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/* crt0.S. C Runtime startup file.

   Copyright (C) 2004, Jacob Bower
   Copyright (C) 2010, Embecosm Limited <info@embecosm.com>

   Contributor Jeremy Bennett <jeremy.bennett@embecosm.com>

   This file is part of Newlib.

   The original work by Jacob Bower is provided as-is without any kind of
   warranty. Use it at your own risk!

   All subsequent work is bound by version 3 of the GPL as follows.

   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 3 of the License, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful, but WITHOUT
   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
   more details.

   You should have received a copy of the GNU General Public License along
   with this program.  If not, see <http://www.gnu.org/licenses/>.            */
/* -------------------------------------------------------------------------- */
/* This program is commented throughout in a fashion suitable for processing
   with Doxygen.                                                              */
/* -------------------------------------------------------------------------- */

#include "spr-defs.h"
#include "or1ksim-board.h"

        
/* -------------------------------------------------------------------------- */
/*!Macro for expressions which do not have their own handler.
  
   Construct the arguments for a call to printf, then exit. Being varargs, the
   arguments to printf must be on the stack, which we update using the
   standard prologue.
  
  @param[in] str  Label for a string describing the macro, suitable for
                  printf.                                                     */
/* -------------------------------------------------------------------------- */
#define UNHANDLED_EXCEPTION(str)                                         \
        l.addi  r1,r1,-20               /* Standard prologue */         ;\
        l.sw    16(r1),r2                                               ;\
        l.addi  r2,r1,20                                                ;\
        l.sw    12(r1),r9                                               ;\
                                                                        ;\
        l.movhi r3,hi(.Lfmt)            /* printf format string */      ;\
        l.ori   r3,r3,lo(.Lfmt)                                         ;\
        l.sw    0(r1),r3                                                ;\
        l.movhi r4,hi(str)              /* Name of exception */         ;\
        l.ori   r4,r4,lo(str)                                           ;\
        l.sw    4(r1),r4                                                ;\
        l.mfspr r5,r0,SPR_EPCR_BASE     /* Source of the interrupt */   ;\
        l.jal   _printf                                                 ;\
        l.sw    8(r1),r5                                                ;\
                                                                        ;\
        l.ori   r3,r0,0xffff            /* Failure RC */                ;\
        l.jal   _exit                                                   ;\
        l.nop                                                           ;\
                                                                        ;\
        l.rfe                           /* Never executed we hope */


/* -------------------------------------------------------------------------- */
/*!Text strings for the different exceptions                                  */
/* -------------------------------------------------------------------------- */
        .section .rodata
.Lfmt:  .string "Unhandled %s exception at address %08p\n"
.L200:  .string "bus error"
.L300:  .string "data page fault"
.L400:  .string "instruction page fault"
.L500:  .string "timer"
.L600:  .string "alignment"
.L700:  .string "illegal instruction"
.L800:  .string "external interrupt"
.L900:  .string "data TLB"
.La00:  .string "instruction TLB"
.Lb00:  .string "range"
.Lc00:  .string "syscall"
.Ld00:  .string "floating point"
.Le00:  .string "trap"
.Lf00:  .string "undefined 0xf00"
.L1000: .string "undefined 0x1000"
.L1100: .string "undefined 0x1100"
.L1200: .string "undefined 0x1200"
.L1300: .string "undefined 0x1300"
.L1400: .string "undefined 0x1400"
.L1500: .string "undefined 0x1500"
.L1600: .string "undefined 0x1600"
.L1700: .string "undefined 0x1700"
.L1800: .string "undefined 0x1800"
.L1900: .string "undefined 0x1900"
.L1a00: .string "undefined 0x1a00"
.L1b00: .string "undefined 0x1b00"
.L1c00: .string "undefined 0x1c00"
.L1d00: .string "undefined 0x1d00"
.L1e00: .string "undefined 0x1e00"
.L1f00: .string "undefined 0x1f00"

        
/* -------------------------------------------------------------------------- */
/*!Exception vectors                                                          */
/* -------------------------------------------------------------------------- */
        .section .vectors,"ax"

        /* 0x100: RESET exception */
        .org    0x100   
_reset:
        /* Jump to program initialisation code */
        l.j     _start
        l.nop

        /* 0x200: BUS exception is special, because during startup we use it
           to detect where the stack should go. So we need some special code
           before we return, which wel will later overwrite with l.nop.

