summaryrefslogtreecommitdiff
path: root/arch/mips/kernel/branch.c
blob: 46c2ad0703a0b1040140b4a2041c179fdaa45b34 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 1996, 97, 2000, 2001 by Ralf Baechle
 * Copyright (C) 2001 MIPS Technologies, Inc.
 */
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/module.h>
#include <asm/branch.h>
#include <asm/cpu.h>
#include <asm/cpu-features.h>
#include <asm/fpu.h>
#include <asm/fpu_emulator.h>
#include <asm/inst.h>
#include <asm/ptrace.h>
#include <asm/uaccess.h>

/*
 * Calculate and return exception PC in case of branch delay slot
 * for microMIPS and MIPS16e. It does not clear the ISA mode bit.
 */
int __isa_exception_epc(struct pt_regs *regs)
{
	unsigned short inst;
	long epc = regs->cp0_epc;

	/* Calculate exception PC in branch delay slot. */
	if (__get_user(inst, (u16 __user *) msk_isa16_mode(epc))) {
		/* This should never happen because delay slot was checked. */
		force_sig(SIGSEGV, current);
		return epc;
	}
	if (cpu_has_mips16) {
		if (((union mips16e_instruction)inst).ri.opcode
				== MIPS16e_jal_op)
			epc += 4;
		else
			epc += 2;
	} else if (mm_insn_16bit(inst))
		epc += 2;
	else
		epc += 4;

	return epc;
}

/*
 * Compute return address and emulate branch in microMIPS mode after an
 * exception only. It does not handle compact branches/jumps and cannot
 * be used in interrupt context. (Compact branches/jumps do not cause
 * exceptions.)
 */
int __microMIPS_compute_return_epc(struct pt_regs *regs)
{
	u16 __user *pc16;
	u16 halfword;
	unsigned int word;
	unsigned long contpc;
	struct mm_decoded_insn mminsn = { 0 };

	mminsn.micro_mips_mode = 1;

	/* This load never faults. */
	pc16 = (unsigned short __user *)msk_isa16_mode(regs->cp0_epc);
	__get_user(halfword, pc16);
	pc16++;
	contpc = regs->cp0_epc + 2;
	word = ((unsigned int)halfword << 16);
	mminsn.pc_inc = 2;

	if (!mm_insn_16bit(halfword)) {
		__get_user(halfword, pc16);
		pc16++;
		contpc = regs->cp0_epc + 4;
		mminsn.pc_inc = 4;
		word |= halfword;
	}
	mminsn.insn = word;

	if (get_user(halfword, pc16))
		goto sigsegv;
	mminsn.next_pc_inc = 2;
	word = ((unsigned int)halfword << 16);

	if (!mm_insn_16bit(halfword)) {
		pc16++;
		if (get_user(halfword, pc16))
			goto sigsegv;
		mminsn.next_pc_inc = 4;
		word |= halfword;
	}
	mminsn.next_insn = word;

	mm_isBranchInstr(regs, mminsn, &contpc);

	regs->cp0_epc = contpc;

	return 0;

sigsegv:
	force_sig(SIGSEGV, current);
	return -EFAULT;
}

/*
 * Compute return address and emulate branch in MIPS16e mode after an
 * exception only. It does not handle compact branches/jumps and cannot
 * be used in interrupt context. (Compact branches/jumps do not cause
 * exceptions.)
 */
int __MIPS16e_compute_return_epc(struct pt_regs *regs)
{
	u16 __user *addr;
	union mips16e_instruction inst;
	u16 inst2;
	u32 fullinst;
	long epc;

	epc = regs->cp0_epc;

	/* Read the instruction. */
	addr = (u16 __user *)msk_isa16_mode(epc);
	if (__get_user(inst.full, addr)) {
		force_sig(SIGSEGV, current);
		return -EFAULT;
	}

	switch (inst.ri.opcode) {
	case MIPS16e_extend_op:
		regs->cp0_epc += 4;
		return 0;

		/*
		 *  JAL and JALX in MIPS16e mode
		 */
	case MIPS16e_jal_op:
		addr += 1;
		if (__get_user(inst2, addr)) {
			force_sig(SIGSEGV, current);
			return -EFAULT;
		}
		fullinst = ((unsigned)inst.full << 16) | inst2;
		regs->regs[31] = epc + 6;
		epc += 4;
		epc >>= 28;
		epc <<= 28;
		/*
		 * JAL:5 X:1 TARGET[20-16]:5 TARGET[25:21]:5 TARGET[15:0]:16
		 *
		 * ......TARGET[15:0].................TARGET[20:16]...........
		 * ......TARGET[25:21]
		 */
		epc |=
		    ((fullinst & 0xffff) << 2) | ((fullinst & 0x3e00000) >> 3) |
		    ((fullinst & 0x1f0000) << 7);
		if (!inst.jal.x)
			set_isa16_mode(epc);	/* Set ISA mode bit. */
		regs->cp0_epc = epc;
		return 0;

