1/*
2 * Copyright 2016, General Dynamics C4 Systems
3 *
4 * This software may be distributed and modified according to the terms of
5 * the GNU General Public License version 2. Note that NO WARRANTY is provided.
6 * See "LICENSE_GPLv2.txt" for details.
7 *
8 * @TAG(GD_GPL)
9 */
10#include <string.h>
11#include <util.h>
12#include <arch/machine.h>
13
14/** @file Support routines for identifying the processor family, model, etc
15 * on INTEL x86 processors, as well as attempting to determine the model string.
16 *
17 * AMD processors would be different.
18 */
19
20const char X86_CPUID_VENDOR_STRING_INTEL[] = {'G', 'e', 'n', 'u', 'i', 'n', 'e', 'I', 'n', 't', 'e', 'l', 0};
21const char X86_CPUID_VENDOR_STRING_AMD_LEGACY[] = { 'A', 'M', 'D', 'i', 's', 'b', 'e', 't', 't', 'e', 'r', '!', 0};
22const char X86_CPUID_VENDOR_STRING_AMD[] = {'A', 'u', 't', 'h', 'e', 'n', 't', 'i', 'c', 'A', 'M', 'D', 0};
23
24BOOT_BSS static cpu_identity_t cpu_identity;
25
26BOOT_CODE cpu_identity_t *x86_cpuid_get_identity(void)
27{
28    return &cpu_identity;
29}
30
31BOOT_CODE x86_cpu_identity_t *x86_cpuid_get_model_info(void)
32{
33    return &cpu_identity.display;
34}
35
36/** Extracts the vendor string from CPUID_000H.E[BCD]X.
37 * Will be one of "GenuineIntel", "AMDisbetter!", "AuthenticAMD", "CentaurHauls"
38 * etc. We don't support x86 CPUs from vendors other than AMD and Intel.
39 */
40BOOT_CODE static void
41x86_cpuid_fill_vendor_string(cpu_identity_t *ci)
42{
43    MAY_ALIAS uint32_t *vendor_string32 = (uint32_t *)ci->vendor_string;
44
45    if (ci == NULL) {
46        return;
47    }
48
49    vendor_string32[0] = x86_cpuid_ebx(0, 0);
50    vendor_string32[1] = x86_cpuid_edx(0, 0);
51    vendor_string32[2] = x86_cpuid_ecx(0, 0);
52
53    ci->vendor_string[X86_CPUID_VENDOR_STRING_MAXLENGTH] = '\0';
54}
55
56struct family_model {
57    uint8_t family, model;
58};
59
60BOOT_CODE static void
61x86_cpuid_intel_identity_initialize(cpu_identity_t *ci,
62                                    struct family_model original)
63{
64    /* Next, there are some values which require additional adjustment, and
65     * require you to take into account an additional extended family and model
66     * ID.
67     *
68     * See Intel manuals vol2, section 3.2 for the literal constants.
69     */
70    if (original.family != 0x0F) {
71        ci->display.family = original.family;
72    } else {
73        ci->display.family = ci->display.extended_family + original.family;
74    }
75
76    /* The Intel manuals' wording would make you think you should use the
77     * original family_ID value read from CPUID.EAX, like:
78     *      if (original->family == 0x06 || original->family == 0x0F) {
79     *
80     * But Linux doesn't do that, Linux uses the family_ID value AFTER
81     * adjustment, like:
82     *      if (ci->display.family == 0x06 || ci->display.family == 0x0F) {
83     *
84     * Additionally, even though the Intel manuals say to adjust the model
85     * number if the family number is 0x6 OR 0xF, Linux just adusts it as long
86     * as the family number is GREATER THAN OR EQUAL to 0x6.
87     *
88     * I have followed Linux in the first case, where it could be a case of
89     * them having the correct interpretation of the text, but in the second case
90     * where they flagrantly disobey the manual, I have not followed them.
91     *
92     * See Linux source at: /arch/x86/lib/cpu.c:
93     *      http://lxr.free-electrons.com/source/arch/x86/lib/cpu.c
94     */
95    if (ci->display.family == 0x06 || ci->display.family == 0x0F) {
96        ci->display.model = (ci->display.extended_model << 4u) + original.model;
97    } else {
98        ci->display.model = original.model;
99    }
100}
101
102BOOT_CODE static void
103x86_cpuid_amd_identity_initialize(cpu_identity_t *ci,
104                                  struct family_model original)
105{
106    /* Intel and AMD's specifications give slightly different ways to compose
107     * the family and model IDs (AMD CPUID manual, section 2.)
108     *
109     * AMD says that if family is LESS THAN 0xF, then adjustments are needed.
110     * Intel says that if family == 0xF || family == 0x6, then adjustments are
111     * needed.
112     */
113    if (original.family < 0xF) {
114        ci->display.family = original.family;
115        ci->display.model = original.model;
116    } else {
117        ci->display.family = original.family + ci->display.extended_family;
118        ci->display.family = (ci->display.extended_model << 4u) + original.model;
119    }
120}
121
122bool_t
123x86_cpuid_initialize(void)
124{
125    cpu_identity_t *ci = x86_cpuid_get_identity();
126    struct family_model original;
127    cpuid_001h_eax_t eax;
128    cpuid_001h_ebx_t ebx;
129
130    memset(ci, 0, sizeof(*ci));
131
132    /* First determine which vendor manufactured the CPU. */
133    x86_cpuid_fill_vendor_string(ci);
134
135    /* Need both eax and ebx ouput values. */
136    eax.words[0] = x86_cpuid_eax(1, 0);
137    ebx.words[0] = x86_cpuid_ebx(1, 0);
138
139    /* We now use EAX for the family, model, stepping values, and EBX for the
140     * brand index. Store the original values from CPUID_001H.EAX.
141     */
142    original.family = cpuid_001h_eax_get_family(eax);
143    original.model = cpuid_001h_eax_get_model(eax);
144    ci->display.stepping = cpuid_001h_eax_get_stepping(eax);
145
146    /* Also store extended family and model values used for adjustment */
147    ci->display.extended_family = cpuid_001h_eax_get_extended_family(eax);
148    ci->display.extended_model = cpuid_001h_eax_get_extended_model(eax);
149
150    /* Also store the brand index value given in EBX */
151    ci->display.brand = cpuid_001h_ebx_get_brand(ebx);
152
153    if (strncmp(ci->vendor_string, X86_CPUID_VENDOR_STRING_INTEL,
154                X86_CPUID_VENDOR_STRING_MAXLENGTH) == 0) {
155        ci->vendor = X86_VENDOR_INTEL;
156        x86_cpuid_intel_identity_initialize(ci, original);
157        return true;
158    } else if (strncmp(ci->vendor_string, X86_CPUID_VENDOR_STRING_AMD_LEGACY,
159                       X86_CPUID_VENDOR_STRING_MAXLENGTH) == 0
160               || strncmp(ci->vendor_string, X86_CPUID_VENDOR_STRING_AMD,
161                          X86_CPUID_VENDOR_STRING_MAXLENGTH) == 0) {
162        ci->vendor = X86_VENDOR_AMD;
163        x86_cpuid_amd_identity_initialize(ci, original);
164        return true;
165    } else {
166        /* CPU from unsupported vendor. Examples could be Cyrix, Centaur, etc.
167         * The old time x86 clones. Return false to the boot and let the upper
168         * level caller decide what to do.
169         */
170        ci->vendor = X86_VENDOR_OTHER;
171        return false;
172    }
173}
174