1/* 2 * Low-level exception handling 3 * 4 * This file is subject to the terms and conditions of the GNU General Public 5 * License. See the file "COPYING" in the main directory of this archive 6 * for more details. 7 * 8 * Copyright (C) 2004 - 2008 by Tensilica Inc. 9 * Copyright (C) 2015 Cadence Design Systems Inc. 10 * 11 * Chris Zankel <chris@zankel.net> 12 * 13 */ 14 15#include <linux/linkage.h> 16#include <asm/asm-offsets.h> 17#include <asm/asmmacro.h> 18#include <asm/processor.h> 19#include <asm/coprocessor.h> 20#include <asm/thread_info.h> 21#include <asm/asm-uaccess.h> 22#include <asm/unistd.h> 23#include <asm/ptrace.h> 24#include <asm/current.h> 25#include <asm/pgtable.h> 26#include <asm/page.h> 27#include <asm/signal.h> 28#include <asm/tlbflush.h> 29#include <variant/tie-asm.h> 30 31/* Unimplemented features. */ 32 33#undef KERNEL_STACK_OVERFLOW_CHECK 34 35/* Not well tested. 36 * 37 * - fast_coprocessor 38 */ 39 40/* 41 * Macro to find first bit set in WINDOWBASE from the left + 1 42 * 43 * 100....0 -> 1 44 * 010....0 -> 2 45 * 000....1 -> WSBITS 46 */ 47 48 .macro ffs_ws bit mask 49 50#if XCHAL_HAVE_NSA 51 nsau \bit, \mask # 32-WSBITS ... 31 (32 iff 0) 52 addi \bit, \bit, WSBITS - 32 + 1 # uppest bit set -> return 1 53#else 54 movi \bit, WSBITS 55#if WSBITS > 16 56 _bltui \mask, 0x10000, 99f 57 addi \bit, \bit, -16 58 extui \mask, \mask, 16, 16 59#endif 60#if WSBITS > 8 6199: _bltui \mask, 0x100, 99f 62 addi \bit, \bit, -8 63 srli \mask, \mask, 8 64#endif 6599: _bltui \mask, 0x10, 99f 66 addi \bit, \bit, -4 67 srli \mask, \mask, 4 6899: _bltui \mask, 0x4, 99f 69 addi \bit, \bit, -2 70 srli \mask, \mask, 2 7199: _bltui \mask, 0x2, 99f 72 addi \bit, \bit, -1 7399: 74 75#endif 76 .endm 77 78 79 .macro irq_save flags tmp 80#if XTENSA_FAKE_NMI 81#if defined(CONFIG_DEBUG_KERNEL) && (LOCKLEVEL | TOPLEVEL) >= XCHAL_DEBUGLEVEL 82 rsr \flags, ps 83 extui \tmp, \flags, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH 84 bgei \tmp, LOCKLEVEL, 99f 85 rsil \tmp, LOCKLEVEL 8699: 87#else 88 movi \tmp, LOCKLEVEL 89 rsr \flags, ps 90 or \flags, \flags, \tmp 91 xsr \flags, ps 92 rsync 93#endif 94#else 95 rsil \flags, LOCKLEVEL 96#endif 97 .endm 98 99/* ----------------- DEFAULT FIRST LEVEL EXCEPTION HANDLERS ----------------- */ 100 101/* 102 * First-level exception handler for user exceptions. 103 * Save some special registers, extra states and all registers in the AR 104 * register file that were in use in the user task, and jump to the common 105 * exception code. 106 * We save SAR (used to calculate WMASK), and WB and WS (we don't have to 107 * save them for kernel exceptions). 108 * 109 * Entry condition for user_exception: 110 * 111 * a0: trashed, original value saved on stack (PT_AREG0) 112 * a1: a1 113 * a2: new stack pointer, original value in depc 114 * a3: a3 115 * depc: a2, original value saved on stack (PT_DEPC) 116 * excsave1: dispatch table 117 * 118 * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC 119 * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception 120 * 121 * Entry condition for _user_exception: 122 * 123 * a0-a3 and depc have been saved to PT_AREG0...PT_AREG3 and PT_DEPC 124 * excsave has been restored, and 125 * stack pointer (a1) has been set. 126 * 127 * Note: _user_exception might be at an odd address. Don't use call0..call12 128 */ 129 .literal_position 130 131ENTRY(user_exception) 132 133 /* Save a1, a2, a3, and set SP. */ 134 135 rsr a0, depc 136 s32i a1, a2, PT_AREG1 137 s32i a0, a2, PT_AREG2 138 s32i a3, a2, PT_AREG3 139 mov a1, a2 140 141 .globl _user_exception 142_user_exception: 143 144 /* Save SAR and turn off single stepping */ 145 146 movi a2, 0 147 wsr a2, depc # terminate user stack trace with 0 148 rsr a3, sar 149 xsr a2, icountlevel 150 s32i a3, a1, PT_SAR 151 s32i a2, a1, PT_ICOUNTLEVEL 152 153#if XCHAL_HAVE_THREADPTR 154 rur a2, threadptr 155 s32i a2, a1, PT_THREADPTR 156#endif 157 158 /* Rotate ws so that the current windowbase is at bit0. */ 159 /* Assume ws = xxwww1yyyy. Rotate ws right, so that a2 = yyyyxxwww1 */ 160 161 rsr a2, windowbase 162 rsr a3, windowstart 163 ssr a2 164 s32i a2, a1, PT_WINDOWBASE 165 s32i a3, a1, PT_WINDOWSTART 166 slli a2, a3, 32-WSBITS 167 src a2, a3, a2 168 srli a2, a2, 32-WSBITS 169 s32i a2, a1, PT_WMASK # needed for restoring registers 170 171 /* Save only live registers. */ 172 173 _bbsi.l a2, 1, 1f 174 s32i a4, a1, PT_AREG4 175 s32i a5, a1, PT_AREG5 176 s32i a6, a1, PT_AREG6 177 s32i a7, a1, PT_AREG7 178 _bbsi.l a2, 2, 1f 179 s32i a8, a1, PT_AREG8 180 s32i a9, a1, PT_AREG9 181 s32i a10, a1, PT_AREG10 182 s32i a11, a1, PT_AREG11 183 _bbsi.l a2, 3, 1f 184 s32i a12, a1, PT_AREG12 185 s32i a13, a1, PT_AREG13 186 s32i a14, a1, PT_AREG14 187 s32i a15, a1, PT_AREG15 188 _bnei a2, 1, 1f # only one valid frame? 189 190 /* Only one valid frame, skip saving regs. */ 191 192 j 2f 193 194 /* Save the remaining registers. 195 * We have to save all registers up to the first '1' from 196 * the right, except the current frame (bit 0). 197 * Assume a2 is: 001001000110001 198 * All register frames starting from the top field to the marked '1' 199 * must be saved. 200 */ 201 2021: addi a3, a2, -1 # eliminate '1' in bit 0: yyyyxxww0 203 neg a3, a3 # yyyyxxww0 -> YYYYXXWW1+1 204 and a3, a3, a2 # max. only one bit is set 205 206 /* Find number of frames to save */ 207 208 ffs_ws a0, a3 # number of frames to the '1' from left 209 210 /* Store information into WMASK: 211 * bits 0..3: xxx1 masked lower 4 bits of the rotated windowstart, 212 * bits 4...: number of valid 4-register frames 213 */ 214 215 slli a3, a0, 4 # number of frames to save in bits 8..4 216 extui a2, a2, 0, 4 # mask for the first 16 registers 217 or a2, a3, a2 218 s32i a2, a1, PT_WMASK # needed when we restore the reg-file 219 220 /* Save 4 registers at a time */ 221 2221: rotw -1 223 s32i a0, a5, PT_AREG_END - 16 224 s32i a1, a5, PT_AREG_END - 12 225 s32i a2, a5, PT_AREG_END - 8 226 s32i a3, a5, PT_AREG_END - 4 227 addi a0, a4, -1 228 addi a1, a5, -16 229 _bnez a0, 1b 230 231 /* WINDOWBASE still in SAR! */ 232 233 rsr a2, sar # original WINDOWBASE 234 movi a3, 1 235 ssl a2 236 sll a3, a3 237 wsr a3, windowstart # set corresponding WINDOWSTART bit 238 wsr a2, windowbase # and WINDOWSTART 239 rsync 240 241 /* We are back to the original stack pointer (a1) */ 242 2432: /* Now, jump to the common exception handler. */ 244 245 j common_exception 246 247ENDPROC(user_exception) 248 249/* 250 * First-level exit handler for kernel exceptions 251 * Save special registers and the live window frame. 252 * Note: Even though we changes the stack pointer, we don't have to do a 253 * MOVSP here, as we do that when we return from the exception. 