3 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
4 * Rewritten by Cort Dougan (cort@fsmlabs.com) for PReP
5 * Copyright (C) 1996 Cort Dougan <cort@fsmlabs.com>
6 * Adapted for Power Macintosh by Paul Mackerras.
7 * Low-level exception handlers and MMU support
8 * rewritten by Paul Mackerras.
9 * Copyright (C) 1996 Paul Mackerras.
10 * MPC8xx modifications Copyright (C) 1997 Dan Malek (dmalek@jlc.net).
12 * This file contains the system call entry code, context switch
13 * code, and exception/interrupt return code for PowerPC.
15 * This program is free software; you can redistribute it and/or
16 * modify it under the terms of the GNU General Public License
17 * as published by the Free Software Foundation; either version
18 * 2 of the License, or (at your option) any later version.
22 #include <linux/errno.h>
23 #include <linux/sys.h>
24 #include <linux/threads.h>
25 #include <asm/processor.h>
28 #include <asm/cputable.h>
29 #include <asm/thread_info.h>
30 #include <asm/ppc_asm.h>
31 #include <asm/asm-offsets.h>
32 #include <asm/unistd.h>
35 #undef SHOW_SYSCALLS_TASK
38 * MSR_KERNEL is > 0x10000 on 4xx/Book-E since it include MSR_CE.
40 #if MSR_KERNEL >= 0x10000
41 #define LOAD_MSR_KERNEL(r, x) lis r,(x)@h; ori r,r,(x)@l
43 #define LOAD_MSR_KERNEL(r, x) li r,(x)
47 #include "head_booke.h"
48 #define TRANSFER_TO_HANDLER_EXC_LEVEL(exc_level) \
49 mtspr exc_level##_SPRG,r8; \
50 BOOKE_LOAD_EXC_LEVEL_STACK(exc_level); \
51 lwz r0,GPR10-INT_FRAME_SIZE(r8); \
53 lwz r0,GPR11-INT_FRAME_SIZE(r8); \
55 mfspr r8,exc_level##_SPRG
57 .globl mcheck_transfer_to_handler
58 mcheck_transfer_to_handler:
59 TRANSFER_TO_HANDLER_EXC_LEVEL(MCHECK)
60 b transfer_to_handler_full
62 .globl debug_transfer_to_handler
63 debug_transfer_to_handler:
64 TRANSFER_TO_HANDLER_EXC_LEVEL(DEBUG)
65 b transfer_to_handler_full
67 .globl crit_transfer_to_handler
68 crit_transfer_to_handler:
69 TRANSFER_TO_HANDLER_EXC_LEVEL(CRIT)
74 .globl crit_transfer_to_handler
75 crit_transfer_to_handler:
84 * This code finishes saving the registers to the exception frame
85 * and jumps to the appropriate handler for the exception, turning
86 * on address translation.
87 * Note that we rely on the caller having set cr0.eq iff the exception
88 * occurred in kernel mode (i.e. MSR:PR = 0).
90 .globl transfer_to_handler_full
91 transfer_to_handler_full:
95 .globl transfer_to_handler
107 tovirt(r2,r2) /* set r2 to current */
108 beq 2f /* if from user, fix up THREAD.regs */
109 addi r11,r1,STACK_FRAME_OVERHEAD
111 #if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
112 /* Check to see if the dbcr0 register is set up to debug. Use the
113 single-step bit to do this. */
114 lwz r12,THREAD_DBCR0(r12)
115 andis. r12,r12,DBCR0_IC@h
117 /* From user and task is ptraced - load up global dbcr0 */
118 li r12,-1 /* clear all pending debug events */
120 lis r11,global_dbcr0@ha
122 addi r11,r11,global_dbcr0@l
131 2: /* if from kernel, check interrupted DOZE/NAP mode and
132 * check for stack overflow
134 lwz r9,THREAD_INFO-THREAD(r12)
135 cmplw r1,r9 /* if r1 <= current->thread_info */
136 ble- stack_ovf /* then the kernel stack overflowed */
139 tophys(r9,r9) /* check local flags */
140 lwz r12,TI_LOCAL_FLAGS(r9)
142 bt- 31-TLF_NAPPING,4f
143 #endif /* CONFIG_6xx */
144 .globl transfer_to_handler_cont
145 transfer_to_handler_cont:
148 lwz r11,0(r9) /* virtual address of handler */
149 lwz r9,4(r9) /* where to go when done */
154 RFI /* jump to handler, enable MMU */
157 4: rlwinm r12,r12,0,~_TLF_NAPPING
158 stw r12,TI_LOCAL_FLAGS(r9)
159 b power_save_6xx_restore
163 * On kernel stack overflow, load up an initial stack pointer
164 * and call StackOverflow(regs), which should not return.
