Initial import

1 files changed, 1132 insertions, 0 deletions

diff --git a/arch/openrisc/kernel/entry.S b/arch/openrisc/kernel/entry.S
new file mode 100644
index 000000000..fec8bf97d
--- /dev/null
+++ b/arch/openrisc/kernel/entry.S
@@ -0,0 +1,1132 @@
+/*
+ * OpenRISC entry.S
+ *
+ * Linux architectural port borrowing liberally from similar works of
+ * others.  All original copyrights apply as per the original source
+ * declaration.
+ *
+ * Modifications for the OpenRISC architecture:
+ * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
+ * Copyright (C) 2005 Gyorgy Jeney <nog@bsemi.com>
+ * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/linkage.h>
+
+#include <asm/processor.h>
+#include <asm/unistd.h>
+#include <asm/thread_info.h>
+#include <asm/errno.h>
+#include <asm/spr_defs.h>
+#include <asm/page.h>
+#include <asm/mmu.h>
+#include <asm/pgtable.h>
+#include <asm/asm-offsets.h>
+
+#define DISABLE_INTERRUPTS(t1,t2)			\
+	l.mfspr t2,r0,SPR_SR				;\
+	l.movhi	t1,hi(~(SPR_SR_IEE|SPR_SR_TEE))		;\
+	l.ori	t1,t1,lo(~(SPR_SR_IEE|SPR_SR_TEE))	;\
+	l.and   t2,t2,t1				;\
+	l.mtspr r0,t2,SPR_SR
+
+#define ENABLE_INTERRUPTS(t1)				\
+	l.mfspr	t1,r0,SPR_SR				;\
+	l.ori	t1,t1,lo(SPR_SR_IEE|SPR_SR_TEE)		;\
+	l.mtspr	r0,t1,SPR_SR
+
+/* =========================================================[ macros ]=== */
+
+/*
+ * We need to disable interrupts at beginning of RESTORE_ALL
+ * since interrupt might come in after we've loaded EPC return address
+ * and overwrite EPC with address somewhere in RESTORE_ALL
+ * which is of course wrong!
+ */
+
+#define RESTORE_ALL						\
+	DISABLE_INTERRUPTS(r3,r4)				;\
+	l.lwz   r3,PT_PC(r1)					;\
+	l.mtspr r0,r3,SPR_EPCR_BASE				;\
+	l.lwz   r3,PT_SR(r1)					;\
+	l.mtspr r0,r3,SPR_ESR_BASE				;\
+	l.lwz   r2,PT_GPR2(r1)					;\
+	l.lwz   r3,PT_GPR3(r1)					;\
+	l.lwz   r4,PT_GPR4(r1)					;\
+	l.lwz   r5,PT_GPR5(r1)					;\
+	l.lwz   r6,PT_GPR6(r1)					;\
+	l.lwz   r7,PT_GPR7(r1)					;\
+	l.lwz   r8,PT_GPR8(r1)					;\
+	l.lwz   r9,PT_GPR9(r1)					;\
+	l.lwz   r10,PT_GPR10(r1)					;\
+	l.lwz   r11,PT_GPR11(r1)					;\
+	l.lwz   r12,PT_GPR12(r1)					;\
+	l.lwz   r13,PT_GPR13(r1)					;\
+	l.lwz   r14,PT_GPR14(r1)					;\
+	l.lwz   r15,PT_GPR15(r1)					;\
+	l.lwz   r16,PT_GPR16(r1)					;\
+	l.lwz   r17,PT_GPR17(r1)					;\
+	l.lwz   r18,PT_GPR18(r1)					;\
+	l.lwz   r19,PT_GPR19(r1)					;\
+	l.lwz   r20,PT_GPR20(r1)					;\
+	l.lwz   r21,PT_GPR21(r1)					;\
+	l.lwz   r22,PT_GPR22(r1)					;\
+	l.lwz   r23,PT_GPR23(r1)					;\
+	l.lwz   r24,PT_GPR24(r1)					;\
+	l.lwz   r25,PT_GPR25(r1)					;\
+	l.lwz   r26,PT_GPR26(r1)					;\
+	l.lwz   r27,PT_GPR27(r1)					;\
+	l.lwz   r28,PT_GPR28(r1)					;\
+	l.lwz   r29,PT_GPR29(r1)					;\
+	l.lwz   r30,PT_GPR30(r1)					;\
+	l.lwz   r31,PT_GPR31(r1)					;\
+	l.lwz   r1,PT_SP(r1)					;\
+	l.rfe
+
+
+#define EXCEPTION_ENTRY(handler)				\
+	.global	handler						;\
+handler:							;\
+	/* r1, EPCR, ESR a already saved */			;\
+	l.sw	PT_GPR2(r1),r2					;\
+	l.sw    PT_GPR3(r1),r3					;\
+	/* r4 already save */					;\
+	l.sw    PT_GPR5(r1),r5					;\
+	l.sw    PT_GPR6(r1),r6					;\
+	l.sw    PT_GPR7(r1),r7					;\
+	l.sw    PT_GPR8(r1),r8					;\
+	l.sw    PT_GPR9(r1),r9					;\
+	/* r10 already saved */					;\
+	l.sw    PT_GPR11(r1),r11					;\
+	/* r12 already saved */					;\
+	l.sw    PT_GPR13(r1),r13					;\
+	l.sw    PT_GPR14(r1),r14					;\
+	l.sw    PT_GPR15(r1),r15					;\
+	l.sw    PT_GPR16(r1),r16					;\
+	l.sw    PT_GPR17(r1),r17					;\
+	l.sw    PT_GPR18(r1),r18					;\
+	l.sw    PT_GPR19(r1),r19					;\
+	l.sw    PT_GPR20(r1),r20					;\
+	l.sw    PT_GPR21(r1),r21					;\
+	l.sw    PT_GPR22(r1),r22					;\