254 * (See comment in the kernel exception exit code) 255 * 256 * Entry condition for kernel_exception: 257 * 258 * a0: trashed, original value saved on stack (PT_AREG0) 259 * a1: a1 260 * a2: new stack pointer, original in DEPC 261 * a3: a3 262 * depc: a2, original value saved on stack (PT_DEPC) 263 * excsave_1: dispatch table 264 * 265 * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC 266 * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception 267 * 268 * Entry condition for _kernel_exception: 269 * 270 * a0-a3 and depc have been saved to PT_AREG0...PT_AREG3 and PT_DEPC 271 * excsave has been restored, and 272 * stack pointer (a1) has been set. 273 * 274 * Note: _kernel_exception might be at an odd address. Don't use call0..call12 275 */ 276 277ENTRY(kernel_exception) 278 279 /* Save a1, a2, a3, and set SP. */ 280 281 rsr a0, depc # get a2 282 s32i a1, a2, PT_AREG1 283 s32i a0, a2, PT_AREG2 284 s32i a3, a2, PT_AREG3 285 mov a1, a2 286 287 .globl _kernel_exception 288_kernel_exception: 289 290 /* Save SAR and turn off single stepping */ 291 292 movi a2, 0 293 rsr a3, sar 294 xsr a2, icountlevel 295 s32i a3, a1, PT_SAR 296 s32i a2, a1, PT_ICOUNTLEVEL 297 298 /* Rotate ws so that the current windowbase is at bit0. */ 299 /* Assume ws = xxwww1yyyy. Rotate ws right, so that a2 = yyyyxxwww1 */ 300 301 rsr a2, windowbase # don't need to save these, we only 302 rsr a3, windowstart # need shifted windowstart: windowmask 303 ssr a2 304 slli a2, a3, 32-WSBITS 305 src a2, a3, a2 306 srli a2, a2, 32-WSBITS 307 s32i a2, a1, PT_WMASK # needed for kernel_exception_exit 308 309 /* Save only the live window-frame */ 310 311 _bbsi.l a2, 1, 1f 312 s32i a4, a1, PT_AREG4 313 s32i a5, a1, PT_AREG5 314 s32i a6, a1, PT_AREG6 315 s32i a7, a1, PT_AREG7 316 _bbsi.l a2, 2, 1f 317 s32i a8, a1, PT_AREG8 318 s32i a9, a1, PT_AREG9 319 s32i a10, a1, PT_AREG10 320 s32i a11, a1, PT_AREG11 321 _bbsi.l a2, 3, 1f 322 s32i a12, a1, PT_AREG12 323 s32i a13, a1, PT_AREG13 324 s32i a14, a1, PT_AREG14 325 s32i a15, a1, PT_AREG15 326 327 _bnei a2, 1, 1f 328 329 /* Copy spill slots of a0 and a1 to imitate movsp 330 * in order to keep exception stack continuous 331 */ 332 l32i a3, a1, PT_SIZE 333 l32i a0, a1, PT_SIZE + 4 334 s32e a3, a1, -16 335 s32e a0, a1, -12 3361: 337 l32i a0, a1, PT_AREG0 # restore saved a0 338 wsr a0, depc 339 340#ifdef KERNEL_STACK_OVERFLOW_CHECK 341 342 /* Stack overflow check, for debugging */ 343 extui a2, a1, TASK_SIZE_BITS,XX 344 movi a3, SIZE?? 345 _bge a2, a3, out_of_stack_panic 346 347#endif 348 349/* 350 * This is the common exception handler. 351 * We get here from the user exception handler or simply by falling through 352 * from the kernel exception handler. 353 * Save the remaining special registers, switch to kernel mode, and jump 354 * to the second-level exception handler. 355 * 356 */ 357 358common_exception: 359 360 /* Save some registers, disable loops and clear the syscall flag. */ 361 362 rsr a2, debugcause 363 rsr a3, epc1 364 s32i a2, a1, PT_DEBUGCAUSE 365 s32i a3, a1, PT_PC 366 367 movi a2, -1 368 rsr a3, excvaddr 369 s32i a2, a1, PT_SYSCALL 370 movi a2, 0 371 s32i a3, a1, PT_EXCVADDR 372#if XCHAL_HAVE_LOOPS 373 xsr a2, lcount 374 s32i a2, a1, PT_LCOUNT 375#endif 376 377 /* It is now save to restore the EXC_TABLE_FIXUP variable. */ 378 379 rsr a2, exccause 380 movi a3, 0 381 rsr a0, excsave1 382 s32i a2, a1, PT_EXCCAUSE 383 s32i a3, a0, EXC_TABLE_FIXUP 384 385 /* All unrecoverable states are saved on stack, now, and a1 is valid. 386 * Now we can allow exceptions again. In case we've got an interrupt 387 * PS.INTLEVEL is set to LOCKLEVEL disabling furhter interrupts, 388 * otherwise it's left unchanged. 389 * 390 * Set PS(EXCM = 0, UM = 0, RING = 0, OWB = 0, WOE = 1, INTLEVEL = X) 391 */ 392 393 rsr a3, ps 394 s32i a3, a1, PT_PS # save ps 395 396#if XTENSA_FAKE_NMI 397 /* Correct PS needs to be saved in the PT_PS: 398 * - in case of exception or level-1 interrupt it's in the PS, 399 * and is already saved. 400 * - in case of medium level interrupt it's in the excsave2. 401 */ 402 movi a0, EXCCAUSE_MAPPED_NMI 403 extui a3, a3, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH 404 beq a2, a0, .Lmedium_level_irq 405 bnei a2, EXCCAUSE_LEVEL1_INTERRUPT, .Lexception 406 beqz a3, .Llevel1_irq # level-1 IRQ sets ps.intlevel to 0 407 408.Lmedium_level_irq: 409 rsr a0, excsave2 410 s32i a0, a1, PT_PS # save medium-level interrupt ps 411 bgei a3, LOCKLEVEL, .Lexception 412 413.Llevel1_irq: 414 movi a3, LOCKLEVEL 415 416.Lexception: 417 movi a0, 1 << PS_WOE_BIT 418 or a3, a3, a0 419#else 420 addi a2, a2, -EXCCAUSE_LEVEL1_INTERRUPT 421 movi a0, LOCKLEVEL 422 extui a3, a3, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH 423 # a3 = PS.INTLEVEL 424 moveqz a3, a0, a2 # a3 = LOCKLEVEL iff interrupt 425 movi a2, 1 << PS_WOE_BIT 426 or a3, a3, a2 427 rsr a2, exccause 428#endif 429 430 /* restore return address (or 0 if return to userspace) */ 431 rsr a0, depc 432 wsr a3, ps 433 rsync # PS.WOE => rsync => overflow 434 435 /* Save lbeg, lend */ 436#if XCHAL_HAVE_LOOPS 437 rsr a4, lbeg 438 rsr a3, lend 439 s32i a4, a1, PT_LBEG 440 s32i a3, a1, PT_LEND 441#endif 442 443 /* Save SCOMPARE1 */ 444 445#if XCHAL_HAVE_S32C1I 446 rsr a3, scompare1 447 s32i a3, a1, PT_SCOMPARE1 448#endif 449 450 /* Save optional registers. */ 451 452 save_xtregs_opt a1 a3 a4 a5 a6 a7 PT_XTREGS_OPT 453 454 /* Go to second-level dispatcher. Set up parameters to pass to the 455 * exception handler and call the exception handler. 456 */ 457 458 rsr a4, excsave1 459 mov a6, a1 # pass stack frame 460 mov a7, a2 # pass EXCCAUSE 461 addx4 a4, a2, a4 462 l32i a4, a4, EXC_TABLE_DEFAULT # load handler 463 464 /* Call the second-level handler */ 465 466 callx4 a4 467 468 /* Jump here for exception exit */ 469 .global common_exception_return 470common_exception_return: 471 472#if XTENSA_FAKE_NMI 473 l32i a2, a1, PT_EXCCAUSE 474 movi a3, EXCCAUSE_MAPPED_NMI 475 beq a2, a3, .LNMIexit 476#endif 4771: 478 irq_save a2, a3 479#ifdef CONFIG_TRACE_IRQFLAGS 480 call4 trace_hardirqs_off 481#endif 482 483 /* Jump if we are returning from kernel exceptions. */ 484 485 l32i a3, a1, PT_PS 486 GET_THREAD_INFO(a2, a1) 487 l32i a4, a2, TI_FLAGS 488 _bbci.l a3, PS_UM_BIT, 6f 489 490 /* Specific to a user exception exit: 491 * We need to check some flags for signal handling and rescheduling, 492 * and have to restore WB and WS, extra states, and all registers 493 * in the register file that were in use in the user task. 494 * Note that we don't disable interrupts here. 495 */ 496 497 _bbsi.l a4, TIF_NEED_RESCHED, 3f 498 _bbsi.l a4, TIF_NOTIFY_RESUME, 2f 499 _bbci.l a4, TIF_SIGPENDING, 5f 500 5012: l32i a4, a1, PT_DEPC 502 bgeui a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 4f 503 504 /* Call do_signal() */ 505 506#ifdef CONFIG_TRACE_IRQFLAGS 507 call4 trace_hardirqs_on 508#endif 509 rsil a2, 0 510 mov