167 /* sometimes we use a statically-allocated stack, which is OK. */
171 ble 5b /* r1 <= &_end is OK */
173 addi r3,r1,STACK_FRAME_OVERHEAD
174 lis r1,init_thread_union@ha
175 addi r1,r1,init_thread_union@l
176 addi r1,r1,THREAD_SIZE-STACK_FRAME_OVERHEAD
177 lis r9,StackOverflow@ha
178 addi r9,r9,StackOverflow@l
179 LOAD_MSR_KERNEL(r10,MSR_KERNEL)
187 * Handle a system call.
189 .stabs "arch/ppc/kernel/",N_SO,0,0,0f
190 .stabs "entry.S",N_SO,0,0,0f
197 lwz r11,_CCR(r1) /* Clear SO bit in CR */
202 #endif /* SHOW_SYSCALLS */
203 rlwinm r10,r1,0,0,18 /* current_thread_info() */
204 lwz r11,TI_FLAGS(r10)
205 andi. r11,r11,_TIF_SYSCALL_T_OR_A
207 syscall_dotrace_cont:
208 cmplwi 0,r0,NR_syscalls
209 lis r10,sys_call_table@h
210 ori r10,r10,sys_call_table@l
213 lwzx r10,r10,r0 /* Fetch system call handler [ptr] */
215 addi r9,r1,STACK_FRAME_OVERHEAD
217 blrl /* Call handler */
218 .globl ret_from_syscall
221 bl do_show_syscall_exit
224 rlwinm r12,r1,0,0,18 /* current_thread_info() */
225 /* disable interrupts so current_thread_info()->flags can't change */
226 LOAD_MSR_KERNEL(r10,MSR_KERNEL) /* doesn't include MSR_EE */
231 andi. r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK)
232 bne- syscall_exit_work
234 blt+ syscall_exit_cont
235 lwz r11,_CCR(r1) /* Load CR */
237 oris r11,r11,0x1000 /* Set SO bit in CR */
240 #if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
241 /* If the process has its own DBCR0 value, load it up. The single
242 step bit tells us that dbcr0 should be loaded. */
243 lwz r0,THREAD+THREAD_DBCR0(r2)
244 andis. r10,r0,DBCR0_IC@h
247 stwcx. r0,0,r1 /* to clear the reservation */
272 /* Traced system call support */
277 addi r3,r1,STACK_FRAME_OVERHEAD
278 bl do_syscall_trace_enter
279 lwz r0,GPR0(r1) /* Restore original registers */
287 b syscall_dotrace_cont
290 andi. r0,r9,_TIF_RESTOREALL
296 andi. r0,r9,_TIF_NOERROR
298 lwz r11,_CCR(r1) /* Load CR */
300 oris r11,r11,0x1000 /* Set SO bit in CR */
303 1: stw r6,RESULT(r1) /* Save result */
304 stw r3,GPR3(r1) /* Update return value */
305 2: andi. r0,r9,(_TIF_PERSYSCALL_MASK)
308 /* Clear per-syscall TIF flags if any are set. */
310 li r11,_TIF_PERSYSCALL_MASK
311 addi r12,r12,TI_FLAGS
314 #ifdef CONFIG_IBM405_ERR77
319 subi r12,r12,TI_FLAGS
321 4: /* Anything which requires enabling interrupts? */
322 andi. r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP)
325 /* Re-enable interrupts */
330 /* Save NVGPRS if they're not saved already */
338 addi r3,r1,STACK_FRAME_OVERHEAD
339 bl do_syscall_trace_leave
340 b ret_from_except_full
344 #ifdef SHOW_SYSCALLS_TASK
345 lis r11,show_syscalls_task@ha
346 lwz r11,show_syscalls_task@l(r11)
377 do_show_syscall_exit:
378 #ifdef SHOW_SYSCALLS_TASK
379 lis r11,show_syscalls_task@ha
380 lwz r11,show_syscalls_task@l(r11)
386 stw r3,RESULT(r1) /* Save result */
396 7: .string "syscall %d(%x, %x, %x, %x, %x, "
397 77: .string "%x), current=%p\n"
398 79: .string " -> %x\n"
401 #ifdef SHOW_SYSCALLS_TASK
403 .globl show_syscalls_task
408 #endif /* SHOW_SYSCALLS */
411 * The fork/clone functions need to copy the full register set into
412 * the child process. Therefore we need to save all the nonvolatile
413 * registers (r13 - r31) before calling the C code.