+	l.sw    PT_GPR23(r1),r23					;\
+	l.sw    PT_GPR24(r1),r24					;\
+	l.sw    PT_GPR25(r1),r25					;\
+	l.sw    PT_GPR26(r1),r26					;\
+	l.sw    PT_GPR27(r1),r27					;\
+	l.sw    PT_GPR28(r1),r28					;\
+	l.sw    PT_GPR29(r1),r29					;\
+	/* r30 already save */					;\
+/*        l.sw    PT_GPR30(r1),r30*/					;\
+	l.sw    PT_GPR31(r1),r31					;\
+	/* Store -1 in orig_gpr11 for non-syscall exceptions */	;\
+	l.addi	r30,r0,-1					;\
+	l.sw	PT_ORIG_GPR11(r1),r30
+
+#define UNHANDLED_EXCEPTION(handler,vector)			\
+	.global	handler						;\
+handler:							;\
+	/* r1, EPCR, ESR already saved */			;\
+	l.sw    PT_GPR2(r1),r2					;\
+	l.sw    PT_GPR3(r1),r3					;\
+	l.sw    PT_GPR5(r1),r5					;\
+	l.sw    PT_GPR6(r1),r6					;\
+	l.sw    PT_GPR7(r1),r7					;\
+	l.sw    PT_GPR8(r1),r8					;\
+	l.sw    PT_GPR9(r1),r9					;\
+	/* r10 already saved */					;\
+	l.sw    PT_GPR11(r1),r11					;\
+	/* r12 already saved */					;\
+	l.sw    PT_GPR13(r1),r13					;\
+	l.sw    PT_GPR14(r1),r14					;\
+	l.sw    PT_GPR15(r1),r15					;\
+	l.sw    PT_GPR16(r1),r16					;\
+	l.sw    PT_GPR17(r1),r17					;\
+	l.sw    PT_GPR18(r1),r18					;\
+	l.sw    PT_GPR19(r1),r19					;\
+	l.sw    PT_GPR20(r1),r20					;\
+	l.sw    PT_GPR21(r1),r21					;\
+	l.sw    PT_GPR22(r1),r22					;\
+	l.sw    PT_GPR23(r1),r23					;\
+	l.sw    PT_GPR24(r1),r24					;\
+	l.sw    PT_GPR25(r1),r25					;\
+	l.sw    PT_GPR26(r1),r26					;\
+	l.sw    PT_GPR27(r1),r27					;\
+	l.sw    PT_GPR28(r1),r28					;\
+	l.sw    PT_GPR29(r1),r29					;\
+	/* r31 already saved */					;\
+	l.sw    PT_GPR30(r1),r30					;\
+/*        l.sw    PT_GPR31(r1),r31	*/				;\
+	/* Store -1 in orig_gpr11 for non-syscall exceptions */	;\
+	l.addi	r30,r0,-1					;\
+	l.sw	PT_ORIG_GPR11(r1),r30				;\
+	l.addi	r3,r1,0						;\
+	/* r4 is exception EA */				;\
+	l.addi	r5,r0,vector					;\
+	l.jal	unhandled_exception				;\
+	 l.nop							;\
+	l.j	_ret_from_exception				;\
+	 l.nop
+
+/*
+ * NOTE: one should never assume that SPR_EPC, SPR_ESR, SPR_EEAR
+ *       contain the same values as when exception we're handling
+ *	 occured. in fact they never do. if you need them use
+ *	 values saved on stack (for SPR_EPC, SPR_ESR) or content
+ *       of r4 (for SPR_EEAR). for details look at EXCEPTION_HANDLE()
+ *       in 'arch/or32/kernel/head.S'
+ */
+
+/* =====================================================[ exceptions] === */
+
+/* ---[ 0x100: RESET exception ]----------------------------------------- */
+
+EXCEPTION_ENTRY(_tng_kernel_start)
+	l.jal	_start
+	 l.andi r0,r0,0
+
+/* ---[ 0x200: BUS exception ]------------------------------------------- */
+
+EXCEPTION_ENTRY(_bus_fault_handler)
+	/* r4: EA of fault (set by EXCEPTION_HANDLE) */
+	l.jal   do_bus_fault
+	 l.addi  r3,r1,0 /* pt_regs */
+
+	l.j     _ret_from_exception
+	 l.nop
+
+/* ---[ 0x300: Data Page Fault exception ]------------------------------- */
+EXCEPTION_ENTRY(_dtlb_miss_page_fault_handler)
+	l.and	r5,r5,r0
+	l.j	1f
+	 l.nop
+
+EXCEPTION_ENTRY(_data_page_fault_handler)
+	/* set up parameters for do_page_fault */
+	l.ori	r5,r0,0x300		   // exception vector
+1:
+	l.addi  r3,r1,0                    // pt_regs
+	/* r4 set be EXCEPTION_HANDLE */   // effective address of fault
+
+	/*
+	 * __PHX__: TODO
+	 *
+	 * all this can be written much simpler. look at
+	 * DTLB miss handler in the CONFIG_GUARD_PROTECTED_CORE part
+	 */
+#ifdef CONFIG_OPENRISC_NO_SPR_SR_DSX
+	l.lwz   r6,PT_PC(r3)                  // address of an offending insn
+	l.lwz   r6,0(r6)                   // instruction that caused pf
+
+	l.srli  r6,r6,26                   // check opcode for jump insn
+	l.sfeqi r6,0                       // l.j
