1 /* SPDX-License-Identifier: GPL-2.0-or-later */
3 * Copyright (c) 1995-1996 Gary Thomas <gdt@linuxppc.org>
4 * Initial PowerPC version.
5 * Copyright (c) 1996 Cort Dougan <cort@cs.nmt.edu>
7 * Copyright (c) 1996 Paul Mackerras <paulus@cs.anu.edu.au>
8 * Low-level exception handers, MMU support, and rewrite.
9 * Copyright (c) 1997 Dan Malek <dmalek@jlc.net>
10 * PowerPC 8xx modifications.
11 * Copyright (c) 1998-1999 TiVo, Inc.
12 * PowerPC 403GCX modifications.
13 * Copyright (c) 1999 Grant Erickson <grant@lcse.umn.edu>
14 * PowerPC 403GCX/405GP modifications.
15 * Copyright 2000 MontaVista Software Inc.
16 * PPC405 modifications
17 * PowerPC 403GCX/405GP modifications.
18 * Author: MontaVista Software, Inc.
19 * frank_rowand@mvista.com or source@mvista.com
20 * debbie_chu@mvista.com
22 * Module name: head_4xx.S
25 * Kernel execution entry point code.
28 #include <linux/init.h>
29 #include <linux/pgtable.h>
30 #include <linux/sizes.h>
31 #include <linux/linkage.h>
33 #include <asm/processor.h>
36 #include <asm/cputable.h>
37 #include <asm/thread_info.h>
38 #include <asm/ppc_asm.h>
39 #include <asm/asm-offsets.h>
40 #include <asm/ptrace.h>
41 #include <asm/export.h>
45 /* As with the other PowerPC ports, it is expected that when code
46 * execution begins here, the following registers contain valid, yet
47 * optional, information:
49 * r3 - Board info structure pointer (DRAM, frequency, MAC address, etc.)
50 * r4 - Starting address of the init RAM disk
51 * r5 - Ending address of the init RAM disk
52 * r6 - Start of kernel command line string (e.g. "mem=96m")
53 * r7 - End of kernel command line string
55 * This is all going to change RSN when we add bi_recs....... -- Dan
61 mr r31,r3 /* save device tree ptr */
63 /* We have to turn on the MMU right away so we get cache modes
68 /* We now have the lower 16 Meg mapped into TLB entries, and the caches
73 ori r0,r0,MSR_KERNEL@l
76 ori r0,r0,start_here@l
79 b . /* prevent prefetch past rfi */
82 * This area is used for temporarily saving registers during the
83 * critical exception prolog.
103 * Exception prolog for critical exceptions. This is a little different
104 * from the normal exception prolog above since a critical exception
105 * can potentially occur at any point during normal exception processing.
106 * Thus we cannot use the same SPRG registers as the normal prolog above.
107 * Instead we use a couple of words of memory at low physical addresses.
108 * This is OK since we don't support SMP on these processors.