           We use registers we know will not interfere in this case. */
        .org    0x200
_buserr:
        l.mfspr r24,r0,SPR_EPCR_BASE
        l.addi  r24,r24,4               /* Return one instruction on */
        l.mtspr r0,r24,SPR_EPCR_BASE
        l.rfe

_buserr_std:
        UNHANDLED_EXCEPTION (.L200)

        /* 0x300: Data Page Fault exception */
        .org    0x300
        UNHANDLED_EXCEPTION (.L300)
        
        /* 0x400: Insn Page Fault exception */
        .org    0x400
        UNHANDLED_EXCEPTION (.L400)

        /* 0x500: Timer exception */
        .org    0x500
        UNHANDLED_EXCEPTION (.L500)

        /* 0x600: Aligment exception */
        .org    0x600
        UNHANDLED_EXCEPTION (.L600)
        
        /* 0x700: Illegal insn exception */
        .org    0x700
        UNHANDLED_EXCEPTION (.L700)

        /* 0x800: External interrupt exception */
        .org    0x800
        UNHANDLED_EXCEPTION (.L800)

        /* 0x900: DTLB miss exception */
        .org    0x900
        UNHANDLED_EXCEPTION (.L900)
        
        /* 0xa00: ITLB miss exception */
        .org    0xa00
        UNHANDLED_EXCEPTION (.La00)
        
        /* 0xb00: Range exception */
        .org    0xb00
        UNHANDLED_EXCEPTION (.Lb00)
        
        /* 0xc00: Syscall exception */
        .org    0xc00
        UNHANDLED_EXCEPTION (.Lc00)
        
        /* 0xd00: floating point exception */
        .org    0xd00
        UNHANDLED_EXCEPTION (.Ld00)
        
        /* 0xe00: Trap exception */
        .org    0xe00
        UNHANDLED_EXCEPTION (.Le00)
        
        /* 0xf00: Reserved exceptions */
        .org    0xf00
        UNHANDLED_EXCEPTION (.Lf00)
        
        .org    0x1000
        UNHANDLED_EXCEPTION (.L1000)
        
        .org    0x1100
        UNHANDLED_EXCEPTION (.L1100)
        
        .org    0x1200
        UNHANDLED_EXCEPTION (.L1200)
        
        .org    0x1300
        UNHANDLED_EXCEPTION (.L1300)
        
        .org    0x1400
        UNHANDLED_EXCEPTION (.L1400)
        
        .org    0x1500
        UNHANDLED_EXCEPTION (.L1500)
        
        .org    0x1600
        UNHANDLED_EXCEPTION (.L1600)
        
        .org    0x1700
        UNHANDLED_EXCEPTION (.L1700)
        
        .org    0x1800
        UNHANDLED_EXCEPTION (.L1800)
        
        .org    0x1900
        UNHANDLED_EXCEPTION (.L1900)
        
        .org    0x1a00
        UNHANDLED_EXCEPTION (.L1a00)
        
        .org    0x1b00
        UNHANDLED_EXCEPTION (.L1b00)
        
        .org    0x1c00
        UNHANDLED_EXCEPTION (.L1c00)
        
        .org    0x1d00
        UNHANDLED_EXCEPTION (.L1d00)
        
        .org    0x1e00
        UNHANDLED_EXCEPTION (.L1e00)
        
        .org    0x1f00
        UNHANDLED_EXCEPTION (.L1f00)

        /* Pad to the end */
        .org    0x1ffc
        l.nop

/* -------------------------------------------------------------------------- */
/*!Main entry point
  
   We initialise the stack and frame pointer first, before we set up the
   caches, since otherwise we'll need to disable the instruction cache when
   patching the bus error vector code.