a6, a1 511 call4 do_notify_resume # int do_notify_resume(struct pt_regs*) 512 j 1b 513 5143: /* Reschedule */ 515 516#ifdef CONFIG_TRACE_IRQFLAGS 517 call4 trace_hardirqs_on 518#endif 519 rsil a2, 0 520 call4 schedule # void schedule (void) 521 j 1b 522 523#ifdef CONFIG_PREEMPT 5246: 525 _bbci.l a4, TIF_NEED_RESCHED, 4f 526 527 /* Check current_thread_info->preempt_count */ 528 529 l32i a4, a2, TI_PRE_COUNT 530 bnez a4, 4f 531 call4 preempt_schedule_irq 532 j 1b 533#endif 534 535#if XTENSA_FAKE_NMI 536.LNMIexit: 537 l32i a3, a1, PT_PS 538 _bbci.l a3, PS_UM_BIT, 4f 539#endif 540 5415: 542#ifdef CONFIG_HAVE_HW_BREAKPOINT 543 _bbci.l a4, TIF_DB_DISABLED, 7f 544 call4 restore_dbreak 5457: 546#endif 547#ifdef CONFIG_DEBUG_TLB_SANITY 548 l32i a4, a1, PT_DEPC 549 bgeui a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 4f 550 call4 check_tlb_sanity 551#endif 5526: 5534: 554#ifdef CONFIG_TRACE_IRQFLAGS 555 extui a4, a3, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH 556 bgei a4, LOCKLEVEL, 1f 557 call4 trace_hardirqs_on 5581: 559#endif 560 /* Restore optional registers. */ 561 562 load_xtregs_opt a1 a2 a4 a5 a6 a7 PT_XTREGS_OPT 563 564 /* Restore SCOMPARE1 */ 565 566#if XCHAL_HAVE_S32C1I 567 l32i a2, a1, PT_SCOMPARE1 568 wsr a2, scompare1 569#endif 570 wsr a3, ps /* disable interrupts */ 571 572 _bbci.l a3, PS_UM_BIT, kernel_exception_exit 573 574user_exception_exit: 575 576 /* Restore the state of the task and return from the exception. */ 577 578 /* Switch to the user thread WINDOWBASE. Save SP temporarily in DEPC */ 579 580 l32i a2, a1, PT_WINDOWBASE 581 l32i a3, a1, PT_WINDOWSTART 582 wsr a1, depc # use DEPC as temp storage 583 wsr a3, windowstart # restore WINDOWSTART 584 ssr a2 # preserve user's WB in the SAR 585 wsr a2, windowbase # switch to user's saved WB 586 rsync 587 rsr a1, depc # restore stack pointer 588 l32i a2, a1, PT_WMASK # register frames saved (in bits 4...9) 589 rotw -1 # we restore a4..a7 590 _bltui a6, 16, 1f # only have to restore current window? 591 592 /* The working registers are a0 and a3. We are restoring to 593 * a4..a7. Be careful not to destroy what we have just restored. 594 * Note: wmask has the format YYYYM: 595 * Y: number of registers saved in groups of 4 596 * M: 4 bit mask of first 16 registers 597 */ 598 599 mov a2, a6 600 mov a3, a5 601 6022: rotw -1 # a0..a3 become a4..a7 603 addi a3, a7, -4*4 # next iteration 604 addi a2, a6, -16 # decrementing Y in WMASK 605 l32i a4, a3, PT_AREG_END + 0 606 l32i a5, a3, PT_AREG_END + 4 607 l32i a6, a3, PT_AREG_END + 8 608 l32i a7, a3, PT_AREG_END + 12 609 _bgeui a2, 16, 2b 610 611 /* Clear unrestored registers (don't leak anything to user-land */ 612 6131: rsr a0, windowbase 614 rsr a3, sar 615 sub a3, a0, a3 616 beqz a3, 2f 617 extui a3, a3, 0, WBBITS 618 6191: rotw -1 620 addi a3, a7, -1 621 movi a4, 0 622 movi a5, 0 623 movi a6, 0 624 movi a7, 0 625 bgei a3, 1, 1b 626 627 /* We are back were we were when we started. 628 * Note: a2 still contains WMASK (if we've returned to the original 629 * frame where we had loaded a2), or at least the lower 4 bits 630 * (if we have restored WSBITS-1 frames). 631 */ 632 6332: 634#if XCHAL_HAVE_THREADPTR 635 l32i a3, a1, PT_THREADPTR 636 wur a3, threadptr 637#endif 638 639 j common_exception_exit 640 641 /* This is the kernel exception exit. 642 * We avoided to do a MOVSP when we entered the exception, but we 643 * have to do it here. 644 */ 645 646kernel_exception_exit: 647 648 /* Check if we have to do a movsp. 649 * 650 * We only have to do a movsp if the previous window-frame has 651 * been spilled to the *temporary* exception stack instead of the 652 * task's stack. This is the case if the corresponding bit in 653 * WINDOWSTART for the previous window-frame was set before 654 * (not spilled) but is zero now (spilled). 655 * If this bit is zero, all other bits except the one for the 656 * current window frame are also zero. So, we can use a simple test: 657 * 'and' WINDOWSTART and WINDOWSTART-1: 658 * 659 * (XXXXXX1[0]* - 1) AND XXXXXX1[0]* = XXXXXX0[0]* 660 * 661 * The result is zero only if one bit was set. 662 * 663 * (Note: We might have gone through several task switches before 664 * we come back to the current task, so WINDOWBASE might be 665 * different from the time the exception occurred.) 666 */ 667 668 /* Test WINDOWSTART before and after the exception. 669 * We actually have WMASK, so we only have to test if it is 1 or not. 670 */ 671 672 l32i a2, a1, PT_WMASK 673 _beqi a2, 1, common_exception_exit # Spilled before exception,jump 674 675 /* Test WINDOWSTART now. If spilled, do the movsp */ 676 677 rsr a3, windowstart 678 addi a0, a3, -1 679 and a3, a3, a0 680 _bnez a3, common_exception_exit 681 682 /* Do a movsp (we returned from a call4, so we have at least a0..a7) */ 683 684 addi a0, a1, -16 685 l32i a3, a0, 0 686 l32i a4, a0, 4 687 s32i a3, a1, PT_SIZE+0 688 s32i a4, a1, PT_SIZE+4 689 l32i a3, a0, 8 690 l32i a4, a0, 12 691 s32i a3, a1, PT_SIZE+8 692 s32i a4, a1, PT_SIZE+12 693 694 /* Common exception exit. 695 * We restore the special register and the current window frame, and 696 * return from the exception. 697 * 698 * Note: We expect a2 to hold PT_WMASK 699 */ 700 701common_exception_exit: 702 703 /* Restore address registers. */ 704 705 _bbsi.l a2, 1, 1f 706 l32i a4, a1, PT_AREG4 707 l32i a5, a1, PT_AREG5 708 l32i a6, a1, PT_AREG6 709 l32i a7, a1, PT_AREG7 710 _bbsi.l a2, 2, 1f 711 l32i a8, a1, PT_AREG8 712 l32i a9, a1, PT_AREG9 713 l32i a10, a1, PT_AREG10 714 l32i a11, a1, PT_AREG11 715 _bbsi.l a2, 3, 1f 716 l32i a12, a1, PT_AREG12 717 l32i a13, a1, PT_AREG13 718 l32i a14, a1, PT_AREG14 719 l32i a15, a1, PT_AREG15 720 721 /* Restore PC, SAR */ 722 7231: l32i a2, a1, PT_PC 724 l32i a3, a1, PT_SAR 725 wsr a2, epc1 726 wsr a3, sar 727 728 /* Restore LBEG, LEND, LCOUNT */ 729#if XCHAL_HAVE_LOOPS 730 l32i a2, a1, PT_LBEG 731 l32i a3, a1, PT_LEND 732 wsr a2, lbeg 733 l32i a2, a1, PT_LCOUNT 734 wsr a3, lend 735 wsr a2, lcount 736#endif 737 738 /* We control single stepping through the ICOUNTLEVEL register. */ 739 740 l32i a2, a1, PT_ICOUNTLEVEL 741 movi a3, -2 742 wsr a2, icountlevel 743 wsr a3, icount 744 745 /* Check if it was double exception. */ 746 747 l32i a0, a1, PT_DEPC 748 l32i a3, a1, PT_AREG3 749 l32i a2, a1, PT_AREG2 750 _bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f 751 752 /* Restore a0...a3 and return */ 753 754 l32i a0, a1, PT_AREG0 755 l32i a1, a1, PT_AREG1 756 rfe 757 7581: wsr a0, depc 759 l32i a0, a1, PT_AREG0 760 l32i a1, a1, PT_AREG1 761 rfde 762 763ENDPROC(kernel_exception) 764 765/* 766 * Debug exception handler. 767 * 768 * Currently, we don't support KGDB, so only user application can be debugged. 