1// SPDX-License-Identifier: GPL-2.0
2#include <linux/types.h>
3#include "bitops.h"
4
5#include <asm/processor-flags.h>
6#include <asm/msr-index.h>
7#include "cpuflags.h"
8
9struct cpu_features cpu;
10u32 cpu_vendor[3];
11
12static bool loaded_flags;
13
14static int has_fpu(void)
15{
16 u16 fcw = -1, fsw = -1;
17 unsigned long cr0;
18
19 asm volatile("mov %%cr0,%0" : "=r" (cr0));
20 if (cr0 & (X86_CR0_EM|X86_CR0_TS)) {
21 cr0 &= ~(X86_CR0_EM|X86_CR0_TS);
22 asm volatile("mov %0,%%cr0" : : "r" (cr0));
23 }
24
25 asm volatile("fninit ; fnstsw %0 ; fnstcw %1"
26 : "+m" (fsw), "+m" (fcw));
27
28 return fsw == 0 && (fcw & 0x103f) == 0x003f;
29}
30
31#ifdef CONFIG_X86_32
32/*
33 * For building the 16-bit code we want to explicitly specify 32-bit
34 * push/pop operations, rather than just saying 'pushf' or 'popf' and
35 * letting the compiler choose.
36 */
37bool has_eflag(unsigned long mask)
38{
39 unsigned long f0, f1;
40
41 asm volatile("pushfl \n\t"
42 "pushfl \n\t"
43 "pop %0 \n\t"
44 "mov %0,%1 \n\t"
45 "xor %2,%1 \n\t"
46 "push %1 \n\t"
47 "popfl \n\t"
48 "pushfl \n\t"
49 "pop %1 \n\t"
50 "popfl"
51 : "=&r" (f0), "=&r" (f1)
52 : "ri" (mask));
53
54 return !!((f0^f1) & mask);
55}
56#endif
57
58void cpuid_count(u32 id, u32 count, u32 *a, u32 *b, u32 *c, u32 *d)
59{
60 asm volatile("cpuid"
61 : "=a" (*a), "=b" (*b), "=c" (*c), "=d" (*d)
62 : "0" (id), "2" (count)
63 );
64}
65
66#define cpuid(id, a, b, c, d) cpuid_count(id, 0, a, b, c, d)
67
68void get_cpuflags(void)
69{
70 u32 max_intel_level, max_amd_level;
71 u32 tfms;
72 u32 ignored;
73
74 if (loaded_flags)
75 return;
76 loaded_flags = true;
77
78 if (has_fpu())
79 set_bit(X86_FEATURE_FPU, addr: cpu.flags);
80
81 if (has_eflag(X86_EFLAGS_ID)) {
82 cpuid(0x0, &max_intel_level, &cpu_vendor[0], &cpu_vendor[2],
83 &cpu_vendor[1]);
84
85 if (max_intel_level >= 0x00000001 &&
86 max_intel_level <= 0x0000ffff) {
87 cpuid(0x1, &tfms, &ignored, &cpu.flags[4],
88 &cpu.flags[0]);
89 cpu.level = (tfms >> 8) & 15;
90 cpu.family = cpu.level;
91 cpu.model = (tfms >> 4) & 15;
92 if (cpu.level >= 6)
93 cpu.model += ((tfms >> 16) & 0xf) << 4;
94 }
95
96 if (max_intel_level >= 0x00000007) {
97 cpuid_count(id: 0x00000007, count: 0, a: &ignored, b: &ignored,
98 c: &cpu.flags[16], d: &ignored);
99 }
100
101 cpuid(0x80000000, &max_amd_level, &ignored, &ignored,
102 &ignored);
103
104 if (max_amd_level >= 0x80000001 &&
105 max_amd_level <= 0x8000ffff) {
106 cpuid(0x80000001, &ignored, &ignored, &cpu.flags[6],
107 &cpu.flags[1]);
108 }
109 }
110}
111

source code of linux/arch/x86/boot/cpuflags.c