+	l.bf    8f
+	l.sfeqi r6,1                       // l.jal
+	l.bf    8f
+	l.sfeqi r6,3                       // l.bnf
+	l.bf    8f
+	l.sfeqi r6,4                       // l.bf
+	l.bf    8f
+	l.sfeqi r6,0x11                    // l.jr
+	l.bf    8f
+	l.sfeqi r6,0x12                    // l.jalr
+	l.bf    8f
+
+	l.nop
+
+	l.j     9f
+	l.nop
+8:
+
+	l.lwz   r6,PT_PC(r3)                  // address of an offending insn
+	l.addi  r6,r6,4
+	l.lwz   r6,0(r6)                   // instruction that caused pf
+	l.srli  r6,r6,26                   // get opcode
+9:
+
+#else
+
+	l.mfspr r6,r0,SPR_SR		   // SR
+//	l.lwz	r6,PT_SR(r3)		   // ESR
+	l.andi	r6,r6,SPR_SR_DSX	   // check for delay slot exception
+	l.sfeqi	r6,0x1			   // exception happened in delay slot
+	l.bnf	7f
+	l.lwz	r6,PT_PC(r3)		   // address of an offending insn
+
+	l.addi	r6,r6,4			   // offending insn is in delay slot
+7:
+	l.lwz   r6,0(r6)                   // instruction that caused pf
+	l.srli  r6,r6,26                   // check opcode for write access
+#endif
+
+	l.sfgeui r6,0x34		   // check opcode for write access
+	l.bnf   1f
+	l.sfleui r6,0x37
+	l.bnf   1f
+	l.ori   r6,r0,0x1                  // write access
+	l.j     2f
+	l.nop
+1:	l.ori   r6,r0,0x0                  // !write access
+2:
+
+	/* call fault.c handler in or32/mm/fault.c */
+	l.jal   do_page_fault
+	l.nop
+	l.j     _ret_from_exception
+	l.nop
+
+/* ---[ 0x400: Insn Page Fault exception ]------------------------------- */
+EXCEPTION_ENTRY(_itlb_miss_page_fault_handler)
+	l.and	r5,r5,r0
+	l.j	1f
+	 l.nop
+
+EXCEPTION_ENTRY(_insn_page_fault_handler)
+	/* set up parameters for do_page_fault */
+	l.ori	r5,r0,0x400		   // exception vector
+1:
+	l.addi  r3,r1,0                    // pt_regs
+	/* r4 set be EXCEPTION_HANDLE */   // effective address of fault
+	l.ori	r6,r0,0x0		   // !write access
+
+	/* call fault.c handler in or32/mm/fault.c */
+	l.jal   do_page_fault
+	l.nop
+	l.j     _ret_from_exception
+	l.nop
+
+
+/* ---[ 0x500: Timer exception ]----------------------------------------- */
+
+EXCEPTION_ENTRY(_timer_handler)
+	l.jal	timer_interrupt
+	 l.addi r3,r1,0 /* pt_regs */
+
+	l.j    _ret_from_intr
+	 l.nop
+
+/* ---[ 0x600: Aligment exception ]-------------------------------------- */
+
+EXCEPTION_ENTRY(_alignment_handler)
+	/* r4: EA of fault (set by EXCEPTION_HANDLE) */
+	l.jal   do_unaligned_access
+	 l.addi  r3,r1,0 /* pt_regs */
+
+	l.j     _ret_from_exception
+	 l.nop
+
+#if 0
+EXCEPTION_ENTRY(_aligment_handler)
+//        l.mfspr r2,r0,SPR_EEAR_BASE     /* Load the efective addres */
+	l.addi	r2,r4,0
+//        l.mfspr r5,r0,SPR_EPCR_BASE     /* Load the insn address */
+	l.lwz   r5,PT_PC(r1)
+
+	l.lwz   r3,0(r5)                /* Load insn */
+	l.srli  r4,r3,26                /* Shift left to get the insn opcode */
+
+	l.sfeqi r4,0x00                 /* Check if the load/store insn is in delay slot */
+	l.bf    jmp
+	l.sfeqi r4,0x01
+	l.bf    jmp
+	l.sfeqi r4,0x03
+	l.bf    jmp
+	l.sfeqi r4,0x04
+	l.bf    jmp
+	l.sfeqi r4,0x11
+	l.bf    jr
+	l.sfeqi r4,0x12
+	l.bf    jr
+	l.nop
+	l.j     1f
+	l.addi  r5,r5,4                 /* Increment PC to get return insn address */
+
+jmp:
+	l.slli  r4,r3,6                 /* Get the signed extended jump length */
+	l.srai  r4,r4,4
+
+	l.lwz   r3,4(r5)                /* Load the real load/store insn */
+
+	l.add   r5,r5,r4                /* Calculate jump target address */
+
+	l.j     1f
+	l.srli  r4,r3,26                /* Shift left to get the insn opcode */
+
+jr:
+	l.slli  r4,r3,9                 /* Shift to get the reg nb */
+	l.andi  r4,r4,0x7c
+
+	l.lwz   r3,4(r5)                /* Load the real load/store insn */
