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1/*
2 * arch/xtensa/kernel/entry.S
3 *
4 * Low-level exception handling
5 *
6 * This file is subject to the terms and conditions of the GNU General Public
7 * License. See the file "COPYING" in the main directory of this archive
8 * for more details.
9 *
10 * Copyright (C) 2004-2005 by Tensilica Inc.
11 *
12 * Chris Zankel <chris@zankel.net>
13 *
14 */
15
16#include <linux/linkage.h>
17#include <asm/offsets.h>
18#include <asm/processor.h>
19#include <asm/thread_info.h>
20#include <asm/uaccess.h>
21#include <asm/unistd.h>
22#include <asm/ptrace.h>
23#include <asm/current.h>
24#include <asm/pgtable.h>
25#include <asm/page.h>
26#include <asm/signal.h>
27#include <xtensa/coreasm.h>
28
29/* Unimplemented features. */
30
31#undef SIGNAL_HANDLING_IN_DOUBLE_EXCEPTION
32#undef KERNEL_STACK_OVERFLOW_CHECK
33#undef PREEMPTIBLE_KERNEL
34#undef ALLOCA_EXCEPTION_IN_IRAM
35
36/* Not well tested.
37 *
38 * - fast_coprocessor
39 */
40
41/*
42 * Macro to find first bit set in WINDOWBASE from the left + 1
43 *
44 * 100....0 -> 1
45 * 010....0 -> 2
46 * 000....1 -> WSBITS
47 */
48
49 .macro ffs_ws bit mask
50
51#if XCHAL_HAVE_NSA
52 nsau \bit, \mask # 32-WSBITS ... 31 (32 iff 0)
53 addi \bit, \bit, WSBITS - 32 + 1 # uppest bit set -> return 1
54#else
55 movi \bit, WSBITS
56#if WSBITS > 16
57 _bltui \mask, 0x10000, 99f
58 addi \bit, \bit, -16
59 extui \mask, \mask, 16, 16
60#endif
61#if WSBITS > 8
6299: _bltui \mask, 0x100, 99f
63 addi \bit, \bit, -8
64 srli \mask, \mask, 8
65#endif
6699: _bltui \mask, 0x10, 99f
67 addi \bit, \bit, -4
68 srli \mask, \mask, 4
6999: _bltui \mask, 0x4, 99f
70 addi \bit, \bit, -2
71 srli \mask, \mask, 2
7299: _bltui \mask, 0x2, 99f
73 addi \bit, \bit, -1
7499:
75
76#endif
77 .endm
78
79/* ----------------- DEFAULT FIRST LEVEL EXCEPTION HANDLERS ----------------- */
80
81/*
82 * First-level exception handler for user exceptions.
83 * Save some special registers, extra states and all registers in the AR
84 * register file that were in use in the user task, and jump to the common
85 * exception code.
86 * We save SAR (used to calculate WMASK), and WB and WS (we don't have to
87 * save them for kernel exceptions).
88 *
89 * Entry condition for user_exception:
90 *
91 * a0: trashed, original value saved on stack (PT_AREG0)
92 * a1: a1
93 * a2: new stack pointer, original value in depc
94 * a3: dispatch table
95 * depc: a2, original value saved on stack (PT_DEPC)
96 * excsave1: a3
97 *
98 * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
99 * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
100 *
101 * Entry condition for _user_exception:
102 *
103 * a0-a3 and depc have been saved to PT_AREG0...PT_AREG3 and PT_DEPC
104 * excsave has been restored, and
105 * stack pointer (a1) has been set.
106 *
107 * Note: _user_exception might be at an odd adress. Don't use call0..call12
108 */
109
110ENTRY(user_exception)
111
112 /* Save a2, a3, and depc, restore excsave_1 and set SP. */
113
114 xsr a3, EXCSAVE_1
115 rsr a0, DEPC
116 s32i a1, a2, PT_AREG1
117 s32i a0, a2, PT_AREG2
118 s32i a3, a2, PT_AREG3
119 mov a1, a2
120
121 .globl _user_exception
122_user_exception:
123
124 /* Save SAR and turn off single stepping */
125
126 movi a2, 0
127 rsr a3, SAR
128 wsr a2, ICOUNTLEVEL
129 s32i a3, a1, PT_SAR
130
131 /* Rotate ws so that the current windowbase is at bit0. */
132 /* Assume ws = xxwww1yyyy. Rotate ws right, so that a2 = yyyyxxwww1 */
133
134 rsr a2, WINDOWBASE
135 rsr a3, WINDOWSTART
136 ssr a2
137 s32i a2, a1, PT_WINDOWBASE
138 s32i a3, a1, PT_WINDOWSTART
139 slli a2, a3, 32-WSBITS
140 src a2, a3, a2
141 srli a2, a2, 32-WSBITS
142 s32i a2, a1, PT_WMASK # needed for restoring registers
143
144 /* Save only live registers. */
145
146 _bbsi.l a2, 1, 1f
147 s32i a4, a1, PT_AREG4
148 s32i a5, a1, PT_AREG5
149 s32i a6, a1, PT_AREG6
150 s32i a7, a1, PT_AREG7
151 _bbsi.l a2, 2, 1f
152 s32i a8, a1, PT_AREG8
153 s32i a9, a1, PT_AREG9
154 s32i a10, a1, PT_AREG10
155 s32i a11, a1, PT_AREG11
156 _bbsi.l a2, 3, 1f
157 s32i a12, a1, PT_AREG12
158 s32i a13, a1, PT_AREG13
159 s32i a14, a1, PT_AREG14
160 s32i a15, a1, PT_AREG15
161 _bnei a2, 1, 1f # only one valid frame?
162
163 /* Only one valid frame, skip saving regs. */
164
165 j 2f
166
167 /* Save the remaining registers.
168 * We have to save all registers up to the first '1' from
169 * the right, except the current frame (bit 0).
170 * Assume a2 is: 001001000110001
171 * All regiser frames starting from the top fiel to the marked '1'
172 * must be saved.
173 */
174
1751: addi a3, a2, -1 # eliminate '1' in bit 0: yyyyxxww0
176 neg a3, a3 # yyyyxxww0 -> YYYYXXWW1+1
177 and a3, a3, a2 # max. only one bit is set
178
179 /* Find number of frames to save */
180
181 ffs_ws a0, a3 # number of frames to the '1' from left
182
183 /* Store information into WMASK:
184 * bits 0..3: xxx1 masked lower 4 bits of the rotated windowstart,
185 * bits 4...: number of valid 4-register frames
186 */
187
188 slli a3, a0, 4 # number of frames to save in bits 8..4
189 extui a2, a2, 0, 4 # mask for the first 16 registers
190 or a2, a3, a2
191 s32i a2, a1, PT_WMASK # needed when we restore the reg-file
192
193 /* Save 4 registers at a time */
194
1951: rotw -1
196 s32i a0, a5, PT_AREG_END - 16
197 s32i a1, a5, PT_AREG_END - 12
198 s32i a2, a5, PT_AREG_END - 8
199 s32i a3, a5, PT_AREG_END - 4
200 addi a0, a4, -1
201 addi a1, a5, -16
202 _bnez a0, 1b
203
204 /* WINDOWBASE still in SAR! */
205
206 rsr a2, SAR # original WINDOWBASE
207 movi a3, 1
208 ssl a2
209 sll a3, a3
210 wsr a3, WINDOWSTART # set corresponding WINDOWSTART bit
211 wsr a2, WINDOWBASE # and WINDOWSTART
212 rsync
213
214 /* We are back to the original stack pointer (a1) */
215
2162:
217#if XCHAL_EXTRA_SA_SIZE
218
219 /* For user exceptions, save the extra state into the user's TCB.
220 * Note: We must assume that xchal_extra_store_funcbody destroys a2..a15
221 */
222
223 GET_CURRENT(a2,a1)
224 addi a2, a2, THREAD_CP_SAVE
225 xchal_extra_store_funcbody
226#endif
227
228 /* Now, jump to the common exception handler. */
229
230 j common_exception
231
232
233/*
234 * First-level exit handler for kernel exceptions
235 * Save special registers and the live window frame.
236 * Note: Even though we changes the stack pointer, we don't have to do a
237 * MOVSP here, as we do that when we return from the exception.
238 * (See comment in the kernel exception exit code)
239 *
240 * Entry condition for kernel_exception:
241 *
242 * a0: trashed, original value saved on stack (PT_AREG0)
243 * a1: a1
244 * a2: new stack pointer, original in DEPC
245 * a3: dispatch table
246 * depc: a2, original value saved on stack (PT_DEPC)
247 * excsave_1: a3
248 *
249 * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
250 * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
251 *
252 * Entry condition for _kernel_exception:
253 *
254 * a0-a3 and depc have been saved to PT_AREG0...PT_AREG3 and PT_DEPC
255 * excsave has been restored, and
256 * stack pointer (a1) has been set.