110 .macro CRITICAL_EXCEPTION_PROLOG trapno name
111 stw r10,crit_r10@l(0) /* save two registers to work with */
112 stw r11,crit_r11@l(0)
115 stw r10,crit_srr0@l(0)
116 stw r11,crit_srr1@l(0)
119 stw r10,crit_dear@l(0)
120 stw r11,crit_esr@l(0)
121 mfcr r10 /* save CR in r10 for now */
122 mfspr r11,SPRN_SRR3 /* check whether user or kernel */
124 lis r11,(critirq_ctx-PAGE_OFFSET)@ha
125 lwz r11,(critirq_ctx-PAGE_OFFSET)@l(r11)
127 /* COMING FROM USER MODE */
128 mfspr r11,SPRN_SPRG_THREAD /* if from user, start at top of */
129 lwz r11,TASK_STACK-THREAD(r11) /* this thread's kernel stack */
130 1: stw r1,crit_r1@l(0)
131 addi r1,r11,THREAD_SIZE-INT_FRAME_SIZE /* Alloc an excpt frm */
132 LOAD_REG_IMMEDIATE(r11, MSR_KERNEL & ~(MSR_ME|MSR_DE|MSR_CE)) /* re-enable MMU */
146 stw r10,_CCR(r11) /* save various registers */
151 lis r9,PAGE_OFFSET@ha
152 lwz r10,crit_r10@l(r9)
153 lwz r12,crit_r11@l(r9)
156 lwz r12,crit_dear@l(r9)
157 lwz r9,crit_esr@l(r9)
158 stw r12,_DEAR(r11) /* since they may have had stuff */
159 stw r9,_ESR(r11) /* exception was taken */
162 rlwinm r9,r9,0,14,12 /* clear MSR_WE (necessary?) */
163 COMMON_EXCEPTION_PROLOG_END \trapno + 2
164 _ASM_NOKPROBE_SYMBOL(\name\()_virt)
168 * State at this point:
169 * r9 saved in stack frame, now saved SRR3 & ~MSR_WE
170 * r10 saved in crit_r10 and in stack frame, trashed
171 * r11 saved in crit_r11 and in stack frame,
172 * now phys stack/exception frame pointer
173 * r12 saved in stack frame, now saved SRR2
174 * CR saved in stack frame, CR0.EQ = !SRR3.PR
175 * LR, DEAR, ESR in stack frame
176 * r1 saved in stack frame, now virt stack/excframe pointer
177 * r0, r3-r8 saved in stack frame
183 #define CRITICAL_EXCEPTION(n, label, hdlr) \
184 START_EXCEPTION(n, label); \
185 CRITICAL_EXCEPTION_PROLOG n label; \
186 prepare_transfer_to_handler; \
191 * 0x0100 - Critical Interrupt Exception
193 CRITICAL_EXCEPTION(0x0100, CriticalInterrupt, unknown_exception)
196 * 0x0200 - Machine Check Exception
198 CRITICAL_EXCEPTION(0x0200, MachineCheck, machine_check_exception)
201 * 0x0300 - Data Storage Exception
202 * This happens for just a few reasons. U0 set (but we don't do that),
203 * or zone protection fault (user violation, write to protected page).
204 * The other Data TLB exceptions bail out to this point
205 * if they can't resolve the lightweight TLB fault.
207 START_EXCEPTION(0x0300, DataStorage)
208 EXCEPTION_PROLOG 0x300 DataStorage handle_dar_dsisr=1
209 prepare_transfer_to_handler
214 * 0x0400 - Instruction Storage Exception
215 * This is caused by a fetch from non-execute or guarded pages.
217 START_EXCEPTION(0x0400, InstructionAccess)
218 EXCEPTION_PROLOG 0x400 InstructionAccess
220 stw r5, _ESR(r11) /* Zero ESR */
221 stw r12, _DEAR(r11) /* SRR0 as DEAR */
222 prepare_transfer_to_handler
226 /* 0x0500 - External Interrupt Exception */
227 EXCEPTION(0x0500, HardwareInterrupt, do_IRQ)
229 /* 0x0600 - Alignment Exception */
230 START_EXCEPTION(0x0600, Alignment)
231 EXCEPTION_PROLOG 0x600 Alignment handle_dar_dsisr=1
232 prepare_transfer_to_handler
233 bl alignment_exception
237 /* 0x0700 - Program Exception */
238 START_EXCEPTION(0x0700, ProgramCheck)
239 EXCEPTION_PROLOG 0x700 ProgramCheck handle_dar_dsisr=1
240 prepare_transfer_to_handler
241 bl program_check_exception
245 EXCEPTION(0x0800, Trap_08, unknown_exception)
246 EXCEPTION(0x0900, Trap_09, unknown_exception)
247 EXCEPTION(0x0A00, Trap_0A, unknown_exception)
248 EXCEPTION(0x0B00, Trap_0B, unknown_exception)
250 /* 0x0C00 - System Call Exception */
251 START_EXCEPTION(0x0C00, SystemCall)
253 /* Trap_0D is commented out to get more space for system call exception */
255 /* EXCEPTION(0x0D00, Trap_0D, unknown_exception) */
256 EXCEPTION(0x0E00, Trap_0E, unknown_exception)
257 EXCEPTION(0x0F00, Trap_0F, unknown_exception)
259 /* 0x1000 - Programmable Interval Timer (PIT) Exception */
260 START_EXCEPTION(0x1000, DecrementerTrap)
263 /* 0x1010 - Fixed Interval Timer (FIT) Exception */
264 START_EXCEPTION(0x1010, FITExceptionTrap)
267 /* 0x1020 - Watchdog Timer (WDT) Exception */
268 START_EXCEPTION(0x1020, WDTExceptionTrap)
271 /* 0x1100 - Data TLB Miss Exception
272 * As the name implies, translation is not in the MMU, so search the
273 * page tables and fix it. The only purpose of this function is to
274 * load TLB entries from the page table if they exist.