+
+	l.add   r4,r4,r1                /* Load the jump register value from the stack */
+	l.lwz   r5,0(r4)
+
+	l.srli  r4,r3,26                /* Shift left to get the insn opcode */
+
+
+1:
+//	  l.mtspr r0,r5,SPR_EPCR_BASE
+	l.sw	PT_PC(r1),r5
+
+	l.sfeqi r4,0x26
+	l.bf    lhs
+	l.sfeqi r4,0x25
+	l.bf    lhz
+	l.sfeqi r4,0x22
+	l.bf    lws
+	l.sfeqi r4,0x21
+	l.bf    lwz
+	l.sfeqi r4,0x37
+	l.bf    sh
+	l.sfeqi r4,0x35
+	l.bf    sw
+	l.nop
+
+1:      l.j     1b                      /* I don't know what to do */
+	l.nop
+
+lhs:    l.lbs   r5,0(r2)
+	l.slli  r5,r5,8
+	l.lbz   r6,1(r2)
+	l.or    r5,r5,r6
+	l.srli  r4,r3,19
+	l.andi  r4,r4,0x7c
+	l.add   r4,r4,r1
+	l.j     align_end
+	l.sw    0(r4),r5
+
+lhz:    l.lbz   r5,0(r2)
+	l.slli  r5,r5,8
+	l.lbz   r6,1(r2)
+	l.or    r5,r5,r6
+	l.srli  r4,r3,19
+	l.andi  r4,r4,0x7c
+	l.add   r4,r4,r1
+	l.j     align_end
+	l.sw    0(r4),r5
+
+lws:    l.lbs   r5,0(r2)
+	l.slli  r5,r5,24
+	l.lbz   r6,1(r2)
+	l.slli  r6,r6,16
+	l.or    r5,r5,r6
+	l.lbz   r6,2(r2)
+	l.slli  r6,r6,8
+	l.or    r5,r5,r6
+	l.lbz   r6,3(r2)
+	l.or    r5,r5,r6
+	l.srli  r4,r3,19
+	l.andi  r4,r4,0x7c
+	l.add   r4,r4,r1
+	l.j     align_end
+	l.sw    0(r4),r5
+
+lwz:    l.lbz   r5,0(r2)
+	l.slli  r5,r5,24
+	l.lbz   r6,1(r2)
+	l.slli  r6,r6,16
+	l.or    r5,r5,r6
+	l.lbz   r6,2(r2)
+	l.slli  r6,r6,8
+	l.or    r5,r5,r6
+	l.lbz   r6,3(r2)
+	l.or    r5,r5,r6
+	l.srli  r4,r3,19
+	l.andi  r4,r4,0x7c
+	l.add   r4,r4,r1
+	l.j     align_end
+	l.sw    0(r4),r5
+
+sh:
+	l.srli  r4,r3,9
+	l.andi  r4,r4,0x7c
+	l.add   r4,r4,r1
+	l.lwz   r5,0(r4)
+	l.sb    1(r2),r5
+	l.srli  r5,r5,8
+	l.j     align_end
+	l.sb    0(r2),r5
+
+sw:
+	l.srli  r4,r3,9
+	l.andi  r4,r4,0x7c
+	l.add   r4,r4,r1
+	l.lwz   r5,0(r4)
+	l.sb    3(r2),r5
+	l.srli  r5,r5,8
+	l.sb    2(r2),r5
+	l.srli  r5,r5,8
+	l.sb    1(r2),r5
+	l.srli  r5,r5,8
+	l.j     align_end
+	l.sb    0(r2),r5
+
+align_end:
+	l.j    _ret_from_intr
+	l.nop
+#endif
+
+/* ---[ 0x700: Illegal insn exception ]---------------------------------- */
+
+EXCEPTION_ENTRY(_illegal_instruction_handler)
+	/* r4: EA of fault (set by EXCEPTION_HANDLE) */
+	l.jal   do_illegal_instruction
+	 l.addi  r3,r1,0 /* pt_regs */
+
+	l.j     _ret_from_exception
+	 l.nop
+
+/* ---[ 0x800: External interrupt exception ]---------------------------- */
+
+EXCEPTION_ENTRY(_external_irq_handler)
+#ifdef CONFIG_OPENRISC_ESR_EXCEPTION_BUG_CHECK
+	l.lwz	r4,PT_SR(r1)		// were interrupts enabled ?
+	l.andi	r4,r4,SPR_SR_IEE
+	l.sfeqi	r4,0
+	l.bnf	1f			// ext irq enabled, all ok.
+	l.nop
+
+	l.addi  r1,r1,-0x8
+	l.movhi r3,hi(42f)
+	l.ori	r3,r3,lo(42f)
+	l.sw    0x0(r1),r3
+	l.jal   printk
+	l.sw    0x4(r1),r4
+	l.addi  r1,r1,0x8
+
+	.section .rodata, "a"
+42:
+		.string "\n\rESR interrupt bug: in _external_irq_handler (ESR %x)\n\r"
+		.align 4
+	.previous
+
+	l.ori	r4,r4,SPR_SR_IEE	// fix the bug
+//	l.sw	PT_SR(r1),r4
+1:
+#endif
+	l.addi	r3,r1,0
+	l.movhi	r8,hi(do_IRQ)
+	l.ori	r8,r8,lo(do_IRQ)
+	l.jalr r8
+	l.nop
+	l.j    _ret_from_intr
+	l.nop
+
+/* ---[ 0x900: DTLB miss exception ]------------------------------------- */
+
+
+/* ---[ 0xa00: ITLB miss exception ]------------------------------------- */
+
+
+/* ---[ 0xb00: Range exception ]----------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0xb00,0xb00)
+
+/* ---[ 0xc00: Syscall exception ]--------------------------------------- */
+
+/*
+ * Syscalls are a special type of exception in that they are
+ * _explicitly_ invoked by userspace and can therefore be
+ * held to conform to the same ABI as normal functions with
+ * respect to whether registers are preserved across the call
+ * or not.