419 rlwinm r0,r0,0,0,30 /* clear LSB to indicate full */
420 stw r0,TRAP(r1) /* register set saved */
427 rlwinm r0,r0,0,0,30 /* clear LSB to indicate full */
428 stw r0,TRAP(r1) /* register set saved */
435 rlwinm r0,r0,0,0,30 /* clear LSB to indicate full */
436 stw r0,TRAP(r1) /* register set saved */
439 .globl ppc_swapcontext
443 rlwinm r0,r0,0,0,30 /* clear LSB to indicate full */
444 stw r0,TRAP(r1) /* register set saved */
448 * Top-level page fault handling.
449 * This is in assembler because if do_page_fault tells us that
450 * it is a bad kernel page fault, we want to save the non-volatile
451 * registers before calling bad_page_fault.
453 .globl handle_page_fault
456 addi r3,r1,STACK_FRAME_OVERHEAD
465 addi r3,r1,STACK_FRAME_OVERHEAD
468 b ret_from_except_full
471 * This routine switches between two different tasks. The process
472 * state of one is saved on its kernel stack. Then the state
473 * of the other is restored from its kernel stack. The memory
474 * management hardware is updated to the second process's state.
475 * Finally, we can return to the second process.
476 * On entry, r3 points to the THREAD for the current task, r4
477 * points to the THREAD for the new task.
479 * This routine is always called with interrupts disabled.
481 * Note: there are two ways to get to the "going out" portion
482 * of this code; either by coming in via the entry (_switch)
483 * or via "fork" which must set up an environment equivalent
484 * to the "_switch" path. If you change this , you'll have to
485 * change the fork code also.
487 * The code which creates the new task context is in 'copy_thread'
488 * in arch/ppc/kernel/process.c
491 stwu r1,-INT_FRAME_SIZE(r1)
493 stw r0,INT_FRAME_SIZE+4(r1)
494 /* r3-r12 are caller saved -- Cort */
496 stw r0,_NIP(r1) /* Return to switch caller */
498 li r0,MSR_FP /* Disable floating-point */
499 #ifdef CONFIG_ALTIVEC
501 oris r0,r0,MSR_VEC@h /* Disable altivec */
502 mfspr r12,SPRN_VRSAVE /* save vrsave register value */
503 stw r12,THREAD+THREAD_VRSAVE(r2)
504 END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
505 #endif /* CONFIG_ALTIVEC */
507 oris r0,r0,MSR_SPE@h /* Disable SPE */
508 mfspr r12,SPRN_SPEFSCR /* save spefscr register value */
509 stw r12,THREAD+THREAD_SPEFSCR(r2)
510 #endif /* CONFIG_SPE */
511 and. r0,r0,r11 /* FP or altivec or SPE enabled? */
519 stw r1,KSP(r3) /* Set old stack pointer */
522 /* We need a sync somewhere here to make sure that if the
523 * previous task gets rescheduled on another CPU, it sees all
524 * stores it has performed on this one.
