1 /*
2 * Copyright (C) 1994 Linus Torvalds
3 *
4 * Cyrix stuff, June 1998 by:
5 * - Rafael R. Reilova (moved everything from head.S),
6 * <rreilova@ececs.uc.edu>
7 * - Channing Corn (tests & fixes),
8 * - Andrew D. Balsa (code cleanup).
9 */
10 #include <linux/init.h>
11 #include <linux/utsname.h>
12 #include <asm/bugs.h>
13 #include <asm/processor.h>
14 #include <asm/processor-flags.h>
15 #include <asm/i387.h>
16 #include <asm/msr.h>
17 #include <asm/paravirt.h>
18 #include <asm/alternative.h>
19
20 static int __init no_halt(char *s)
21 {
22 boot_cpu_data.hlt_works_ok = 0;
23 return 1;
24 }
25
26 __setup("no-hlt", no_halt);
27
28 static int __init no_387(char *s)
29 {
30 boot_cpu_data.hard_math = 0;
31 write_cr0(X86_CR0_TS | X86_CR0_EM | X86_CR0_MP | read_cr0());
32 return 1;
33 }
34
35 __setup("no387", no_387);
36
37 static double __initdata x = 4195835.0;
38 static double __initdata y = 3145727.0;
39
40 /*
41 * This used to check for exceptions..
42 * However, it turns out that to support that,
43 * the XMM trap handlers basically had to
44 * be buggy. So let's have a correct XMM trap
45 * handler, and forget about printing out
46 * some status at boot.
47 *
48 * We should really only care about bugs here
49 * anyway. Not features.
50 */
51 static void __init check_fpu(void)
52 {
53 s32 fdiv_bug;
54
55 if (!boot_cpu_data.hard_math) {
56 #ifndef CONFIG_MATH_EMULATION
57 printk(KERN_EMERG "No coprocessor found and no math emulation present.\n");
58 printk(KERN_EMERG "Giving up.\n");
59 for (;;) ;
60 #endif
61 return;
62 }
63
64 /*
65 * trap_init() enabled FXSR and company _before_ testing for FP
66 * problems here.
67 *
68 * Test for the divl bug..
69 */
70 __asm__("fninit\n\t"
71 "fldl %1\n\t"
72 "fdivl %2\n\t"
73 "fmull %2\n\t"
74 "fldl %1\n\t"
75 "fsubp %%st,%%st(1)\n\t"
76 "fistpl %0\n\t"
77 "fwait\n\t"
78 "fninit"
79 : "=m" (*&fdiv_bug)
80 : "m" (*&x), "m" (*&y));
81
82 boot_cpu_data.fdiv_bug = fdiv_bug;
83 if (boot_cpu_data.fdiv_bug)
84 printk("Hmm, FPU with FDIV bug.\n");
85 }
86
87 static void __init check_hlt(void)
88 {
89 if (paravirt_enabled())
90 return;
91
92 printk(KERN_INFO "Checking 'hlt' instruction... ");
93 if (!boot_cpu_data.hlt_works_ok) {
94 printk("disabled\n");
95 return;
96 }
97 halt();
98 halt();
99 halt();
100 halt();
101 printk("OK.\n");
102 }
103
104 /*
105 * Most 386 processors have a bug where a POPAD can lock the
106 * machine even from user space.
107 */
108
109 static void __init check_popad(void)
110 {
111 #ifndef CONFIG_X86_POPAD_OK
112 int res, inp = (int) &res;
113
114 printk(KERN_INFO "Checking for popad bug... ");
115 __asm__ __volatile__(
116 "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx "
117 : "=&a" (res)
118 : "d" (inp)
119 : "ecx", "edi");
120 /*
121 * If this fails, it means that any user program may lock the
122 * CPU hard. Too bad.
123 */
124 if (res != 12345678)
125 printk("Buggy.\n");
126 else
127 printk("OK.\n");
128 #endif
129 }
130
131 /*
132 * Check whether we are able to run this kernel safely on SMP.
133 *
134 * - In order to run on a i386, we need to be compiled for i386
135 * (for due to lack of "invlpg" and working WP on a i386)
136 * - In order to run on anything without a TSC, we need to be
137 * compiled for a i486.
138 */
139
140 static void __init check_config(void)
141 {
142 /*
143 * We'd better not be a i386 if we're configured to use some
144 * i486+ only features! (WP works in supervisor mode and the
145 * new "invlpg" and "bswap" instructions)
146 */
147 #if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || \
148 defined(CONFIG_X86_BSWAP)
149 if (boot_cpu_data.x86 == 3)
150 panic("Kernel requires i486+ for 'invlpg' and other features");
151 #endif
152 }
153
154
155 void __init check_bugs(void)
156 {
157 identify_boot_cpu();
158 #ifndef CONFIG_SMP
159 printk("CPU: ");
160 print_cpu_info(&boot_cpu_data);
161 #endif
162 check_config();
163 check_fpu();
164 check_hlt();
165 check_popad();
166 init_utsname()->machine[1] =
167 '' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
168 alternative_instructions();
169 }
170
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