4 * Linux architectural port borrowing liberally from similar works of
5 * others. All original copyrights apply as per the original source
8 * Modifications for the OpenRISC architecture:
9 * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
10 * Copyright (C) 2005 Gyorgy Jeney <nog@bsemi.com>
11 * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
13 * This program is free software; you can redistribute it and/or
14 * modify it under the terms of the GNU General Public License
15 * as published by the Free Software Foundation; either version
16 * 2 of the License, or (at your option) any later version.
19 #include <linux/linkage.h>
21 #include <asm/processor.h>
22 #include <asm/unistd.h>
23 #include <asm/thread_info.h>
24 #include <asm/errno.h>
25 #include <asm/spr_defs.h>
28 #include <asm/pgtable.h>
29 #include <asm/asm-offsets.h>
31 #define DISABLE_INTERRUPTS(t1,t2) \
32 l.mfspr t2,r0,SPR_SR ;\
33 l.movhi t1,hi(~(SPR_SR_IEE|SPR_SR_TEE)) ;\
34 l.ori t1,t1,lo(~(SPR_SR_IEE|SPR_SR_TEE)) ;\
38 #define ENABLE_INTERRUPTS(t1) \
39 l.mfspr t1,r0,SPR_SR ;\
40 l.ori t1,t1,lo(SPR_SR_IEE|SPR_SR_TEE) ;\
43 /* =========================================================[ macros ]=== */
46 * We need to disable interrupts at beginning of RESTORE_ALL
47 * since interrupt might come in after we've loaded EPC return address
48 * and overwrite EPC with address somewhere in RESTORE_ALL
49 * which is of course wrong!
53 DISABLE_INTERRUPTS(r3,r4) ;\
55 l.mtspr r0,r3,SPR_EPCR_BASE ;\
57 l.mtspr r0,r3,SPR_ESR_BASE ;\
58 l.lwz r2,PT_GPR2(r1) ;\
59 l.lwz r3,PT_GPR3(r1) ;\
60 l.lwz r4,PT_GPR4(r1) ;\
61 l.lwz r5,PT_GPR5(r1) ;\
62 l.lwz r6,PT_GPR6(r1) ;\
63 l.lwz r7,PT_GPR7(r1) ;\
64 l.lwz r8,PT_GPR8(r1) ;\
65 l.lwz r9,PT_GPR9(r1) ;\
66 l.lwz r10,PT_GPR10(r1) ;\
67 l.lwz r11,PT_GPR11(r1) ;\
68 l.lwz r12,PT_GPR12(r1) ;\
69 l.lwz r13,PT_GPR13(r1) ;\
70 l.lwz r14,PT_GPR14(r1) ;\
71 l.lwz r15,PT_GPR15(r1) ;\
72 l.lwz r16,PT_GPR16(r1) ;\
73 l.lwz r17,PT_GPR17(r1) ;\
74 l.lwz r18,PT_GPR18(r1) ;\
75 l.lwz r19,PT_GPR19(r1) ;\
76 l.lwz r20,PT_GPR20(r1) ;\
77 l.lwz r21,PT_GPR21(r1) ;\
78 l.lwz r22,PT_GPR22(r1) ;\
79 l.lwz r23,PT_GPR23(r1) ;\
80 l.lwz r24,PT_GPR24(r1) ;\
81 l.lwz r25,PT_GPR25(r1) ;\
82 l.lwz r26,PT_GPR26(r1) ;\
83 l.lwz r27,PT_GPR27(r1) ;\
84 l.lwz r28,PT_GPR28(r1) ;\
85 l.lwz r29,PT_GPR29(r1) ;\
86 l.lwz r30,PT_GPR30(r1) ;\
87 l.lwz r31,PT_GPR31(r1) ;\
92 #define EXCEPTION_ENTRY(handler) \
95 /* r1, EPCR, ESR a already saved */ ;\
96 l.sw PT_GPR2(r1),r2 ;\
97 l.sw PT_GPR3(r1),r3 ;\
98 /* r4 already save */ ;\
99 l.sw PT_GPR5(r1),r5 ;\
100 l.sw PT_GPR6(r1),r6 ;\
101 l.sw PT_GPR7(r1),r7 ;\
102 l.sw PT_GPR8(r1),r8 ;\
103 l.sw PT_GPR9(r1),r9 ;\
104 /* r10 already saved */ ;\
105 l.sw PT_GPR11(r1),r11 ;\
106 /* r12 already saved */ ;\
107 l.sw PT_GPR13(r1),r13 ;\
108 l.sw PT_GPR14(r1),r14 ;\
109 l.sw PT_GPR15(r1),r15 ;\
110 l.sw PT_GPR16(r1),r16 ;\
111 l.sw PT_GPR17(r1),r17 ;\
112 l.sw PT_GPR18(r1),r18 ;\
113 l.sw PT_GPR19(r1),r19 ;\
114 l.sw PT_GPR20(r1),r20 ;\