276 START_EXCEPTION(0x1100, DTLBMiss)
277 mtspr SPRN_SPRG_SCRATCH5, r10 /* Save some working registers */
278 mtspr SPRN_SPRG_SCRATCH6, r11
279 mtspr SPRN_SPRG_SCRATCH3, r12
280 mtspr SPRN_SPRG_SCRATCH4, r9
283 rlwimi r12, r9, 0, 0xff
284 mfspr r10, SPRN_DEAR /* Get faulting address */
286 /* If we are faulting a kernel address, we have to use the
287 * kernel page tables.
289 lis r11, PAGE_OFFSET@h
292 lis r11, swapper_pg_dir@h
293 ori r11, r11, swapper_pg_dir@l
295 mtspr SPRN_PID, r9 /* TLB will have 0 TID */
298 /* Get the PGD for the current thread.
301 mfspr r11,SPRN_SPRG_THREAD
303 #ifdef CONFIG_PPC_KUAP
304 rlwinm. r9, r9, 0, 0xff
305 beq 5f /* Kuap fault */
309 rlwimi r11, r10, 12, 20, 29 /* Create L1 (pgdir/pmd) address */
310 lwz r11, 0(r11) /* Get L1 entry */
311 andi. r9, r11, _PMD_PRESENT /* Check if it points to a PTE page */
312 beq 2f /* Bail if no table */
314 rlwimi r11, r10, 22, 20, 29 /* Compute PTE address */
315 lwz r11, 0(r11) /* Get Linux PTE */
316 li r9, _PAGE_PRESENT | _PAGE_ACCESSED
317 andc. r9, r9, r11 /* Check permission */
320 rlwinm r9, r11, 1, _PAGE_RW /* dirty => rw */
321 and r9, r9, r11 /* hwwrite = dirty & rw */
322 rlwimi r11, r9, 0, _PAGE_RW /* replace rw by hwwrite */
324 /* Create TLB tag. This is the faulting address plus a static
325 * set of bits. These are size, valid, E, U0.
328 rlwimi r10, r9, 0, 20, 31
332 2: /* Check for possible large-page pmd entry */
333 rlwinm. r9, r11, 2, 22, 24
336 /* Create TLB tag. This is the faulting address, plus a static
337 * set of bits (valid, E, U0) plus the size from the PMD.
340 rlwimi r10, r9, 0, 20, 31
345 /* The bailout. Restore registers to pre-exception conditions
346 * and call the heavyweights to help us out.
350 mfspr r9, SPRN_SPRG_SCRATCH4
351 mfspr r12, SPRN_SPRG_SCRATCH3
352 mfspr r11, SPRN_SPRG_SCRATCH6
353 mfspr r10, SPRN_SPRG_SCRATCH5
356 /* 0x1200 - Instruction TLB Miss Exception
357 * Nearly the same as above, except we get our information from different
358 * registers and bailout to a different point.