527 #endif /* CONFIG_SMP */
531 mtspr SPRN_SPRG3,r0 /* Update current THREAD phys addr */
532 lwz r1,KSP(r4) /* Load new stack pointer */
534 /* save the old current 'last' for return value */
536 addi r2,r4,-THREAD /* Update current */
538 #ifdef CONFIG_ALTIVEC
540 lwz r0,THREAD+THREAD_VRSAVE(r2)
541 mtspr SPRN_VRSAVE,r0 /* if G4, restore VRSAVE reg */
542 END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
543 #endif /* CONFIG_ALTIVEC */
545 lwz r0,THREAD+THREAD_SPEFSCR(r2)
546 mtspr SPRN_SPEFSCR,r0 /* restore SPEFSCR reg */
547 #endif /* CONFIG_SPE */
551 /* r3-r12 are destroyed -- Cort */
554 lwz r4,_NIP(r1) /* Return to _switch caller in new task */
556 addi r1,r1,INT_FRAME_SIZE
559 .globl fast_exception_return
560 fast_exception_return:
561 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
562 andi. r10,r9,MSR_RI /* check for recoverable interrupt */
563 beq 1f /* if not, we've got problems */
566 2: REST_4GPRS(3, r11)
581 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
582 /* check if the exception happened in a restartable section */
583 1: lis r3,exc_exit_restart_end@ha
584 addi r3,r3,exc_exit_restart_end@l
587 lis r4,exc_exit_restart@ha
588 addi r4,r4,exc_exit_restart@l
591 lis r3,fee_restarts@ha
593 lwz r5,fee_restarts@l(r3)
595 stw r5,fee_restarts@l(r3)
596 mr r12,r4 /* restart at exc_exit_restart */
605 /* aargh, a nonrecoverable interrupt, panic */
606 /* aargh, we don't know which trap this is */
607 /* but the 601 doesn't implement the RI bit, so assume it's OK */
611 END_FTR_SECTION_IFSET(CPU_FTR_601)
614 addi r3,r1,STACK_FRAME_OVERHEAD
616 ori r10,r10,MSR_KERNEL@l
617 bl transfer_to_handler_full
618 .long nonrecoverable_exception
619 .long ret_from_except
622 .globl ret_from_except_full
623 ret_from_except_full:
627 .globl ret_from_except
629 /* Hard-disable interrupts so that current_thread_info()->flags
630 * can't change between when we test it and when we return
631 * from the interrupt. */
632 LOAD_MSR_KERNEL(r10,MSR_KERNEL)
633 SYNC /* Some chip revs have problems here... */
634 MTMSRD(r10) /* disable interrupts */
636 lwz r3,_MSR(r1) /* Returning to user mode? */
640 user_exc_return: /* r10 contains MSR_KERNEL here */
641 /* Check current_thread_info()->flags */
644 andi. r0,r9,(_TIF_SIGPENDING|_TIF_RESTORE_SIGMASK|_TIF_NEED_RESCHED)
648 #if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
649 /* Check whether this process has its own DBCR0 value. The single
650 step bit tells us that dbcr0 should be loaded. */
651 lwz r0,THREAD+THREAD_DBCR0(r2)
652 andis. r10,r0,DBCR0_IC@h
656 #ifdef CONFIG_PREEMPT
659 /* N.B. the only way to get here is from the beq following ret_from_except. */
661 /* check current_thread_info->preempt_count */
663 lwz r0,TI_PREEMPT(r9)
664 cmpwi 0,r0,0 /* if non-zero, just restore regs and return */
667 andi. r0,r0,_TIF_NEED_RESCHED
669 andi. r0,r3,MSR_EE /* interrupts off? */
670 beq restore /* don't schedule if so */
671 1: bl preempt_schedule_irq
674 andi. r0,r3,_TIF_NEED_RESCHED
678 #endif /* CONFIG_PREEMPT */
680 /* interrupts are hard-disabled at this point */
693 stwcx. r0,0,r1 /* to clear the reservation */
695 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
697 andi. r10,r9,MSR_RI /* check if this exception occurred */
698 beql nonrecoverable /* at a bad place (MSR:RI = 0) */
706 * Once we put values in SRR0 and SRR1, we are in a state
707 * where exceptions are not recoverable, since taking an
708 * exception will trash SRR0 and SRR1. Therefore we clear the
709 * MSR:RI bit to indicate this. If we do take an exception,
710 * we can't return to the point of the exception but we
711 * can restart the exception exit path at the label
712 * exc_exit_restart below. -- paulus
714 LOAD_MSR_KERNEL(r10,MSR_KERNEL & ~MSR_RI)
716 MTMSRD(r10) /* clear the RI bit */
717 .globl exc_exit_restart
726 .globl exc_exit_restart_end
727 exc_exit_restart_end:
731 #else /* !(CONFIG_4xx || CONFIG_BOOKE) */
733 * This is a bit different on 4xx/Book-E because it doesn't have
734 * the RI bit in the MSR.
735 * The TLB miss handler checks if we have interrupted
736 * the exception exit path and restarts it if so
737 * (well maybe one day it will... :).