   The remaining tasks are then:
   - optionally set up instruction and/or data caches
   - clear BSS
   - call global and static constructors
   - set up destructors to be called from exit
   - initialize the UART (may be dummy, if no UART supported)
   - jump to the main function
   - call exit if the main function ever returns.
   - loop forever (should never get here)                                     */
/* -------------------------------------------------------------------------- */
        /* The stack grows down from the top of writable memory. */
        .section .data
        .global _stack
_stack: .space  4,0

        .section .text
        .global _start
        .type   _start,@function

_start: 
        /* Determine where the stack should end. Must be somewhere above the
           end of loaded memory. We look in blocks of 64KB. */
        l.movhi r30,hi(end)
        l.ori   r30,r30,lo(end)
        l.srli  r30,r30,16              /* Round down to 64KB boundary */
        l.slli  r30,r30,16

        l.addi  r28,r0,1                /* Constant 64KB in register */
        l.slli  r28,r28,16

        l.add   r30,r30,r28
        l.addi  r30,r30,-4              /* SP one word inside next 64KB? */

        l.movhi r26,0xaaaa              /* Test pattern to store in memory */
        l.ori   r26,r26,0xaaaa

        /* Is this a writeable location? */
.L3:
        l.sw    0(r30),r26
        l.lwz   r24,0(r30)
        l.sfeq  r24,r26
        l.bnf   .L4
        l.nop
        
        l.j     .L3
        l.add   r30,r30,r28             /* Try 64KB higher */

.L4:
        l.sub   r30,r30,r28             /* Previous value was wanted */
        l.movhi r26,hi(_stack)
        l.ori   r26,r26,lo(_stack)
        l.sw    0(r26),r30

        /* Initialise stack and frame pointer (set to same value) */
        l.add   r1,r30,r0
        l.add   r2,r30,r0

        /* Clear out the bus error vector special code. */
        l.movhi r30,hi(_buserr)
        l.ori   r30,r30,lo(_buserr)
        l.movhi r28,hi(_buserr_std)
        l.ori   r28,r28,lo(_buserr_std)
        l.movhi r26,0x1500              /* l.nop 0 */
        l.ori   r26,r26,0x0000

.L5:
        l.sfeq  r28,r30
        l.bf    .L6
        l.nop

        l.sw    0(r30),r26              /* Patch the instruction */
        l.j     .L5
        l.addi  r30,r30,4               /* Delay slot: next instruction */

.L6:
        /* Cache initialisation. Enable IC and/or DC */
.if IC_ENABLE || DC_ENABLE
        l.mfspr r10,r0,SPR_SR
.if IC_ENABLE
        l.ori   r10,r10,SPR_SR_ICE
.endif
.if DC_ENABLE
        l.ori   r10,r10,SPR_SR_DCE
.endif
        l.mtspr r0,r10,SPR_SR
        l.nop                           /* Flush the pipeline. */
        l.nop
        l.nop
        l.nop
        l.nop
.endif

        /* Clear BSS */
        l.movhi r28,hi(__bss_start)
        l.ori   r28,r28,lo(__bss_start)
        l.movhi r30,hi(end)
        l.ori   r30,r30,lo(end)

.L1:
        l.sw    (0)(r28),r0
        l.sfltu r28,r30
        l.bf    .L1
        l.addi  r28,r28,4               /* Delay slot */

        /* Call global and static constructors */
        l.jal   init
        l.nop
        
        /* Set up destructors to be called from exit if main never returns */
        l.movhi r3,hi(fini)
        l.jal   _atexit
        l.ori   r3,r3,lo(fini)          /* Delay slot */

        /* Initialise UART in a C function. If the UART isn't present, we'll */
        /* link against a dummy function. */
        l.jal    __uart_init
        l.nop

        /* Jump to main program entry point (argc = argv = envp = 0) */
        l.or    r3,r0,r0
        l.or    r4,r0,r0
        l.jal   _main
        l.or    r5,r0,r0                /* Delay slot */

        /* If program exits, call exit routine */
        l.jal   _exit
        l.addi  r3,r11,0                /* Delay slot */

        /* Loop forever */
.L2:
        l.j     .L2
        l.nop
        
        .size   _start, .-_start