360 START_EXCEPTION(0x1200, ITLBMiss)
361 mtspr SPRN_SPRG_SCRATCH5, r10 /* Save some working registers */
362 mtspr SPRN_SPRG_SCRATCH6, r11
363 mtspr SPRN_SPRG_SCRATCH3, r12
364 mtspr SPRN_SPRG_SCRATCH4, r9
367 rlwimi r12, r9, 0, 0xff
368 mfspr r10, SPRN_SRR0 /* Get faulting address */
370 /* If we are faulting a kernel address, we have to use the
371 * kernel page tables.
373 lis r11, PAGE_OFFSET@h
376 lis r11, swapper_pg_dir@h
377 ori r11, r11, swapper_pg_dir@l
379 mtspr SPRN_PID, r9 /* TLB will have 0 TID */
382 /* Get the PGD for the current thread.
385 mfspr r11,SPRN_SPRG_THREAD
387 #ifdef CONFIG_PPC_KUAP
388 rlwinm. r9, r9, 0, 0xff
389 beq 5f /* Kuap fault */
393 rlwimi r11, r10, 12, 20, 29 /* Create L1 (pgdir/pmd) address */
394 lwz r11, 0(r11) /* Get L1 entry */
395 andi. r9, r11, _PMD_PRESENT /* Check if it points to a PTE page */
396 beq 2f /* Bail if no table */
398 rlwimi r11, r10, 22, 20, 29 /* Compute PTE address */
399 lwz r11, 0(r11) /* Get Linux PTE */
400 li r9, _PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_EXEC
401 andc. r9, r9, r11 /* Check permission */
404 rlwinm r9, r11, 1, _PAGE_RW /* dirty => rw */
405 and r9, r9, r11 /* hwwrite = dirty & rw */
406 rlwimi r11, r9, 0, _PAGE_RW /* replace rw by hwwrite */
408 /* Create TLB tag. This is the faulting address plus a static
409 * set of bits. These are size, valid, E, U0.
412 rlwimi r10, r9, 0, 20, 31
416 2: /* Check for possible large-page pmd entry */
417 rlwinm. r9, r11, 2, 22, 24
420 /* Create TLB tag. This is the faulting address, plus a static
421 * set of bits (valid, E, U0) plus the size from the PMD.
424 rlwimi r10, r9, 0, 20, 31
429 /* The bailout. Restore registers to pre-exception conditions
430 * and call the heavyweights to help us out.
434 mfspr r9, SPRN_SPRG_SCRATCH4
435 mfspr r12, SPRN_SPRG_SCRATCH3
436 mfspr r11, SPRN_SPRG_SCRATCH6
437 mfspr r10, SPRN_SPRG_SCRATCH5
440 EXCEPTION(0x1300, Trap_13, unknown_exception)
441 EXCEPTION(0x1400, Trap_14, unknown_exception)
442 EXCEPTION(0x1500, Trap_15, unknown_exception)
443 EXCEPTION(0x1600, Trap_16, unknown_exception)
444 EXCEPTION(0x1700, Trap_17, unknown_exception)
445 EXCEPTION(0x1800, Trap_18, unknown_exception)
446 EXCEPTION(0x1900, Trap_19, unknown_exception)
447 EXCEPTION(0x1A00, Trap_1A, unknown_exception)
448 EXCEPTION(0x1B00, Trap_1B, unknown_exception)
449 EXCEPTION(0x1C00, Trap_1C, unknown_exception)
450 EXCEPTION(0x1D00, Trap_1D, unknown_exception)
451 EXCEPTION(0x1E00, Trap_1E, unknown_exception)
452 EXCEPTION(0x1F00, Trap_1F, unknown_exception)
454 /* Check for a single step debug exception while in an exception
455 * handler before state has been saved. This is to catch the case
456 * where an instruction that we are trying to single step causes
457 * an exception (eg ITLB/DTLB miss) and thus the first instruction of
458 * the exception handler generates a single step debug exception.