257 *
258 * Note: _kernel_exception might be at an odd adress. Don't use call0..call12
259 */
260
261ENTRY(kernel_exception)
262
263 /* Save a0, a2, a3, DEPC and set SP. */
264
265 xsr a3, EXCSAVE_1 # restore a3, excsave_1
266 rsr a0, DEPC # get a2
267 s32i a1, a2, PT_AREG1
268 s32i a0, a2, PT_AREG2
269 s32i a3, a2, PT_AREG3
270 mov a1, a2
271
272 .globl _kernel_exception
273_kernel_exception:
274
275 /* Save SAR and turn off single stepping */
276
277 movi a2, 0
278 rsr a3, SAR
279 wsr a2, ICOUNTLEVEL
280 s32i a3, a1, PT_SAR
281
282 /* Rotate ws so that the current windowbase is at bit0. */
283 /* Assume ws = xxwww1yyyy. Rotate ws right, so that a2 = yyyyxxwww1 */
284
285 rsr a2, WINDOWBASE # don't need to save these, we only
286 rsr a3, WINDOWSTART # need shifted windowstart: windowmask
287 ssr a2
288 slli a2, a3, 32-WSBITS
289 src a2, a3, a2
290 srli a2, a2, 32-WSBITS
291 s32i a2, a1, PT_WMASK # needed for kernel_exception_exit
292
293 /* Save only the live window-frame */
294
295 _bbsi.l a2, 1, 1f
296 s32i a4, a1, PT_AREG4
297 s32i a5, a1, PT_AREG5
298 s32i a6, a1, PT_AREG6
299 s32i a7, a1, PT_AREG7
300 _bbsi.l a2, 2, 1f
301 s32i a8, a1, PT_AREG8
302 s32i a9, a1, PT_AREG9
303 s32i a10, a1, PT_AREG10
304 s32i a11, a1, PT_AREG11
305 _bbsi.l a2, 3, 1f
306 s32i a12, a1, PT_AREG12
307 s32i a13, a1, PT_AREG13
308 s32i a14, a1, PT_AREG14
309 s32i a15, a1, PT_AREG15
310
3111:
312
313#ifdef KERNEL_STACK_OVERFLOW_CHECK
314
315 /* Stack overflow check, for debugging */
316 extui a2, a1, TASK_SIZE_BITS,XX
317 movi a3, SIZE??
318 _bge a2, a3, out_of_stack_panic
319
320#endif
321
322/*
323 * This is the common exception handler.
324 * We get here from the user exception handler or simply by falling through
325 * from the kernel exception handler.
326 * Save the remaining special registers, switch to kernel mode, and jump
327 * to the second-level exception handler.
328 *
329 */
330
331common_exception:
332
333 /* Save EXCVADDR, DEBUGCAUSE, and PC, and clear LCOUNT */
334
335 rsr a2, DEBUGCAUSE
336 rsr a3, EPC_1
337 s32i a2, a1, PT_DEBUGCAUSE
338 s32i a3, a1, PT_PC
339
340 rsr a3, EXCVADDR
341 movi a2, 0
342 s32i a3, a1, PT_EXCVADDR
343 xsr a2, LCOUNT
344 s32i a2, a1, PT_LCOUNT
345
346 /* It is now save to restore the EXC_TABLE_FIXUP variable. */
347
348 rsr a0, EXCCAUSE
349 movi a3, 0
350 rsr a2, EXCSAVE_1
351 s32i a0, a1, PT_EXCCAUSE
352 s32i a3, a2, EXC_TABLE_FIXUP
353
354 /* All unrecoverable states are saved on stack, now, and a1 is valid,
355 * so we can allow exceptions and interrupts (*) again.
356 * Set PS(EXCM = 0, UM = 0, RING = 0, OWB = 0, WOE = 1, INTLEVEL = X)
357 *
358 * (*) We only allow interrupts if PS.INTLEVEL was not set to 1 before
359 * (interrupts disabled) and if this exception is not an interrupt.
360 */
361
362 rsr a3, PS
363 addi a0, a0, -4
364 movi a2, 1
365 extui a3, a3, 0, 1 # a3 = PS.INTLEVEL[0]
366 moveqz a3, a2, a0 # a3 = 1 iff interrupt exception
367 movi a2, PS_WOE_MASK
368 or a3, a3, a2
369 rsr a0, EXCCAUSE
370 xsr a3, PS
371
372 s32i a3, a1, PT_PS # save ps
373
374 /* Save LBEG, LEND */
375
376 rsr a2, LBEG
377 rsr a3, LEND
378 s32i a2, a1, PT_LBEG
379 s32i a3, a1, PT_LEND
380
381 /* Go to second-level dispatcher. Set up parameters to pass to the
382 * exception handler and call the exception handler.
383 */
384
385 movi a4, exc_table
386 mov a6, a1 # pass stack frame
387 mov a7, a0 # pass EXCCAUSE
388 addx4 a4, a0, a4
389 l32i a4, a4, EXC_TABLE_DEFAULT # load handler
390
391 /* Call the second-level handler */
392
393 callx4 a4
394
395 /* Jump here for exception exit */
396
397common_exception_return:
398
399 /* Jump if we are returning from kernel exceptions. */
400
4011: l32i a3, a1, PT_PS
402 _bbsi.l a3, PS_UM_SHIFT, 2f
403 j kernel_exception_exit
404
405 /* Specific to a user exception exit:
406 * We need to check some flags for signal handling and rescheduling,
407 * and have to restore WB and WS, extra states, and all registers
408 * in the register file that were in use in the user task.
409 */
410
4112: wsr a3, PS /* disable interrupts */
412
413 /* Check for signals (keep interrupts disabled while we read TI_FLAGS)
414 * Note: PS.INTLEVEL = 0, PS.EXCM = 1
415 */
416
417 GET_THREAD_INFO(a2,a1)
418 l32i a4, a2, TI_FLAGS
419
420 /* Enable interrupts again.
421 * Note: When we get here, we certainly have handled any interrupts.
422 * (Hint: There is only one user exception frame on stack)
423 */
424
425 movi a3, PS_WOE_MASK
426
427 _bbsi.l a4, TIF_NEED_RESCHED, 3f
428 _bbci.l a4, TIF_SIGPENDING, 4f
429
430#ifndef SIGNAL_HANDLING_IN_DOUBLE_EXCEPTION
431 l32i a4, a1, PT_DEPC
432 bgeui a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 4f
433#endif
434
435 /* Reenable interrupts and call do_signal() */
436
437 wsr a3, PS
438 movi a4, do_signal # int do_signal(struct pt_regs*, sigset_t*)
439 mov a6, a1
440 movi a7, 0
441 callx4 a4
442 j 1b
443
4443: /* Reenable interrupts and reschedule */
445
446 wsr a3, PS
447 movi a4, schedule # void schedule (void)
448 callx4 a4
449 j 1b
450
451 /* Restore the state of the task and return from the exception. */
452
453
454 /* If we are returning from a user exception, and the process
455 * to run next has PT_SINGLESTEP set, we want to setup
456 * ICOUNT and ICOUNTLEVEL to step one instruction.
457 * PT_SINGLESTEP is set by sys_ptrace (ptrace.c)
458 */
459
4604: /* a2 holds GET_CURRENT(a2,a1) */
461
462 l32i a3, a2, TI_TASK
463 l32i a3, a3, TASK_PTRACE
464 bbci.l a3, PT_SINGLESTEP_BIT, 1f # jump if single-step flag is not set
465
466 movi a3, -2 # PT_SINGLESTEP flag is set,
467 movi a4, 1 # icountlevel of 1 means it won't
468 wsr a3, ICOUNT # start counting until after rfe
469 wsr a4, ICOUNTLEVEL # so setup icount & icountlevel.
470 isync
471
4721:
473
474#if XCHAL_EXTRA_SA_SIZE
475
476 /* For user exceptions, restore the extra state from the user's TCB. */
477
478 /* Note: a2 still contains GET_CURRENT(a2,a1) */
479 addi a2, a2, THREAD_CP_SAVE
480 xchal_extra_load_funcbody
481
482 /* We must assume that xchal_extra_store_funcbody destroys
483 * registers a2..a15. FIXME, this list can eventually be
484 * reduced once real register requirements of the macro are
485 * finalized. */
486
487#endif /* XCHAL_EXTRA_SA_SIZE */
488
489
490 /* Switch to the user thread WINDOWBASE. Save SP temporarily in DEPC */
491
492 l32i a2, a1, PT_WINDOWBASE
493 l32i a3, a1, PT_WINDOWSTART
494 wsr a1, DEPC # use DEPC as temp storage
495 wsr a3, WINDOWSTART # restore WINDOWSTART
496 ssr a2 # preserve user's WB in the SAR
497 wsr a2, WINDOWBASE # switch to user's saved WB
498 rsync
499 rsr a1, DEPC # restore stack pointer
500 l32i a2, a1, PT_WMASK # register frames saved (in bits 4...9)
501 rotw -1 # we restore a4..a7
502 _bltui a6, 16, 1f # only have to restore current window?