115 l.sw PT_GPR21(r1),r21 ;\
116 l.sw PT_GPR22(r1),r22 ;\
117 l.sw PT_GPR23(r1),r23 ;\
118 l.sw PT_GPR24(r1),r24 ;\
119 l.sw PT_GPR25(r1),r25 ;\
120 l.sw PT_GPR26(r1),r26 ;\
121 l.sw PT_GPR27(r1),r27 ;\
122 l.sw PT_GPR28(r1),r28 ;\
123 l.sw PT_GPR29(r1),r29 ;\
124 /* r30 already save */ ;\
125 /* l.sw PT_GPR30(r1),r30*/ ;\
126 l.sw PT_GPR31(r1),r31 ;\
127 /* Store -1 in orig_gpr11 for non-syscall exceptions */ ;\
129 l.sw PT_ORIG_GPR11(r1),r30
131 #define UNHANDLED_EXCEPTION(handler,vector) \
134 /* r1, EPCR, ESR already saved */ ;\
135 l.sw PT_GPR2(r1),r2 ;\
136 l.sw PT_GPR3(r1),r3 ;\
137 l.sw PT_GPR5(r1),r5 ;\
138 l.sw PT_GPR6(r1),r6 ;\
139 l.sw PT_GPR7(r1),r7 ;\
140 l.sw PT_GPR8(r1),r8 ;\
141 l.sw PT_GPR9(r1),r9 ;\
142 /* r10 already saved */ ;\
143 l.sw PT_GPR11(r1),r11 ;\
144 /* r12 already saved */ ;\
145 l.sw PT_GPR13(r1),r13 ;\
146 l.sw PT_GPR14(r1),r14 ;\
147 l.sw PT_GPR15(r1),r15 ;\
148 l.sw PT_GPR16(r1),r16 ;\
149 l.sw PT_GPR17(r1),r17 ;\
150 l.sw PT_GPR18(r1),r18 ;\
151 l.sw PT_GPR19(r1),r19 ;\
152 l.sw PT_GPR20(r1),r20 ;\
153 l.sw PT_GPR21(r1),r21 ;\
154 l.sw PT_GPR22(r1),r22 ;\
155 l.sw PT_GPR23(r1),r23 ;\
156 l.sw PT_GPR24(r1),r24 ;\
157 l.sw PT_GPR25(r1),r25 ;\
158 l.sw PT_GPR26(r1),r26 ;\
159 l.sw PT_GPR27(r1),r27 ;\
160 l.sw PT_GPR28(r1),r28 ;\
161 l.sw PT_GPR29(r1),r29 ;\
162 /* r31 already saved */ ;\
163 l.sw PT_GPR30(r1),r30 ;\
164 /* l.sw PT_GPR31(r1),r31 */ ;\
165 /* Store -1 in orig_gpr11 for non-syscall exceptions */ ;\
167 l.sw PT_ORIG_GPR11(r1),r30 ;\
169 /* r4 is exception EA */ ;\
170 l.addi r5,r0,vector ;\
171 l.jal unhandled_exception ;\
173 l.j _ret_from_exception ;\
177 * NOTE: one should never assume that SPR_EPC, SPR_ESR, SPR_EEAR
178 * contain the same values as when exception we're handling
179 * occured. in fact they never do. if you need them use
180 * values saved on stack (for SPR_EPC, SPR_ESR) or content
181 * of r4 (for SPR_EEAR). for details look at EXCEPTION_HANDLE()
182 * in 'arch/openrisc/kernel/head.S'
185 /* =====================================================[ exceptions] === */
187 /* ---[ 0x100: RESET exception ]----------------------------------------- */
189 EXCEPTION_ENTRY(_tng_kernel_start)
193 /* ---[ 0x200: BUS exception ]------------------------------------------- */
195 EXCEPTION_ENTRY(_bus_fault_handler)
196 /* r4: EA of fault (set by EXCEPTION_HANDLE) */
198 l.addi r3,r1,0 /* pt_regs */
200 l.j _ret_from_exception
203 /* ---[ 0x300: Data Page Fault exception ]------------------------------- */
204 EXCEPTION_ENTRY(_dtlb_miss_page_fault_handler)
209 EXCEPTION_ENTRY(_data_page_fault_handler)
210 /* set up parameters for do_page_fault */
211 l.ori r5,r0,0x300 // exception vector
213 l.addi r3,r1,0 // pt_regs
214 /* r4 set be EXCEPTION_HANDLE */ // effective address of fault
219 * all this can be written much simpler. look at
220 * DTLB miss handler in the CONFIG_GUARD_PROTECTED_CORE part
222 #ifdef CONFIG_OPENRISC_NO_SPR_SR_DSX
