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[GitHub/mt8127/android_kernel_alcatel_ttab.git] / arch / mips / kernel / branch.c
1 /*
2 * This file is subject to the terms and conditions of the GNU General Public
3 * License. See the file "COPYING" in the main directory of this archive
4 * for more details.
5 *
6 * Copyright (C) 1996, 97, 2000, 2001 by Ralf Baechle
7 * Copyright (C) 2001 MIPS Technologies, Inc.
8 */
9 #include <linux/kernel.h>
10 #include <linux/sched.h>
11 #include <linux/signal.h>
12 #include <linux/module.h>
13 #include <asm/branch.h>
14 #include <asm/cpu.h>
15 #include <asm/cpu-features.h>
16 #include <asm/fpu.h>
17 #include <asm/fpu_emulator.h>
18 #include <asm/inst.h>
19 #include <asm/ptrace.h>
20 #include <asm/uaccess.h>
21
22 /*
23 * Calculate and return exception PC in case of branch delay slot
24 * for microMIPS and MIPS16e. It does not clear the ISA mode bit.
25 */
26 int __isa_exception_epc(struct pt_regs *regs)
27 {
28 unsigned short inst;
29 long epc = regs->cp0_epc;
30
31 /* Calculate exception PC in branch delay slot. */
32 if (__get_user(inst, (u16 __user *) msk_isa16_mode(epc))) {
33 /* This should never happen because delay slot was checked. */
34 force_sig(SIGSEGV, current);
35 return epc;
36 }
37 if (cpu_has_mips16) {
38 if (((union mips16e_instruction)inst).ri.opcode
39 == MIPS16e_jal_op)
40 epc += 4;
41 else
42 epc += 2;
43 } else if (mm_insn_16bit(inst))
44 epc += 2;
45 else
46 epc += 4;
47
48 return epc;
49 }
50
51 /*
52 * Compute return address and emulate branch in microMIPS mode after an
53 * exception only. It does not handle compact branches/jumps and cannot
54 * be used in interrupt context. (Compact branches/jumps do not cause
55 * exceptions.)
56 */
57 int __microMIPS_compute_return_epc(struct pt_regs *regs)
58 {
59 u16 __user *pc16;
60 u16 halfword;
61 unsigned int word;
62 unsigned long contpc;
63 struct mm_decoded_insn mminsn = { 0 };
64
65 mminsn.micro_mips_mode = 1;
66
67 /* This load never faults. */
68 pc16 = (unsigned short __user *)msk_isa16_mode(regs->cp0_epc);
69 __get_user(halfword, pc16);
70 pc16++;
71 contpc = regs->cp0_epc + 2;
72 word = ((unsigned int)halfword << 16);
73 mminsn.pc_inc = 2;
74
75 if (!mm_insn_16bit(halfword)) {
76 __get_user(halfword, pc16);
77 pc16++;
78 contpc = regs->cp0_epc + 4;
79 mminsn.pc_inc = 4;
80 word |= halfword;
81 }
82 mminsn.insn = word;
83
84 if (get_user(halfword, pc16))
85 goto sigsegv;
86 mminsn.next_pc_inc = 2;
87 word = ((unsigned int)halfword << 16);
88
89 if (!mm_insn_16bit(halfword)) {
90 pc16++;
91 if (get_user(halfword, pc16))
92 goto sigsegv;
93 mminsn.next_pc_inc = 4;
94 word |= halfword;
95 }
96 mminsn.next_insn = word;
97
98 mm_isBranchInstr(regs, mminsn, &contpc);
99
100 regs->cp0_epc = contpc;
101
102 return 0;
103
104 sigsegv:
105 force_sig(SIGSEGV, current);
106 return -EFAULT;
107 }
108
109 /*
110 * Compute return address and emulate branch in MIPS16e mode after an
111 * exception only. It does not handle compact branches/jumps and cannot
112 * be used in interrupt context. (Compact branches/jumps do not cause
113 * exceptions.)