+ */
+
+/* Upon syscall entry we just save the callee-saved registers
+ * and not the call-clobbered ones.
+ */
+
+_string_syscall_return:
+	.string "syscall return %ld \n\r\0"
+	.align 4
+
+ENTRY(_sys_call_handler)
+	/* syscalls run with interrupts enabled */
+	ENABLE_INTERRUPTS(r29)		// enable interrupts, r29 is temp
+
+	/* r1, EPCR, ESR a already saved */
+	l.sw	PT_GPR2(r1),r2
+	/* r3-r8 must be saved because syscall restart relies
+	 * on us being able to restart the syscall args... technically
+	 * they should be clobbered, otherwise
+	 */
+	l.sw    PT_GPR3(r1),r3
+	/* r4 already saved */
+	/* r4 holds the EEAR address of the fault, load the original r4 */
+	l.lwz	r4,PT_GPR4(r1)
+	l.sw    PT_GPR5(r1),r5
+	l.sw    PT_GPR6(r1),r6
+	l.sw    PT_GPR7(r1),r7
+	l.sw    PT_GPR8(r1),r8
+	l.sw    PT_GPR9(r1),r9
+	/* r10 already saved */
+	l.sw    PT_GPR11(r1),r11
+	/* orig_gpr11 must be set for syscalls */
+	l.sw    PT_ORIG_GPR11(r1),r11
+	/* r12,r13 already saved */
+
+	/* r14-r28 (even) aren't touched by the syscall fast path below
+	 * so we don't need to save them.  However, the functions that return
+	 * to userspace via a call to switch() DO need to save these because
+	 * switch() effectively clobbers them... saving these registers for
+	 * such functions is handled in their syscall wrappers (see fork, vfork,
+	 * and clone, below).
+
+	/* r30 is the only register we clobber in the fast path */
+	/* r30 already saved */
+/*	l.sw    PT_GPR30(r1),r30 */
+
+_syscall_check_trace_enter:
+	/* If TIF_SYSCALL_TRACE is set, then we want to do syscall tracing */
+	l.lwz	r30,TI_FLAGS(r10)
+	l.andi	r30,r30,_TIF_SYSCALL_TRACE
+	l.sfne	r30,r0
+	l.bf	_syscall_trace_enter
+	 l.nop
+
+_syscall_check:
+	/* Ensure that the syscall number is reasonable */
+	l.sfgeui r11,__NR_syscalls
+	l.bf	_syscall_badsys
+	 l.nop
+
+_syscall_call:
+	l.movhi r29,hi(sys_call_table)
+	l.ori   r29,r29,lo(sys_call_table)
+	l.slli  r11,r11,2
+	l.add   r29,r29,r11
+	l.lwz   r29,0(r29)
+
+	l.jalr  r29
+	 l.nop
+
+_syscall_return:
+	/* All syscalls return here... just pay attention to ret_from_fork
+	 * which does it in a round-about way.
+	 */
+	l.sw    PT_GPR11(r1),r11           // save return value
+
+#if 0
+_syscall_debug:
+	l.movhi r3,hi(_string_syscall_return)
+	l.ori   r3,r3,lo(_string_syscall_return)
+	l.ori   r27,r0,1
+	l.sw    -4(r1),r27
+	l.sw    -8(r1),r11
+	l.addi  r1,r1,-8
+	l.movhi r27,hi(printk)
+	l.ori   r27,r27,lo(printk)
+	l.jalr  r27
+	 l.nop
+	l.addi  r1,r1,8
+#endif
+
+_syscall_check_trace_leave:
+	/* r30 is a callee-saved register so this should still hold the
+	 * _TIF_SYSCALL_TRACE flag from _syscall_check_trace_enter above...
+	 * _syscall_trace_leave expects syscall result to be in pt_regs->r11.
+	 */
+	l.sfne	r30,r0
+	l.bf	_syscall_trace_leave
+	 l.nop
+
+/* This is where the exception-return code begins... interrupts need to be
+ * disabled the rest of the way here because we can't afford to miss any
+ * interrupts that set NEED_RESCHED or SIGNALPENDING... really true? */
+
+_syscall_check_work:
+	/* Here we need to disable interrupts */
+	DISABLE_INTERRUPTS(r27,r29)
+	l.lwz	r30,TI_FLAGS(r10)
+	l.andi	r30,r30,_TIF_WORK_MASK
+	l.sfne	r30,r0
+
+	l.bnf	_syscall_resume_userspace
+	 l.nop
+
+	/* Work pending follows a different return path, so we need to
+	 * make sure that all the call-saved registers get into pt_regs
+	 * before branching...
+	 */
+	l.sw    PT_GPR14(r1),r14
+	l.sw    PT_GPR16(r1),r16
+	l.sw    PT_GPR18(r1),r18
+	l.sw    PT_GPR20(r1),r20
+	l.sw    PT_GPR22(r1),r22
+	l.sw    PT_GPR24(r1),r24
+	l.sw    PT_GPR26(r1),r26
+	l.sw    PT_GPR28(r1),r28
+
+	/* _work_pending needs to be called with interrupts disabled */
+	l.j	_work_pending
+	 l.nop
+
+_syscall_resume_userspace:
+//	ENABLE_INTERRUPTS(r29)
+
+
+/* This is the hot path for returning to userspace from a syscall.  If there's
+ * work to be done and the branch to _work_pending was taken above, then the
+ * return to userspace will be done via the normal exception return path...
+ * that path restores _all_ registers and will overwrite the "clobbered"
+ * registers with whatever garbage is in pt_regs -- that's OK because those
+ * registers are clobbered anyway and because the extra work is insignificant
+ * in the context of the extra work that _work_pending is doing.
