xref: /openssl/crypto/cpuid.c (revision 556009c5)
1 /*
2  * Copyright 1998-2023 The OpenSSL Project Authors. All Rights Reserved.
3  *
4  * Licensed under the Apache License 2.0 (the "License").  You may not use
5  * this file except in compliance with the License.  You can obtain a copy
6  * in the file LICENSE in the source distribution or at
7  * https://www.openssl.org/source/license.html
8  */
9 
10 #include "internal/e_os.h"
11 #include "crypto/cryptlib.h"
12 
13 #if     defined(__i386)   || defined(__i386__)   || defined(_M_IX86) || \
14         defined(__x86_64) || defined(__x86_64__) || \
15         defined(_M_AMD64) || defined(_M_X64)
16 
17 extern unsigned int OPENSSL_ia32cap_P[4];
18 
19 # if defined(OPENSSL_CPUID_OBJ)
20 
21 /*
22  * Purpose of these minimalistic and character-type-agnostic subroutines
23  * is to break dependency on MSVCRT (on Windows) and locale. This makes
24  * OPENSSL_cpuid_setup safe to use as "constructor". "Character-type-
25  * agnostic" means that they work with either wide or 8-bit characters,
26  * exploiting the fact that first 127 characters can be simply casted
27  * between the sets, while the rest would be simply rejected by ossl_is*
28  * subroutines.
29  */
30 #  ifdef _WIN32
31 typedef WCHAR variant_char;
32 
ossl_getenv(const char * name)33 static variant_char *ossl_getenv(const char *name)
34 {
35     /*
36      * Since we pull only one environment variable, it's simpler to
37      * just ignore |name| and use equivalent wide-char L-literal.
38      * As well as to ignore excessively long values...
39      */
40     static WCHAR value[48];
41     DWORD len = GetEnvironmentVariableW(L"OPENSSL_ia32cap", value, 48);
42 
43     return (len > 0 && len < 48) ? value : NULL;
44 }
45 #  else
46 typedef char variant_char;
47 #   define ossl_getenv getenv
48 #  endif
49 
50 #  include "crypto/ctype.h"
51 
todigit(variant_char c)52 static int todigit(variant_char c)
53 {
54     if (ossl_isdigit(c))
55         return c - '0';
56     else if (ossl_isxdigit(c))
57         return ossl_tolower(c) - 'a' + 10;
58 
59     /* return largest base value to make caller terminate the loop */
60     return 16;
61 }
62 
ossl_strtouint64(const variant_char * str)63 static uint64_t ossl_strtouint64(const variant_char *str)
64 {
65     uint64_t ret = 0;
66     unsigned int digit, base = 10;
67 
68     if (*str == '0') {
69         base = 8, str++;
70         if (ossl_tolower(*str) == 'x')
71             base = 16, str++;
72     }
73 
74     while ((digit = todigit(*str++)) < base)
75         ret = ret * base + digit;
76 
77     return ret;
78 }
79 
ossl_strchr(const variant_char * str,char srch)80 static variant_char *ossl_strchr(const variant_char *str, char srch)
81 {   variant_char c;
82 
83     while ((c = *str)) {
84         if (c == srch)
85             return (variant_char *)str;
86         str++;
87     }
88 
89     return NULL;
90 }
91 
92 #  define OPENSSL_CPUID_SETUP
93 typedef uint64_t IA32CAP;
94 
OPENSSL_cpuid_setup(void)95 void OPENSSL_cpuid_setup(void)
96 {
97     static int trigger = 0;
98     IA32CAP OPENSSL_ia32_cpuid(unsigned int *);
99     IA32CAP vec;
100     const variant_char *env;
101 
102     if (trigger)
103         return;
104 
105     trigger = 1;
106     if ((env = ossl_getenv("OPENSSL_ia32cap")) != NULL) {
107         int off = (env[0] == '~') ? 1 : 0;
108 
109         vec = ossl_strtouint64(env + off);
110 
111         if (off) {
112             IA32CAP mask = vec;
113             vec = OPENSSL_ia32_cpuid(OPENSSL_ia32cap_P) & ~mask;
114             if (mask & (1<<24)) {
115                 /*
116                  * User disables FXSR bit, mask even other capabilities
117                  * that operate exclusively on XMM, so we don't have to
118                  * double-check all the time. We mask PCLMULQDQ, AMD XOP,
119                  * AES-NI and AVX. Formally speaking we don't have to
120                  * do it in x86_64 case, but we can safely assume that
121                  * x86_64 users won't actually flip this flag.