114 */
115 int __MIPS16e_compute_return_epc(struct pt_regs *regs)
116 {
117 u16 __user *addr;
118 union mips16e_instruction inst;
119 u16 inst2;
120 u32 fullinst;
121 long epc;
122
123 epc = regs->cp0_epc;
124
125 /* Read the instruction. */
126 addr = (u16 __user *)msk_isa16_mode(epc);
127 if (__get_user(inst.full, addr)) {
128 force_sig(SIGSEGV, current);
129 return -EFAULT;
130 }
131
132 switch (inst.ri.opcode) {
133 case MIPS16e_extend_op:
134 regs->cp0_epc += 4;
135 return 0;
136
137 /*
138 * JAL and JALX in MIPS16e mode
139 */
140 case MIPS16e_jal_op:
141 addr += 1;
142 if (__get_user(inst2, addr)) {
143 force_sig(SIGSEGV, current);
144 return -EFAULT;
145 }
146 fullinst = ((unsigned)inst.full << 16) | inst2;
147 regs->regs[31] = epc + 6;
148 epc += 4;
149 epc >>= 28;
150 epc <<= 28;
151 /*
152 * JAL:5 X:1 TARGET[20-16]:5 TARGET[25:21]:5 TARGET[15:0]:16
153 *
154 * ......TARGET[15:0].................TARGET[20:16]...........
155 * ......TARGET[25:21]
156 */
157 epc |=
158 ((fullinst & 0xffff) << 2) | ((fullinst & 0x3e00000) >> 3) |
159 ((fullinst & 0x1f0000) << 7);
160 if (!inst.jal.x)
161 set_isa16_mode(epc); /* Set ISA mode bit. */
162 regs->cp0_epc = epc;
163 return 0;
164
165 /*
166 * J(AL)R(C)
167 */
168 case MIPS16e_rr_op:
169 if (inst.rr.func == MIPS16e_jr_func) {
170
171 if (inst.rr.ra)
172 regs->cp0_epc = regs->regs[31];
173 else
174 regs->cp0_epc =
175 regs->regs[reg16to32[inst.rr.rx]];
176
177 if (inst.rr.l) {
178 if (inst.rr.nd)
179 regs->regs[31] = epc + 2;
180 else
181 regs->regs[31] = epc + 4;
182 }
183 return 0;
184 }
185 break;
186 }
187
188 /*
189 * All other cases have no branch delay slot and are 16-bits.
190 * Branches do not cause an exception.
191 */
192 regs->cp0_epc += 2;
193
194 return 0;
195 }
196
197 /**
198 * __compute_return_epc_for_insn - Computes the return address and do emulate
199 * branch simulation, if required.
200 *
201 * @regs: Pointer to pt_regs
202 * @insn: branch instruction to decode
203 * @returns: -EFAULT on error and forces SIGBUS, and on success
204 * returns 0 or BRANCH_LIKELY_TAKEN as appropriate after
205 * evaluating the branch.
206 */
207 int __compute_return_epc_for_insn(struct pt_regs *regs,
208 union mips_instruction insn)
209 {
210 unsigned int bit, fcr31, dspcontrol;
211 long epc = regs->cp0_epc;
212 int ret = 0;
213
214 switch (insn.i_format.opcode) {
215 /*
216 * jr and jalr are in r_format format.
217 */
218 case spec_op:
219 switch (insn.r_format.func) {
220 case jalr_op:
221 regs->regs[insn.r_format.rd] = epc + 8;
222 /* Fall through */
223 case jr_op:
224 regs->cp0_epc = regs->regs[insn.r_format.rs];
225 break;
226 }
227 break;
228
229 /*
230 * This group contains:
231 * bltz_op, bgez_op, bltzl_op, bgezl_op,
232 * bltzal_op, bgezal_op, bltzall_op, bgezall_op.