223 l.lwz r6,PT_PC(r3) // address of an offending insn
224 l.lwz r6,0(r6) // instruction that caused pf
226 l.srli r6,r6,26 // check opcode for jump insn
229 l.sfeqi r6,1 // l.jal
231 l.sfeqi r6,3 // l.bnf
235 l.sfeqi r6,0x11 // l.jr
237 l.sfeqi r6,0x12 // l.jalr
246 l.lwz r6,PT_PC(r3) // address of an offending insn
248 l.lwz r6,0(r6) // instruction that caused pf
249 l.srli r6,r6,26 // get opcode
254 l.mfspr r6,r0,SPR_SR // SR
255 // l.lwz r6,PT_SR(r3) // ESR
256 l.andi r6,r6,SPR_SR_DSX // check for delay slot exception
257 l.sfeqi r6,0x1 // exception happened in delay slot
259 l.lwz r6,PT_PC(r3) // address of an offending insn
261 l.addi r6,r6,4 // offending insn is in delay slot
263 l.lwz r6,0(r6) // instruction that caused pf
264 l.srli r6,r6,26 // check opcode for write access
267 l.sfgeui r6,0x34 // check opcode for write access
271 l.ori r6,r0,0x1 // write access
274 1: l.ori r6,r0,0x0 // !write access
277 /* call fault.c handler in or32/mm/fault.c */
280 l.j _ret_from_exception
283 /* ---[ 0x400: Insn Page Fault exception ]------------------------------- */
284 EXCEPTION_ENTRY(_itlb_miss_page_fault_handler)
289 EXCEPTION_ENTRY(_insn_page_fault_handler)
290 /* set up parameters for do_page_fault */
291 l.ori r5,r0,0x400 // exception vector
293 l.addi r3,r1,0 // pt_regs
294 /* r4 set be EXCEPTION_HANDLE */ // effective address of fault
295 l.ori r6,r0,0x0 // !write access
297 /* call fault.c handler in or32/mm/fault.c */
300 l.j _ret_from_exception
304 /* ---[ 0x500: Timer exception ]----------------------------------------- */
306 EXCEPTION_ENTRY(_timer_handler)
307 l.jal timer_interrupt
308 l.addi r3,r1,0 /* pt_regs */
313 /* ---[ 0x600: Aligment exception ]-------------------------------------- */
315 EXCEPTION_ENTRY(_alignment_handler)
316 /* r4: EA of fault (set by EXCEPTION_HANDLE) */
317 l.jal do_unaligned_access
318 l.addi r3,r1,0 /* pt_regs */
320 l.j _ret_from_exception
324 EXCEPTION_ENTRY(_aligment_handler)
325 // l.mfspr r2,r0,SPR_EEAR_BASE /* Load the efective addres */
327 // l.mfspr r5,r0,SPR_EPCR_BASE /* Load the insn address */
330 l.lwz r3,0(r5) /* Load insn */
331 l.srli r4,r3,26 /* Shift left to get the insn opcode */
333 l.sfeqi r4,0x00 /* Check if the load/store insn is in delay slot */
347 l.addi r5,r5,4 /* Increment PC to get return insn address */
350 l.slli r4,r3,6 /* Get the signed extended jump length */
353 l.lwz r3,4(r5) /* Load the real load/store insn */
355 l.add r5,r5,r4 /* Calculate jump target address */
358 l.srli r4,r3,26 /* Shift left to get the insn opcode */
361 l.slli r4,r3,9 /* Shift to get the reg nb */
364 l.lwz r3,4(r5) /* Load the real load/store insn */
366 l.add r4,r4,r1 /* Load the jump register value from the stack */
369 l.srli r4,r3,26 /* Shift left to get the insn opcode */
373 // l.mtspr r0,r5,SPR_EPCR_BASE
390 1: l.j 1b /* I don't know what to do */
474 /* ---[ 0x700: Illegal insn exception ]---------------------------------- */
476 EXCEPTION_ENTRY(_illegal_instruction_handler)
