path: root/firmware/crt0.S

/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id$
 *
 * Copyright (C) 2002 by Linus Nielsen Feltzing
 *
 * All files in this archive are subject to the GNU General Public License.
 * See the file COPYING in the source tree root for full license agreement.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/
#include "config.h"
#include "cpu.h"

#if defined(CPU_ARM)
    .section .init.text,"ax",%progbits
#else
    .section .init.text,"ax",@progbits
#endif

    .global    start
start:

#if defined(CPU_ARM)

/* iPod bootloader and startup code based on startup.s from the iPodLinux loader
 *
 * Copyright (c) 2003, Daniel Palffy (dpalffy (at) rainstorm.org)
 * Copyright (c) 2005, Bernard Leach <leachbj@bouncycastle.org>
 *
 */

    msr    cpsr_c, #0xd3 /* enter supervisor mode, disable IRQ */

#ifndef BOOTLOADER
#if CONFIG_CPU == PP5002 || CONFIG_CPU == PP5020
    b      pad_skip
.space 50*4 /* (more than enough) space for exception vectors */
pad_skip:
    /* We need to remap memory from wherever SDRAM is mapped natively, to
       base address 0, so we can put our exception vectors there. We don't
       want to do this remapping while executing from SDRAM, so we copy the
       remapping code to IRAM, then execute from there. Hence, the following
       code is compiled for address 0, but is currently executing at either
       0x28000000 or 0x10000000, depending on chipset version. Do not use any
       absolute addresses until remapping has been done. */
    ldr    r1, =0x40000000
    ldr    r2, =remap_start
    ldr    r3, =remap_end

    and    r5, pc, #0xff000000 /* adjust for execute address */
    orr    r2, r2, r5
    orr    r3, r3, r5

    /* copy the code to 0x40000000 */
1:
    ldr    r4, [r2], #4
    str    r4, [r1], #4
    cmp    r2, r3
    ble    1b

    ldr    r3, =0x3f84     /* r3 and r1 values here are magic, don't touch */
    orr    r3, r3, r5      /* adjust for execute address */
    ldr    r2, =0xf000f014
    mov    r1, #0x3a00
    ldr    r0, =0xf000f010
    mov    pc, #0x40000000 

remap_start:
    str    r1, [r0]
    str    r3, [r2]
    ldr    r0, L_post_remap
    mov    pc, r0
L_post_remap: .word remap_end
remap_end:

#elif CONFIG_CPU == PNX0101

#ifndef DEBUG
    ldr    r0, =0x80105000
    mov    r1, #1
    str    r1, [r0, #4]
    mov    r1, #0
    str    r1, [r0, #4]
1:  ldr    r1, [r0]
    cmp    r1, #0
    bne    1b
    mov    r1, #0x74
    str    r1, [r0, #8]
    mov    r1, #2
    str    r1, [r0, #0x18]	
    mov    r1, #0x120
    str    r1, [r0, #0x30]
    mov    r1, #6
    str    r1, [r0, #4]
    ldr    r0, =1f
    mov    r15, r0
1:
#endif /* !DEBUG */
#endif /* chipset specific */

#ifndef DEBUG
    /* Copy exception handler code to address 0 */
    ldr    r2, =_vectorsstart
    ldr    r3, =_vectorsend
    ldr    r4, =_vectorscopy
1:
    cmp    r3, r2
    ldrhi  r5, [r4], #4
    strhi  r5, [r2], #4
    bhi    1b
#else
    ldr    r1, =vectors
    ldr    r0, =irq_handler
    str    r0, [r1, #24]
    ldr    r0, =fiq_handler
    str    r0, [r1, #28]
#endif
    
#ifndef STUB
    /* Zero out IBSS */
    ldr    r2, =_iedata
    ldr    r3, =_iend
    mov    r4, #0
1:
    cmp    r3, r2
    strhi  r4, [r2], #4
    bhi    1b

    /* Copy the IRAM */
    ldr    r2, =_iramcopy
    ldr    r3, =_iramstart
    ldr    r4, =_iramend
1:
    cmp    r4, r3
    ldrhi  r5, [r2], #4
    strhi  r5, [r3], #4
    bhi    1b
#endif /* !STUB */
#endif /* !BOOTLOADER */

    /* Initialise bss section to zero */
    ldr    r2, =_edata
    ldr    r3, =_end
    mov    r4, #0
1:
    cmp    r3, r2
    strhi  r4, [r2], #4
    bhi    1b
    
    /* Set up some stack and munge it with 0xdeadbeef */
    ldr    sp, =stackend
    mov    r3, sp
    ldr    r2, =stackbegin
    ldr    r4, =0xdeadbeef
1:
    cmp    r3, r2
    strhi  r4, [r2], #4
    bhi    1b

