x86_amd64_features.c revision b32f58018498ea2225959b0ba11c18f0c433deef 
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
18typedef int    Bool;
19
20
21#if defined(VGA_x86) || defined(VGA_amd64)
22static 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
33static 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
45static 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
123static 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//---------------------------------------------------------------------------
134int 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