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 // viz:
16 #define FEATURE_PRESENT 0
17 #define FEATURE_NOT_PRESENT 1
18 #define UNRECOGNISED_FEATURE 2
19 #define USAGE_ERROR 3
20
21
22 #define False 0
23 #define True 1
24 typedef int Bool;
25
26
27 #if defined(VGA_x86) || defined(VGA_amd64)
cpuid(unsigned int n,unsigned int * a,unsigned int * b,unsigned int * c,unsigned int * d)28 static void cpuid ( unsigned int n,
29 unsigned int* a, unsigned int* b,
30 unsigned int* c, unsigned int* d )
31 {
32 __asm__ __volatile__ (
33 "cpuid"
34 : "=a" (*a), "=b" (*b), "=c" (*c), "=d" (*d) /* output */
35 : "0" (n) /* input */
36 );
37 }
38
vendorStringEquals(char * str)39 static Bool vendorStringEquals ( char* str )
40 {
41 char vstr[13];
42 unsigned int a, b, c, d;
43 cpuid(0, &a, &b, &c, &d);
44 memcpy(&vstr[0], &b, 4);
45 memcpy(&vstr[4], &d, 4);
46 memcpy(&vstr[8], &c, 4);
47 vstr[12] = 0;
48 return 0 == strcmp(vstr, str);
49 }
50
have_xgetbv(void)51 static Bool have_xgetbv ( void )
52 {
53 #if defined(VGA_amd64)
54 unsigned long long int w;
55 __asm__ __volatile__("movq $0,%%rcx ; "
56 ".byte 0x0F,0x01,0xD0 ; " /* xgetbv */
57 "movq %%rax,%0"
58 :/*OUT*/"=r"(w) :/*IN*/
59 :/*TRASH*/"rdx","rcx");
60 if ((w & 6) == 6) {
61 /* OS has enabled both XMM and YMM state support */
62 return True;
63 } else {
64 return False;
65 }
66 #else
67 return False;
68 #endif
69 }
70
go(char * cpu)71 static Bool go(char* cpu)
72 {
73 unsigned int level = 0, cmask = 0, dmask = 0, a, b, c, d;
74 Bool require_amd = False;
75 Bool require_xgetbv = False;
76 if ( strcmp( cpu, "x86-fpu" ) == 0 ) {
77 level = 1;
78 dmask = 1 << 0;
79 } else if ( strcmp( cpu, "x86-cmov" ) == 0 ) {
80 level = 1;
81 dmask = 1 << 15;
82 } else if ( strcmp( cpu, "x86-mmx" ) == 0 ) {
83 level = 1;
84 dmask = 1 << 23;
85 } else if ( strcmp( cpu, "x86-mmxext" ) == 0 ) {
86 level = 0x80000001;
87 dmask = 1 << 22;
88 } else if ( strcmp( cpu, "x86-sse" ) == 0 ) {
89 level = 1;
90 dmask = 1 << 25;
91 } else if ( strcmp( cpu, "x86-sse2" ) == 0 ) {
92 level = 1;
93 dmask = 1 << 26;
94 } else if ( strcmp( cpu, "x86-sse3" ) == 0 ) {
95 level = 1;
96 cmask = 1 << 0;
97 } else if ( strcmp( cpu, "x86-ssse3" ) == 0 ) {
98 level = 1;
99 cmask = 1 << 9;
100 } else if ( strcmp( cpu, "x86-lzcnt" ) == 0 ) {
101 level = 0x80000001;
102 cmask = 1 << 5;
103 require_amd = True;
104 #if defined(VGA_amd64)
105 } else if ( strcmp( cpu, "amd64-sse3" ) == 0 ) {
106 level = 1;
107 cmask = 1 << 0;
108 } else if ( strcmp( cpu, "amd64-pclmulqdq" ) == 0 ) {
109 level = 1;
110 cmask = 1 << 1;
111 } else if ( strcmp( cpu, "amd64-ssse3" ) == 0 ) {
112 level = 1;
113 cmask = 1 << 9;
114 } else if ( strcmp( cpu, "amd64-cx16" ) == 0 ) {
115 level = 1;
116 cmask = 1 << 13;
117 } else if ( strcmp( cpu, "amd64-lzcnt" ) == 0 ) {
118 level = 0x80000001;
119 cmask = 1 << 5;
120 require_amd = True;
121 } else if ( strcmp( cpu, "amd64-sse42" ) == 0 ) {
122 level = 1;
123 cmask = 1 << 20;
124 } else if ( strcmp( cpu, "amd64-avx" ) == 0 ) {
125 level = 1;
126 cmask = (1 << 27) | (1 << 28);
127 require_xgetbv = True;
128 #endif
129 } else {
130 return UNRECOGNISED_FEATURE;
131 }
132
133 assert( !(cmask != 0 && dmask != 0) );
134 assert( !(cmask == 0 && dmask == 0) );
135
136 if (require_amd && !vendorStringEquals("AuthenticAMD"))
137 return FEATURE_NOT_PRESENT;
138 // regardless of what that feature actually is
139
140 cpuid( level & 0x80000000, &a, &b, &c, &d );
141
142 if ( a >= level ) {
143 cpuid( level, &a, &b, &c, &d );
144
145 if (dmask > 0 && (d & dmask) == dmask) {
146 if (require_xgetbv && !have_xgetbv())
147 return FEATURE_NOT_PRESENT;
148 else
149 return FEATURE_PRESENT;
150 }
151 if (cmask > 0 && (c & cmask) == cmask) {
152 if (require_xgetbv && !have_xgetbv())
153 return FEATURE_NOT_PRESENT;
154 else
155 return FEATURE_PRESENT;
156 }
157 }
158 return FEATURE_NOT_PRESENT;
159 }
160
161 #else
162
go(char * cpu)163 static Bool go(char* cpu)
164 {
165 // Feature not recognised (non-x86/AMD64 machine!)
166 return UNRECOGNISED_FEATURE;
167 }
168
169 #endif // defined(VGA_x86) || defined(VGA_amd64)
170
171
172 //---------------------------------------------------------------------------
173 // main
174 //---------------------------------------------------------------------------
main(int argc,char ** argv)175 int main(int argc, char **argv)
176 {
177 if ( argc != 2 ) {
178 fprintf( stderr, "usage: x86_amd64_features <feature>\n" );
179 exit(USAGE_ERROR);
180 }
181 return go(argv[1]);
182 }
183