\n", (eax >> 20) & 0xFF); // Bit 27-20
  
  // if smx set - SGX global enable is supported
  printf("smx: %d\n", (ecx >> 6) & 1); // CPUID.1:ECX.[bit6]

  /* Extended feature bits (EAX=07H, ECX=0H)*/
  printf("\nExtended feature bits (EAX=07H, ECX=0H)\n");
  eax = 7;
  ecx = 0;
  native_cpuid(&eax, &ebx, &ecx, &edx);
  printf("eax: %x ebx: %x ecx: %x edx: %x\n", eax, ebx, ecx, edx);

  //CPUID.(EAX=07H, ECX=0H):EBX.SGX = 1,
  printf("sgx available: %d\n", (ebx >> 2) & 0x1);

  /* SGX has to be enabled in MSR.IA32_Feature_Control.SGX_Enable
	check with msr-tools: rdmsr -ax 0x3a
	SGX_Enable is Bit 18
	if SGX_Enable = 0 no leaf information will appear. 
     for more information check Intel Docs Architectures-software-developer-system-programming-manual - 35.1 Architectural MSRS
  */	

  /* CPUID Leaf 12H, Sub-Leaf 0 Enumeration of Intel SGX Capabilities (EAX=12H,ECX=0) */
  printf("\nCPUID Leaf 12H, Sub-Leaf 0 of Intel SGX Capabilities (EAX=12H,ECX=0)\n");
  eax = 0x12;
  ecx = 0;
  native_cpuid(&eax, &ebx, &ecx, &edx);
  printf("eax: %x ebx: %x ecx: %x edx: %x\n", eax, ebx, ecx, edx);

  printf("sgx 1 supported: %d\n", eax & 0x1);
	printf("sgx 2 supported: %d\n", (eax >> 1) & 0x1);
  printf("MaxEnclaveSize_Not64: %x\n", edx & 0xFF);
  printf("MaxEnclaveSize_64: %x\n", (edx >> 8) & 0xFF);

  /* CPUID Leaf 12H, Sub-Leaf 1 Enumeration of Intel SGX Capabilities (EAX=12H,ECX=1) */
  printf("\nCPUID Leaf 12H, Sub-Leaf 1 of Intel SGX Capabilities (EAX=12H,ECX=1)\n");
  eax = 0x12;
  ecx = 1;
  native_cpuid(&eax, &ebx, &ecx, &edx);
  printf("eax: %x ebx: %x ecx: %x edx: %x\n", eax, ebx, ecx, edx);

	int i;
  for (i=2; i<10; i++) {
	  /* CPUID Leaf 12H, Sub-Leaf i Enumeration of Intel SGX Capabilities (EAX=12H,ECX=i) */
	  printf("\nCPUID Leaf 12H, Sub-Leaf %d of Intel SGX Capabilities (EAX=12H,ECX=%d)\n",i,i);
	  eax = 0x12;
	  ecx = i;
	  native_cpuid(&eax, &ebx, &ecx, &edx);
	  printf("eax: %x ebx: %x ecx: %x edx: %x\n", eax, ebx, ecx, edx);
  }



}

For more information about the availability of SGX for your system check: https://github.com/ayeks/SGX-hardware
Example output from a SGX enabled CPU is provided at the end of the Readme in that repo.

This GIST won't be updated, however it will stay because it is linked in Stackoverflow.