+
+/* Once again, syscalls are special and only guarantee to preserve the
+ * same registers as a normal function call */
+
+/* The assumption here is that the registers r14-r28 (even) are untouched and
+ * don't need to be restored... be sure that that's really the case!
+ */
+
+/* This is still too much... we should only be restoring what we actually
+ * clobbered... we should even be using 'scratch' (odd) regs above so that
+ * we don't need to restore anything, hardly...
+ */
+
+	l.lwz	r2,PT_GPR2(r1)
+
+	/* Restore args */
+	/* r3-r8 are technically clobbered, but syscall restart needs these
+	 * to be restored...
+	 */
+	l.lwz	r3,PT_GPR3(r1)
+	l.lwz	r4,PT_GPR4(r1)
+	l.lwz	r5,PT_GPR5(r1)
+	l.lwz	r6,PT_GPR6(r1)
+	l.lwz	r7,PT_GPR7(r1)
+	l.lwz	r8,PT_GPR8(r1)
+
+	l.lwz	r9,PT_GPR9(r1)
+	l.lwz	r10,PT_GPR10(r1)
+	l.lwz	r11,PT_GPR11(r1)
+
+	/* r30 is the only register we clobber in the fast path */
+	l.lwz	r30,PT_GPR30(r1)
+
+	/* Here we use r13-r19 (odd) as scratch regs */
+	l.lwz   r13,PT_PC(r1)
+	l.lwz   r15,PT_SR(r1)
+	l.lwz	r1,PT_SP(r1)
+	/* Interrupts need to be disabled for setting EPCR and ESR
+	 * so that another interrupt doesn't come in here and clobber
+	 * them before we can use them for our l.rfe */
+	DISABLE_INTERRUPTS(r17,r19)
+	l.mtspr r0,r13,SPR_EPCR_BASE
+	l.mtspr r0,r15,SPR_ESR_BASE
+	l.rfe
+
+/* End of hot path!
+ * Keep the below tracing and error handling out of the hot path...
+*/
+
+_syscall_trace_enter:
+	/* Here we pass pt_regs to do_syscall_trace_enter.  Make sure
+	 * that function is really getting all the info it needs as
+	 * pt_regs isn't a complete set of userspace regs, just the
+	 * ones relevant to the syscall...
+	 *
+	 * Note use of delay slot for setting argument.
+	 */
+	l.jal	do_syscall_trace_enter
+	 l.addi	r3,r1,0
+
+	/* Restore arguments (not preserved across do_syscall_trace_enter)
+	 * so that we can do the syscall for real and return to the syscall
+	 * hot path.
+	 */
+	l.lwz	r11,PT_GPR11(r1)
+	l.lwz	r3,PT_GPR3(r1)
+	l.lwz	r4,PT_GPR4(r1)
+	l.lwz	r5,PT_GPR5(r1)
+	l.lwz	r6,PT_GPR6(r1)
+	l.lwz	r7,PT_GPR7(r1)
+
+	l.j	_syscall_check
+	 l.lwz	r8,PT_GPR8(r1)
+
+_syscall_trace_leave:
+	l.jal	do_syscall_trace_leave
+	 l.addi	r3,r1,0
+
+	l.j	_syscall_check_work
+	 l.nop
+
+_syscall_badsys:
+	/* Here we effectively pretend to have executed an imaginary
+	 * syscall that returns -ENOSYS and then return to the regular
+	 * syscall hot path.
+	 * Note that "return value" is set in the delay slot...
+	 */
+	l.j	_syscall_return
+	 l.addi	r11,r0,-ENOSYS
+
+/******* END SYSCALL HANDLING *******/
+
+/* ---[ 0xd00: Trap exception ]------------------------------------------ */
+
+UNHANDLED_EXCEPTION(_vector_0xd00,0xd00)
+
+/* ---[ 0xe00: Trap exception ]------------------------------------------ */
+
+EXCEPTION_ENTRY(_trap_handler)
+	/* r4: EA of fault (set by EXCEPTION_HANDLE) */
+	l.jal   do_trap
+	 l.addi  r3,r1,0 /* pt_regs */
+
+	l.j     _ret_from_exception
+	 l.nop
+
+/* ---[ 0xf00: Reserved exception ]-------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0xf00,0xf00)
+
+/* ---[ 0x1000: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1000,0x1000)
+
+/* ---[ 0x1100: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1100,0x1100)
+
+/* ---[ 0x1200: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1200,0x1200)
+
+/* ---[ 0x1300: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1300,0x1300)
+
+/* ---[ 0x1400: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1400,0x1400)
+
+/* ---[ 0x1500: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1500,0x1500)
+
+/* ---[ 0x1600: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1600,0x1600)
+
+/* ---[ 0x1700: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1700,0x1700)
+
+/* ---[ 0x1800: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1800,0x1800)
+
+/* ---[ 0x1900: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1900,0x1900)
+
+/* ---[ 0x1a00: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1a00,0x1a00)
+
+/* ---[ 0x1b00: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1b00,0x1b00)
+
+/* ---[ 0x1c00: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1c00,0x1c00)
+
+/* ---[ 0x1d00: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1d00,0x1d00)
+
+/* ---[ 0x1e00: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1e00,0x1e00)
+
+/* ---[ 0x1f00: Reserved exception ]------------------------------------- */
+
+UNHANDLED_EXCEPTION(_vector_0x1f00,0x1f00)
+
+/* ========================================================[ return ] === */
+
+_resume_userspace:
+	DISABLE_INTERRUPTS(r3,r4)
+	l.lwz	r4,TI_FLAGS(r10)
+	l.andi	r13,r4,_TIF_WORK_MASK
