1/*
2 * Copyright 2016, General Dynamics C4 Systems
3 *
4 * SPDX-License-Identifier: GPL-2.0-only
5 */
6
7#include <string.h>
8#include <util.h>
9#include <arch/machine.h>
10
11/** @file Support routines for identifying the processor family, model, etc
12 * on INTEL x86 processors, as well as attempting to determine the model string.
13 *
14 * AMD processors would be different.
15 */
16
17const char X86_CPUID_VENDOR_STRING_INTEL[] = {'G', 'e', 'n', 'u', 'i', 'n', 'e', 'I', 'n', 't', 'e', 'l', 0};
18const char X86_CPUID_VENDOR_STRING_AMD_LEGACY[] = { 'A', 'M', 'D', 'i', 's', 'b', 'e', 't', 't', 'e', 'r', '!', 0};
19const char X86_CPUID_VENDOR_STRING_AMD[] = {'A', 'u', 't', 'h', 'e', 'n', 't', 'i', 'c', 'A', 'M', 'D', 0};
20
21BOOT_BSS static cpu_identity_t cpu_identity;
22
23BOOT_CODE cpu_identity_t *x86_cpuid_get_identity(void)
24{
25    return &cpu_identity;
26}
27
28BOOT_CODE x86_cpu_identity_t *x86_cpuid_get_model_info(void)
29{
30    return &cpu_identity.display;
31}
32
33/** Extracts the vendor string from CPUID_000H.E[BCD]X.
34 * Will be one of "GenuineIntel", "AMDisbetter!", "AuthenticAMD", "CentaurHauls"
35 * etc. We don't support x86 CPUs from vendors other than AMD and Intel.
36 */
37BOOT_CODE static void x86_cpuid_fill_vendor_string(cpu_identity_t *ci)
38{
39    MAY_ALIAS uint32_t *vendor_string32 = (uint32_t *)ci->vendor_string;
40
41    if (ci == NULL) {
42        return;
43    }
44
45    vendor_string32[0] = x86_cpuid_ebx(0, 0);
46    vendor_string32[1] = x86_cpuid_edx(0, 0);
47    vendor_string32[2] = x86_cpuid_ecx(0, 0);
48
49    ci->vendor_string[X86_CPUID_VENDOR_STRING_MAXLENGTH] = '\0';
50}
51
52struct family_model {
53    uint8_t family, model;
54};
55
56BOOT_CODE static void x86_cpuid_intel_identity_initialize(cpu_identity_t *ci,
57                                                          struct family_model original)
58{
59    /* Next, there are some values which require additional adjustment, and
60     * require you to take into account an additional extended family and model
61     * ID.
62     *
63     * See Intel manuals vol2, section 3.2 for the literal constants.
64     */
65    if (original.family != 0x0F) {
66        ci->display.family = original.family;
67    } else {
68        ci->display.family = ci->display.extended_family + original.family;
69    }
70
71    /* The Intel manuals' wording would make you think you should use the
72     * original family_ID value read from CPUID.EAX, like:
73     *      if (original->family == 0x06 || original->family == 0x0F) {
74     *
75     * But Linux doesn't do that, Linux uses the family_ID value AFTER
76     * adjustment, like:
77     *      if (ci->display.family == 0x06 || ci->display.family == 0x0F) {
78     *
79     * Additionally, even though the Intel manuals say to adjust the model
80     * number if the family number is 0x6 OR 0xF, Linux just adusts it as long
81     * as the family number is GREATER THAN OR EQUAL to 0x6.
82     *
83     * I have followed Linux in the first case, where it could be a case of
84     * them having the correct interpretation of the text, but in the second case
85     * where they flagrantly disobey the manual, I have not followed them.
86     *
87     * See Linux source at: /arch/x86/lib/cpu.c:
88     *      http://lxr.free-electrons.com/source/arch/x86/lib/cpu.c
89     */
90    if (ci->display.family == 0x06 || ci->display.family == 0x0F) {
91        ci->display.model = (ci->display.extended_model << 4u) + original.model;
92    } else {
93        ci->display.model = original.model;
94    }
95}
96
97BOOT_CODE static void x86_cpuid_amd_identity_initialize(cpu_identity_t *ci,
98                                                        struct family_model original)
99{
100    /* Intel and AMD's specifications give slightly different ways to compose
101     * the family and model IDs (AMD CPUID manual, section 2.)
102     *
103     * AMD says that if family is LESS THAN 0xF, then adjustments are needed.
104     * Intel says that if family == 0xF || family == 0x6, then adjustments are
105     * needed.
106     */
107    if (original.family < 0xF) {
108        ci->display.family = original.family;
109        ci->display.model = original.model;
110    } else {
111        ci->display.family = original.family + ci->display.extended_family;
112        ci->display.family = (ci->display.extended_model << 4u) + original.model;
113    }
114}
115
116bool_t x86_cpuid_initialize(void)
117{
118    cpu_identity_t *ci = x86_cpuid_get_identity();
119    struct family_model original;
120    cpuid_001h_eax_t eax;
121    cpuid_001h_ebx_t ebx;
122
123    memset(ci, 0, sizeof(*ci));
124
125    /* First determine which vendor manufactured the CPU. */
126    x86_cpuid_fill_vendor_string(ci);
127
128    /* Need both eax and ebx ouput values. */
129    eax.words[0] = x86_cpuid_eax(1, 0);
130    ebx.words[0] = x86_cpuid_ebx(1, 0);
131
132    /* We now use EAX for the family, model, stepping values, and EBX for the
133     * brand index. Store the original values from CPUID_001H.EAX.
134     */
135    original.family = cpuid_001h_eax_get_family(eax);
136    original.model = cpuid_001h_eax_get_model(eax);
137    ci->display.stepping = cpuid_001h_eax_get_stepping(eax);
138
139    /* Also store extended family and model values used for adjustment */
140    ci->display.extended_family = cpuid_001h_eax_get_extended_family(eax);
141    ci->display.extended_model = cpuid_001h_eax_get_extended_model(eax);
142
143    /* Also store the brand index value given in EBX */
144    ci->display.brand = cpuid_001h_ebx_get_brand(ebx);
145
146    if (strncmp(ci->vendor_string, X86_CPUID_VENDOR_STRING_INTEL,
147                X86_CPUID_VENDOR_STRING_MAXLENGTH) == 0) {
148        ci->vendor = X86_VENDOR_INTEL;
149        x86_cpuid_intel_identity_initialize(ci, original);
150        return true;
151    } else if (strncmp(ci->vendor_string, X86_CPUID_VENDOR_STRING_AMD_LEGACY,
152                       X86_CPUID_VENDOR_STRING_MAXLENGTH) == 0
153               || strncmp(ci->vendor_string, X86_CPUID_VENDOR_STRING_AMD,
154                          X86_CPUID_VENDOR_STRING_MAXLENGTH) == 0) {
155        ci->vendor = X86_VENDOR_AMD;
156        x86_cpuid_amd_identity_initialize(ci, original);
157        return true;
158    } else {
159        /* CPU from unsupported vendor. Examples could be Cyrix, Centaur, etc.
160         * The old time x86 clones. Return false to the boot and let the upper
161         * level caller decide what to do.
162         */
163        ci->vendor = X86_VENDOR_OTHER;
164        return false;
165    }
166}
167