#ifdef BOOTLOADER
#if CONFIG_CPU == PP5002 || CONFIG_CPU == PP5020
    .equ    PP5002_PROC_ID,  0xc4000000
    .equ    PP5002_COP_CTRL, 0xcf004058
    .equ    PP5020_PROC_ID,  0x60000000
    .equ    PP5020_COP_CTRL, 0x60007004
    /* TODO: the high part of the address is probably dependent on CONFIG_CPU.
       Since we tend to use ifdefs for each chipset target
       anyway, we might as well just hardcode it here.
     */
       
    /* get the high part of our execute address */
    ldr    r0, =0xff000000
    and    r8, pc, r0             @ r8 is used later

#if CONFIG_CPU==PP5002
    mov    r0, #PP5002_PROC_ID
#else
    mov    r0, #PP5020_PROC_ID
#endif
    ldr    r0, [r0]
    and    r0, r0, #0xff
    cmp    r0, #0x55
    beq    1f

    /* put us (co-processor) to sleep */
#if CONFIG_CPU==PP5002
    ldr    r4, =PP5002_COP_CTRL
    mov    r3, #0xca
#else
    ldr    r4, =PP5020_COP_CTRL
    mov    r3, #0x80000000
#endif
    str    r3, [r4]


    ldr    pc, =cop_wake_start

cop_wake_start:
    /* jump the COP to startup */
    ldr    r0, =startup_loc
    ldr    pc, [r0]

1:
    
    /* get the high part of our execute address */
    ldr    r2, =0xffffff00
    and    r4, pc, r2

    /* Copy bootloader to safe area - 0x40000000 */
    mov    r5, #0x40000000
    ldr    r6, = _dataend
    sub    r0, r6, r5       /* length of loader */
    add    r0, r4, r0     /* r0 points to start of loader */
1:
    cmp    r5, r6
    ldrcc  r2, [r4], #4
    strcc  r2, [r5], #4
    bcc    1b

    ldr    pc, =start_loc    /* jump to the relocated start_loc:  */
    
start_loc:

    /* execute the loader - this will load an image to 0x10000000 */
    bl     main

    /* The loader only returns if it is loading the Apple firmware or Linux -
       the following code isn't executed when starting Rockbox */

    /* save the startup address for the COP */
    ldr    r1, =startup_loc
    str    r0, [r1]

#if CONFIG_CPU==PP5002
    /* make sure COP is sleeping */
    ldr    r4, =0xcf004050
1:
    ldr    r3, [r4]
    ands   r3, r3, #0x4000
    beq    1b

    /* wake up COP */
    ldr    r4, =PP5002_COP_CTRL
    mov    r3, #0xce
    strh   r3, [r4]
#else
    /* make sure COP is sleeping */
    ldr    r4, =PP5020_COP_CTRL
1:
    ldr    r3, [r4]
    ands   r3, r3, #0x80000000
    beq    1b

    /* wake up COP */
    @ldr    r4, =PP5020_COP_CTRL
    mov    r3, #0x0
    str    r3, [r4]
#endif
    /* jump to start location */
    mov    pc, r0

startup_loc:
    .word    0x0

.align 8    /* starts at 0x100 */
.global boot_table
boot_table:
    /* here comes the boot table, don't move its offset */
    .space 400
#endif /* PP specific */
/* Code for ARM bootloader targets other than iPod go here */
#else /* BOOTLOADER */
    
    /* Set up stack for IRQ mode */ 
    msr    cpsr_c, #0xd2
    ldr    sp, =irq_stack
    /* Set up stack for FIQ mode */ 
    msr    cpsr_c, #0xd1
    ldr    sp, =fiq_stack
#if CONFIG_CPU == PP5020 || CONFIG_CPU == PP5002
    /* We'll load the banked FIQ mode registers with useful values here.
       These values will be used in the FIQ handler in pcm_playback.c */
    ldr    r12, =0x70002800 /* IISCONFIG */
    ldr    r11, =p
#endif
    /* Let abort mode use IRQ stack */
    msr    cpsr_c, #0xd7
    ldr    sp, =irq_stack
    /* Switch to supervisor mode */
    msr    cpsr_c, #0xd3
    ldr    sp, =stackend
    bl     main
    /* main() should never return */

/* Exception handlers. Will be copied to address 0 after memory remapping */
    .section .vectors,"aw"
    ldr    pc, [pc, #24]
    ldr    pc, [pc, #24]
    ldr    pc, [pc, #24]
    ldr    pc, [pc, #24]
    ldr    pc, [pc, #24]
    ldr    pc, [pc, #24]
    ldr    pc, [pc, #24]
    ldr    pc, [pc, #24]