+	l.sfeqi	r13,0
+	l.bf	_restore_all
+	 l.nop
+
+_work_pending:
+	l.lwz	r5,PT_ORIG_GPR11(r1)
+	l.sfltsi r5,0
+	l.bnf	1f
+	 l.nop
+	l.andi	r5,r5,0
+1:
+	l.jal	do_work_pending
+	 l.ori	r3,r1,0			/* pt_regs */
+
+	l.sfeqi	r11,0
+	l.bf	_restore_all
+	 l.nop
+	l.sfltsi r11,0
+	l.bnf	1f
+	 l.nop
+	l.and	r11,r11,r0
+	l.ori	r11,r11,__NR_restart_syscall
+	l.j	_syscall_check_trace_enter
+	 l.nop
+1:
+	l.lwz	r11,PT_ORIG_GPR11(r1)
+	/* Restore arg registers */
+	l.lwz	r3,PT_GPR3(r1)
+	l.lwz	r4,PT_GPR4(r1)
+	l.lwz	r5,PT_GPR5(r1)
+	l.lwz	r6,PT_GPR6(r1)
+	l.lwz	r7,PT_GPR7(r1)
+	l.j	_syscall_check_trace_enter
+	 l.lwz	r8,PT_GPR8(r1)
+
+_restore_all:
+	RESTORE_ALL
+	/* This returns to userspace code */
+
+
+ENTRY(_ret_from_intr)
+ENTRY(_ret_from_exception)
+	l.lwz	r4,PT_SR(r1)
+	l.andi	r3,r4,SPR_SR_SM
+	l.sfeqi	r3,0
+	l.bnf	_restore_all
+	 l.nop
+	l.j	_resume_userspace
+	 l.nop
+
+ENTRY(ret_from_fork)
+	l.jal	schedule_tail
+	 l.nop
+
+	/* Check if we are a kernel thread */
+	l.sfeqi	r20,0
+	l.bf	1f
+	 l.nop
+
+	/* ...we are a kernel thread so invoke the requested callback */
+	l.jalr	r20
+	 l.or	r3,r22,r0
+
+1:
+	/* _syscall_returns expect r11 to contain return value */
+	l.lwz	r11,PT_GPR11(r1)
+
+	/* The syscall fast path return expects call-saved registers
+	 * r12-r28 to be untouched, so we restore them here as they
+	 * will have been effectively clobbered when arriving here
+	 * via the call to switch()
+	 */
+	l.lwz	r12,PT_GPR12(r1)
+	l.lwz	r14,PT_GPR14(r1)
+	l.lwz	r16,PT_GPR16(r1)
+	l.lwz	r18,PT_GPR18(r1)
+	l.lwz	r20,PT_GPR20(r1)
+	l.lwz	r22,PT_GPR22(r1)
+	l.lwz	r24,PT_GPR24(r1)
+	l.lwz	r26,PT_GPR26(r1)
+	l.lwz	r28,PT_GPR28(r1)
+
+	l.j	_syscall_return
+	 l.nop
+
+/* ========================================================[ switch ] === */
+
+/*
+ * This routine switches between two different tasks.  The process
+ * state of one is saved on its kernel stack.  Then the state
+ * of the other is restored from its kernel stack.  The memory
+ * management hardware is updated to the second process's state.
+ * Finally, we can return to the second process, via the 'return'.
+ *
+ * Note: there are two ways to get to the "going out" portion
+ * of this code; either by coming in via the entry (_switch)
+ * or via "fork" which must set up an environment equivalent
+ * to the "_switch" path.  If you change this (or in particular, the
+ * SAVE_REGS macro), you'll have to change the fork code also.
+ */
+
+
+/* _switch MUST never lay on page boundry, cause it runs from
+ * effective addresses and beeing interrupted by iTLB miss would kill it.
+ * dTLB miss seams to never accour in the bad place since data accesses
+ * are from task structures which are always page aligned.
+ *
+ * The problem happens in RESTORE_ALL_NO_R11 where we first set the EPCR
+ * register, then load the previous register values and only at the end call
+ * the l.rfe instruction. If get TLB miss in beetwen the EPCR register gets
+ * garbled and we end up calling l.rfe with the wrong EPCR. (same probably
+ * holds for ESR)
+ *
+ * To avoid this problems it is sufficient to align _switch to
+ * some nice round number smaller than it's size...
+ */
+
+/* ABI rules apply here... we either enter _switch via schedule() or via
+ * an imaginary call to which we shall return at return_from_fork.  Either
+ * way, we are a function call and only need to preserve the callee-saved
+ * registers when we return.  As such, we don't need to save the registers
+ * on the stack that we won't be returning as they were...
+ */
+
+	.align 0x400
+ENTRY(_switch)
+	/* We don't store SR as _switch only gets called in a context where
+	 * the SR will be the same going in and coming out... */
+
+	/* Set up new pt_regs struct for saving task state */
+	l.addi  r1,r1,-(INT_FRAME_SIZE)
+
+	/* No need to store r1/PT_SP as it goes into KSP below */
+	l.sw    PT_GPR2(r1),r2
+	l.sw    PT_GPR9(r1),r9
+	/* This is wrong, r12 shouldn't be here... but GCC is broken for the time being
+	 * and expects r12 to be callee-saved... */
+	l.sw    PT_GPR12(r1),r12
+	l.sw    PT_GPR14(r1),r14
+	l.sw    PT_GPR16(r1),r16
+	l.sw    PT_GPR18(r1),r18
+	l.sw    PT_GPR20(r1),r20
+	l.sw    PT_GPR22(r1),r22
+	l.sw    PT_GPR24(r1),r24
+	l.sw    PT_GPR26(r1),r26
+	l.sw    PT_GPR28(r1),r28
+	l.sw    PT_GPR30(r1),r30
+
+	l.addi	r11,r10,0			/* Save old 'current' to 'last' return value*/
+
+	/* We use thread_info->ksp for storing the address of the above
+	 * structure so that we can get back to it later... we don't want
+	 * to lose the value of thread_info->ksp, though, so store it as
+	 * pt_regs->sp so that we can easily restore it when we are made
+	 * live again...