503
504 /* The working registers are a0 and a3. We are restoring to
505 * a4..a7. Be careful not to destroy what we have just restored.
506 * Note: wmask has the format YYYYM:
507 * Y: number of registers saved in groups of 4
508 * M: 4 bit mask of first 16 registers
509 */
510
511 mov a2, a6
512 mov a3, a5
513
5142: rotw -1 # a0..a3 become a4..a7
515 addi a3, a7, -4*4 # next iteration
516 addi a2, a6, -16 # decrementing Y in WMASK
517 l32i a4, a3, PT_AREG_END + 0
518 l32i a5, a3, PT_AREG_END + 4
519 l32i a6, a3, PT_AREG_END + 8
520 l32i a7, a3, PT_AREG_END + 12
521 _bgeui a2, 16, 2b
522
523 /* Clear unrestored registers (don't leak anything to user-land */
524
5251: rsr a0, WINDOWBASE
526 rsr a3, SAR
527 sub a3, a0, a3
528 beqz a3, 2f
529 extui a3, a3, 0, WBBITS
530
5311: rotw -1
532 addi a3, a7, -1
533 movi a4, 0
534 movi a5, 0
535 movi a6, 0
536 movi a7, 0
537 bgei a3, 1, 1b
538
539 /* We are back were we were when we started.
540 * Note: a2 still contains WMASK (if we've returned to the original
541 * frame where we had loaded a2), or at least the lower 4 bits
542 * (if we have restored WSBITS-1 frames).
543 */
544
5452: j common_exception_exit
546
547 /* This is the kernel exception exit.
548 * We avoided to do a MOVSP when we entered the exception, but we
549 * have to do it here.
550 */
551
552kernel_exception_exit:
553
554 /* Disable interrupts (a3 holds PT_PS) */
555
556 wsr a3, PS
557
558#ifdef PREEMPTIBLE_KERNEL
559
560#ifdef CONFIG_PREEMPT
561
562 /*
563 * Note: We've just returned from a call4, so we have
564 * at least 4 addt'l regs.
565 */
566
567 /* Check current_thread_info->preempt_count */
568
569 GET_THREAD_INFO(a2)
570 l32i a3, a2, TI_PREEMPT
571 bnez a3, 1f
572
573 l32i a2, a2, TI_FLAGS
574
5751:
576
577#endif
578
579#endif
580
581 /* Check if we have to do a movsp.
582 *
583 * We only have to do a movsp if the previous window-frame has
584 * been spilled to the *temporary* exception stack instead of the
585 * task's stack. This is the case if the corresponding bit in
586 * WINDOWSTART for the previous window-frame was set before
587 * (not spilled) but is zero now (spilled).
588 * If this bit is zero, all other bits except the one for the
589 * current window frame are also zero. So, we can use a simple test:
590 * 'and' WINDOWSTART and WINDOWSTART-1:
591 *
592 * (XXXXXX1[0]* - 1) AND XXXXXX1[0]* = XXXXXX0[0]*
593 *
594 * The result is zero only if one bit was set.
595 *
596 * (Note: We might have gone through several task switches before
597 * we come back to the current task, so WINDOWBASE might be
598 * different from the time the exception occurred.)
599 */
600
601 /* Test WINDOWSTART before and after the exception.
602 * We actually have WMASK, so we only have to test if it is 1 or not.
603 */
604
605 l32i a2, a1, PT_WMASK
606 _beqi a2, 1, common_exception_exit # Spilled before exception,jump
607
608 /* Test WINDOWSTART now. If spilled, do the movsp */
609
610 rsr a3, WINDOWSTART
611 addi a0, a3, -1
612 and a3, a3, a0
613 _bnez a3, common_exception_exit
614
615 /* Do a movsp (we returned from a call4, so we have at least a0..a7) */
616
617 addi a0, a1, -16
618 l32i a3, a0, 0
619 l32i a4, a0, 4
620 s32i a3, a1, PT_SIZE+0
621 s32i a4, a1, PT_SIZE+4
622 l32i a3, a0, 8
623 l32i a4, a0, 12
624 s32i a3, a1, PT_SIZE+8
625 s32i a4, a1, PT_SIZE+12
626
627 /* Common exception exit.
628 * We restore the special register and the current window frame, and
629 * return from the exception.
630 *
631 * Note: We expect a2 to hold PT_WMASK
632 */
633
634common_exception_exit:
635
636 _bbsi.l a2, 1, 1f
637 l32i a4, a1, PT_AREG4
638 l32i a5, a1, PT_AREG5
639 l32i a6, a1, PT_AREG6
640 l32i a7, a1, PT_AREG7
641 _bbsi.l a2, 2, 1f
642 l32i a8, a1, PT_AREG8
643 l32i a9, a1, PT_AREG9
644 l32i a10, a1, PT_AREG10
645 l32i a11, a1, PT_AREG11
646 _bbsi.l a2, 3, 1f
647 l32i a12, a1, PT_AREG12
648 l32i a13, a1, PT_AREG13
649 l32i a14, a1, PT_AREG14
650 l32i a15, a1, PT_AREG15
651
652 /* Restore PC, SAR */
653
6541: l32i a2, a1, PT_PC
655 l32i a3, a1, PT_SAR
656 wsr a2, EPC_1
657 wsr a3, SAR
658
659 /* Restore LBEG, LEND, LCOUNT */
660
661 l32i a2, a1, PT_LBEG
662 l32i a3, a1, PT_LEND
663 wsr a2, LBEG
664 l32i a2, a1, PT_LCOUNT
665 wsr a3, LEND
666 wsr a2, LCOUNT
667
668 /* Check if it was double exception. */
669
670 l32i a0, a1, PT_DEPC
671 l32i a3, a1, PT_AREG3
672 l32i a2, a1, PT_AREG2
673 _bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f
674
675 /* Restore a0...a3 and return */
676
677 l32i a0, a1, PT_AREG0
678 l32i a1, a1, PT_AREG1
679 rfe
680
6811: wsr a0, DEPC
682 l32i a0, a1, PT_AREG0
683 l32i a1, a1, PT_AREG1
684 rfde
685
686/*
687 * Debug exception handler.
688 *
689 * Currently, we don't support KGDB, so only user application can be debugged.
690 *
691 * When we get here, a0 is trashed and saved to excsave[debuglevel]
692 */
693
694ENTRY(debug_exception)
695
696 rsr a0, EPS + XCHAL_DEBUGLEVEL
697 bbsi.l a0, PS_EXCM_SHIFT, 1f # exception mode
698
699 /* Set EPC_1 and EXCCAUSE */
700
701 wsr a2, DEPC # save a2 temporarily
702 rsr a2, EPC + XCHAL_DEBUGLEVEL
703 wsr a2, EPC_1
704
705 movi a2, EXCCAUSE_MAPPED_DEBUG
706 wsr a2, EXCCAUSE
707
708 /* Restore PS to the value before the debug exc but with PS.EXCM set.*/
709
710 movi a2, 1 << PS_EXCM_SHIFT
711 or a2, a0, a2
712 movi a0, debug_exception # restore a3, debug jump vector
713 wsr a2, PS
714 xsr a0, EXCSAVE + XCHAL_DEBUGLEVEL
715
716 /* Switch to kernel/user stack, restore jump vector, and save a0 */
717
718 bbsi.l a2, PS_UM_SHIFT, 2f # jump if user mode
719
720 addi a2, a1, -16-PT_SIZE # assume kernel stack
721 s32i a0, a2, PT_AREG0
722 movi a0, 0
723 s32i a1, a2, PT_AREG1
724 s32i a0, a2, PT_DEPC # mark it as a regular exception
725 xsr a0, DEPC
726 s32i a3, a2, PT_AREG3
727 s32i a0, a2, PT_AREG2
728 mov a1, a2
729 j _kernel_exception
730
7312: rsr a2, EXCSAVE_1
732 l32i a2, a2, EXC_TABLE_KSTK # load kernel stack pointer
733 s32i a0, a2, PT_AREG0
734 movi a0, 0
735 s32i a1, a2, PT_AREG1
736 s32i a0, a2, PT_DEPC
737 xsr a0, DEPC
738 s32i a3, a2, PT_AREG3
739 s32i a0, a2, PT_AREG2
740 mov a1, a2
741 j _user_exception
742
743 /* Debug exception while in exception mode. */
7441: j 1b // FIXME!!
745
746
747/*
748 * We get here in case of an unrecoverable exception.
749 * The only thing we can do is to be nice and print a panic message.