477 /* r4: EA of fault (set by EXCEPTION_HANDLE) */
478 l.jal do_illegal_instruction
479 l.addi r3,r1,0 /* pt_regs */
481 l.j _ret_from_exception
484 /* ---[ 0x800: External interrupt exception ]---------------------------- */
486 EXCEPTION_ENTRY(_external_irq_handler)
487 #ifdef CONFIG_OPENRISC_ESR_EXCEPTION_BUG_CHECK
488 l.lwz r4,PT_SR(r1) // were interrupts enabled ?
489 l.andi r4,r4,SPR_SR_IEE
491 l.bnf 1f // ext irq enabled, all ok.
503 .section .rodata, "a"
505 .string "\n\rESR interrupt bug: in _external_irq_handler (ESR %x)\n\r"
510 l.ori r4,r4,SPR_SR_IEE // fix the bug
515 l.movhi r8,hi(do_IRQ)
516 l.ori r8,r8,lo(do_IRQ)
522 /* ---[ 0x900: DTLB miss exception ]------------------------------------- */
525 /* ---[ 0xa00: ITLB miss exception ]------------------------------------- */
528 /* ---[ 0xb00: Range exception ]----------------------------------------- */
530 UNHANDLED_EXCEPTION(_vector_0xb00,0xb00)
532 /* ---[ 0xc00: Syscall exception ]--------------------------------------- */
535 * Syscalls are a special type of exception in that they are
536 * _explicitly_ invoked by userspace and can therefore be
537 * held to conform to the same ABI as normal functions with
538 * respect to whether registers are preserved across the call
542 /* Upon syscall entry we just save the callee-saved registers
543 * and not the call-clobbered ones.
546 _string_syscall_return:
547 .string "syscall return %ld \n\r\0"
550 ENTRY(_sys_call_handler)
551 /* syscalls run with interrupts enabled */
552 ENABLE_INTERRUPTS(r29) // enable interrupts, r29 is temp
554 /* r1, EPCR, ESR a already saved */
556 /* r3-r8 must be saved because syscall restart relies
557 * on us being able to restart the syscall args... technically
558 * they should be clobbered, otherwise
561 /* r4 already saved */
562 /* r4 holds the EEAR address of the fault, load the original r4 */
569 /* r10 already saved */
570 l.sw PT_GPR11(r1),r11
571 /* orig_gpr11 must be set for syscalls */
572 l.sw PT_ORIG_GPR11(r1),r11
573 /* r12,r13 already saved */
575 /* r14-r28 (even) aren't touched by the syscall fast path below
576 * so we don't need to save them. However, the functions that return
577 * to userspace via a call to switch() DO need to save these because
578 * switch() effectively clobbers them... saving these registers for
579 * such functions is handled in their syscall wrappers (see fork, vfork,
582 /* r30 is the only register we clobber in the fast path */
583 /* r30 already saved */
584 /* l.sw PT_GPR30(r1),r30 */
586 _syscall_check_trace_enter:
587 /* If TIF_SYSCALL_TRACE is set, then we want to do syscall tracing */
588 l.lwz r30,TI_FLAGS(r10)
589 l.andi r30,r30,_TIF_SYSCALL_TRACE
591 l.bf _syscall_trace_enter
595 /* Ensure that the syscall number is reasonable */
596 l.sfgeui r11,__NR_syscalls
601 l.movhi r29,hi(sys_call_table)
602 l.ori r29,r29,lo(sys_call_table)
611 /* All syscalls return here... just pay attention to ret_from_fork
612 * which does it in a round-about way.
