1 /*
2 * Copyright (C) 2003, 2004, 2007 Maciej W. Rozycki
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version
7 * 2 of the License, or (at your option) any later version.
8 */
9 #include <linux/init.h>
10 #include <linux/kernel.h>
11 #include <linux/ptrace.h>
12 #include <linux/stddef.h>
13
14 #include <asm/bugs.h>
15 #include <asm/compiler.h>
16 #include <asm/cpu.h>
17 #include <asm/fpu.h>
18 #include <asm/mipsregs.h>
19 #include <asm/setup.h>
20
21 static char bug64hit[] __initdata =
22 "reliable operation impossible!\n%s";
23 static char nowar[] __initdata =
24 "Please report to <linux-mips@linux-mips.org>.";
25 static char r4kwar[] __initdata =
26 "Enable CPU_R4000_WORKAROUNDS to rectify.";
27 static char daddiwar[] __initdata =
28 "Enable CPU_DADDI_WORKAROUNDS to rectify.";
29
align_mod(const int align,const int mod)30 static inline void align_mod(const int align, const int mod)
31 {
32 asm volatile(
33 ".set push\n\t"
34 ".set noreorder\n\t"
35 ".balign %0\n\t"
36 ".rept %1\n\t"
37 "nop\n\t"
38 ".endr\n\t"
39 ".set pop"
40 :
41 : GCC_IMM_ASM() (align), GCC_IMM_ASM() (mod));
42 }
43
mult_sh_align_mod(long * v1,long * v2,long * w,const int align,const int mod)44 static inline void mult_sh_align_mod(long *v1, long *v2, long *w,
45 const int align, const int mod)
46 {
47 unsigned long flags;
48 int m1, m2;
49 long p, s, lv1, lv2, lw;
50
51 /*
52 * We want the multiply and the shift to be isolated from the
53 * rest of the code to disable gcc optimizations. Hence the
54 * asm statements that execute nothing, but make gcc not know
55 * what the values of m1, m2 and s are and what lv2 and p are
56 * used for.
57 */
58
59 local_irq_save(flags);
60 /*
61 * The following code leads to a wrong result of the first
62 * dsll32 when executed on R4000 rev. 2.2 or 3.0 (PRId
63 * 00000422 or 00000430, respectively).
64 *
65 * See "MIPS R4000PC/SC Errata, Processor Revision 2.2 and
66 * 3.0" by MIPS Technologies, Inc., errata #16 and #28 for
67 * details. I got no permission to duplicate them here,
68 * sigh... --macro
69 */
70 asm volatile(
71 ""
72 : "=r" (m1), "=r" (m2), "=r" (s)
73 : "0" (5), "1" (8), "2" (5));
74 align_mod(align, mod);
75 /*
76 * The trailing nop is needed to fulfill the two-instruction
77 * requirement between reading hi/lo and staring a mult/div.
78 * Leaving it out may cause gas insert a nop itself breaking
79 * the desired alignment of the next chunk.
80 */
81 asm volatile(
82 ".set push\n\t"
83 ".set noat\n\t"
84 ".set noreorder\n\t"
85 ".set nomacro\n\t"
86 "mult %2, %3\n\t"
87 "dsll32 %0, %4, %5\n\t"
88 "mflo $0\n\t"
89 "dsll32 %1, %4, %5\n\t"
90 "nop\n\t"
91 ".set pop"
92 : "=&r" (lv1), "=r" (lw)
93 : "r" (m1), "r" (m2), "r" (s), "I" (0)
94 : "hi", "lo", GCC_REG_ACCUM);
95 /* We have to use single integers for m1 and m2 and a double
96 * one for p to be sure the mulsidi3 gcc's RTL multiplication
97 * instruction has the workaround applied. Older versions of
98 * gcc have correct umulsi3 and mulsi3, but other
99 * multiplication variants lack the workaround.
100 */
101 asm volatile(
102 ""
103 : "=r" (m1), "=r" (m2), "=r" (s)
104 : "0" (m1), "1" (m2), "2" (s));
105 align_mod(align, mod);
106 p = m1 * m2;
107 lv2 = s << 32;
108 asm volatile(
109 ""
110 : "=r" (lv2)
111 : "0" (lv2), "r" (p));
112 local_irq_restore(flags);
113
114 *v1 = lv1;
115 *v2 = lv2;
116 *w = lw;
117 }
118
check_mult_sh(void)119 static inline void check_mult_sh(void)
120 {
121 long v1[8], v2[8], w[8];
122 int bug, fix, i;
123
124 printk("Checking for the multiply/shift bug... ");
125
126 /*
127 * Testing discovered false negatives for certain code offsets
128 * into cache lines. Hence we test all possible offsets for
129 * the worst assumption of an R4000 I-cache line width of 32
130 * bytes.
131 *
132 * We can't use a loop as alignment directives need to be
133 * immediates.