744 .globl exc_exit_restart
753 .globl exc_exit_restart_end
754 exc_exit_restart_end:
757 b . /* prevent prefetch past rfi */
760 * Returning from a critical interrupt in user mode doesn't need
761 * to be any different from a normal exception. For a critical
762 * interrupt in the kernel, we just return (without checking for
763 * preemption) since the interrupt may have happened at some crucial
764 * place (e.g. inside the TLB miss handler), and because we will be
765 * running with r1 pointing into critical_stack, not the current
766 * process's kernel stack (and therefore current_thread_info() will
767 * give the wrong answer).
768 * We have to restore various SPRs that may have been in use at the
769 * time of the critical interrupt.
773 #define PPC_40x_TURN_OFF_MSR_DR \
774 /* avoid any possible TLB misses here by turning off MSR.DR, we \
775 * assume the instructions here are mapped by a pinned TLB entry */ \
781 #define PPC_40x_TURN_OFF_MSR_DR
784 #define RET_FROM_EXC_LEVEL(exc_lvl_srr0, exc_lvl_srr1, exc_lvl_rfi) \
787 andi. r3,r3,MSR_PR; \
788 LOAD_MSR_KERNEL(r10,MSR_KERNEL); \
789 bne user_exc_return; \
796 mtspr SPRN_XER,r10; \
798 PPC405_ERR77(0,r1); \
799 stwcx. r0,0,r1; /* to clear the reservation */ \
804 PPC_40x_TURN_OFF_MSR_DR; \
807 mtspr SPRN_DEAR,r9; \
808 mtspr SPRN_ESR,r10; \
811 mtspr exc_lvl_srr0,r11; \
812 mtspr exc_lvl_srr1,r12; \
820 b .; /* prevent prefetch past exc_lvl_rfi */
822 .globl ret_from_crit_exc
824 RET_FROM_EXC_LEVEL(SPRN_CSRR0, SPRN_CSRR1, RFCI)
827 .globl ret_from_debug_exc
829 RET_FROM_EXC_LEVEL(SPRN_DSRR0, SPRN_DSRR1, RFDI)
831 .globl ret_from_mcheck_exc
833 RET_FROM_EXC_LEVEL(SPRN_MCSRR0, SPRN_MCSRR1, RFMCI)
834 #endif /* CONFIG_BOOKE */
837 * Load the DBCR0 value for a task that is being ptraced,
838 * having first saved away the global DBCR0. Note that r0
839 * has the dbcr0 value to set upon entry to this.
842 mfmsr r10 /* first disable debug exceptions */
843 rlwinm r10,r10,0,~MSR_DE
847 lis r11,global_dbcr0@ha
848 addi r11,r11,global_dbcr0@l
855 mtspr SPRN_DBSR,r11 /* clear all pending debug events */
863 #endif /* !(CONFIG_4xx || CONFIG_BOOKE) */
865 do_work: /* r10 contains MSR_KERNEL here */
866 andi. r0,r9,_TIF_NEED_RESCHED
869 do_resched: /* r10 contains MSR_KERNEL here */
872 MTMSRD(r10) /* hard-enable interrupts */
875 LOAD_MSR_KERNEL(r10,MSR_KERNEL)
877 MTMSRD(r10) /* disable interrupts */
880 andi. r0,r9,_TIF_NEED_RESCHED
882 andi. r0,r9,_TIF_SIGPENDING
884 do_user_signal: /* r10 contains MSR_KERNEL here */
887 MTMSRD(r10) /* hard-enable interrupts */
888 /* save r13-r31 in the exception frame, if not already done */
896 addi r4,r1,STACK_FRAME_OVERHEAD
902 * We come here when we are at the end of handling an exception
903 * that occurred at a place where taking an exception will lose
904 * state information, such as the contents of SRR0 and SRR1.
907 lis r10,exc_exit_restart_end@ha
908 addi r10,r10,exc_exit_restart_end@l
911 lis r11,exc_exit_restart@ha
912 addi r11,r11,exc_exit_restart@l
915 lis r10,ee_restarts@ha
916 lwz r12,ee_restarts@l(r10)
918 stw r12,ee_restarts@l(r10)
919 mr r12,r11 /* restart at exc_exit_restart */
921 3: /* OK, we can't recover, kill this process */
922 /* but the 601 doesn't implement the RI bit, so assume it's OK */
925 END_FTR_SECTION_IFSET(CPU_FTR_601)
932 4: addi r3,r1,STACK_FRAME_OVERHEAD
933 bl nonrecoverable_exception
934 /* shouldn't return */