    /* Exception vectors */
    .global vectors
vectors:
    .word  start 
    .word  undef_instr_handler
    .word  software_int_handler
    .word  prefetch_abort_handler
    .word  data_abort_handler
    .word  reserved_handler
    .word  irq_handler
    .word  fiq_handler

    .text

#ifndef STUB
    .global irq
    .global fiq
    .global UIE
#endif

/* All illegal exceptions call into UIE with exception address as first
   parameter. This is calculated differently depending on which exception
   we're in. Second parameter is exception number, used for a string lookup
   in UIE.
 */
undef_instr_handler:
    mov    r0, lr
    mov    r1, #0
    b      UIE

/* We run supervisor mode most of the time, and should never see a software
   exception being thrown. Perhaps make it illegal and call UIE?
 */
software_int_handler:
reserved_handler:
    movs   pc, lr

prefetch_abort_handler:
    sub    r0, lr, #4
    mov    r1, #1
    b      UIE

fiq_handler:
#if CONFIG_CPU == PP5020
    @ Branch straight to FIQ handler in pcm_playback.c. This also handles the
    @ the correct return sequence.
    ldr    pc, =fiq
#else
    stmfd  sp!, {r0-r3, r12, lr}
    mov    lr, pc
    ldr    pc, =fiq
    ldmfd  sp!, {r0-r3, r12, lr}
    subs   pc, lr, #4
#endif

data_abort_handler:
    sub    r0, lr, #8 
    mov    r1, #2
    b      UIE

irq_handler:
#ifndef STUB
    stmfd  sp!, {r0-r3, r12, lr}
    bl     irq
    ldmfd  sp!, {r0-r3, r12, lr}
#endif
    subs   pc, lr, #4

#ifdef STUB
UIE:
    b UIE
#endif

/* 256 words of IRQ stack */
    .space 256*4
irq_stack:

/* 256 words of FIQ stack */
    .space 256*4
fiq_stack:

#endif /* BOOTLOADER */ 

#elif CONFIG_CPU == TCC730
    /* Platform:     Gmini 120/SP */
    ;; disable all interrupts
     clrsr fe
    clrsr ie
    clrsr te
    ld a14, #0x3F0000

    ld r5, 0xA5
    ldb @[a14 + 6], r5    ; disable watchdog

    ld a11, #(_datacopy)    ; where the data section is in the flash
    ld a8, #(_datastart)    ; destination

    ;; copy data section from flash to ram.
    ld a9, #_datasize
    ld r6, e9
    cmp eq, r6, #0
    brf .data_copy_loop
    cmp eq, r9, #0
    brt .data_copy_end
.data_copy_loop:
    ldc r2, @a11
    ldw @[a8 + 0], r2
    add a11, #0x2
    add a8, #0x2
    sub r9, #0x2
    sbc r6, #0
    cmp ugt, r6, #0
    brt .data_copy_loop
    cmp ugt, r9, #0
    brt .data_copy_loop
.data_copy_end:

    ;; zero out bss
    ld r2, #0
    ld a8, #(_bssstart)    ; destination
    ld a9, #_bsssize
    ld r6, e9

    cmp eq, r6, #0
    brf .bss_init_loop
    cmp eq, r9, #0
    brt .bss_init_end
.bss_init_loop:
    ldw @[a8 + 0], r2
    add a8, #0x2
    sub r9, #0x2
    sbc r6, #0
    cmp ugt, r6, #0
    brt .bss_init_loop
    cmp ugt, r9, #0
    brt .bss_init_loop
.bss_init_end:

    ;; set stack pointer
    ld a15, _stackend

    ;; go!
    jsr _main

    ;; soft reset
    ld a10, #0
    ldc r10, @a10
    jmp a10


    .section .vectors, "ax"
irq_handler:

    push r0, r1
    push r2, r3
    push r4, r5
    push r6, r7
    push a8, a9
    push a10, a11
    push a12, a13
    push a14
    ld a13, #0x3f0000
    ldb r0, @[a13 + 0x26]
    add r0, r0
    ld a10, #_interrupt_vector
    ldw a13, @[a10 + r0]
    jsr a13
    pop a14
    pop a13, a12
    pop a11, a10
    pop a9, a8
    pop r7, r6
    pop r5, r4
    pop r3, r2
    pop r1, r0
    ret_irq

