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7 .TH CPUID 7D "April 9, 2016"
8 .SH NAME
9 cpuid \- CPU identification driver
10 .SH SYNOPSIS
11 .LP
12 .nf
13 \fB/dev/cpu/self/cpuid\fR
14 .fi
15
16 .SH DESCRIPTION
17 .SS "SPARC and x86 system"
18 .LP
19 This device provides implementation-private information via ioctls about
20 various aspects of the implementation to Solaris libraries and utilities.
21 .SS "x86 systems only"
22 .LP
23 This device also provides a file-like view of the namespace and return values
24 of the x86 cpuid instruction. The cpuid instruction takes a single 32-bit
25 integer function code, and returns four 32-bit integer values corresponding to
26 the input value that describe various aspects of the capabilities and
27 configuration of the processor.
28 .LP
29 The API for the character device consists of using the seek offset to set the
30 function code value, and using a \fBread\fR(2) or \fBpread\fR(2) of 16 bytes to
31 fetch the four 32-bit return values of the instruction in the order %\fBeax\fR,
32 %\fBebx\fR, %\fBecx\fR and %\fBedx\fR.
33 .LP
34 No data can be written to the device. Like the \fBcpuid\fR instruction, no
35 special privileges are required to use the device.
36 .LP
37 The device is useful to enable low-level configuration information to be
38 extracted from the CPU without having to write any assembler code to invoke the
39 \fBcpuid\fR instruction directly. It also allows the kernel to attempt to
40 correct any erroneous data returned by the instruction (prompted by occasional
41 errors in the information exported by various processor implementations over
42 the years).
43 .LP
44 See the processor manufacturers documentation for further information about the
45 syntax and semantics of the wide variety of information available from this
46 instruction.
47 .LP
48 Some systems can be configured to limit the cpuid opcodes which are accessible.
49 While illumos handles this condition, other software may malfunction when such
50 limits are enabled. Those settings are typically manipulated in the BIOS.
51 .SH EXAMPLE
52 .LP
53 This example allows you to determine if the current x86 processor supports
54 "long mode," which is a necessary (but not sufficient) condition for running
55 the 64-bit Solaris kernel on the processor.
56 .sp
57 .in +2
58 .nf
59 /*
60
61 #include <sys/types.h>
62 #include <sys/stat.h>
63 #include <fcntl.h>
64 #include <unistd.h>
65 #include <string.h>
66 #include <errno.h>
67 #include <stdio.h>
68
69 static const char devname[] = "/dev/cpu/self/cpuid";
70
71 /*ARGSUSED*/
72 int
73 main(int argc, char *argv[])
74 {
75 struct {
76 uint32_t r_eax, r_ebx, r_ecx, r_edx;
77 } _r, *rp = &_r;
78 int d;
79 char *s;
80
81 if ((d = open(devname, O_RDONLY)) == -1) {
82 perror(devname);
83 return (1);
84 }
85
86 if (pread(d, rp, sizeof (*rp), 0) != sizeof (*rp)) {
87 perror(devname);
88 goto fail;
89 }
90
91 s = (char *)&rp->r_ebx;
92 if (strncmp(s, "Auth" "cAMD" "enti", 12) != 0 &&
93 strncmp(s, "Genu" "ntel" "ineI", 12) != 0)
94 goto fail;
95
96 if (pread(d, rp, sizeof (*rp), 0x80000001) == sizeof (*rp)) {
97 /*
98 * Read extended feature word; check bit 29
99 */
100 (void) close(d);
101 if ((rp->r_edx >> 29) & 1) {
102 (void) printf("processor supports long mode\en");
103 return (0);
104 }
105 }
106 fail:
107 (void) close(d);
108 return (1);
109 }
110 .fi
111 .in -2
112
113 .SH ERRORS
114 .ne 2
115 .na
116 \fBENXIO\fR
117 .ad
118 .RS 10n
119 Results from attempting to read data from the device on a system that does not
120 support the CPU identification interfaces
121 .RE
122
123 .sp
124 .ne 2
125 .na
126 \fBEINVAL\fR
127 .ad
128 .RS 10n
129 Results from reading from an offset larger than UINT_MAX, or attempting to read
130 with a size that is not multiple of 16 bytes.
131 .RE
132
133 .SH FILES
134 .ne 2
135 .na
136 \fB\fB/dev/cpu/self/cpuid\fR\fR
137 .ad
138 .RS 23n
139 Provides access to CPU identification data.
140 .RE
141
142 .SH ATTRIBUTES
143 .LP
144 See \fBattributes\fR(5) for descriptions of the following attributes:
145 .sp
146
147 .sp
148 .TS
149 box;
150 c | c
151 l | l .
152 ATTRIBUTE TYPE ATTRIBUTE VALUE
153 _
154 Interface Stability Evolving
155 .TE
156
157 .SH SEE ALSO
158 .LP
159 \fBpsrinfo\fR(1M), \fBprtconf\fR(1M), \fBpread\fR(2), \fBread\fR(2),
160 \fBattributes\fR(5)