233 */
234 case bcond_op:
235 switch (insn.i_format.rt) {
236 case bltz_op:
237 case bltzl_op:
238 if ((long)regs->regs[insn.i_format.rs] < 0) {
239 epc = epc + 4 + (insn.i_format.simmediate << 2);
240 if (insn.i_format.rt == bltzl_op)
241 ret = BRANCH_LIKELY_TAKEN;
242 } else
243 epc += 8;
244 regs->cp0_epc = epc;
245 break;
246
247 case bgez_op:
248 case bgezl_op:
249 if ((long)regs->regs[insn.i_format.rs] >= 0) {
250 epc = epc + 4 + (insn.i_format.simmediate << 2);
251 if (insn.i_format.rt == bgezl_op)
252 ret = BRANCH_LIKELY_TAKEN;
253 } else
254 epc += 8;
255 regs->cp0_epc = epc;
256 break;
257
258 case bltzal_op:
259 case bltzall_op:
260 regs->regs[31] = epc + 8;
261 if ((long)regs->regs[insn.i_format.rs] < 0) {
262 epc = epc + 4 + (insn.i_format.simmediate << 2);
263 if (insn.i_format.rt == bltzall_op)
264 ret = BRANCH_LIKELY_TAKEN;
265 } else
266 epc += 8;
267 regs->cp0_epc = epc;
268 break;
269
270 case bgezal_op:
271 case bgezall_op:
272 regs->regs[31] = epc + 8;
273 if ((long)regs->regs[insn.i_format.rs] >= 0) {
274 epc = epc + 4 + (insn.i_format.simmediate << 2);
275 if (insn.i_format.rt == bgezall_op)
276 ret = BRANCH_LIKELY_TAKEN;
277 } else
278 epc += 8;
279 regs->cp0_epc = epc;
280 break;
281
282 case bposge32_op:
283 if (!cpu_has_dsp)
284 goto sigill;
285
286 dspcontrol = rddsp(0x01);
287
288 if (dspcontrol >= 32) {
289 epc = epc + 4 + (insn.i_format.simmediate << 2);
290 } else
291 epc += 8;
292 regs->cp0_epc = epc;
293 break;
294 }
295 break;
296
297 /*
298 * These are unconditional and in j_format.
299 */
300 case jal_op:
301 regs->regs[31] = regs->cp0_epc + 8;
302 case j_op:
303 epc += 4;
304 epc >>= 28;
305 epc <<= 28;
306 epc |= (insn.j_format.target << 2);
307 regs->cp0_epc = epc;
308 if (insn.i_format.opcode == jalx_op)
309 set_isa16_mode(regs->cp0_epc);
310 break;
311
312 /*
313 * These are conditional and in i_format.
314 */
315 case beq_op:
316 case beql_op:
317 if (regs->regs[insn.i_format.rs] ==
318 regs->regs[insn.i_format.rt]) {
319 epc = epc + 4 + (insn.i_format.simmediate << 2);
320 if (insn.i_format.rt == beql_op)
321 ret = BRANCH_LIKELY_TAKEN;
322 } else
323 epc += 8;
324 regs->cp0_epc = epc;
325 break;
326
327 case bne_op:
328 case bnel_op:
329 if (regs->regs[insn.i_format.rs] !=
330 regs->regs[insn.i_format.rt]) {
331 epc = epc + 4 + (insn.i_format.simmediate << 2);
332 if (insn.i_format.rt == bnel_op)
333 ret = BRANCH_LIKELY_TAKEN;
334 } else
335 epc += 8;
336 regs->cp0_epc = epc;
337 break;
338
339 case blez_op: /* not really i_format */
340 case blezl_op:
341 /* rt field assumed to be zero */
342 if ((long)regs->regs[insn.i_format.rs] <= 0) {
343 epc = epc + 4 + (insn.i_format.simmediate << 2);
344 if (insn.i_format.rt == bnel_op)
345 ret = BRANCH_LIKELY_TAKEN;
346 } else
347 epc += 8;
348 regs->cp0_epc = epc;
349 break;
350
351 case bgtz_op:
352 case bgtzl_op:
353 /* rt field assumed to be zero */
354 if ((long)regs->regs[insn.i_format.rs] > 0) {
355 epc = epc + 4 + (insn.i_format.simmediate << 2);
356 if (insn.i_format.rt == bnel_op)
357 ret = BRANCH_LIKELY_TAKEN;
358 } else
359 epc += 8;
360 regs->cp0_epc = epc;
361 break;
362
363 /*
364 * And now the FPA/cp1 branch instructions.