769 * 770 * When we get here, a0 is trashed and saved to excsave[debuglevel] 771 */ 772 773 .literal_position 774 775ENTRY(debug_exception) 776 777 rsr a0, SREG_EPS + XCHAL_DEBUGLEVEL 778 bbsi.l a0, PS_EXCM_BIT, 1f # exception mode 779 780 /* Set EPC1 and EXCCAUSE */ 781 782 wsr a2, depc # save a2 temporarily 783 rsr a2, SREG_EPC + XCHAL_DEBUGLEVEL 784 wsr a2, epc1 785 786 movi a2, EXCCAUSE_MAPPED_DEBUG 787 wsr a2, exccause 788 789 /* Restore PS to the value before the debug exc but with PS.EXCM set.*/ 790 791 movi a2, 1 << PS_EXCM_BIT 792 or a2, a0, a2 793 wsr a2, ps 794 795 /* Switch to kernel/user stack, restore jump vector, and save a0 */ 796 797 bbsi.l a2, PS_UM_BIT, 2f # jump if user mode 798 799 addi a2, a1, -16-PT_SIZE # assume kernel stack 8003: 801 l32i a0, a3, DT_DEBUG_SAVE 802 s32i a1, a2, PT_AREG1 803 s32i a0, a2, PT_AREG0 804 movi a0, 0 805 s32i a0, a2, PT_DEPC # mark it as a regular exception 806 xsr a3, SREG_EXCSAVE + XCHAL_DEBUGLEVEL 807 xsr a0, depc 808 s32i a3, a2, PT_AREG3 809 s32i a0, a2, PT_AREG2 810 mov a1, a2 811 812 /* Debug exception is handled as an exception, so interrupts will 813 * likely be enabled in the common exception handler. Disable 814 * preemption if we have HW breakpoints to preserve DEBUGCAUSE.DBNUM 815 * meaning. 816 */ 817#if defined(CONFIG_PREEMPT_COUNT) && defined(CONFIG_HAVE_HW_BREAKPOINT) 818 GET_THREAD_INFO(a2, a1) 819 l32i a3, a2, TI_PRE_COUNT 820 addi a3, a3, 1 821 s32i a3, a2, TI_PRE_COUNT 822#endif 823 824 rsr a2, ps 825 bbsi.l a2, PS_UM_BIT, _user_exception 826 j _kernel_exception 827 8282: rsr a2, excsave1 829 l32i a2, a2, EXC_TABLE_KSTK # load kernel stack pointer 830 j 3b 831 832#ifdef CONFIG_HAVE_HW_BREAKPOINT 833 /* Debug exception while in exception mode. This may happen when 834 * window overflow/underflow handler or fast exception handler hits 835 * data breakpoint, in which case save and disable all data 836 * breakpoints, single-step faulting instruction and restore data 837 * breakpoints. 838 */ 8391: 840 bbci.l a0, PS_UM_BIT, 1b # jump if kernel mode 841 842 rsr a0, debugcause 843 bbsi.l a0, DEBUGCAUSE_DBREAK_BIT, .Ldebug_save_dbreak 844 845 .set _index, 0 846 .rept XCHAL_NUM_DBREAK 847 l32i a0, a3, DT_DBREAKC_SAVE + _index * 4 848 wsr a0, SREG_DBREAKC + _index 849 .set _index, _index + 1 850 .endr 851 852 l32i a0, a3, DT_ICOUNT_LEVEL_SAVE 853 wsr a0, icountlevel 854 855 l32i a0, a3, DT_ICOUNT_SAVE 856 xsr a0, icount 857 858 l32i a0, a3, DT_DEBUG_SAVE 859 xsr a3, SREG_EXCSAVE + XCHAL_DEBUGLEVEL 860 rfi XCHAL_DEBUGLEVEL 861 862.Ldebug_save_dbreak: 863 .set _index, 0 864 .rept XCHAL_NUM_DBREAK 865 movi a0, 0 866 xsr a0, SREG_DBREAKC + _index 867 s32i a0, a3, DT_DBREAKC_SAVE + _index * 4 868 .set _index, _index + 1 869 .endr 870 871 movi a0, XCHAL_EXCM_LEVEL + 1 872 xsr a0, icountlevel 873 s32i a0, a3, DT_ICOUNT_LEVEL_SAVE 874 875 movi a0, 0xfffffffe 876 xsr a0, icount 877 s32i a0, a3, DT_ICOUNT_SAVE 878 879 l32i a0, a3, DT_DEBUG_SAVE 880 xsr a3, SREG_EXCSAVE + XCHAL_DEBUGLEVEL 881 rfi XCHAL_DEBUGLEVEL 882#else 883 /* Debug exception while in exception mode. Should not happen. */ 8841: j 1b // FIXME!! 885#endif 886 887ENDPROC(debug_exception) 888 889/* 890 * We get here in case of an unrecoverable exception. 891 * The only thing we can do is to be nice and print a panic message. 892 * We only produce a single stack frame for panic, so ??? 893 * 894 * 895 * Entry conditions: 896 * 897 * - a0 contains the caller address; original value saved in excsave1. 898 * - the original a0 contains a valid return address (backtrace) or 0. 899 * - a2 contains a valid stackpointer 900 * 901 * Notes: 902 * 903 * - If the stack pointer could be invalid, the caller has to setup a 904 * dummy stack pointer (e.g. the stack of the init_task) 905 * 906 * - If the return address could be invalid, the caller has to set it 907 * to 0, so the backtrace would stop. 908 * 909 */ 910 .align 4 911unrecoverable_text: 912 .ascii "Unrecoverable error in exception handler\0" 913 914 .literal_position 915 916ENTRY(unrecoverable_exception) 917 918 movi a0, 1 919 movi a1, 0 920 921 wsr a0, windowstart 922 wsr a1, windowbase 923 rsync 924 925 movi a1, (1 << PS_WOE_BIT) | LOCKLEVEL 926 wsr a1, ps 927 rsync 928 929 movi a1, init_task 930 movi a0, 0 931 addi a1, a1, PT_REGS_OFFSET 932 933 movi a6, unrecoverable_text 934 call4 panic 935 9361: j 1b 937 938ENDPROC(unrecoverable_exception) 939 940/* -------------------------- FAST EXCEPTION HANDLERS ----------------------- */ 941 942/* 943 * Fast-handler for alloca exceptions 944 * 945 * The ALLOCA handler is entered when user code executes the MOVSP 946 * instruction and the caller's frame is not in the register file. 947 * 948 * This algorithm was taken from the Ross Morley's RTOS Porting Layer: 949 * 950 * /home/ross/rtos/porting/XtensaRTOS-PortingLayer-20090507/xtensa_vectors.S 951 * 952 * It leverages the existing window spill/fill routines and their support for 953 * double exceptions. The 'movsp' instruction will only cause an exception if 954 * the next window needs to be loaded. In fact this ALLOCA exception may be 955 * replaced at some point by changing the hardware to do a underflow exception 956 * of the proper size instead. 957 * 958 * This algorithm simply backs out the register changes started by the user 959 * excpetion handler, makes it appear that we have started a window underflow 960 * by rotating the window back and then setting the old window base (OWB) in 961 * the 'ps' register with the rolled back window base. The 'movsp' instruction 962 * will be re-executed and this time since the next window frames is in the 963 * active AR registers it won't cause an exception. 964 * 965 * If the WindowUnderflow code gets a TLB miss the page will get mapped 966 * the the partial windeowUnderflow will be handeled in the double exception 967 * handler. 968 * 969 * Entry condition: 970 * 971 * a0: trashed, original value saved on stack (PT_AREG0) 972 * a1: a1 973 * a2: new stack pointer, original in DEPC 974 * a3: a3 975 * depc: a2, original value saved on stack (PT_DEPC) 976 * excsave_1: dispatch table 977 * 978 * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC 979 * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception 980 */ 981 982ENTRY(fast_alloca) 983 rsr a0, windowbase 984 rotw -1 985 rsr a2, ps 986 extui a3, a2, PS_OWB_SHIFT, PS_OWB_WIDTH 987 xor a3, a3, a4 988 l32i a4, a6, PT_AREG0 989 l32i a1, a6, PT_DEPC 990 rsr a6, depc 991 wsr a1, depc 992 slli a3, a3, PS_OWB_SHIFT 993 xor a2, a2, a3 994 wsr a2, ps 995 rsync 996 997 _bbci.l a4, 31, 4f 998 rotw -1 999 _bbci.l a8, 30, 8f 1000 rotw -1 1001 j _WindowUnderflow12 10028: j _WindowUnderflow8 10034: j _WindowUnderflow4 1004ENDPROC(fast_alloca) 1005 1006/* 1007 * fast system calls. 1008 * 1009 * WARNING: The kernel doesn't save the entire user context before 1010 * handling a fast system call. These functions are small and short, 1011 * usually offering some functionality not available to user tasks. 