614 l.sw PT_GPR11(r1),r11 // save return value
618 l.movhi r3,hi(_string_syscall_return)
619 l.ori r3,r3,lo(_string_syscall_return)
624 l.movhi r27,hi(printk)
625 l.ori r27,r27,lo(printk)
631 _syscall_check_trace_leave:
632 /* r30 is a callee-saved register so this should still hold the
633 * _TIF_SYSCALL_TRACE flag from _syscall_check_trace_enter above...
634 * _syscall_trace_leave expects syscall result to be in pt_regs->r11.
637 l.bf _syscall_trace_leave
640 /* This is where the exception-return code begins... interrupts need to be
641 * disabled the rest of the way here because we can't afford to miss any
642 * interrupts that set NEED_RESCHED or SIGNALPENDING... really true? */
645 /* Here we need to disable interrupts */
646 DISABLE_INTERRUPTS(r27,r29)
647 l.lwz r30,TI_FLAGS(r10)
648 l.andi r30,r30,_TIF_WORK_MASK
651 l.bnf _syscall_resume_userspace
654 /* Work pending follows a different return path, so we need to
655 * make sure that all the call-saved registers get into pt_regs
656 * before branching...
658 l.sw PT_GPR14(r1),r14
659 l.sw PT_GPR16(r1),r16
660 l.sw PT_GPR18(r1),r18
661 l.sw PT_GPR20(r1),r20
662 l.sw PT_GPR22(r1),r22
663 l.sw PT_GPR24(r1),r24
664 l.sw PT_GPR26(r1),r26
665 l.sw PT_GPR28(r1),r28
667 /* _work_pending needs to be called with interrupts disabled */
671 _syscall_resume_userspace:
672 // ENABLE_INTERRUPTS(r29)
675 /* This is the hot path for returning to userspace from a syscall. If there's
676 * work to be done and the branch to _work_pending was taken above, then the
677 * return to userspace will be done via the normal exception return path...
678 * that path restores _all_ registers and will overwrite the "clobbered"
679 * registers with whatever garbage is in pt_regs -- that's OK because those
680 * registers are clobbered anyway and because the extra work is insignificant
681 * in the context of the extra work that _work_pending is doing.
683 /* Once again, syscalls are special and only guarantee to preserve the
684 * same registers as a normal function call */
686 /* The assumption here is that the registers r14-r28 (even) are untouched and
687 * don't need to be restored... be sure that that's really the case!
690 /* This is still too much... we should only be restoring what we actually
691 * clobbered... we should even be using 'scratch' (odd) regs above so that
692 * we don't need to restore anything, hardly...
698 /* r3-r8 are technically clobbered, but syscall restart needs these
709 l.lwz r10,PT_GPR10(r1)
710 l.lwz r11,PT_GPR11(r1)
712 /* r30 is the only register we clobber in the fast path */
713 l.lwz r30,PT_GPR30(r1)
715 /* Here we use r13-r19 (odd) as scratch regs */
719 /* Interrupts need to be disabled for setting EPCR and ESR
720 * so that another interrupt doesn't come in here and clobber
721 * them before we can use them for our l.rfe */
722 DISABLE_INTERRUPTS(r17,r19)
723 l.mtspr r0,r13,SPR_EPCR_BASE
724 l.mtspr r0,r15,SPR_ESR_BASE
728 * Keep the below tracing and error handling out of the hot path...
731 _syscall_trace_enter:
732 /* Here we pass pt_regs to do_syscall_trace_enter. Make sure
733 * that function is really getting all the info it needs as
734 * pt_regs isn't a complete set of userspace regs, just the
735 * ones relevant to the syscall...
737 * Note use of delay slot for setting argument.