750 * We only produce a single stack frame for panic, so ???
751 *
752 *
753 * Entry conditions:
754 *
755 * - a0 contains the caller address; original value saved in excsave1.
756 * - the original a0 contains a valid return address (backtrace) or 0.
757 * - a2 contains a valid stackpointer
758 *
759 * Notes:
760 *
761 * - If the stack pointer could be invalid, the caller has to setup a
762 * dummy stack pointer (e.g. the stack of the init_task)
763 *
764 * - If the return address could be invalid, the caller has to set it
765 * to 0, so the backtrace would stop.
766 *
767 */
768 .align 4
769unrecoverable_text:
770 .ascii "Unrecoverable error in exception handler\0"
771
772ENTRY(unrecoverable_exception)
773
774 movi a0, 1
775 movi a1, 0
776
777 wsr a0, WINDOWSTART
778 wsr a1, WINDOWBASE
779 rsync
780
781 movi a1, PS_WOE_MASK | 1
782 wsr a1, PS
783 rsync
784
785 movi a1, init_task
786 movi a0, 0
787 addi a1, a1, PT_REGS_OFFSET
788
789 movi a4, panic
790 movi a6, unrecoverable_text
791
792 callx4 a4
793
7941: j 1b
795
796
797/* -------------------------- FAST EXCEPTION HANDLERS ----------------------- */
798
799/*
800 * Fast-handler for alloca exceptions
801 *
802 * The ALLOCA handler is entered when user code executes the MOVSP
803 * instruction and the caller's frame is not in the register file.
804 * In this case, the caller frame's a0..a3 are on the stack just
805 * below sp (a1), and this handler moves them.
806 *
807 * For "MOVSP <ar>,<as>" without destination register a1, this routine
808 * simply moves the value from <as> to <ar> without moving the save area.
809 *
810 * Entry condition:
811 *
812 * a0: trashed, original value saved on stack (PT_AREG0)
813 * a1: a1
814 * a2: new stack pointer, original in DEPC
815 * a3: dispatch table
816 * depc: a2, original value saved on stack (PT_DEPC)
817 * excsave_1: a3
818 *
819 * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
820 * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
821 */
822
823#if XCHAL_HAVE_BE
824#define _EXTUI_MOVSP_SRC(ar) extui ar, ar, 4, 4
825#define _EXTUI_MOVSP_DST(ar) extui ar, ar, 0, 4
826#else
827#define _EXTUI_MOVSP_SRC(ar) extui ar, ar, 0, 4
828#define _EXTUI_MOVSP_DST(ar) extui ar, ar, 4, 4
829#endif
830
831ENTRY(fast_alloca)
832
833 /* We shouldn't be in a double exception. */
834
835 l32i a0, a2, PT_DEPC
836 _bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, .Lunhandled_double
837
838 rsr a0, DEPC # get a2
839 s32i a4, a2, PT_AREG4 # save a4 and
840 s32i a0, a2, PT_AREG2 # a2 to stack
841
842 /* Exit critical section. */
843
844 movi a0, 0
845 s32i a0, a3, EXC_TABLE_FIXUP
846
847 /* Restore a3, excsave_1 */
848
849 xsr a3, EXCSAVE_1 # make sure excsave_1 is valid for dbl.
850 rsr a4, EPC_1 # get exception address
851 s32i a3, a2, PT_AREG3 # save a3 to stack
852
853#ifdef ALLOCA_EXCEPTION_IN_IRAM
854#error iram not supported
855#else
856 /* Note: l8ui not allowed in IRAM/IROM!! */
857 l8ui a0, a4, 1 # read as(src) from MOVSP instruction
858#endif
859 movi a3, .Lmovsp_src
860 _EXTUI_MOVSP_SRC(a0) # extract source register number
861 addx8 a3, a0, a3
862 jx a3
863
864.Lunhandled_double:
865 wsr a0, EXCSAVE_1
866 movi a0, unrecoverable_exception
867 callx0 a0
868
869 .align 8
870.Lmovsp_src:
871 l32i a3, a2, PT_AREG0; _j 1f; .align 8
872 mov a3, a1; _j 1f; .align 8
873 l32i a3, a2, PT_AREG2; _j 1f; .align 8
874 l32i a3, a2, PT_AREG3; _j 1f; .align 8
875 l32i a3, a2, PT_AREG4; _j 1f; .align 8
876 mov a3, a5; _j 1f; .align 8
877 mov a3, a6; _j 1f; .align 8
878 mov a3, a7; _j 1f; .align 8
879 mov a3, a8; _j 1f; .align 8
880 mov a3, a9; _j 1f; .align 8
881 mov a3, a10; _j 1f; .align 8
882 mov a3, a11; _j 1f; .align 8
883 mov a3, a12; _j 1f; .align 8
884 mov a3, a13; _j 1f; .align 8
885 mov a3, a14; _j 1f; .align 8
886 mov a3, a15; _j 1f; .align 8
887
8881:
889
890#ifdef ALLOCA_EXCEPTION_IN_IRAM
891#error iram not supported
892#else
893 l8ui a0, a4, 0 # read ar(dst) from MOVSP instruction
894#endif
895 addi a4, a4, 3 # step over movsp
896 _EXTUI_MOVSP_DST(a0) # extract destination register
897 wsr a4, EPC_1 # save new epc_1
898
899 _bnei a0, 1, 1f # no 'movsp a1, ax': jump
900
901 /* Move the save area. This implies the use of the L32E
902 * and S32E instructions, because this move must be done with
903 * the user's PS.RING privilege levels, not with ring 0
904 * (kernel's) privileges currently active with PS.EXCM
905 * set. Note that we have stil registered a fixup routine with the
906 * double exception vector in case a double exception occurs.
907 */
908
909 /* a0,a4:avail a1:old user stack a2:exc. stack a3:new user stack. */
910
911 l32e a0, a1, -16
912 l32e a4, a1, -12
913 s32e a0, a3, -16
914 s32e a4, a3, -12
915 l32e a0, a1, -8
916 l32e a4, a1, -4
917 s32e a0, a3, -8
918 s32e a4, a3, -4
919
920 /* Restore stack-pointer and all the other saved registers. */
921
922 mov a1, a3
923
924 l32i a4, a2, PT_AREG4
925 l32i a3, a2, PT_AREG3
926 l32i a0, a2, PT_AREG0
927 l32i a2, a2, PT_AREG2
928 rfe
929
930 /* MOVSP <at>,<as> was invoked with <at> != a1.
931 * Because the stack pointer is not being modified,
932 * we should be able to just modify the pointer
933 * without moving any save area.
934 * The processor only traps these occurrences if the
935 * caller window isn't live, so unfortunately we can't
936 * use this as an alternate trap mechanism.
937 * So we just do the move. This requires that we
938 * resolve the destination register, not just the source,
939 * so there's some extra work.
940 * (PERHAPS NOT REALLY NEEDED, BUT CLEANER...)
941 */
942
943 /* a0 dst-reg, a1 user-stack, a2 stack, a3 value of src reg. */
944
9451: movi a4, .Lmovsp_dst
946 addx8 a4, a0, a4
947 jx a4
948
949 .align 8
950.Lmovsp_dst:
951 s32i a3, a2, PT_AREG0; _j 1f; .align 8
952 mov a1, a3; _j 1f; .align 8
953 s32i a3, a2, PT_AREG2; _j 1f; .align 8
954 s32i a3, a2, PT_AREG3; _j 1f; .align 8
955 s32i a3, a2, PT_AREG4; _j 1f; .align 8
956 mov a5, a3; _j 1f; .align 8
957 mov a6, a3; _j 1f; .align 8
958 mov a7, a3; _j 1f; .align 8
959 mov a8, a3; _j 1f; .align 8
960 mov a9, a3; _j 1f; .align 8
961 mov a10, a3; _j 1f; .align 8
962 mov a11, a3; _j 1f; .align 8
963 mov a12, a3; _j 1f; .align 8
964 mov a13, a3; _j 1f; .align 8
965 mov a14, a3; _j 1f; .align 8
966 mov a15, a3; _j 1f; .align 8
967
9681: l32i a4, a2, PT_AREG4
969 l32i a3, a2, PT_AREG3
970 l32i a0, a2, PT_AREG0
971 l32i a2, a2, PT_AREG2
972 rfe
973
974
975/*
976 * fast system calls.
977 *
978 * WARNING: The kernel doesn't save the entire user context before
979 * handling a fast system call. These functions are small and short,
980 * usually offering some functionality not available to user tasks.
981 *
982 * BE CAREFUL TO PRESERVE THE USER'S CONTEXT.