122                  */
123                 vec &= ~((IA32CAP)(1<<1|1<<11|1<<25|1<<28) << 32);
124             }
125         } else if (env[0] == ':') {
126             vec = OPENSSL_ia32_cpuid(OPENSSL_ia32cap_P);
127         }
128 
129         if ((env = ossl_strchr(env, ':')) != NULL) {
130             IA32CAP vecx;
131 
132             env++;
133             off = (env[0] == '~') ? 1 : 0;
134             vecx = ossl_strtouint64(env + off);
135             if (off) {
136                 OPENSSL_ia32cap_P[2] &= ~(unsigned int)vecx;
137                 OPENSSL_ia32cap_P[3] &= ~(unsigned int)(vecx >> 32);
138             } else {
139                 OPENSSL_ia32cap_P[2] = (unsigned int)vecx;
140                 OPENSSL_ia32cap_P[3] = (unsigned int)(vecx >> 32);
141             }
142         } else {
143             OPENSSL_ia32cap_P[2] = 0;
144             OPENSSL_ia32cap_P[3] = 0;
145         }
146     } else {
147         vec = OPENSSL_ia32_cpuid(OPENSSL_ia32cap_P);
148     }
149 
150     /*
151      * |(1<<10) sets a reserved bit to signal that variable
152      * was initialized already... This is to avoid interference
153      * with cpuid snippets in ELF .init segment.
154      */
155     OPENSSL_ia32cap_P[0] = (unsigned int)vec | (1 << 10);
156     OPENSSL_ia32cap_P[1] = (unsigned int)(vec >> 32);
157 }
158 # else
159 unsigned int OPENSSL_ia32cap_P[4];
160 # endif
161 #endif
162 
163 #ifndef OPENSSL_CPUID_OBJ
164 # ifndef OPENSSL_CPUID_SETUP
OPENSSL_cpuid_setup(void)165 void OPENSSL_cpuid_setup(void)
166 {
167 }
168 # endif
169 
170 /*
171  * The rest are functions that are defined in the same assembler files as
172  * the CPUID functionality.
173  */
174 
175 /*
176  * The volatile is used to ensure that the compiler generates code that reads
177  * all values from the array and doesn't try to optimize this away. The standard
178  * doesn't actually require this behavior if the original data pointed to is
179  * not volatile, but compilers do this in practice anyway.
180  *
181  * There are also assembler versions of this function.
182  */
183 # undef CRYPTO_memcmp
CRYPTO_memcmp(const void * in_a,const void * in_b,size_t len)184 int CRYPTO_memcmp(const void *in_a, const void *in_b, size_t len)
185 {
186     size_t i;
187     const volatile unsigned char *a = in_a;
188     const volatile unsigned char *b = in_b;
189     unsigned char x = 0;
190 
191     for (i = 0; i < len; i++)
192         x |= a[i] ^ b[i];
193 
194     return x;
195 }
196 
197 /*
198  * For systems that don't provide an instruction counter register or equivalent.
199  */
OPENSSL_rdtsc(void)200 uint32_t OPENSSL_rdtsc(void)
201 {
202     return 0;
203 }
204 
OPENSSL_instrument_bus(unsigned int * out,size_t cnt)205 size_t OPENSSL_instrument_bus(unsigned int *out, size_t cnt)
206 {
207     return 0;
208 }
209 
OPENSSL_instrument_bus2(unsigned int * out,size_t cnt,size_t max)210 size_t OPENSSL_instrument_bus2(unsigned int *out, size_t cnt, size_t max)
211 {
212     return 0;
213 }
214 #endif
215