739 l.jal do_syscall_trace_enter
742 /* Restore arguments (not preserved across do_syscall_trace_enter)
743 * so that we can do the syscall for real and return to the syscall
746 l.lwz r11,PT_GPR11(r1)
756 _syscall_trace_leave:
757 l.jal do_syscall_trace_leave
760 l.j _syscall_check_work
764 /* Here we effectively pretend to have executed an imaginary
765 * syscall that returns -ENOSYS and then return to the regular
767 * Note that "return value" is set in the delay slot...
770 l.addi r11,r0,-ENOSYS
772 /******* END SYSCALL HANDLING *******/
774 /* ---[ 0xd00: Trap exception ]------------------------------------------ */
776 UNHANDLED_EXCEPTION(_vector_0xd00,0xd00)
778 /* ---[ 0xe00: Trap exception ]------------------------------------------ */
780 EXCEPTION_ENTRY(_trap_handler)
781 /* r4: EA of fault (set by EXCEPTION_HANDLE) */
783 l.addi r3,r1,0 /* pt_regs */
785 l.j _ret_from_exception
788 /* ---[ 0xf00: Reserved exception ]-------------------------------------- */
790 UNHANDLED_EXCEPTION(_vector_0xf00,0xf00)
792 /* ---[ 0x1000: Reserved exception ]------------------------------------- */
794 UNHANDLED_EXCEPTION(_vector_0x1000,0x1000)
796 /* ---[ 0x1100: Reserved exception ]------------------------------------- */
798 UNHANDLED_EXCEPTION(_vector_0x1100,0x1100)
800 /* ---[ 0x1200: Reserved exception ]------------------------------------- */
802 UNHANDLED_EXCEPTION(_vector_0x1200,0x1200)
804 /* ---[ 0x1300: Reserved exception ]------------------------------------- */
806 UNHANDLED_EXCEPTION(_vector_0x1300,0x1300)
808 /* ---[ 0x1400: Reserved exception ]------------------------------------- */
810 UNHANDLED_EXCEPTION(_vector_0x1400,0x1400)
812 /* ---[ 0x1500: Reserved exception ]------------------------------------- */
814 UNHANDLED_EXCEPTION(_vector_0x1500,0x1500)
816 /* ---[ 0x1600: Reserved exception ]------------------------------------- */
818 UNHANDLED_EXCEPTION(_vector_0x1600,0x1600)
820 /* ---[ 0x1700: Reserved exception ]------------------------------------- */
822 UNHANDLED_EXCEPTION(_vector_0x1700,0x1700)
824 /* ---[ 0x1800: Reserved exception ]------------------------------------- */
826 UNHANDLED_EXCEPTION(_vector_0x1800,0x1800)
828 /* ---[ 0x1900: Reserved exception ]------------------------------------- */
830 UNHANDLED_EXCEPTION(_vector_0x1900,0x1900)
832 /* ---[ 0x1a00: Reserved exception ]------------------------------------- */
834 UNHANDLED_EXCEPTION(_vector_0x1a00,0x1a00)
836 /* ---[ 0x1b00: Reserved exception ]------------------------------------- */
838 UNHANDLED_EXCEPTION(_vector_0x1b00,0x1b00)
840 /* ---[ 0x1c00: Reserved exception ]------------------------------------- */
842 UNHANDLED_EXCEPTION(_vector_0x1c00,0x1c00)
844 /* ---[ 0x1d00: Reserved exception ]------------------------------------- */
846 UNHANDLED_EXCEPTION(_vector_0x1d00,0x1d00)
848 /* ---[ 0x1e00: Reserved exception ]------------------------------------- */
850 UNHANDLED_EXCEPTION(_vector_0x1e00,0x1e00)
852 /* ---[ 0x1f00: Reserved exception ]------------------------------------- */
854 UNHANDLED_EXCEPTION(_vector_0x1f00,0x1f00)
856 /* ========================================================[ return ] === */
859 DISABLE_INTERRUPTS(r3,r4)
860 l.lwz r4,TI_FLAGS(r10)
861 l.andi r13,r4,_TIF_WORK_MASK
867 l.lwz r5,PT_ORIG_GPR11(r1)
873 l.jal do_work_pending
874 l.ori r3,r1,0 /* pt_regs */
883 l.ori r11,r11,__NR_restart_syscall
884 l.j _syscall_check_trace_enter
887 l.lwz r11,PT_ORIG_GPR11(r1)
888 /* Restore arg registers */
894 l.j _syscall_check_trace_enter
899 /* This returns to userspace code */
902 ENTRY(_ret_from_intr)
903 ENTRY(_ret_from_exception)
905 l.andi r3,r4,SPR_SR_SM
909 l.j _resume_userspace
916 /* Check if we are a kernel thread */
921 /* ...we are a kernel thread so invoke the requested callback */
926 /* _syscall_returns expect r11 to contain return value */