		/*
		 *  J(AL)R(C)
		 */
	case MIPS16e_rr_op:
		if (inst.rr.func == MIPS16e_jr_func) {

			if (inst.rr.ra)
				regs->cp0_epc = regs->regs[31];
			else
				regs->cp0_epc =
				    regs->regs[reg16to32[inst.rr.rx]];

			if (inst.rr.l) {
				if (inst.rr.nd)
					regs->regs[31] = epc + 2;
				else
					regs->regs[31] = epc + 4;
			}
			return 0;
		}
		break;
	}

	/*
	 * All other cases have no branch delay slot and are 16-bits.
	 * Branches do not cause an exception.
	 */
	regs->cp0_epc += 2;

	return 0;
}

/**
 * __compute_return_epc_for_insn - Computes the return address and do emulate
 *				    branch simulation, if required.
 *
 * @regs:	Pointer to pt_regs
 * @insn:	branch instruction to decode
 * @returns:	-EFAULT on error and forces SIGBUS, and on success
 *		returns 0 or BRANCH_LIKELY_TAKEN as appropriate after
 *		evaluating the branch.
 */
int __compute_return_epc_for_insn(struct pt_regs *regs,
				   union mips_instruction insn)
{
	unsigned int bit, fcr31, dspcontrol;
	long epc = regs->cp0_epc;
	int ret = 0;

	switch (insn.i_format.opcode) {
	/*
	 * jr and jalr are in r_format format.
	 */
	case spec_op:
		switch (insn.r_format.func) {
		case jalr_op:
			regs->regs[insn.r_format.rd] = epc + 8;
			/* Fall through */
		case jr_op:
			regs->cp0_epc = regs->regs[insn.r_format.rs];
			break;
		}
		break;

	/*
	 * This group contains:
	 * bltz_op, bgez_op, bltzl_op, bgezl_op,
	 * bltzal_op, bgezal_op, bltzall_op, bgezall_op.
	 */
	case bcond_op:
		switch (insn.i_format.rt) {
		case bltz_op:
		case bltzl_op:
			if ((long)regs->regs[insn.i_format.rs] < 0) {
				epc = epc + 4 + (insn.i_format.simmediate << 2);
				if (insn.i_format.rt == bltzl_op)
					ret = BRANCH_LIKELY_TAKEN;
			} else
				epc += 8;
			regs->cp0_epc = epc;
			break;

		case bgez_op:
		case bgezl_op:
			if ((long)regs->regs[insn.i_format.rs] >= 0) {
				epc = epc + 4 + (insn.i_format.simmediate << 2);
				if (insn.i_format.rt == bgezl_op)
					ret = BRANCH_LIKELY_TAKEN;
			} else
				epc += 8;
			regs->cp0_epc = epc;
			break;

		case bltzal_op:
		case bltzall_op:
			regs->regs[31] = epc + 8;
			if ((long)regs->regs[insn.i_format.rs] < 0) {
				epc = epc + 4 + (insn.i_format.simmediate << 2);
				if (insn.i_format.rt == bltzall_op)
					ret = BRANCH_LIKELY_TAKEN;
			} else
				epc += 8;
			regs->cp0_epc = epc;
			break;

		case bgezal_op:
		case bgezall_op:
			regs->regs[31] = epc + 8;
			if ((long)regs->regs[insn.i_format.rs] >= 0) {
				epc = epc + 4 + (insn.i_format.simmediate << 2);
				if (insn.i_format.rt == bgezall_op)
					ret = BRANCH_LIKELY_TAKEN;
			} else
				epc += 8;
			regs->cp0_epc = epc;
			break;

		case bposge32_op:
			if (!cpu_has_dsp)
				goto sigill;

			dspcontrol = rddsp(0x01);

			if (dspcontrol >= 32) {
				epc = epc + 4 + (insn.i_format.simmediate << 2);
			} else
				epc += 8;
			regs->cp0_epc = epc;
			break;
		}
		break;

	/*
	 * These are unconditional and in j_format.
	 */
	case jal_op:
		regs->regs[31] = regs->cp0_epc + 8;
	case j_op:
		epc += 4;
		epc >>= 28;
		epc <<= 28;
		epc |= (insn.j_format.target << 2);
		regs->cp0_epc = epc;
		if (insn.i_format.opcode == jalx_op)
			set_isa16_mode(regs->cp0_epc);
		break;