365 */
366 case cop1_op:
367 preempt_disable();
368 if (is_fpu_owner())
369 asm volatile("cfc1\t%0,$31" : "=r" (fcr31));
370 else
371 fcr31 = current->thread.fpu.fcr31;
372 preempt_enable();
373
374 bit = (insn.i_format.rt >> 2);
375 bit += (bit != 0);
376 bit += 23;
377 switch (insn.i_format.rt & 3) {
378 case 0: /* bc1f */
379 case 2: /* bc1fl */
380 if (~fcr31 & (1 << bit)) {
381 epc = epc + 4 + (insn.i_format.simmediate << 2);
382 if (insn.i_format.rt == 2)
383 ret = BRANCH_LIKELY_TAKEN;
384 } else
385 epc += 8;
386 regs->cp0_epc = epc;
387 break;
388
389 case 1: /* bc1t */
390 case 3: /* bc1tl */
391 if (fcr31 & (1 << bit)) {
392 epc = epc + 4 + (insn.i_format.simmediate << 2);
393 if (insn.i_format.rt == 3)
394 ret = BRANCH_LIKELY_TAKEN;
395 } else
396 epc += 8;
397 regs->cp0_epc = epc;
398 break;
399 }
400 break;
401 #ifdef CONFIG_CPU_CAVIUM_OCTEON
402 case lwc2_op: /* This is bbit0 on Octeon */
403 if ((regs->regs[insn.i_format.rs] & (1ull<<insn.i_format.rt))
404 == 0)
405 epc = epc + 4 + (insn.i_format.simmediate << 2);
406 else
407 epc += 8;
408 regs->cp0_epc = epc;
409 break;
410 case ldc2_op: /* This is bbit032 on Octeon */
411 if ((regs->regs[insn.i_format.rs] &
412 (1ull<<(insn.i_format.rt+32))) == 0)
413 epc = epc + 4 + (insn.i_format.simmediate << 2);
414 else
415 epc += 8;
416 regs->cp0_epc = epc;
417 break;
418 case swc2_op: /* This is bbit1 on Octeon */
419 if (regs->regs[insn.i_format.rs] & (1ull<<insn.i_format.rt))
420 epc = epc + 4 + (insn.i_format.simmediate << 2);
421 else
422 epc += 8;
423 regs->cp0_epc = epc;
424 break;
425 case sdc2_op: /* This is bbit132 on Octeon */
426 if (regs->regs[insn.i_format.rs] &
427 (1ull<<(insn.i_format.rt+32)))
428 epc = epc + 4 + (insn.i_format.simmediate << 2);
429 else
430 epc += 8;
431 regs->cp0_epc = epc;
432 break;
433 #endif
434 }
435
436 return ret;
437
438 sigill:
439 printk("%s: DSP branch but not DSP ASE - sending SIGBUS.\n", current->comm);
440 force_sig(SIGBUS, current);
441 return -EFAULT;
442 }
443 EXPORT_SYMBOL_GPL(__compute_return_epc_for_insn);
444
445 int __compute_return_epc(struct pt_regs *regs)
446 {
447 unsigned int __user *addr;
448 long epc;
449 union mips_instruction insn;
450
451 epc = regs->cp0_epc;
452 if (epc & 3)
453 goto unaligned;
454
455 /*
456 * Read the instruction
457 */
458 addr = (unsigned int __user *) epc;
459 if (__get_user(insn.word, addr)) {
460 force_sig(SIGSEGV, current);
461 return -EFAULT;
462 }
463
464 return __compute_return_epc_for_insn(regs, insn);
465
466 unaligned:
467 printk("%s: unaligned epc - sending SIGBUS.\n", current->comm);
468 force_sig(SIGBUS, current);
469 return -EFAULT;
470
471 }
kernel source for telekom puls (alcatel/mediatek)