927 l.lwz r11,PT_GPR11(r1)
929 /* The syscall fast path return expects call-saved registers
930 * r12-r28 to be untouched, so we restore them here as they
931 * will have been effectively clobbered when arriving here
932 * via the call to switch()
934 l.lwz r12,PT_GPR12(r1)
935 l.lwz r14,PT_GPR14(r1)
936 l.lwz r16,PT_GPR16(r1)
937 l.lwz r18,PT_GPR18(r1)
938 l.lwz r20,PT_GPR20(r1)
939 l.lwz r22,PT_GPR22(r1)
940 l.lwz r24,PT_GPR24(r1)
941 l.lwz r26,PT_GPR26(r1)
942 l.lwz r28,PT_GPR28(r1)
947 /* ========================================================[ switch ] === */
950 * This routine switches between two different tasks. The process
951 * state of one is saved on its kernel stack. Then the state
952 * of the other is restored from its kernel stack. The memory
953 * management hardware is updated to the second process's state.
954 * Finally, we can return to the second process, via the 'return'.
956 * Note: there are two ways to get to the "going out" portion
957 * of this code; either by coming in via the entry (_switch)
958 * or via "fork" which must set up an environment equivalent
959 * to the "_switch" path. If you change this (or in particular, the
960 * SAVE_REGS macro), you'll have to change the fork code also.
964 /* _switch MUST never lay on page boundry, cause it runs from
965 * effective addresses and beeing interrupted by iTLB miss would kill it.
966 * dTLB miss seams to never accour in the bad place since data accesses
967 * are from task structures which are always page aligned.
969 * The problem happens in RESTORE_ALL_NO_R11 where we first set the EPCR
970 * register, then load the previous register values and only at the end call
971 * the l.rfe instruction. If get TLB miss in beetwen the EPCR register gets
972 * garbled and we end up calling l.rfe with the wrong EPCR. (same probably
975 * To avoid this problems it is sufficient to align _switch to
976 * some nice round number smaller than it's size...
979 /* ABI rules apply here... we either enter _switch via schedule() or via
980 * an imaginary call to which we shall return at return_from_fork. Either
981 * way, we are a function call and only need to preserve the callee-saved
982 * registers when we return. As such, we don't need to save the registers
983 * on the stack that we won't be returning as they were...
988 /* We don't store SR as _switch only gets called in a context where
989 * the SR will be the same going in and coming out... */
991 /* Set up new pt_regs struct for saving task state */
992 l.addi r1,r1,-(INT_FRAME_SIZE)
994 /* No need to store r1/PT_SP as it goes into KSP below */
997 /* This is wrong, r12 shouldn't be here... but GCC is broken for the time being
998 * and expects r12 to be callee-saved... */
999 l.sw PT_GPR12(r1),r12
1000 l.sw PT_GPR14(r1),r14
1001 l.sw PT_GPR16(r1),r16
1002 l.sw PT_GPR18(r1),r18
1003 l.sw PT_GPR20(r1),r20
1004 l.sw PT_GPR22(r1),r22
1005 l.sw PT_GPR24(r1),r24
1006 l.sw PT_GPR26(r1),r26
1007 l.sw PT_GPR28(r1),r28
1008 l.sw PT_GPR30(r1),r30
1010 l.addi r11,r10,0 /* Save old 'current' to 'last' return value*/
1012 /* We use thread_info->ksp for storing the address of the above
1013 * structure so that we can get back to it later... we don't want
1014 * to lose the value of thread_info->ksp, though, so store it as
1015 * pt_regs->sp so that we can easily restore it when we are made
1019 /* Save the old value of thread_info->ksp as pt_regs->sp */
1020 l.lwz r29,TI_KSP(r10)
1023 /* Swap kernel stack pointers */
1024 l.sw TI_KSP(r10),r1 /* Save old stack pointer */
1025 l.or r10,r4,r0 /* Set up new current_thread_info */
1026 l.lwz r1,TI_KSP(r10) /* Load new stack pointer */
1028 /* Restore the old value of thread_info->ksp */
1030 l.sw TI_KSP(r10),r29
1032 /* ...and restore the registers, except r11 because the return value
1033 * has already been set above.