983 *
984 * Entry condition:
985 *
986 * a0: trashed, original value saved on stack (PT_AREG0)
987 * a1: a1
988 * a2: new stack pointer, original in DEPC
989 * a3: dispatch table
990 * depc: a2, original value saved on stack (PT_DEPC)
991 * excsave_1: a3
992 */
993
994ENTRY(fast_syscall_kernel)
995
996 /* Skip syscall. */
997
998 rsr a0, EPC_1
999 addi a0, a0, 3
1000 wsr a0, EPC_1
1001
1002 l32i a0, a2, PT_DEPC
1003 bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, fast_syscall_unrecoverable
1004
1005 rsr a0, DEPC # get syscall-nr
1006 _beqz a0, fast_syscall_spill_registers
1007
1008 addi a0, a0, -__NR_sysxtensa
1009 _beqz a0, fast_syscall_sysxtensa
1010
1011 j kernel_exception
1012
1013
1014ENTRY(fast_syscall_user)
1015
1016 /* Skip syscall. */
1017
1018 rsr a0, EPC_1
1019 addi a0, a0, 3
1020 wsr a0, EPC_1
1021
1022 l32i a0, a2, PT_DEPC
1023 bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, fast_syscall_unrecoverable
1024
1025 rsr a0, DEPC # get syscall-nr
1026 _beqz a0, fast_syscall_spill_registers
1027
1028 addi a0, a0, -__NR_sysxtensa
1029 _beqz a0, fast_syscall_sysxtensa
1030
1031 j user_exception
1032
1033ENTRY(fast_syscall_unrecoverable)
1034
1035 /* Restore all states. */
1036
1037 l32i a0, a2, PT_AREG0 # restore a0
1038 xsr a2, DEPC # restore a2, depc
1039 rsr a3, EXCSAVE_1
1040
1041 wsr a0, EXCSAVE_1
1042 movi a0, unrecoverable_exception
1043 callx0 a0
1044
1045
1046
1047/*
1048 * sysxtensa syscall handler
1049 *
1050 * int sysxtensa (XTENSA_ATOMIC_SET, ptr, val, unused);
1051 * int sysxtensa (XTENSA_ATOMIC_ADD, ptr, val, unused);
1052 * int sysxtensa (XTENSA_ATOMIC_EXG_ADD, ptr, val, unused);
1053 * int sysxtensa (XTENSA_ATOMIC_CMP_SWP, ptr, oldval, newval);
1054 * a2 a6 a3 a4 a5
1055 *
1056 * Entry condition:
1057 *
1058 * a0: trashed, original value saved on stack (PT_AREG0)
1059 * a1: a1
1060 * a2: new stack pointer, original in DEPC
1061 * a3: dispatch table
1062 * depc: a2, original value saved on stack (PT_DEPC)
1063 * excsave_1: a3
1064 *
1065 * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
1066 * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
1067 *
1068 * Note: we don't have to save a2; a2 holds the return value
1069 *
1070 * We use the two macros TRY and CATCH:
1071 *
1072 * TRY adds an entry to the __ex_table fixup table for the immediately
1073 * following instruction.
1074 *
1075 * CATCH catches any exception that occurred at one of the preceeding TRY
1076 * statements and continues from there
1077 *
1078 * Usage TRY l32i a0, a1, 0
1079 * <other code>
1080 * done: rfe
1081 * CATCH <set return code>
1082 * j done
1083 */
1084
1085#define TRY \
1086 .section __ex_table, "a"; \
1087 .word 66f, 67f; \
1088 .text; \
108966:
1090
1091#define CATCH \
109267:
1093
1094ENTRY(fast_syscall_sysxtensa)
1095
1096 _beqz a6, 1f
1097 _blti a6, SYSXTENSA_COUNT, 2f
1098
10991: j user_exception
1100
11012: xsr a3, EXCSAVE_1 # restore a3, excsave1
1102 s32i a7, a2, PT_AREG7
1103
1104 movi a7, 4 # sizeof(unsigned int)
1105 verify_area a3, a7, a0, a2, .Leac
1106
1107 _beqi a6, SYSXTENSA_ATOMIC_SET, .Lset
1108 _beqi a6, SYSXTENSA_ATOMIC_EXG_ADD, .Lexg
1109 _beqi a6, SYSXTENSA_ATOMIC_ADD, .Ladd
1110
1111 /* Fall through for SYSXTENSA_ATOMIC_CMP_SWP */
1112
1113.Lswp: /* Atomic compare and swap */
1114
1115TRY l32i a7, a3, 0 # read old value
1116 bne a7, a4, 1f # same as old value? jump
1117 s32i a5, a3, 0 # different, modify value
1118 movi a7, 1 # and return 1
1119 j .Lret
1120
11211: movi a7, 0 # same values: return 0
1122 j .Lret
1123
1124.Ladd: /* Atomic add */
1125.Lexg: /* Atomic (exchange) add */
1126
1127TRY l32i a7, a3, 0
1128 add a4, a4, a7
1129 s32i a4, a3, 0
1130 j .Lret
1131
1132.Lset: /* Atomic set */
1133
1134TRY l32i a7, a3, 0 # read old value as return value
1135 s32i a4, a3, 0 # write new value
1136
1137.Lret: mov a0, a2
1138 mov a2, a7
1139 l32i a7, a0, PT_AREG7
1140 l32i a3, a0, PT_AREG3
1141 l32i a0, a0, PT_AREG0
1142 rfe
1143
1144CATCH
1145.Leac: movi a7, -EFAULT
1146 j .Lret
1147
1148
1149
1150/* fast_syscall_spill_registers.
1151 *
1152 * Entry condition:
1153 *
1154 * a0: trashed, original value saved on stack (PT_AREG0)
1155 * a1: a1
1156 * a2: new stack pointer, original in DEPC
1157 * a3: dispatch table
1158 * depc: a2, original value saved on stack (PT_DEPC)
1159 * excsave_1: a3
1160 *
1161 * Note: We assume the stack pointer is EXC_TABLE_KSTK in the fixup handler.
1162 * Note: We don't need to save a2 in depc (return value)
1163 */
1164
1165ENTRY(fast_syscall_spill_registers)
1166
1167 /* Register a FIXUP handler (pass current wb as a parameter) */
1168
1169 movi a0, fast_syscall_spill_registers_fixup
1170 s32i a0, a3, EXC_TABLE_FIXUP
1171 rsr a0, WINDOWBASE
1172 s32i a0, a3, EXC_TABLE_PARAM
1173
1174 /* Save a3 and SAR on stack. */
1175
1176 rsr a0, SAR
1177 xsr a3, EXCSAVE_1 # restore a3 and excsave_1
1178 s32i a0, a2, PT_AREG4 # store SAR to PT_AREG4
1179 s32i a3, a2, PT_AREG3
1180
1181 /* The spill routine might clobber a7, a11, and a15. */
1182
1183 s32i a7, a2, PT_AREG5
1184 s32i a11, a2, PT_AREG6
1185 s32i a15, a2, PT_AREG7
1186
1187 call0 _spill_registers # destroys a3, DEPC, and SAR
1188
1189 /* Advance PC, restore registers and SAR, and return from exception. */
1190
1191 l32i a3, a2, PT_AREG4
1192 l32i a0, a2, PT_AREG0
1193 wsr a3, SAR
1194 l32i a3, a2, PT_AREG3
1195
1196 /* Restore clobbered registers. */
1197
1198 l32i a7, a2, PT_AREG5
1199 l32i a11, a2, PT_AREG6
1200 l32i a15, a2, PT_AREG7
1201
1202 movi a2, 0
1203 rfe
1204
1205/* Fixup handler.
1206 *
1207 * We get here if the spill routine causes an exception, e.g. tlb miss.
1208 * We basically restore WINDOWBASE and WINDOWSTART to the condition when
1209 * we entered the spill routine and jump to the user exception handler.
1210 *
1211 * a0: value of depc, original value in depc
1212 * a2: trashed, original value in EXC_TABLE_DOUBLE_SAVE
1213 * a3: exctable, original value in excsave1
1214 */
1215
1216fast_syscall_spill_registers_fixup:
1217
1218 rsr a2, WINDOWBASE # get current windowbase (a2 is saved)
1219 xsr a0, DEPC # restore depc and a0
1220 ssl a2 # set shift (32 - WB)
1221
1222 /* We need to make sure the current registers (a0-a3) are preserved.
1223 * To do this, we simply set the bit for the current window frame
1224 * in WS, so that the exception handlers save them to the task stack.
1225 */
1226
1227 rsr a3, EXCSAVE_1 # get spill-mask
1228 slli a2, a3, 1 # shift left by one
1229
1230 slli a3, a2, 32-WSBITS
1231 src a2, a2, a3 # a1 = xxwww1yyxxxwww1yy......
1232 wsr a2, WINDOWSTART # set corrected windowstart
1233
1234 movi a3, exc_table
1235 l32i a2, a3, EXC_TABLE_DOUBLE_SAVE # restore a2
1236 l32i a3, a3, EXC_TABLE_PARAM # original WB (in user task)
1237
1238 /* Return to the original (user task) WINDOWBASE.