460 * If we get a debug trap on the first instruction of an exception handler,
461 * we reset the MSR_DE in the _exception handler's_ MSR (the debug trap is
462 * a critical exception, so we are using SPRN_CSRR1 to manipulate the MSR).
463 * The exception handler was handling a non-critical interrupt, so it will
464 * save (and later restore) the MSR via SPRN_SRR1, which will still have
465 * the MSR_DE bit set.
467 /* 0x2000 - Debug Exception */
468 START_EXCEPTION(0x2000, DebugTrap)
469 CRITICAL_EXCEPTION_PROLOG 0x2000 DebugTrap
472 * If this is a single step or branch-taken exception in an
473 * exception entry sequence, it was probably meant to apply to
474 * the code where the exception occurred (since exception entry
475 * doesn't turn off DE automatically). We simulate the effect
476 * of turning off DE on entry to an exception handler by turning
477 * off DE in the SRR3 value and clearing the debug status.
479 mfspr r10,SPRN_DBSR /* check single-step/branch taken */
480 andis. r10,r10,DBSR_IC@h
483 andi. r10,r9,MSR_IR|MSR_PR /* check supervisor + MMU off */
484 beq 1f /* branch and fix it up */
486 mfspr r10,SPRN_SRR2 /* Faulting instruction address */
488 bgt+ 2f /* address above exception vectors */
490 /* here it looks like we got an inappropriate debug exception. */
491 1: rlwinm r9,r9,0,~MSR_DE /* clear DE in the SRR3 value */
492 lis r10,DBSR_IC@h /* clear the IC event */
494 /* restore state and get out */
503 lwz r10,crit_r10@l(0)
504 lwz r11,crit_r11@l(0)
508 /* continue normal handling for a critical exception... */
509 2: mfspr r4,SPRN_DBSR
510 stw r4,_ESR(r11) /* DebugException takes DBSR in _ESR */
511 prepare_transfer_to_handler
515 /* Programmable Interval Timer (PIT) Exception. (from 0x1000) */
518 EXCEPTION_PROLOG 0x1000 Decrementer
520 mtspr SPRN_TSR,r0 /* Clear the PIT exception */
521 prepare_transfer_to_handler
525 /* Fixed Interval Timer (FIT) Exception. (from 0x1010) */
528 EXCEPTION_PROLOG 0x1010 FITException
529 prepare_transfer_to_handler
533 /* Watchdog Timer (WDT) Exception. (from 0x1020) */
536 CRITICAL_EXCEPTION_PROLOG 0x1020 WDTException
537 prepare_transfer_to_handler
541 /* Other PowerPC processors, namely those derived from the 6xx-series
542 * have vectors from 0x2100 through 0x2F00 defined, but marked as reserved.
543 * However, for the 4xx-series processors these are neither defined nor
548 /* Damn, I came up one instruction too many to fit into the
549 * exception space :-). Both the instruction and data TLB
550 * miss get to this point to load the TLB.
551 * r10 - TLB_TAG value
553 * r9 - available to use
554 * PID - loaded with proper value when we get here
555 * Upon exit, we reload everything and RFI.
556 * Actually, it will fit now, but oh well.....a common place
563 * Clear out the software-only bits in the PTE to generate the
564 * TLB_DATA value. These are the bottom 2 bits of the RPM, the
565 * top 3 bits of the zone field, and M.
570 /* load the next available TLB index. */
571 lwz r9, tlb_4xx_index@l(0)
573 andi. r9, r9, PPC40X_TLB_SIZE - 1
574 stw r9, tlb_4xx_index@l(0)
576 tlbwe r11, r9, TLB_DATA /* Load TLB LO */
577 tlbwe r10, r9, TLB_TAG /* Load TLB HI */
579 /* Done...restore registers and get out of here.