#elif defined(CPU_COLDFIRE)
    move.w  #0x2700,%sr

    move.l  #vectors,%d0
    movec.l %d0,%vbr
        
    move.l  #MBAR+1,%d0
    movec.l %d0,%mbar
        
    move.l  #MBAR2+1,%d0
    movec.l %d0,%mbar2

    lea     MBAR,%a0
    lea     MBAR2,%a1
        
    clr.l  (0x180,%a1)  /* PLLCR = 0 */

    /* 64K DMA-capable SRAM at 0x10000000
       DMA is enabled and has priority in both banks
       All types of accesses are allowed
       (We might want to restrict that to save power) */
    move.l  #0x10000e01,%d0
    movec.l %d0,%rambar1

    /* 32K Non-DMA SRAM at 0x10010000
       All types of accesses are allowed
       (We might want to restrict that to save power) */
    move.l  #0x10010001,%d0
    movec.l %d0,%rambar0

    /* Chip select 0 - Flash ROM */
    moveq.l #0x00,%d0      /* CSAR0 - Base = 0x00000000 */
    move.l  %d0,(0x080,%a0)
    move.l  #FLASH_SIZE-0x10000+1,%d0 /* CSMR0 - All access */
    move.l  %d0,(0x084,%a0)
    move.l  #0x00000180,%d0 /* CSCR0 - no wait states, 16 bits, no bursts */
    move.l  %d0,(0x088,%a0)
        
    /* Chip select 1 - LCD controller */
    move.l  #0xf0000000,%d0 /* CSAR1 - Base = 0xf0000000 */
    move.l  %d0,(0x08c,%a0)
    moveq.l #0x1,%d0      /* CSMR1 - 64K */
    move.l  %d0,(0x090,%a0)
    move.l  #0x00000180,%d0 /* CSCR1 - no wait states, 16 bits, no bursts */
    move.l  %d0,(0x094,%a0)
        
    /* Chip select 2 - ATA controller */
    move.l  #0x20000000,%d0 /* CSAR2 - Base = 0x20000000 */
    move.l  %d0,(0x098,%a0)
    move.l  #0x000f0001,%d0 /* CSMR2 - 64K, Only data access */
    move.l  %d0,(0x09c,%a0)
    move.l  #0x00000080,%d0 /* CSCR2 - no wait states, 16 bits, no bursts */
    move.l  %d0,(0x0a0,%a0) /* NOTE:  I'm not sure about the wait states.
                               We have to be careful with the access times,
                               since IORDY isn't connected to the HDD. */
        

#ifdef BOOTLOADER
    /* The cookie is not reset. This must mean that the boot loader
       has crashed. Let's start the original firmware immediately. */
    lea     0x10017ffc,%a2
    move.l  (%a2),%d0
    move.l  #0xc0015a17,%d1
    cmp.l   %d0,%d1
    bne.b   .nocookie
    /* Clear the cookie again */
    clr.l   (%a2)
    jmp     8

.nocookie:
    /* Set the cookie */
    move.l  %d1,(%a2)

    /* Set up the DRAM controller. The refresh is based on the 11.2896MHz
       clock (5.6448MHz bus frequency). We haven't yet started the PLL */
#if MEM < 32
    move.w  #0x8004,%d0 /* DCR - Synchronous, 80 cycle refresh */
#else
    move.w  #0x8001,%d0 /* DCR - Synchronous, 32 cycle refresh */
#endif
    move.w  %d0,(0x100,%a0)

    /* Note on 32Mbyte models:
       We place the SDRAM on an 0x1000000 (16M) offset because
       the 5249 BGA chip has a fault which disables the use of A24. The
       suggested workaround by FreeScale is to offset the base address by
       half the DRAM size and increase the mask to the double.
       In our case this means that we set the base address 16M ahead and
       use a 64M mask.
    */
#if MEM < 32
    move.l  #0x31002324,%d0 /* DACR0 - Base 0x31000000, Banks on 21 and up,
                               CAS latency 1, Page mode, No refresh yet */
    move.l  %d0,(0x108,%a0)
    move.l  #0x00fc0001,%d0 /* Size: 16M */
    move.l  %d0,(0x10c,%a0) /* DMR0 - 32Mb */
#else
    move.l  #0x31002524,%d0 /* DACR0 - Base 0x31000000, Banks on 23 and up,
                               CAS latency 1, Page mode, No refresh yet */
    move.l  %d0,(0x108,%a0)
    move.l  #0x03fc0001,%d0 /* Size: 64M because of workaround above */
    move.l  %d0,(0x10c,%a0) /* DMR0 - 32Mb */
#endif