1239 * We leave the following frame behind:
1240 * a0, a1, a2 same
1241 * a3: trashed (saved in excsave_1)
1242 * depc: depc (we have to return to that address)
1243 * excsave_1: a3
1244 */
1245
1246 wsr a3, WINDOWBASE
1247 rsync
1248
1249 /* We are now in the original frame when we entered _spill_registers:
1250 * a0: return address
1251 * a1: used, stack pointer
1252 * a2: kernel stack pointer
1253 * a3: available, saved in EXCSAVE_1
1254 * depc: exception address
1255 * excsave: a3
1256 * Note: This frame might be the same as above.
1257 */
1258
1259#ifdef SIGNAL_HANDLING_IN_DOUBLE_EXCEPTION
1260 /* Restore registers we precautiously saved.
1261 * We have the value of the 'right' a3
1262 */
1263
1264 l32i a7, a2, PT_AREG5
1265 l32i a11, a2, PT_AREG6
1266 l32i a15, a2, PT_AREG7
1267#endif
1268
1269 /* Setup stack pointer. */
1270
1271 addi a2, a2, -PT_USER_SIZE
1272 s32i a0, a2, PT_AREG0
1273
1274 /* Make sure we return to this fixup handler. */
1275
1276 movi a3, fast_syscall_spill_registers_fixup_return
1277 s32i a3, a2, PT_DEPC # setup depc
1278
1279 /* Jump to the exception handler. */
1280
1281 movi a3, exc_table
1282 rsr a0, EXCCAUSE
1283 addx4 a0, a0, a3 # find entry in table
1284 l32i a0, a0, EXC_TABLE_FAST_USER # load handler
1285 jx a0
1286
1287fast_syscall_spill_registers_fixup_return:
1288
1289 /* When we return here, all registers have been restored (a2: DEPC) */
1290
1291 wsr a2, DEPC # exception address
1292
1293 /* Restore fixup handler. */
1294
1295 xsr a3, EXCSAVE_1
1296 movi a2, fast_syscall_spill_registers_fixup
1297 s32i a2, a3, EXC_TABLE_FIXUP
1298 rsr a2, WINDOWBASE
1299 s32i a2, a3, EXC_TABLE_PARAM
1300 l32i a2, a3, EXC_TABLE_KSTK
1301
1302#ifdef SIGNAL_HANDLING_IN_DOUBLE_EXCEPTION
1303 /* Save registers again that might be clobbered. */
1304
1305 s32i a7, a2, PT_AREG5
1306 s32i a11, a2, PT_AREG6
1307 s32i a15, a2, PT_AREG7
1308#endif
1309
1310 /* Load WB at the time the exception occurred. */
1311
1312 rsr a3, SAR # WB is still in SAR
1313 neg a3, a3
1314 wsr a3, WINDOWBASE
1315 rsync
1316
1317 /* Restore a3 and return. */
1318
1319 movi a3, exc_table
1320 xsr a3, EXCSAVE_1
1321
1322 rfde
1323
1324
1325/*
1326 * spill all registers.
1327 *
1328 * This is not a real function. The following conditions must be met:
1329 *
1330 * - must be called with call0.
1331 * - uses DEPC, a3 and SAR.
1332 * - the last 'valid' register of each frame are clobbered.
1333 * - the caller must have registered a fixup handler
1334 * (or be inside a critical section)
1335 * - PS_EXCM must be set (PS_WOE cleared?)
1336 */
1337
1338ENTRY(_spill_registers)
1339
1340 /*
1341 * Rotate ws so that the current windowbase is at bit 0.
1342 * Assume ws = xxxwww1yy (www1 current window frame).
1343 * Rotate ws right so that a2 = yyxxxwww1.
1344 */
1345
1346 wsr a2, DEPC # preserve a2
1347 rsr a2, WINDOWBASE
1348 rsr a3, WINDOWSTART
1349 ssr a2 # holds WB
1350 slli a2, a3, WSBITS
1351 or a3, a3, a2 # a2 = xxxwww1yyxxxwww1yy
1352 srl a3, a3
1353
1354 /* We are done if there are no more than the current register frame. */
1355
1356 extui a3, a3, 1, WSBITS-2 # a3 = 0yyxxxwww
1357 movi a2, (1 << (WSBITS-1))
1358 _beqz a3, .Lnospill # only one active frame? jump
1359
1360 /* We want 1 at the top, so that we return to the current windowbase */
1361
1362 or a3, a3, a2 # 1yyxxxwww
1363
1364 /* Skip empty frames - get 'oldest' WINDOWSTART-bit. */
1365
1366 wsr a3, WINDOWSTART # save shifted windowstart
1367 neg a2, a3
1368 and a3, a2, a3 # first bit set from right: 000010000
1369
1370 ffs_ws a2, a3 # a2: shifts to skip empty frames
1371 movi a3, WSBITS
1372 sub a2, a3, a2 # WSBITS-a2:number of 0-bits from right
1373 ssr a2 # save in SAR for later.
1374
1375 rsr a3, WINDOWBASE
1376 add a3, a3, a2
1377 rsr a2, DEPC # restore a2
1378 wsr a3, WINDOWBASE
1379 rsync
1380
1381 rsr a3, WINDOWSTART
1382 srl a3, a3 # shift windowstart
1383
1384 /* WB is now just one frame below the oldest frame in the register
1385 window. WS is shifted so the oldest frame is in bit 0, thus, WB
1386 and WS differ by one 4-register frame. */
1387
1388 /* Save frames. Depending what call was used (call4, call8, call12),
1389 * we have to save 4,8. or 12 registers.
1390 */
1391
1392 _bbsi.l a3, 1, .Lc4
1393 _bbsi.l a3, 2, .Lc8
1394
1395 /* Special case: we have a call12-frame starting at a4. */
1396
1397 _bbci.l a3, 3, .Lc12 # bit 3 shouldn't be zero! (Jump to Lc12 first)
1398
1399 s32e a4, a1, -16 # a1 is valid with an empty spill area
1400 l32e a4, a5, -12
1401 s32e a8, a4, -48
1402 mov a8, a4
1403 l32e a4, a1, -16
1404 j .Lc12c
1405
1406.Lloop: _bbsi.l a3, 1, .Lc4
1407 _bbci.l a3, 2, .Lc12
1408
1409.Lc8: s32e a4, a13, -16
1410 l32e a4, a5, -12
1411 s32e a8, a4, -32
1412 s32e a5, a13, -12
1413 s32e a6, a13, -8
1414 s32e a7, a13, -4
1415 s32e a9, a4, -28
1416 s32e a10, a4, -24
1417 s32e a11, a4, -20
1418
1419 srli a11, a3, 2 # shift windowbase by 2
1420 rotw 2
1421 _bnei a3, 1, .Lloop
1422
1423.Lexit: /* Done. Do the final rotation, set WS, and return. */
1424
1425 rotw 1
1426 rsr a3, WINDOWBASE
1427 ssl a3
1428 movi a3, 1
1429 sll a3, a3
1430 wsr a3, WINDOWSTART
1431
1432.Lnospill:
1433 jx a0
1434
1435.Lc4: s32e a4, a9, -16
1436 s32e a5, a9, -12
1437 s32e a6, a9, -8
1438 s32e a7, a9, -4
1439
1440 srli a7, a3, 1
1441 rotw 1
1442 _bnei a3, 1, .Lloop
1443 j .Lexit
1444
1445.Lc12: _bbci.l a3, 3, .Linvalid_mask # bit 2 shouldn't be zero!
1446
1447 /* 12-register frame (call12) */
1448
1449 l32e a2, a5, -12
1450 s32e a8, a2, -48
1451 mov a8, a2
1452
1453.Lc12c: s32e a9, a8, -44
1454 s32e a10, a8, -40
1455 s32e a11, a8, -36
1456 s32e a12, a8, -32
1457 s32e a13, a8, -28
1458 s32e a14, a8, -24
1459 s32e a15, a8, -20
1460 srli a15, a3, 3
1461
1462 /* The stack pointer for a4..a7 is out of reach, so we rotate the
1463 * window, grab the stackpointer, and rotate back.
1464 * Alternatively, we could also use the following approach, but that
1465 * makes the fixup routine much more complicated:
1466 * rotw 1
1467 * s32e a0, a13, -16
1468 * ...
1469 * rotw 2
1470 */
1471
1472 rotw 1
1473 mov a5, a13
1474 rotw -1
1475
1476 s32e a4, a9, -16
1477 s32e a5, a9, -12
1478 s32e a6, a9, -8
1479 s32e a7, a9, -4
1480
1481 rotw 3
1482
1483 _beqi a3, 1, .Lexit
1484 j .Lloop
1485
1486.Linvalid_mask:
1487
1488 /* We get here because of an unrecoverable error in the window
1489 * registers. If we are in user space, we kill the application,
1490 * however, this condition is unrecoverable in kernel space.