1012 * 1013 * BE CAREFUL TO PRESERVE THE USER'S CONTEXT. 1014 * 1015 * Entry condition: 1016 * 1017 * a0: trashed, original value saved on stack (PT_AREG0) 1018 * a1: a1 1019 * a2: new stack pointer, original in DEPC 1020 * a3: a3 1021 * depc: a2, original value saved on stack (PT_DEPC) 1022 * excsave_1: dispatch table 1023 */ 1024 1025ENTRY(fast_syscall_kernel) 1026 1027 /* Skip syscall. */ 1028 1029 rsr a0, epc1 1030 addi a0, a0, 3 1031 wsr a0, epc1 1032 1033 l32i a0, a2, PT_DEPC 1034 bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, fast_syscall_unrecoverable 1035 1036 rsr a0, depc # get syscall-nr 1037 _beqz a0, fast_syscall_spill_registers 1038 _beqi a0, __NR_xtensa, fast_syscall_xtensa 1039 1040 j kernel_exception 1041 1042ENDPROC(fast_syscall_kernel) 1043 1044ENTRY(fast_syscall_user) 1045 1046 /* Skip syscall. */ 1047 1048 rsr a0, epc1 1049 addi a0, a0, 3 1050 wsr a0, epc1 1051 1052 l32i a0, a2, PT_DEPC 1053 bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, fast_syscall_unrecoverable 1054 1055 rsr a0, depc # get syscall-nr 1056 _beqz a0, fast_syscall_spill_registers 1057 _beqi a0, __NR_xtensa, fast_syscall_xtensa 1058 1059 j user_exception 1060 1061ENDPROC(fast_syscall_user) 1062 1063ENTRY(fast_syscall_unrecoverable) 1064 1065 /* Restore all states. */ 1066 1067 l32i a0, a2, PT_AREG0 # restore a0 1068 xsr a2, depc # restore a2, depc 1069 1070 wsr a0, excsave1 1071 call0 unrecoverable_exception 1072 1073ENDPROC(fast_syscall_unrecoverable) 1074 1075/* 1076 * sysxtensa syscall handler 1077 * 1078 * int sysxtensa (SYS_XTENSA_ATOMIC_SET, ptr, val, unused); 1079 * int sysxtensa (SYS_XTENSA_ATOMIC_ADD, ptr, val, unused); 1080 * int sysxtensa (SYS_XTENSA_ATOMIC_EXG_ADD, ptr, val, unused); 1081 * int sysxtensa (SYS_XTENSA_ATOMIC_CMP_SWP, ptr, oldval, newval); 1082 * a2 a6 a3 a4 a5 1083 * 1084 * Entry condition: 1085 * 1086 * a0: a2 (syscall-nr), original value saved on stack (PT_AREG0) 1087 * a1: a1 1088 * a2: new stack pointer, original in a0 and DEPC 1089 * a3: a3 1090 * a4..a15: unchanged 1091 * depc: a2, original value saved on stack (PT_DEPC) 1092 * excsave_1: dispatch table 1093 * 1094 * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC 1095 * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception 1096 * 1097 * Note: we don't have to save a2; a2 holds the return value 1098 */ 1099 1100 .literal_position 1101 1102#ifdef CONFIG_FAST_SYSCALL_XTENSA 1103 1104ENTRY(fast_syscall_xtensa) 1105 1106 s32i a7, a2, PT_AREG7 # we need an additional register 1107 movi a7, 4 # sizeof(unsigned int) 1108 access_ok a3, a7, a0, a2, .Leac # a0: scratch reg, a2: sp 1109 1110 _bgeui a6, SYS_XTENSA_COUNT, .Lill 1111 _bnei a6, SYS_XTENSA_ATOMIC_CMP_SWP, .Lnswp 1112 1113 /* Fall through for ATOMIC_CMP_SWP. */ 1114 1115.Lswp: /* Atomic compare and swap */ 1116 1117EX(.Leac) l32i a0, a3, 0 # read old value 1118 bne a0, a4, 1f # same as old value? jump 1119EX(.Leac) s32i a5, a3, 0 # different, modify value 1120 l32i a7, a2, PT_AREG7 # restore a7 1121 l32i a0, a2, PT_AREG0 # restore a0 1122 movi a2, 1 # and return 1 1123 rfe 1124 11251: l32i a7, a2, PT_AREG7 # restore a7 1126 l32i a0, a2, PT_AREG0 # restore a0 1127 movi a2, 0 # return 0 (note that we cannot set 1128 rfe 1129 1130.Lnswp: /* Atomic set, add, and exg_add. */ 1131 1132EX(.Leac) l32i a7, a3, 0 # orig 1133 addi a6, a6, -SYS_XTENSA_ATOMIC_SET 1134 add a0, a4, a7 # + arg 1135 moveqz a0, a4, a6 # set 1136 addi a6, a6, SYS_XTENSA_ATOMIC_SET 1137EX(.Leac) s32i a0, a3, 0 # write new value 1138 1139 mov a0, a2 1140 mov a2, a7 1141 l32i a7, a0, PT_AREG7 # restore a7 1142 l32i a0, a0, PT_AREG0 # restore a0 1143 rfe 1144 1145.Leac: l32i a7, a2, PT_AREG7 # restore a7 1146 l32i a0, a2, PT_AREG0 # restore a0 1147 movi a2, -EFAULT 1148 rfe 1149 1150.Lill: l32i a7, a2, PT_AREG7 # restore a7 1151 l32i a0, a2, PT_AREG0 # restore a0 1152 movi a2, -EINVAL 1153 rfe 1154 1155ENDPROC(fast_syscall_xtensa) 1156 1157#else /* CONFIG_FAST_SYSCALL_XTENSA */ 1158 1159ENTRY(fast_syscall_xtensa) 1160 1161 l32i a0, a2, PT_AREG0 # restore a0 1162 movi a2, -ENOSYS 1163 rfe 1164 1165ENDPROC(fast_syscall_xtensa) 1166 1167#endif /* CONFIG_FAST_SYSCALL_XTENSA */ 1168 1169 1170/* fast_syscall_spill_registers. 1171 * 1172 * Entry condition: 1173 * 1174 * a0: trashed, original value saved on stack (PT_AREG0) 1175 * a1: a1 1176 * a2: new stack pointer, original in DEPC 1177 * a3: a3 1178 * depc: a2, original value saved on stack (PT_DEPC) 1179 * excsave_1: dispatch table 1180 * 1181 * Note: We assume the stack pointer is EXC_TABLE_KSTK in the fixup handler. 1182 */ 1183 1184#ifdef CONFIG_FAST_SYSCALL_SPILL_REGISTERS 1185 1186ENTRY(fast_syscall_spill_registers) 1187 1188 /* Register a FIXUP handler (pass current wb as a parameter) */ 1189 1190 xsr a3, excsave1 1191 movi a0, fast_syscall_spill_registers_fixup 1192 s32i a0, a3, EXC_TABLE_FIXUP 1193 rsr a0, windowbase 1194 s32i a0, a3, EXC_TABLE_PARAM 1195 xsr a3, excsave1 # restore a3 and excsave_1 1196 1197 /* Save a3, a4 and SAR on stack. */ 1198 1199 rsr a0, sar 1200 s32i a3, a2, PT_AREG3 1201 s32i a0, a2, PT_SAR 1202 1203 /* The spill routine might clobber a4, a7, a8, a11, a12, and a15. */ 1204 1205 s32i a4, a2, PT_AREG4 1206 s32i a7, a2, PT_AREG7 1207 s32i a8, a2, PT_AREG8 1208 s32i a11, a2, PT_AREG11 1209 s32i a12, a2, PT_AREG12 1210 s32i a15, a2, PT_AREG15 1211 1212 /* 1213 * Rotate ws so that the current windowbase is at bit 0. 1214 * Assume ws = xxxwww1yy (www1 current window frame). 1215 * Rotate ws right so that a4 = yyxxxwww1. 1216 */ 1217 1218 rsr a0, windowbase 1219 rsr a3, windowstart # a3 = xxxwww1yy 1220 ssr a0 # holds WB 1221 slli a0, a3, WSBITS 1222 or a3, a3, a0 # a3 = xxxwww1yyxxxwww1yy 1223 srl a3, a3 # a3 = 00xxxwww1yyxxxwww1 1224 1225 /* We are done if there are no more than the current register frame. */ 1226 1227 extui a3, a3, 1, WSBITS-1 # a3 = 0yyxxxwww 1228 movi a0, (1 << (WSBITS-1)) 1229 _beqz a3, .Lnospill # only one active frame? jump 1230 1231 /* We want 1 at the top, so that we return to the current windowbase */ 1232 1233 or a3, a3, a0 # 1yyxxxwww 1234 1235 /* Skip empty frames - get 'oldest' WINDOWSTART-bit. */ 1236 1237 wsr a3, windowstart # save shifted windowstart 1238 neg a0, a3 1239 and a3, a0, a3 # first bit set from right: 000010000 1240 1241 ffs_ws a0, a3 # a0: shifts to skip empty frames 1242 movi a3, WSBITS 1243 sub a0, a3, a0 # WSBITS-a0:number of 0-bits from right 1244 ssr a0 # save in SAR for later. 1245 1246 rsr a3, windowbase 1247 add a3, a3, a0 1248 wsr a3, windowbase 1249 rsync 1250 1251 rsr a3, windowstart 1252 srl a3, a3 # shift windowstart 1253 1254 /* WB is now just one frame below the oldest frame in the register 1255 window. WS is shifted so the oldest frame is in bit 0, thus, WB 1256 and WS differ by one 4-register frame. */ 1257 1258 /* Save frames. Depending what call was used (call4, call8, call12), 1259 * we have to save 4,8. or 12 registers. 