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      1 
      2 #include <stdio.h>
      3 #include <stdlib.h>
      4 #include <string.h>
      5 #include <assert.h>
      6 
      7 // This file determines x86/AMD64 features a processor supports.
      8 //
      9 // We return:
     10 // - 0 if the machine matches the asked-for feature.
     11 // - 1 if the machine does not.
     12 // - 2 if the asked-for feature isn't recognised (this will be the case for
     13 //     any feature if run on a non-x86/AMD64 machine).
     14 // - 3 if there was a usage error (it also prints an error message).
     15 
     16 #define False  0
     17 #define True   1
     18 typedef int    Bool;
     19 
     20 
     21 #if defined(VGA_x86) || defined(VGA_amd64)
     22 static void cpuid ( unsigned int n,
     23                     unsigned int* a, unsigned int* b,
     24                     unsigned int* c, unsigned int* d )
     25 {
     26    __asm__ __volatile__ (
     27       "cpuid"
     28       : "=a" (*a), "=b" (*b), "=c" (*c), "=d" (*d)      /* output */
     29       : "0" (n)         /* input */
     30    );
     31 }
     32 
     33 static Bool vendorStringEquals ( char* str )
     34 {
     35    char vstr[13];
     36    unsigned int a, b, c, d;
     37    cpuid(0, &a, &b, &c, &d);
     38    memcpy(&vstr[0], &b, 4);
     39    memcpy(&vstr[4], &d, 4);
     40    memcpy(&vstr[8], &c, 4);
     41    vstr[12] = 0;
     42    return 0 == strcmp(vstr, str);
     43 }
     44 
     45 static Bool go(char* cpu)
     46 {
     47    unsigned int level = 0, cmask = 0, dmask = 0, a, b, c, d;
     48    Bool require_amd = False;
     49 
     50    if        ( strcmp( cpu, "x86-fpu" ) == 0 ) {
     51      level = 1;
     52      dmask = 1 << 0;
     53    } else if ( strcmp( cpu, "x86-cmov" ) == 0 ) {
     54      level = 1;
     55      dmask = 1 << 15;
     56    } else if ( strcmp( cpu, "x86-mmx" ) == 0 ) {
     57      level = 1;
     58      dmask = 1 << 23;
     59    } else if ( strcmp( cpu, "x86-mmxext" ) == 0 ) {
     60      level = 0x80000001;
     61      dmask = 1 << 22;
     62    } else if ( strcmp( cpu, "x86-sse" ) == 0 ) {
     63      level = 1;
     64      dmask = 1 << 25;
     65    } else if ( strcmp( cpu, "x86-sse2" ) == 0 ) {
     66      level = 1;
     67      dmask = 1 << 26;
     68    } else if ( strcmp( cpu, "x86-sse3" ) == 0 ) {
     69      level = 1;
     70      cmask = 1 << 0;
     71    } else if ( strcmp( cpu, "x86-ssse3" ) == 0 ) {
     72      level = 1;
     73      cmask = 1 << 9;
     74    } else if ( strcmp( cpu, "x86-lzcnt" ) == 0 ) {
     75      level = 0x80000001;
     76      cmask = 1 << 5;
     77      require_amd = True;
     78 #if defined(VGA_amd64)
     79    } else if ( strcmp( cpu, "amd64-sse3" ) == 0 ) {
     80      level = 1;
     81      cmask = 1 << 0;
     82    } else if ( strcmp( cpu, "amd64-pclmulqdq" ) == 0 ) {
     83      level = 1;
     84      cmask = 1 << 1;
     85    } else if ( strcmp( cpu, "amd64-ssse3" ) == 0 ) {
     86      level = 1;
     87      cmask = 1 << 9;
     88    } else if ( strcmp( cpu, "amd64-cx16" ) == 0 ) {
     89      level = 1;
     90      cmask = 1 << 13;
     91    } else if ( strcmp( cpu, "amd64-lzcnt" ) == 0 ) {
     92      level = 0x80000001;
     93      cmask = 1 << 5;
     94      require_amd = True;
     95    } else if ( strcmp( cpu, "amd64-sse42" ) == 0 ) {
     96      level = 1;
     97      cmask = 1 << 20;
     98 #endif
     99    } else {
    100      return 2;          // Unrecognised feature.
    101    }
    102 
    103    assert( !(cmask != 0 && dmask != 0) );
    104    assert( !(cmask == 0 && dmask == 0) );
    105 
    106    if (require_amd && !vendorStringEquals("AuthenticAMD"))
    107       return 1; // Feature not present
    108       // regardless of what that feature actually is
    109 
    110    cpuid( level & 0x80000000, &a, &b, &c, &d );
    111 
    112    if ( a >= level ) {
    113       cpuid( level, &a, &b, &c, &d );
    114 
    115       if (dmask > 0 && (d & dmask) != 0) return 0;    // Feature present.
    116       if (cmask > 0 && (c & cmask) != 0) return 0;    // Feature present.
    117    }
    118    return 1;                                          // Feature not present.
    119 }
    120 
    121 #else
    122 
    123 static Bool go(char* cpu)
    124 {
    125    return 2;      // Feature not recognised (non-x86/AMD64 machine!)
    126 }
    127 
    128 #endif   // defined(VGA_x86)  || defined(VGA_amd64)
    129 
    130 
    131 //---------------------------------------------------------------------------
    132 // main
    133 //---------------------------------------------------------------------------
    134 int main(int argc, char **argv)
    135 {
    136    if ( argc != 2 ) {
    137       fprintf( stderr, "usage: x86_amd64_features <feature>\n" );
    138       exit(3);                // Usage error.
    139    }
    140    return go(argv[1]);
    141 }
    142