1491 */
1492
1493 rsr a0, PS
1494 _bbci.l a0, PS_UM_SHIFT, 1f
1495
1496 /* User space: Setup a dummy frame and kill application.
1497 * Note: We assume EXC_TABLE_KSTK contains a valid stack pointer.
1498 */
1499
1500 movi a0, 1
1501 movi a1, 0
1502
1503 wsr a0, WINDOWSTART
1504 wsr a1, WINDOWBASE
1505 rsync
1506
1507 movi a0, 0
1508
1509 movi a3, exc_table
1510 l32i a1, a3, EXC_TABLE_KSTK
1511 wsr a3, EXCSAVE_1
1512
1513 movi a4, PS_WOE_MASK | 1
1514 wsr a4, PS
1515 rsync
1516
1517 movi a6, SIGSEGV
1518 movi a4, do_exit
1519 callx4 a4
1520
15211: /* Kernel space: PANIC! */
1522
1523 wsr a0, EXCSAVE_1
1524 movi a0, unrecoverable_exception
1525 callx0 a0 # should not return
15261: j 1b
1527
1528/*
1529 * We should never get here. Bail out!
1530 */
1531
1532ENTRY(fast_second_level_miss_double_kernel)
1533
15341: movi a0, unrecoverable_exception
1535 callx0 a0 # should not return
15361: j 1b
1537
1538/* First-level entry handler for user, kernel, and double 2nd-level
1539 * TLB miss exceptions. Note that for now, user and kernel miss
1540 * exceptions share the same entry point and are handled identically.
1541 *
1542 * An old, less-efficient C version of this function used to exist.
1543 * We include it below, interleaved as comments, for reference.
1544 *
1545 * Entry condition:
1546 *
1547 * a0: trashed, original value saved on stack (PT_AREG0)
1548 * a1: a1
1549 * a2: new stack pointer, original in DEPC
1550 * a3: dispatch table
1551 * depc: a2, original value saved on stack (PT_DEPC)
1552 * excsave_1: a3
1553 *
1554 * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
1555 * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
1556 */
1557
1558ENTRY(fast_second_level_miss)
1559
1560 /* Save a1. Note: we don't expect a double exception. */
1561
1562 s32i a1, a2, PT_AREG1
1563
1564 /* We need to map the page of PTEs for the user task. Find
1565 * the pointer to that page. Also, it's possible for tsk->mm
1566 * to be NULL while tsk->active_mm is nonzero if we faulted on
1567 * a vmalloc address. In that rare case, we must use
1568 * active_mm instead to avoid a fault in this handler. See
1569 *
1570 * http://mail.nl.linux.org/linux-mm/2002-08/msg00258.html
1571 * (or search Internet on "mm vs. active_mm")
1572 *
1573 * if (!mm)
1574 * mm = tsk->active_mm;
1575 * pgd = pgd_offset (mm, regs->excvaddr);
1576 * pmd = pmd_offset (pgd, regs->excvaddr);
1577 * pmdval = *pmd;
1578 */
1579
1580 GET_CURRENT(a1,a2)
1581 l32i a0, a1, TASK_MM # tsk->mm
1582 beqz a0, 9f
1583
15848: rsr a1, EXCVADDR # fault address
1585 _PGD_OFFSET(a0, a1, a1)
1586 l32i a0, a0, 0 # read pmdval
1587 //beqi a0, _PAGE_USER, 2f
1588 beqz a0, 2f
1589
1590 /* Read ptevaddr and convert to top of page-table page.
1591 *
1592 * vpnval = read_ptevaddr_register() & PAGE_MASK;
1593 * vpnval += DTLB_WAY_PGTABLE;
1594 * pteval = mk_pte (virt_to_page(pmd_val(pmdval)), PAGE_KERNEL);
1595 * write_dtlb_entry (pteval, vpnval);
1596 *
1597 * The messy computation for 'pteval' above really simplifies
1598 * into the following:
1599 *
1600 * pteval = ((pmdval - PAGE_OFFSET) & PAGE_MASK) | PAGE_KERNEL
1601 */
1602
1603 movi a1, -PAGE_OFFSET
1604 add a0, a0, a1 # pmdval - PAGE_OFFSET
1605 extui a1, a0, 0, PAGE_SHIFT # ... & PAGE_MASK
1606 xor a0, a0, a1
1607
1608
1609 movi a1, PAGE_DIRECTORY
1610 or a0, a0, a1 # ... | PAGE_DIRECTORY
1611
1612 rsr a1, PTEVADDR
1613 srli a1, a1, PAGE_SHIFT
1614 slli a1, a1, PAGE_SHIFT # ptevaddr & PAGE_MASK
1615 addi a1, a1, DTLB_WAY_PGTABLE # ... + way_number
1616
1617 wdtlb a0, a1
1618 dsync
1619
1620 /* Exit critical section. */
1621
1622 movi a0, 0
1623 s32i a0, a3, EXC_TABLE_FIXUP
1624
1625 /* Restore the working registers, and return. */
1626
1627 l32i a0, a2, PT_AREG0
1628 l32i a1, a2, PT_AREG1
1629 l32i a2, a2, PT_DEPC
1630 xsr a3, EXCSAVE_1
1631
1632 bgeui a2, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f
1633
1634 /* Restore excsave1 and return. */
1635
1636 rsr a2, DEPC
1637 rfe
1638
1639 /* Return from double exception. */
1640
16411: xsr a2, DEPC
1642 esync
1643 rfde
1644
16459: l32i a0, a1, TASK_ACTIVE_MM # unlikely case mm == 0
1646 j 8b
1647
16482: /* Invalid PGD, default exception handling */
1649
1650 rsr a1, DEPC
1651 xsr a3, EXCSAVE_1
1652 s32i a1, a2, PT_AREG2
1653 s32i a3, a2, PT_AREG3
1654 mov a1, a2
1655
1656 rsr a2, PS
1657 bbsi.l a2, PS_UM_SHIFT, 1f
1658 j _kernel_exception
16591: j _user_exception
1660
1661
1662/*
1663 * StoreProhibitedException
1664 *
1665 * Update the pte and invalidate the itlb mapping for this pte.
1666 *
1667 * Entry condition:
1668 *
1669 * a0: trashed, original value saved on stack (PT_AREG0)
1670 * a1: a1
1671 * a2: new stack pointer, original in DEPC
1672 * a3: dispatch table
1673 * depc: a2, original value saved on stack (PT_DEPC)
1674 * excsave_1: a3
1675 *
1676 * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
1677 * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
1678 */
1679
1680ENTRY(fast_store_prohibited)
1681
1682 /* Save a1 and a4. */
1683
1684 s32i a1, a2, PT_AREG1
1685 s32i a4, a2, PT_AREG4
1686
1687 GET_CURRENT(a1,a2)
1688 l32i a0, a1, TASK_MM # tsk->mm
1689 beqz a0, 9f
1690
16918: rsr a1, EXCVADDR # fault address
1692 _PGD_OFFSET(a0, a1, a4)
1693 l32i a0, a0, 0
1694 //beqi a0, _PAGE_USER, 2f # FIXME use _PAGE_INVALID
1695 beqz a0, 2f
1696
1697 _PTE_OFFSET(a0, a1, a4)
1698 l32i a4, a0, 0 # read pteval
1699 movi a1, _PAGE_VALID | _PAGE_RW
1700 bnall a4, a1, 2f
1701
1702 movi a1, _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_WRENABLE
1703 or a4, a4, a1
1704 rsr a1, EXCVADDR
1705 s32i a4, a0, 0
1706
1707 /* We need to flush the cache if we have page coloring. */
1708#if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK
1709 dhwb a0, 0
1710#endif
1711 pdtlb a0, a1
1712 beqz a0, 1f
1713 idtlb a0 // FIXME do we need this?