1260 */ 1261 1262 1263.Lloop: _bbsi.l a3, 1, .Lc4 1264 _bbci.l a3, 2, .Lc12 1265 1266.Lc8: s32e a4, a13, -16 1267 l32e a4, a5, -12 1268 s32e a8, a4, -32 1269 s32e a5, a13, -12 1270 s32e a6, a13, -8 1271 s32e a7, a13, -4 1272 s32e a9, a4, -28 1273 s32e a10, a4, -24 1274 s32e a11, a4, -20 1275 srli a11, a3, 2 # shift windowbase by 2 1276 rotw 2 1277 _bnei a3, 1, .Lloop 1278 j .Lexit 1279 1280.Lc4: s32e a4, a9, -16 1281 s32e a5, a9, -12 1282 s32e a6, a9, -8 1283 s32e a7, a9, -4 1284 1285 srli a7, a3, 1 1286 rotw 1 1287 _bnei a3, 1, .Lloop 1288 j .Lexit 1289 1290.Lc12: _bbci.l a3, 3, .Linvalid_mask # bit 2 shouldn't be zero! 1291 1292 /* 12-register frame (call12) */ 1293 1294 l32e a0, a5, -12 1295 s32e a8, a0, -48 1296 mov a8, a0 1297 1298 s32e a9, a8, -44 1299 s32e a10, a8, -40 1300 s32e a11, a8, -36 1301 s32e a12, a8, -32 1302 s32e a13, a8, -28 1303 s32e a14, a8, -24 1304 s32e a15, a8, -20 1305 srli a15, a3, 3 1306 1307 /* The stack pointer for a4..a7 is out of reach, so we rotate the 1308 * window, grab the stackpointer, and rotate back. 1309 * Alternatively, we could also use the following approach, but that 1310 * makes the fixup routine much more complicated: 1311 * rotw 1 1312 * s32e a0, a13, -16 1313 * ... 1314 * rotw 2 1315 */ 1316 1317 rotw 1 1318 mov a4, a13 1319 rotw -1 1320 1321 s32e a4, a8, -16 1322 s32e a5, a8, -12 1323 s32e a6, a8, -8 1324 s32e a7, a8, -4 1325 1326 rotw 3 1327 1328 _beqi a3, 1, .Lexit 1329 j .Lloop 1330 1331.Lexit: 1332 1333 /* Done. Do the final rotation and set WS */ 1334 1335 rotw 1 1336 rsr a3, windowbase 1337 ssl a3 1338 movi a3, 1 1339 sll a3, a3 1340 wsr a3, windowstart 1341.Lnospill: 1342 1343 /* Advance PC, restore registers and SAR, and return from exception. */ 1344 1345 l32i a3, a2, PT_SAR 1346 l32i a0, a2, PT_AREG0 1347 wsr a3, sar 1348 l32i a3, a2, PT_AREG3 1349 1350 /* Restore clobbered registers. */ 1351 1352 l32i a4, a2, PT_AREG4 1353 l32i a7, a2, PT_AREG7 1354 l32i a8, a2, PT_AREG8 1355 l32i a11, a2, PT_AREG11 1356 l32i a12, a2, PT_AREG12 1357 l32i a15, a2, PT_AREG15 1358 1359 movi a2, 0 1360 rfe 1361 1362.Linvalid_mask: 1363 1364 /* We get here because of an unrecoverable error in the window 1365 * registers, so set up a dummy frame and kill the user application. 1366 * Note: We assume EXC_TABLE_KSTK contains a valid stack pointer. 1367 */ 1368 1369 movi a0, 1 1370 movi a1, 0 1371 1372 wsr a0, windowstart 1373 wsr a1, windowbase 1374 rsync 1375 1376 movi a0, 0 1377 1378 rsr a3, excsave1 1379 l32i a1, a3, EXC_TABLE_KSTK 1380 1381 movi a4, (1 << PS_WOE_BIT) | LOCKLEVEL 1382 wsr a4, ps 1383 rsync 1384 1385 movi a6, SIGSEGV 1386 call4 do_exit 1387 1388 /* shouldn't return, so panic */ 1389 1390 wsr a0, excsave1 1391 call0 unrecoverable_exception # should not return 13921: j 1b 1393 1394 1395ENDPROC(fast_syscall_spill_registers) 1396 1397/* Fixup handler. 1398 * 1399 * We get here if the spill routine causes an exception, e.g. tlb miss. 1400 * We basically restore WINDOWBASE and WINDOWSTART to the condition when 1401 * we entered the spill routine and jump to the user exception handler. 1402 * 1403 * Note that we only need to restore the bits in windowstart that have not 1404 * been spilled yet by the _spill_register routine. Luckily, a3 contains a 1405 * rotated windowstart with only those bits set for frames that haven't been 1406 * spilled yet. Because a3 is rotated such that bit 0 represents the register 1407 * frame for the current windowbase - 1, we need to rotate a3 left by the 1408 * value of the current windowbase + 1 and move it to windowstart. 1409 * 1410 * a0: value of depc, original value in depc 1411 * a2: trashed, original value in EXC_TABLE_DOUBLE_SAVE 1412 * a3: exctable, original value in excsave1 1413 */ 1414 1415ENTRY(fast_syscall_spill_registers_fixup) 1416 1417 rsr a2, windowbase # get current windowbase (a2 is saved) 1418 xsr a0, depc # restore depc and a0 1419 ssl a2 # set shift (32 - WB) 1420 1421 /* We need to make sure the current registers (a0-a3) are preserved. 1422 * To do this, we simply set the bit for the current window frame 1423 * in WS, so that the exception handlers save them to the task stack. 1424 * 1425 * Note: we use a3 to set the windowbase, so we take a special care 1426 * of it, saving it in the original _spill_registers frame across 1427 * the exception handler call. 1428 */ 1429 1430 xsr a3, excsave1 # get spill-mask 1431 slli a3, a3, 1 # shift left by one 1432 addi a3, a3, 1 # set the bit for the current window frame 1433 1434 slli a2, a3, 32-WSBITS 1435 src a2, a3, a2 # a2 = xxwww1yyxxxwww1yy...... 1436 wsr a2, windowstart # set corrected windowstart 1437 1438 srli a3, a3, 1 1439 rsr a2, excsave1 1440 l32i a2, a2, EXC_TABLE_DOUBLE_SAVE # restore a2 1441 xsr a2, excsave1 1442 s32i a3, a2, EXC_TABLE_DOUBLE_SAVE # save a3 1443 l32i a3, a2, EXC_TABLE_PARAM # original WB (in user task) 1444 xsr a2, excsave1 1445 1446 /* Return to the original (user task) WINDOWBASE. 1447 * We leave the following frame behind: 1448 * a0, a1, a2 same 1449 * a3: trashed (saved in EXC_TABLE_DOUBLE_SAVE) 1450 * depc: depc (we have to return to that address) 1451 * excsave_1: exctable 1452 */ 1453 1454 wsr a3, windowbase 1455 rsync 1456 1457 /* We are now in the original frame when we entered _spill_registers: 1458 * a0: return address 1459 * a1: used, stack pointer 1460 * a2: kernel stack pointer 1461 * a3: available 1462 * depc: exception address 1463 * excsave: exctable 1464 * Note: This frame might be the same as above. 1465 */ 1466 1467 /* Setup stack pointer. */ 1468 1469 addi a2, a2, -PT_USER_SIZE 1470 s32i a0, a2, PT_AREG0 1471 1472 /* Make sure we return to this fixup handler. */ 1473 1474 movi a3, fast_syscall_spill_registers_fixup_return 1475 s32i a3, a2, PT_DEPC # setup depc 1476 1477 /* Jump to the exception handler. */ 1478 1479 rsr a3, excsave1 1480 rsr a0, exccause 1481 addx4 a0, a0, a3 # find entry in table 1482 l32i a0, a0, EXC_TABLE_FAST_USER # load handler 1483 l32i a3, a3, EXC_TABLE_DOUBLE_SAVE 1484 jx a0 1485 1486ENDPROC(fast_syscall_spill_registers_fixup) 1487 1488ENTRY(fast_syscall_spill_registers_fixup_return) 1489 1490 /* When we return here, all registers have been restored (a2: DEPC) */ 1491 1492 wsr a2, depc # exception address 1493 1494 /* Restore fixup handler. */ 1495 1496 rsr a2, excsave1 1497 s32i a3, a2, EXC_TABLE_DOUBLE_SAVE 1498 movi a3, fast_syscall_spill_registers_fixup 1499 s32i a3, a2, EXC_TABLE_FIXUP 1500 rsr a3, windowbase 1501 s32i a3, a2, EXC_TABLE_PARAM 1502 l32i a2, a2, EXC_TABLE_KSTK 1503 1504 /* Load WB at the time the exception occurred. */ 1505 1506 rsr a3, sar # WB is still in SAR 1507 neg a3, a3 1508 wsr a3, windowbase 1509 rsync 1510 1511 rsr a3, excsave1 1512 l32i a3, a3, EXC_TABLE_DOUBLE_SAVE 1513 1514 rfde 1515 1516ENDPROC(fast_syscall_spill_registers_fixup_return) 1517 1518#else /* CONFIG_FAST_SYSCALL_SPILL_REGISTERS */ 1519 1520ENTRY(fast_syscall_spill_registers) 1521 1522 l32i a0, a2, PT_AREG0 # restore a0 1523 movi a2, -ENOSYS 1524 rfe 1525 1526ENDPROC(fast_syscall_spill_registers) 1527 1528#endif /* CONFIG_FAST_SYSCALL_SPILL_REGISTERS */ 1529 1530#ifdef CONFIG_MMU 1531/* 1532 * We should never get here. Bail out! 1533 */ 1534 1535ENTRY(fast_second_level_miss_double_kernel) 1536 15371: 1538 call0 unrecoverable_exception # should not return 15391: j 1b 1540 1541ENDPROC(fast_second_level_miss_double_kernel) 1542 1543/* First-level entry handler for user, kernel, and double 2nd-level 1544 * TLB miss exceptions. Note that for now, user and kernel miss 1545 * exceptions share the same entry point and are handled identically. 