	/*
	 * These are conditional and in i_format.
	 */
	case beq_op:
	case beql_op:
		if (regs->regs[insn.i_format.rs] ==
		    regs->regs[insn.i_format.rt]) {
			epc = epc + 4 + (insn.i_format.simmediate << 2);
			if (insn.i_format.rt == beql_op)
				ret = BRANCH_LIKELY_TAKEN;
		} else
			epc += 8;
		regs->cp0_epc = epc;
		break;

	case bne_op:
	case bnel_op:
		if (regs->regs[insn.i_format.rs] !=
		    regs->regs[insn.i_format.rt]) {
			epc = epc + 4 + (insn.i_format.simmediate << 2);
			if (insn.i_format.rt == bnel_op)
				ret = BRANCH_LIKELY_TAKEN;
		} else
			epc += 8;
		regs->cp0_epc = epc;
		break;

	case blez_op: /* not really i_format */
	case blezl_op:
		/* rt field assumed to be zero */
		if ((long)regs->regs[insn.i_format.rs] <= 0) {
			epc = epc + 4 + (insn.i_format.simmediate << 2);
			if (insn.i_format.rt == bnel_op)
				ret = BRANCH_LIKELY_TAKEN;
		} else
			epc += 8;
		regs->cp0_epc = epc;
		break;

	case bgtz_op:
	case bgtzl_op:
		/* rt field assumed to be zero */
		if ((long)regs->regs[insn.i_format.rs] > 0) {
			epc = epc + 4 + (insn.i_format.simmediate << 2);
			if (insn.i_format.rt == bnel_op)
				ret = BRANCH_LIKELY_TAKEN;
		} else
			epc += 8;
		regs->cp0_epc = epc;
		break;

	/*
	 * And now the FPA/cp1 branch instructions.
	 */
	case cop1_op:
		preempt_disable();
		if (is_fpu_owner())
			asm volatile("cfc1\t%0,$31" : "=r" (fcr31));
		else
			fcr31 = current->thread.fpu.fcr31;
		preempt_enable();

		bit = (insn.i_format.rt >> 2);
		bit += (bit != 0);
		bit += 23;
		switch (insn.i_format.rt & 3) {
		case 0: /* bc1f */
		case 2: /* bc1fl */
			if (~fcr31 & (1 << bit)) {
				epc = epc + 4 + (insn.i_format.simmediate << 2);
				if (insn.i_format.rt == 2)
					ret = BRANCH_LIKELY_TAKEN;
			} else
				epc += 8;
			regs->cp0_epc = epc;
			break;

		case 1: /* bc1t */
		case 3: /* bc1tl */
			if (fcr31 & (1 << bit)) {
				epc = epc + 4 + (insn.i_format.simmediate << 2);
				if (insn.i_format.rt == 3)
					ret = BRANCH_LIKELY_TAKEN;
			} else
				epc += 8;
			regs->cp0_epc = epc;
			break;
		}
		break;
#ifdef CONFIG_CPU_CAVIUM_OCTEON
	case lwc2_op: /* This is bbit0 on Octeon */
		if ((regs->regs[insn.i_format.rs] & (1ull<<insn.i_format.rt))
		     == 0)
			epc = epc + 4 + (insn.i_format.simmediate << 2);
		else
			epc += 8;
		regs->cp0_epc = epc;
		break;
	case ldc2_op: /* This is bbit032 on Octeon */
		if ((regs->regs[insn.i_format.rs] &
		    (1ull<<(insn.i_format.rt+32))) == 0)
			epc = epc + 4 + (insn.i_format.simmediate << 2);
		else
			epc += 8;
		regs->cp0_epc = epc;
		break;
	case swc2_op: /* This is bbit1 on Octeon */
		if (regs->regs[insn.i_format.rs] & (1ull<<insn.i_format.rt))
			epc = epc + 4 + (insn.i_format.simmediate << 2);
		else
			epc += 8;
		regs->cp0_epc = epc;
		break;
	case sdc2_op: /* This is bbit132 on Octeon */
		if (regs->regs[insn.i_format.rs] &
		    (1ull<<(insn.i_format.rt+32)))
			epc = epc + 4 + (insn.i_format.simmediate << 2);
		else
			epc += 8;
		regs->cp0_epc = epc;
		break;
#endif
	}

	return ret;

sigill:
	printk("%s: DSP branch but not DSP ASE - sending SIGBUS.\n", current->comm);
	force_sig(SIGBUS, current);
	return -EFAULT;
}
EXPORT_SYMBOL_GPL(__compute_return_epc_for_insn);

int __compute_return_epc(struct pt_regs *regs)
{
	unsigned int __user *addr;
	long epc;
	union mips_instruction insn;

	epc = regs->cp0_epc;
	if (epc & 3)
		goto unaligned;

	/*
	 * Read the instruction
	 */
	addr = (unsigned int __user *) epc;
	if (__get_user(insn.word, addr)) {
		force_sig(SIGSEGV, current);
		return -EFAULT;
	}

	return __compute_return_epc_for_insn(regs, insn);

unaligned:
	printk("%s: unaligned epc - sending SIGBUS.\n", current->comm);
	force_sig(SIGBUS, current);
	return -EFAULT;

}