134 */
135 mult_sh_align_mod(&v1[0], &v2[0], &w[0], 32, 0);
136 mult_sh_align_mod(&v1[1], &v2[1], &w[1], 32, 1);
137 mult_sh_align_mod(&v1[2], &v2[2], &w[2], 32, 2);
138 mult_sh_align_mod(&v1[3], &v2[3], &w[3], 32, 3);
139 mult_sh_align_mod(&v1[4], &v2[4], &w[4], 32, 4);
140 mult_sh_align_mod(&v1[5], &v2[5], &w[5], 32, 5);
141 mult_sh_align_mod(&v1[6], &v2[6], &w[6], 32, 6);
142 mult_sh_align_mod(&v1[7], &v2[7], &w[7], 32, 7);
143
144 bug = 0;
145 for (i = 0; i < 8; i++)
146 if (v1[i] != w[i])
147 bug = 1;
148
149 if (bug == 0) {
150 printk("no.\n");
151 return;
152 }
153
154 printk("yes, workaround... ");
155
156 fix = 1;
157 for (i = 0; i < 8; i++)
158 if (v2[i] != w[i])
159 fix = 0;
160
161 if (fix == 1) {
162 printk("yes.\n");
163 return;
164 }
165
166 printk("no.\n");
167 panic(bug64hit, !R4000_WAR ? r4kwar : nowar);
168 }
169
170 static volatile int daddi_ov __cpuinitdata;
171
do_daddi_ov(struct pt_regs * regs)172 asmlinkage void __init do_daddi_ov(struct pt_regs *regs)
173 {
174 daddi_ov = 1;
175 regs->cp0_epc += 4;
176 }
177
check_daddi(void)178 static inline void check_daddi(void)
179 {
180 extern asmlinkage void handle_daddi_ov(void);
181 unsigned long flags;
182 void *handler;
183 long v, tmp;
184
185 printk("Checking for the daddi bug... ");
186
187 local_irq_save(flags);
188 handler = set_except_vector(12, handle_daddi_ov);
189 /*
190 * The following code fails to trigger an overflow exception
191 * when executed on R4000 rev. 2.2 or 3.0 (PRId 00000422 or
192 * 00000430, respectively).
193 *
194 * See "MIPS R4000PC/SC Errata, Processor Revision 2.2 and
195 * 3.0" by MIPS Technologies, Inc., erratum #23 for details.
196 * I got no permission to duplicate it here, sigh... --macro
197 */
198 asm volatile(
199 ".set push\n\t"
200 ".set noat\n\t"
201 ".set noreorder\n\t"
202 ".set nomacro\n\t"
203 "addiu %1, $0, %2\n\t"
204 "dsrl %1, %1, 1\n\t"
205 #ifdef HAVE_AS_SET_DADDI
206 ".set daddi\n\t"
207 #endif
208 "daddi %0, %1, %3\n\t"
209 ".set pop"
210 : "=r" (v), "=&r" (tmp)
211 : "I" (0xffffffffffffdb9aUL), "I" (0x1234));
212 set_except_vector(12, handler);
213 local_irq_restore(flags);
214
215 if (daddi_ov) {
216 printk("no.\n");
217 return;
218 }
219
220 printk("yes, workaround... ");
221
222 local_irq_save(flags);
223 handler = set_except_vector(12, handle_daddi_ov);
224 asm volatile(
225 "addiu %1, $0, %2\n\t"
226 "dsrl %1, %1, 1\n\t"
227 "daddi %0, %1, %3"
228 : "=r" (v), "=&r" (tmp)
229 : "I" (0xffffffffffffdb9aUL), "I" (0x1234));
230 set_except_vector(12, handler);
231 local_irq_restore(flags);
232
233 if (daddi_ov) {
234 printk("yes.\n");
235 return;
236 }
237
238 printk("no.\n");
239 panic(bug64hit, !DADDI_WAR ? daddiwar : nowar);
240 }
241
242 int daddiu_bug = -1;
243
check_daddiu(void)244 static inline void check_daddiu(void)
245 {
246 long v, w, tmp;
247
248 printk("Checking for the daddiu bug... ");
249
250 /*
251 * The following code leads to a wrong result of daddiu when
252 * executed on R4400 rev. 1.0 (PRId 00000440).
253 *
254 * See "MIPS R4400PC/SC Errata, Processor Revision 1.0" by
255 * MIPS Technologies, Inc., erratum #7 for details.
256 *
257 * According to "MIPS R4000PC/SC Errata, Processor Revision
258 * 2.2 and 3.0" by MIPS Technologies, Inc., erratum #41 this
259 * problem affects R4000 rev. 2.2 and 3.0 (PRId 00000422 and
260 * 00000430, respectively), too. Testing failed to trigger it
261 * so far.
262 *
263 * I got no permission to duplicate the errata here, sigh...
264 * --macro
265 */
266 asm volatile(
267 ".set push\n\t"
268 ".set noat\n\t"
269 ".set noreorder\n\t"
270 ".set nomacro\n\t"
271 "addiu %2, $0, %3\n\t"
272 "dsrl %2, %2, 1\n\t"
273 #ifdef HAVE_AS_SET_DADDI
274 ".set daddi\n\t"
275 #endif
276 "daddiu %0, %2, %4\n\t"
277 "addiu %1, $0, %4\n\t"
278 "daddu %1, %2\n\t"
279 ".set pop"
280 : "=&r" (v), "=&r" (w), "=&r" (tmp)
281 : "I" (0xffffffffffffdb9aUL), "I" (0x1234));
282
283 daddiu_bug = v != w;
284
285 if (!daddiu_bug) {
286 printk("no.\n");
287 return;
288 }
289
290 printk("yes, workaround... ");
291
292 asm volatile(
293 "addiu %2, $0, %3\n\t"
294 "dsrl %2, %2, 1\n\t"
295 "daddiu %0, %2, %4\n\t"
296 "addiu %1, $0, %4\n\t"
297 "daddu %1, %2"
298 : "=&r" (v), "=&r" (w), "=&r" (tmp)
299 : "I" (0xffffffffffffdb9aUL), "I" (0x1234));
300
301 if (v == w) {
302 printk("yes.\n");
303 return;
304 }
305
306 printk("no.\n");
307 panic(bug64hit, !DADDI_WAR ? daddiwar : nowar);
308 }
309
check_bugs64_early(void)310 void __init check_bugs64_early(void)
311 {
312 check_mult_sh();
313 check_daddiu();
314 }
315
check_bugs64(void)316 void __init check_bugs64(void)
317 {
318 check_daddi();
319 }
320