1546 * 1547 * An old, less-efficient C version of this function used to exist. 1548 * We include it below, interleaved as comments, for reference. 1549 * 1550 * Entry condition: 1551 * 1552 * a0: trashed, original value saved on stack (PT_AREG0) 1553 * a1: a1 1554 * a2: new stack pointer, original in DEPC 1555 * a3: a3 1556 * depc: a2, original value saved on stack (PT_DEPC) 1557 * excsave_1: dispatch table 1558 * 1559 * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC 1560 * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception 1561 */ 1562 1563ENTRY(fast_second_level_miss) 1564 1565 /* Save a1 and a3. Note: we don't expect a double exception. */ 1566 1567 s32i a1, a2, PT_AREG1 1568 s32i a3, a2, PT_AREG3 1569 1570 /* We need to map the page of PTEs for the user task. Find 1571 * the pointer to that page. Also, it's possible for tsk->mm 1572 * to be NULL while tsk->active_mm is nonzero if we faulted on 1573 * a vmalloc address. In that rare case, we must use 1574 * active_mm instead to avoid a fault in this handler. See 1575 * 1576 * http://mail.nl.linux.org/linux-mm/2002-08/msg00258.html 1577 * (or search Internet on "mm vs. active_mm") 1578 * 1579 * if (!mm) 1580 * mm = tsk->active_mm; 1581 * pgd = pgd_offset (mm, regs->excvaddr); 1582 * pmd = pmd_offset (pgd, regs->excvaddr); 1583 * pmdval = *pmd; 1584 */ 1585 1586 GET_CURRENT(a1,a2) 1587 l32i a0, a1, TASK_MM # tsk->mm 1588 beqz a0, 9f 1589 15908: rsr a3, excvaddr # fault address 1591 _PGD_OFFSET(a0, a3, a1) 1592 l32i a0, a0, 0 # read pmdval 1593 beqz a0, 2f 1594 1595 /* Read ptevaddr and convert to top of page-table page. 1596 * 1597 * vpnval = read_ptevaddr_register() & PAGE_MASK; 1598 * vpnval += DTLB_WAY_PGTABLE; 1599 * pteval = mk_pte (virt_to_page(pmd_val(pmdval)), PAGE_KERNEL); 1600 * write_dtlb_entry (pteval, vpnval); 1601 * 1602 * The messy computation for 'pteval' above really simplifies 1603 * into the following: 1604 * 1605 * pteval = ((pmdval - PAGE_OFFSET + PHYS_OFFSET) & PAGE_MASK) 1606 * | PAGE_DIRECTORY 1607 */ 1608 1609 movi a1, (PHYS_OFFSET - PAGE_OFFSET) & 0xffffffff 1610 add a0, a0, a1 # pmdval - PAGE_OFFSET 1611 extui a1, a0, 0, PAGE_SHIFT # ... & PAGE_MASK 1612 xor a0, a0, a1 1613 1614 movi a1, _PAGE_DIRECTORY 1615 or a0, a0, a1 # ... | PAGE_DIRECTORY 1616 1617 /* 1618 * We utilize all three wired-ways (7-9) to hold pmd translations. 1619 * Memory regions are mapped to the DTLBs according to bits 28 and 29. 1620 * This allows to map the three most common regions to three different 1621 * DTLBs: 1622 * 0,1 -> way 7 program (0040.0000) and virtual (c000.0000) 1623 * 2 -> way 8 shared libaries (2000.0000) 1624 * 3 -> way 0 stack (3000.0000) 1625 */ 1626 1627 extui a3, a3, 28, 2 # addr. bit 28 and 29 0,1,2,3 1628 rsr a1, ptevaddr 1629 addx2 a3, a3, a3 # -> 0,3,6,9 1630 srli a1, a1, PAGE_SHIFT 1631 extui a3, a3, 2, 2 # -> 0,0,1,2 1632 slli a1, a1, PAGE_SHIFT # ptevaddr & PAGE_MASK 1633 addi a3, a3, DTLB_WAY_PGD 1634 add a1, a1, a3 # ... + way_number 1635 16363: wdtlb a0, a1 1637 dsync 1638 1639 /* Exit critical section. */ 1640 16414: rsr a3, excsave1 1642 movi a0, 0 1643 s32i a0, a3, EXC_TABLE_FIXUP 1644 1645 /* Restore the working registers, and return. */ 1646 1647 l32i a0, a2, PT_AREG0 1648 l32i a1, a2, PT_AREG1 1649 l32i a3, a2, PT_AREG3 1650 l32i a2, a2, PT_DEPC 1651 1652 bgeui a2, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f 1653 1654 /* Restore excsave1 and return. */ 1655 1656 rsr a2, depc 1657 rfe 1658 1659 /* Return from double exception. */ 1660 16611: xsr a2, depc 1662 esync 1663 rfde 1664 16659: l32i a0, a1, TASK_ACTIVE_MM # unlikely case mm == 0 1666 bnez a0, 8b 1667 1668 /* Even more unlikely case active_mm == 0. 1669 * We can get here with NMI in the middle of context_switch that 1670 * touches vmalloc area. 1671 */ 1672 movi a0, init_mm 1673 j 8b 1674 1675#if (DCACHE_WAY_SIZE > PAGE_SIZE) 1676 16772: /* Special case for cache aliasing. 1678 * We (should) only get here if a clear_user_page, copy_user_page 1679 * or the aliased cache flush functions got preemptively interrupted 1680 * by another task. Re-establish temporary mapping to the 1681 * TLBTEMP_BASE areas. 1682 */ 1683 1684 /* We shouldn't be in a double exception */ 1685 1686 l32i a0, a2, PT_DEPC 1687 bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, 2f 1688 1689 /* Make sure the exception originated in the special functions */ 1690 1691 movi a0, __tlbtemp_mapping_start 1692 rsr a3, epc1 1693 bltu a3, a0, 2f 1694 movi a0, __tlbtemp_mapping_end 1695 bgeu a3, a0, 2f 1696 1697 /* Check if excvaddr was in one of the TLBTEMP_BASE areas. */ 1698 1699 movi a3, TLBTEMP_BASE_1 1700 rsr a0, excvaddr 1701 bltu a0, a3, 2f 1702 1703 addi a1, a0, -TLBTEMP_SIZE 1704 bgeu a1, a3, 2f 1705 1706 /* Check if we have to restore an ITLB mapping. */ 1707 1708 movi a1, __tlbtemp_mapping_itlb 1709 rsr a3, epc1 1710 sub a3, a3, a1 1711 1712 /* Calculate VPN */ 1713 1714 movi a1, PAGE_MASK 1715 and a1, a1, a0 1716 1717 /* Jump for ITLB entry */ 1718 1719 bgez a3, 1f 1720 1721 /* We can use up to two TLBTEMP areas, one for src and one for dst. */ 1722 1723 extui a3, a0, PAGE_SHIFT + DCACHE_ALIAS_ORDER, 1 1724 add a1, a3, a1 1725 1726 /* PPN is in a6 for the first TLBTEMP area and in a7 for the second. */ 1727 1728 mov a0, a6 1729 movnez a0, a7, a3 1730 j 3b 1731 1732 /* ITLB entry. We only use dst in a6. */ 1733 17341: witlb a6, a1 1735 isync 1736 j 4b 1737 1738 1739#endif // DCACHE_WAY_SIZE > PAGE_SIZE 1740 1741 17422: /* Invalid PGD, default exception handling */ 1743 1744 rsr a1, depc 1745 s32i a1, a2, PT_AREG2 1746 mov a1, a2 1747 1748 rsr a2, ps 1749 bbsi.l a2, PS_UM_BIT, 1f 1750 j _kernel_exception 17511: j _user_exception 1752 1753ENDPROC(fast_second_level_miss) 1754 1755/* 1756 * StoreProhibitedException 1757 * 1758 * Update the pte and invalidate the itlb mapping for this pte. 1759 * 1760 * Entry condition: 1761 * 1762 * a0: trashed, original value saved on stack (PT_AREG0) 1763 * a1: a1 1764 * a2: new stack pointer, original in DEPC 1765 * a3: a3 1766 * depc: a2, original value saved on stack (PT_DEPC) 1767 * excsave_1: dispatch table 1768 * 1769 * PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC 1770 * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception 1771 */ 1772 1773ENTRY(fast_store_prohibited) 1774 1775 /* Save a1 and a3. */ 1776 1777 s32i a1, a2, PT_AREG1 1778 s32i a3, a2, PT_AREG3 1779 1780 GET_CURRENT(a1,a2) 1781 l32i a0, a1, TASK_MM # tsk->mm 1782 beqz a0, 9f 1783 17848: rsr a1, excvaddr # fault address 1785 _PGD_OFFSET(a0, a1, a3) 1786 l32i a0, a0, 0 1787 beqz a0, 2f 1788 1789 /* 1790 * Note that we test _PAGE_WRITABLE_BIT only if PTE is present 1791 * and is not PAGE_NONE. See pgtable.h for possible PTE layouts. 