+	 */
+
+	/* Save the old value of thread_info->ksp as pt_regs->sp */
+	l.lwz	r29,TI_KSP(r10)
+	l.sw	PT_SP(r1),r29
+
+	/* Swap kernel stack pointers */
+	l.sw    TI_KSP(r10),r1			/* Save old stack pointer */
+	l.or	r10,r4,r0			/* Set up new current_thread_info */
+	l.lwz   r1,TI_KSP(r10)			/* Load new stack pointer */
+
+	/* Restore the old value of thread_info->ksp */
+	l.lwz	r29,PT_SP(r1)
+	l.sw	TI_KSP(r10),r29
+
+	/* ...and restore the registers, except r11 because the return value
+	 * has already been set above.
+	 */
+	l.lwz   r2,PT_GPR2(r1)
+	l.lwz   r9,PT_GPR9(r1)
+	/* No need to restore r10 */
+	/* ...and do not restore r11 */
+
+	/* This is wrong, r12 shouldn't be here... but GCC is broken for the time being
+	 * and expects r12 to be callee-saved... */
+	l.lwz   r12,PT_GPR12(r1)
+	l.lwz   r14,PT_GPR14(r1)
+	l.lwz   r16,PT_GPR16(r1)
+	l.lwz   r18,PT_GPR18(r1)
+	l.lwz   r20,PT_GPR20(r1)
+	l.lwz   r22,PT_GPR22(r1)
+	l.lwz   r24,PT_GPR24(r1)
+	l.lwz   r26,PT_GPR26(r1)
+	l.lwz   r28,PT_GPR28(r1)
+	l.lwz   r30,PT_GPR30(r1)
+
+	/* Unwind stack to pre-switch state */
+	l.addi  r1,r1,(INT_FRAME_SIZE)
+
+	/* Return via the link-register back to where we 'came from', where
+	 * that may be either schedule(), ret_from_fork(), or
+	 * ret_from_kernel_thread().  If we are returning to a new thread,
+	 * we are expected to have set up the arg to schedule_tail already,
+	 * hence we do so here unconditionally:
+	 */
+	l.lwz   r3,TI_TASK(r3)		/* Load 'prev' as schedule_tail arg */
+	l.jr	r9
+	 l.nop
+
+/* ==================================================================== */
+
+/* These all use the delay slot for setting the argument register, so the
+ * jump is always happening after the l.addi instruction.
+ *
+ * These are all just wrappers that don't touch the link-register r9, so the
+ * return from the "real" syscall function will return back to the syscall
+ * code that did the l.jal that brought us here.
+ */
+
+/* fork requires that we save all the callee-saved registers because they
+ * are all effectively clobbered by the call to _switch.  Here we store
+ * all the registers that aren't touched by the syscall fast path and thus
+ * weren't saved there.
+ */
+
+_fork_save_extra_regs_and_call:
+	l.sw    PT_GPR14(r1),r14
+	l.sw    PT_GPR16(r1),r16
+	l.sw    PT_GPR18(r1),r18
+	l.sw    PT_GPR20(r1),r20
+	l.sw    PT_GPR22(r1),r22
+	l.sw    PT_GPR24(r1),r24
+	l.sw    PT_GPR26(r1),r26
+	l.jr	r29
+	 l.sw    PT_GPR28(r1),r28
+
+ENTRY(__sys_clone)
+	l.movhi	r29,hi(sys_clone)
+	l.ori	r29,r29,lo(sys_clone)
+	l.j	_fork_save_extra_regs_and_call
+	 l.addi	r7,r1,0
+
+ENTRY(__sys_fork)
+	l.movhi	r29,hi(sys_fork)
+	l.ori	r29,r29,lo(sys_fork)
+	l.j	_fork_save_extra_regs_and_call
+	 l.addi	r3,r1,0
+
+ENTRY(sys_rt_sigreturn)
+	l.j	_sys_rt_sigreturn
+	 l.addi	r3,r1,0
+
+/* This is a catch-all syscall for atomic instructions for the OpenRISC 1000.
+ * The functions takes a variable number of parameters depending on which
+ * particular flavour of atomic you want... parameter 1 is a flag identifying
+ * the atomic in question.  Currently, this function implements the
+ * following variants:
+ *
+ * XCHG:
+ *  @flag: 1
+ *  @ptr1:
+ *  @ptr2:
+ * Atomically exchange the values in pointers 1 and 2.
+ *
+ */
+
+ENTRY(sys_or1k_atomic)
+	/* FIXME: This ignores r3 and always does an XCHG */
+	DISABLE_INTERRUPTS(r17,r19)
+	l.lwz	r29,0(r4)
+	l.lwz	r27,0(r5)
+	l.sw	0(r4),r27
+	l.sw	0(r5),r29
+	ENABLE_INTERRUPTS(r17)
+	l.jr	r9
+	 l.or	r11,r0,r0
+
+/* ============================================================[ EOF ]=== */