1035 l.lwz r2,PT_GPR2(r1)
1036 l.lwz r9,PT_GPR9(r1)
1037 /* No need to restore r10 */
1038 /* ...and do not restore r11 */
1040 /* This is wrong, r12 shouldn't be here... but GCC is broken for the time being
1041 * and expects r12 to be callee-saved... */
1042 l.lwz r12,PT_GPR12(r1)
1043 l.lwz r14,PT_GPR14(r1)
1044 l.lwz r16,PT_GPR16(r1)
1045 l.lwz r18,PT_GPR18(r1)
1046 l.lwz r20,PT_GPR20(r1)
1047 l.lwz r22,PT_GPR22(r1)
1048 l.lwz r24,PT_GPR24(r1)
1049 l.lwz r26,PT_GPR26(r1)
1050 l.lwz r28,PT_GPR28(r1)
1051 l.lwz r30,PT_GPR30(r1)
1053 /* Unwind stack to pre-switch state */
1054 l.addi r1,r1,(INT_FRAME_SIZE)
1056 /* Return via the link-register back to where we 'came from', where
1057 * that may be either schedule(), ret_from_fork(), or
1058 * ret_from_kernel_thread(). If we are returning to a new thread,
1059 * we are expected to have set up the arg to schedule_tail already,
1060 * hence we do so here unconditionally:
1062 l.lwz r3,TI_TASK(r3) /* Load 'prev' as schedule_tail arg */
1066 /* ==================================================================== */
1068 /* These all use the delay slot for setting the argument register, so the
1069 * jump is always happening after the l.addi instruction.
1071 * These are all just wrappers that don't touch the link-register r9, so the
1072 * return from the "real" syscall function will return back to the syscall
1073 * code that did the l.jal that brought us here.
1076 /* fork requires that we save all the callee-saved registers because they
1077 * are all effectively clobbered by the call to _switch. Here we store
1078 * all the registers that aren't touched by the syscall fast path and thus
1079 * weren't saved there.
1082 _fork_save_extra_regs_and_call:
1083 l.sw PT_GPR14(r1),r14
1084 l.sw PT_GPR16(r1),r16
1085 l.sw PT_GPR18(r1),r18
1086 l.sw PT_GPR20(r1),r20
1087 l.sw PT_GPR22(r1),r22
1088 l.sw PT_GPR24(r1),r24
1089 l.sw PT_GPR26(r1),r26
1091 l.sw PT_GPR28(r1),r28
1094 l.movhi r29,hi(sys_clone)
1095 l.ori r29,r29,lo(sys_clone)
1096 l.j _fork_save_extra_regs_and_call
1100 l.movhi r29,hi(sys_fork)
1101 l.ori r29,r29,lo(sys_fork)
1102 l.j _fork_save_extra_regs_and_call
1105 ENTRY(sys_rt_sigreturn)
1106 l.j _sys_rt_sigreturn
1109 /* This is a catch-all syscall for atomic instructions for the OpenRISC 1000.
1110 * The functions takes a variable number of parameters depending on which
1111 * particular flavour of atomic you want... parameter 1 is a flag identifying
1112 * the atomic in question. Currently, this function implements the
1113 * following variants:
1119 * Atomically exchange the values in pointers 1 and 2.
1123 ENTRY(sys_or1k_atomic)
1124 /* FIXME: This ignores r3 and always does an XCHG */
1125 DISABLE_INTERRUPTS(r17,r19)
1130 ENABLE_INTERRUPTS(r17)
1134 /* ============================================================[ EOF ]=== */