1714 wdtlb a4, a0
17151:
1716
1717 /* Exit critical section. */
1718
1719 movi a0, 0
1720 s32i a0, a3, EXC_TABLE_FIXUP
1721
1722 /* Restore the working registers, and return. */
1723
1724 l32i a4, a2, PT_AREG4
1725 l32i a1, a2, PT_AREG1
1726 l32i a0, a2, PT_AREG0
1727 l32i a2, a2, PT_DEPC
1728
1729 /* Restore excsave1 and a3. */
1730
1731 xsr a3, EXCSAVE_1
1732 bgeui a2, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f
1733
1734 rsr a2, DEPC
1735 rfe
1736
1737 /* Double exception. Restore FIXUP handler and return. */
1738
17391: xsr a2, DEPC
1740 esync
1741 rfde
1742
17439: l32i a0, a1, TASK_ACTIVE_MM # unlikely case mm == 0
1744 j 8b
1745
17462: /* If there was a problem, handle fault in C */
1747
1748 rsr a4, DEPC # still holds a2
1749 xsr a3, EXCSAVE_1
1750 s32i a4, a2, PT_AREG2
1751 s32i a3, a2, PT_AREG3
1752 l32i a4, a2, PT_AREG4
1753 mov a1, a2
1754
1755 rsr a2, PS
1756 bbsi.l a2, PS_UM_SHIFT, 1f
1757 j _kernel_exception
17581: j _user_exception
1759
1760
1761#if XCHAL_EXTRA_SA_SIZE
1762
1763#warning fast_coprocessor untested
1764
1765/*
1766 * Entry condition:
1767 *
1768 * a0: trashed, original value saved on stack (PT_AREG0)
1769 * a1: a1
1770 * a2: new stack pointer, original in DEPC
1771 * a3: dispatch table
1772 * depc: a2, original value saved on stack (PT_DEPC)
1773 * excsave_1: a3
1774 *
1775 * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
1776 * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
1777 */
1778
1779ENTRY(fast_coprocessor_double)
1780 wsr a0, EXCSAVE_1
1781 movi a0, unrecoverable_exception
1782 callx0 a0
1783
1784ENTRY(fast_coprocessor)
1785
1786 /* Fatal if we are in a double exception. */
1787
1788 l32i a0, a2, PT_DEPC
1789 _bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, fast_coprocessor_double
1790
1791 /* Save some registers a1, a3, a4, SAR */
1792
1793 xsr a3, EXCSAVE_1
1794 s32i a3, a2, PT_AREG3
1795 rsr a3, SAR
1796 s32i a4, a2, PT_AREG4
1797 s32i a1, a2, PT_AREG1
1798 s32i a5, a1, PT_AREG5
1799 s32i a3, a2, PT_SAR
1800 mov a1, a2
1801
1802 /* Currently, the HAL macros only guarantee saving a0 and a1.
1803 * These can and will be refined in the future, but for now,
1804 * just save the remaining registers of a2...a15.
1805 */
1806 s32i a6, a1, PT_AREG6
1807 s32i a7, a1, PT_AREG7
1808 s32i a8, a1, PT_AREG8
1809 s32i a9, a1, PT_AREG9
1810 s32i a10, a1, PT_AREG10
1811 s32i a11, a1, PT_AREG11
1812 s32i a12, a1, PT_AREG12
1813 s32i a13, a1, PT_AREG13
1814 s32i a14, a1, PT_AREG14
1815 s32i a15, a1, PT_AREG15
1816
1817 /* Find coprocessor number. Subtract first CP EXCCAUSE from EXCCAUSE */
1818
1819 rsr a0, EXCCAUSE
1820 addi a3, a0, -XCHAL_EXCCAUSE_COPROCESSOR0_DISABLED
1821
1822 /* Set corresponding CPENABLE bit */
1823
1824 movi a4, 1
1825 ssl a3 # SAR: 32 - coprocessor_number
1826 rsr a5, CPENABLE
1827 sll a4, a4
1828 or a4, a5, a4
1829 wsr a4, CPENABLE
1830 rsync
1831 movi a5, coprocessor_info # list of owner and offset into cp_save
1832 addx8 a0, a4, a5 # entry for CP
1833
1834 bne a4, a5, .Lload # bit wasn't set before, cp not in use
1835
1836 /* Now compare the current task with the owner of the coprocessor.
1837 * If they are the same, there is no reason to save or restore any
1838 * coprocessor state. Having already enabled the coprocessor,
1839 * branch ahead to return.
1840 */
1841 GET_CURRENT(a5,a1)
1842 l32i a4, a0, COPROCESSOR_INFO_OWNER # a4: current owner for this CP
1843 beq a4, a5, .Ldone
1844
1845 /* Find location to dump current coprocessor state:
1846 * task_struct->task_cp_save_offset + coprocessor_offset[coprocessor]
1847 *
1848 * Note: a0 pointer to the entry in the coprocessor owner table,
1849 * a3 coprocessor number,
1850 * a4 current owner of coprocessor.
1851 */
1852 l32i a5, a0, COPROCESSOR_INFO_OFFSET
1853 addi a2, a4, THREAD_CP_SAVE
1854 add a2, a2, a5
1855
1856 /* Store current coprocessor states. (a5 still has CP number) */
1857
1858 xchal_cpi_store_funcbody
1859
1860 /* The macro might have destroyed a3 (coprocessor number), but
1861 * SAR still has 32 - coprocessor_number!
1862 */
1863 movi a3, 32
1864 rsr a4, SAR
1865 sub a3, a3, a4
1866
1867.Lload: /* A new task now owns the corpocessors. Save its TCB pointer into
1868 * the coprocessor owner table.
1869 *
1870 * Note: a0 pointer to the entry in the coprocessor owner table,
1871 * a3 coprocessor number.
1872 */
1873 GET_CURRENT(a4,a1)
1874 s32i a4, a0, 0
1875
1876 /* Find location from where to restore the current coprocessor state.*/
1877
1878 l32i a5, a0, COPROCESSOR_INFO_OFFSET
1879 addi a2, a4, THREAD_CP_SAVE
1880 add a2, a2, a4
1881
1882 xchal_cpi_load_funcbody
1883
1884 /* We must assume that the xchal_cpi_store_funcbody macro destroyed
1885 * registers a2..a15.
1886 */
1887
1888.Ldone: l32i a15, a1, PT_AREG15
1889 l32i a14, a1, PT_AREG14
1890 l32i a13, a1, PT_AREG13
1891 l32i a12, a1, PT_AREG12
1892 l32i a11, a1, PT_AREG11
1893 l32i a10, a1, PT_AREG10
1894 l32i a9, a1, PT_AREG9
1895 l32i a8, a1, PT_AREG8
1896 l32i a7, a1, PT_AREG7
1897 l32i a6, a1, PT_AREG6
1898 l32i a5, a1, PT_AREG5
1899 l32i a4, a1, PT_AREG4
1900 l32i a3, a1, PT_AREG3
1901 l32i a2, a1, PT_AREG2
1902 l32i a0, a1, PT_AREG0
1903 l32i a1, a1, PT_AREG1
1904
1905 rfe
1906
1907#endif /* XCHAL_EXTRA_SA_SIZE */
1908
1909/*
1910 * Task switch.
1911 *
1912 * struct task* _switch_to (struct task* prev, struct task* next)
1913 * a2 a2 a3
1914 */
1915
1916ENTRY(_switch_to)
1917
1918 entry a1, 16
1919
1920 mov a4, a3 # preserve a3
1921
1922 s32i a0, a2, THREAD_RA # save return address
1923 s32i a1, a2, THREAD_SP # save stack pointer
1924
1925 /* Disable ints while we manipulate the stack pointer; spill regs. */
1926
1927 movi a5, PS_EXCM_MASK | LOCKLEVEL
1928 xsr a5, PS
1929 rsr a3, EXCSAVE_1
1930 rsync
1931 s32i a3, a3, EXC_TABLE_FIXUP /* enter critical section */
1932
1933 call0 _spill_registers
1934
1935 /* Set kernel stack (and leave critical section)
1936 * Note: It's save to set it here. The stack will not be overwritten
1937 * because the kernel stack will only be loaded again after
1938 * we return from kernel space.
1939 */
1940
1941 l32i a0, a4, TASK_THREAD_INFO
1942 rsr a3, EXCSAVE_1 # exc_table
1943 movi a1, 0
1944 addi a0, a0, PT_REGS_OFFSET
1945 s32i a1, a3, EXC_TABLE_FIXUP
1946 s32i a0, a3, EXC_TABLE_KSTK
1947
1948 /* restore context of the task that 'next' addresses */
1949
1950 l32i a0, a4, THREAD_RA /* restore return address */
1951 l32i a1, a4, THREAD_SP /* restore stack pointer */
1952
1953 wsr a5, PS
1954 rsync
1955
1956 retw
1957
1958
1959ENTRY(ret_from_fork)
1960
1961 /* void schedule_tail (struct task_struct *prev)
1962 * Note: prev is still in a6 (return value from fake call4 frame)
1963 */
1964 movi a4, schedule_tail
1965 callx4 a4
1966
1967 movi a4, do_syscall_trace
1968 callx4 a4
1969
1970 j common_exception_return
1971
1972
1973
1974/*
1975 * Table of syscalls
1976 */
1977
1978.data
1979.align 4
1980.global sys_call_table
1981sys_call_table:
1982
1983#define SYSCALL(call, narg) .word call
1984#include "syscalls.h"
1985
1986/*
1987 * Number of arguments of each syscall
1988 */
1989
1990.global sys_narg_table
1991sys_narg_table:
1992
1993#undef SYSCALL
1994#define SYSCALL(call, narg) .byte narg
1995#include "syscalls.h"
1996
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