583 mfspr r9, SPRN_SPRG_SCRATCH4
584 mfspr r12, SPRN_SPRG_SCRATCH3
585 mfspr r11, SPRN_SPRG_SCRATCH6
586 mfspr r10, SPRN_SPRG_SCRATCH5
587 rfi /* Should sync shadow TLBs */
588 b . /* prevent prefetch past rfi */
590 /* This is where the main kernel code starts.
596 ori r2,r2,init_task@l
598 /* ptr to phys current thread */
600 addi r4,r4,THREAD /* init task's THREAD */
601 mtspr SPRN_SPRG_THREAD,r4
604 lis r1,init_thread_union@ha
605 addi r1,r1,init_thread_union@l
607 stwu r0,THREAD_SIZE-STACK_FRAME_MIN_SIZE(r1)
609 bl early_init /* We have to do this with MMU on */
612 * Decide what sort of machine this is and initialize the MMU.
622 /* Go back to running unmapped so we can load up new values
623 * and change to using our exception vectors.
624 * On the 4xx, all we have to do is invalidate the TLB to clear
625 * the old 16M byte TLB mappings.
630 lis r3,(MSR_KERNEL & ~(MSR_IR|MSR_DR))@h
631 ori r3,r3,(MSR_KERNEL & ~(MSR_IR|MSR_DR))@l
635 b . /* prevent prefetch past rfi */
637 /* Load up the kernel context */
639 sync /* Flush to memory before changing TLB */
641 isync /* Flush shadow TLBs */
643 /* set up the PTE pointers for the Abatron bdiGDB.
645 lis r6, swapper_pg_dir@h
646 ori r6, r6, swapper_pg_dir@l
647 lis r5, abatron_pteptrs@h
648 ori r5, r5, abatron_pteptrs@l
649 stw r5, 0xf0(0) /* Must match your Abatron config file */
653 /* Now turn on the MMU for real! */
655 ori r4,r4,MSR_KERNEL@l
656 lis r3,start_kernel@h
657 ori r3,r3,start_kernel@l
660 rfi /* enable MMU and jump to start_kernel */
661 b . /* prevent prefetch past rfi */
663 /* Set up the initial MMU state so we can do the first level of
664 * kernel initialization. This maps the first 32 MBytes of memory 1:1
665 * virtual to physical and more importantly sets the cache mode.
667 SYM_FUNC_START_LOCAL(initial_mmu)
668 tlbia /* Invalidate all TLB entries */
671 /* We should still be executing code at physical address 0x0000xxxx
672 * at this point. However, start_here is at virtual address
673 * 0xC000xxxx. So, set up a TLB mapping to cover this once
674 * translation is enabled.
677 lis r3,KERNELBASE@h /* Load the kernel virtual address */
678 ori r3,r3,KERNELBASE@l
679 tophys(r4,r3) /* Load the kernel physical address */
681 iccci r0,r3 /* Invalidate the i-cache before use */
683 /* Load the kernel PID.
689 /* Configure and load one entry into TLB slots 63 */
690 clrrwi r4,r4,10 /* Mask off the real page number */
691 ori r4,r4,(TLB_WR | TLB_EX) /* Set the write and execute bits */
693 clrrwi r3,r3,10 /* Mask off the effective page number */
694 ori r3,r3,(TLB_VALID | TLB_PAGESZ(PAGESZ_16M))
696 li r0,63 /* TLB slot 63 */
698 tlbwe r4,r0,TLB_DATA /* Load the data portion of the entry */
699 tlbwe r3,r0,TLB_TAG /* Load the tag portion of the entry */
701 li r0,62 /* TLB slot 62 */
704 tlbwe r4,r0,TLB_DATA /* Load the data portion of the entry */
705 tlbwe r3,r0,TLB_TAG /* Load the tag portion of the entry */
709 /* Establish the exception vector base
711 lis r4,KERNELBASE@h /* EVPR only uses the high 16-bits */
712 tophys(r0,r4) /* Use the physical address */
716 SYM_FUNC_END(initial_mmu)
720 oris r13,r13,DBCR0_RST_SYSTEM@h