1792 */ 1793 1794 _PTE_OFFSET(a0, a1, a3) 1795 l32i a3, a0, 0 # read pteval 1796 movi a1, _PAGE_CA_INVALID 1797 ball a3, a1, 2f 1798 bbci.l a3, _PAGE_WRITABLE_BIT, 2f 1799 1800 movi a1, _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_HW_WRITE 1801 or a3, a3, a1 1802 rsr a1, excvaddr 1803 s32i a3, a0, 0 1804 1805 /* We need to flush the cache if we have page coloring. */ 1806#if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK 1807 dhwb a0, 0 1808#endif 1809 pdtlb a0, a1 1810 wdtlb a3, a0 1811 1812 /* Exit critical section. */ 1813 1814 movi a0, 0 1815 rsr a3, excsave1 1816 s32i a0, a3, EXC_TABLE_FIXUP 1817 1818 /* Restore the working registers, and return. */ 1819 1820 l32i a3, a2, PT_AREG3 1821 l32i a1, a2, PT_AREG1 1822 l32i a0, a2, PT_AREG0 1823 l32i a2, a2, PT_DEPC 1824 1825 bgeui a2, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f 1826 1827 rsr a2, depc 1828 rfe 1829 1830 /* Double exception. Restore FIXUP handler and return. */ 1831 18321: xsr a2, depc 1833 esync 1834 rfde 1835 18369: l32i a0, a1, TASK_ACTIVE_MM # unlikely case mm == 0 1837 j 8b 1838 18392: /* If there was a problem, handle fault in C */ 1840 1841 rsr a3, depc # still holds a2 1842 s32i a3, a2, PT_AREG2 1843 mov a1, a2 1844 1845 rsr a2, ps 1846 bbsi.l a2, PS_UM_BIT, 1f 1847 j _kernel_exception 18481: j _user_exception 1849 1850ENDPROC(fast_store_prohibited) 1851 1852#endif /* CONFIG_MMU */ 1853 1854/* 1855 * System Calls. 1856 * 1857 * void system_call (struct pt_regs* regs, int exccause) 1858 * a2 a3 1859 */ 1860 .literal_position 1861 1862ENTRY(system_call) 1863 1864 entry a1, 32 1865 1866 /* regs->syscall = regs->areg[2] */ 1867 1868 l32i a3, a2, PT_AREG2 1869 mov a6, a2 1870 s32i a3, a2, PT_SYSCALL 1871 call4 do_syscall_trace_enter 1872 mov a3, a6 1873 1874 /* syscall = sys_call_table[syscall_nr] */ 1875 1876 movi a4, sys_call_table 1877 movi a5, __NR_syscall_count 1878 movi a6, -ENOSYS 1879 bgeu a3, a5, 1f 1880 1881 addx4 a4, a3, a4 1882 l32i a4, a4, 0 1883 movi a5, sys_ni_syscall; 1884 beq a4, a5, 1f 1885 1886 /* Load args: arg0 - arg5 are passed via regs. */ 1887 1888 l32i a6, a2, PT_AREG6 1889 l32i a7, a2, PT_AREG3 1890 l32i a8, a2, PT_AREG4 1891 l32i a9, a2, PT_AREG5 1892 l32i a10, a2, PT_AREG8 1893 l32i a11, a2, PT_AREG9 1894 1895 /* Pass one additional argument to the syscall: pt_regs (on stack) */ 1896 s32i a2, a1, 0 1897 1898 callx4 a4 1899 19001: /* regs->areg[2] = return_value */ 1901 1902 s32i a6, a2, PT_AREG2 1903 mov a6, a2 1904 call4 do_syscall_trace_leave 1905 retw 1906 1907ENDPROC(system_call) 1908 1909/* 1910 * Spill live registers on the kernel stack macro. 1911 * 1912 * Entry condition: ps.woe is set, ps.excm is cleared 1913 * Exit condition: windowstart has single bit set 1914 * May clobber: a12, a13 1915 */ 1916 .macro spill_registers_kernel 1917 1918#if XCHAL_NUM_AREGS > 16 1919 call12 1f 1920 _j 2f 1921 retw 1922 .align 4 19231: 1924 _entry a1, 48 1925 addi a12, a0, 3 1926#if XCHAL_NUM_AREGS > 32 1927 .rept (XCHAL_NUM_AREGS - 32) / 12 1928 _entry a1, 48 1929 mov a12, a0 1930 .endr 1931#endif 1932 _entry a1, 16 1933#if XCHAL_NUM_AREGS % 12 == 0 1934 mov a8, a8 1935#elif XCHAL_NUM_AREGS % 12 == 4 1936 mov a12, a12 1937#elif XCHAL_NUM_AREGS % 12 == 8 1938 mov a4, a4 1939#endif 1940 retw 19412: 1942#else 1943 mov a12, a12 1944#endif 1945 .endm 1946 1947/* 1948 * Task switch. 1949 * 1950 * struct task* _switch_to (struct task* prev, struct task* next) 1951 * a2 a2 a3 1952 */ 1953 1954ENTRY(_switch_to) 1955 1956 entry a1, 48 1957 1958 mov a11, a3 # and 'next' (a3) 1959 1960 l32i a4, a2, TASK_THREAD_INFO 1961 l32i a5, a3, TASK_THREAD_INFO 1962 1963 save_xtregs_user a4 a6 a8 a9 a12 a13 THREAD_XTREGS_USER 1964 1965#if THREAD_RA > 1020 || THREAD_SP > 1020 1966 addi a10, a2, TASK_THREAD 1967 s32i a0, a10, THREAD_RA - TASK_THREAD # save return address 1968 s32i a1, a10, THREAD_SP - TASK_THREAD # save stack pointer 1969#else 1970 s32i a0, a2, THREAD_RA # save return address 1971 s32i a1, a2, THREAD_SP # save stack pointer 1972#endif 1973 1974#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP) 1975 movi a6, __stack_chk_guard 1976 l32i a8, a3, TASK_STACK_CANARY 1977 s32i a8, a6, 0 1978#endif 1979 1980 /* Disable ints while we manipulate the stack pointer. */ 1981 1982 irq_save a14, a3 1983 rsync 1984 1985 /* Switch CPENABLE */ 1986 1987#if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS) 1988 l32i a3, a5, THREAD_CPENABLE 1989 xsr a3, cpenable 1990 s32i a3, a4, THREAD_CPENABLE 1991#endif 1992 1993 /* Flush register file. */ 1994 1995 spill_registers_kernel 1996 1997 /* Set kernel stack (and leave critical section) 1998 * Note: It's save to set it here. The stack will not be overwritten 1999 * because the kernel stack will only be loaded again after 2000 * we return from kernel space. 2001 */ 2002 2003 rsr a3, excsave1 # exc_table 2004 addi a7, a5, PT_REGS_OFFSET 2005 s32i a7, a3, EXC_TABLE_KSTK 2006 2007 /* restore context of the task 'next' */ 2008 2009 l32i a0, a11, THREAD_RA # restore return address 2010 l32i a1, a11, THREAD_SP # restore stack pointer 2011 2012 load_xtregs_user a5 a6 a8 a9 a12 a13 THREAD_XTREGS_USER 2013 2014 wsr a14, ps 2015 rsync 2016 2017 retw 2018 2019ENDPROC(_switch_to) 2020 2021ENTRY(ret_from_fork) 2022 2023 /* void schedule_tail (struct task_struct *prev) 2024 * Note: prev is still in a6 (return value from fake call4 frame) 2025 */ 2026 call4 schedule_tail 2027 2028 mov a6, a1 2029 call4 do_syscall_trace_leave 2030 2031 j common_exception_return 2032 2033ENDPROC(ret_from_fork) 2034 2035/* 2036 * Kernel thread creation helper 2037 * On entry, set up by copy_thread: a2 = thread_fn, a3 = thread_fn arg 2038 * left from _switch_to: a6 = prev 2039 */ 2040ENTRY(ret_from_kernel_thread) 2041 2042 call4 schedule_tail 2043 mov a6, a3 2044 callx4 a2 2045 j common_exception_return 2046 2047ENDPROC(ret_from_kernel_thread) 2048