    /* Precharge */
    moveq.l #8,%d0
    or.l    %d0,(0x108,%a0) /* DACR0[IP] = 1, next access will issue a
                               Precharge command */
    move.l  #0xabcd1234,%d0
    move.l  %d0,0x31000000  /* Issue precharge command */

    move.l  #0x8000,%d0
    or.l    %d0,(0x108,%a0) /* Enable refresh */

    /* Let it refresh */
    move.l  #500,%d0
.delayloop:
    subq.l  #1,%d0
    bne.b   .delayloop

    /* Mode Register init */
    moveq.l #0x40,%d0       /* DACR0[IMRS] = 1, next access will set the
                               Mode Register */
    or.l    %d0,(0x108,%a0)

    move.l  #0xabcd1234,%d0
    move.l  %d0,0x31000800  /* A12=1 means CASL=1 (a0 is not connected) */

    /* DACR0[IMRS] gets deactivated by the SDRAM controller */
#endif /* BOOTLOADER */

    /* Invalicate cache */
    move.l  #0x01000000,%d0
    movec.l %d0,%cacr
        
    /* Enable cache, default=non-cacheable,no buffered writes */
    move.l  #0x80000000,%d0
    movec.l %d0,%cacr

    /* Cache enabled in SDRAM only, buffered writes enabled */
    move.l  #0x3103c020,%d0
    movec.l %d0,%acr0
    moveq.l #0,%d0
    movec.l %d0,%acr1

#ifndef BOOTLOADER
    /* zero out .ibss */
    lea     _iedata,%a2
    lea     _iend,%a4
    bra.b   .iedatastart
.iedataloop:
    clr.l   (%a2)+
.iedatastart:
    cmp.l   %a2,%a4
    bhi.b   .iedataloop

    /* copy the .iram section */
    lea     _iramcopy,%a2
    lea     _iramstart,%a3
    lea     _iramend,%a4
    bra.b   .iramstart
.iramloop:
    move.l  (%a2)+,(%a3)+
.iramstart:
    cmp.l   %a3,%a4
    bhi.b   .iramloop
#endif /* !BOOTLOADER */

#ifdef IRIVER_H300_SERIES
    /* Set KEEP_ACT before doing the lengthy copy and zero-fill operations */
    move.l #0x00080000,%d0
    or.l %d0,(0xb4,%a1)
    or.l %d0,(0xb8,%a1)
    or.l %d0,(0xbc,%a1)
#endif

    /* zero out bss */
    lea     _edata,%a2
    lea     _end,%a4
    bra.b   .edatastart
.edataloop:
    clr.l   (%a2)+
.edatastart:
    cmp.l   %a2,%a4
    bhi.b   .edataloop

    /* copy the .data section */
    lea     _datacopy,%a2
    lea     _datastart,%a3
    cmp.l   %a2,%a3
    beq.b   .nodatacopy   /* Don't copy if src and dest are equal */
    lea     _dataend,%a4
    bra.b   .datastart
.dataloop:
    move.l  (%a2)+,(%a3)+
.datastart:
    cmp.l   %a3,%a4
    bhi.b   .dataloop
.nodatacopy:

    /* Munge the main stack */
    lea     stackbegin,%a2
    lea     stackend,%a4
    move.l  %a4,%sp
    move.l  #0xdeadbeef,%d0
.mungeloop:
    move.l  %d0,(%a2)+
    cmp.l   %a2,%a4
    bhi.b   .mungeloop

    jsr     main
.hoo:
    bra.b   .hoo

    .section .resetvectors
vectors:
    .long   stackend
    .long   start
#else
    /* Platform:     Archos Jukebox */

    mov.l   .vbr_k,r1
#ifdef DEBUG
    /* If we have built our code to be loaded via the standalone GDB
     * stub, we will have out VBR at some other location than 0x9000000.
     * We must copy the trap vectors for the GDB stub to our vector table. */
    mov.l   .orig_vbr_k,r2

    /* Move the invalid instruction vector (4) */
    mov     #4,r0
    shll2   r0
    mov.l   @(r0,r2),r3
    mov.l   r3,@(r0,r1)

    /* Move the invalid slot vector (6) */
    mov     #6,r0
    shll2   r0
    mov.l   @(r0,r2),r3
    mov.l   r3,@(r0,r1)

    /* Move the bus error vector (9) */
    mov     #9,r0
    shll2   r0
    mov.l   @(r0,r2),r3
    mov.l   r3,@(r0,r1)

    /* Move the DMA bus error vector (10) */
    mov     #10,r0
    shll2   r0
    mov.l   @(r0,r2),r3
    mov.l   r3,@(r0,r1)

    /* Move the NMI vector as well (11) */
    mov     #11,r0
    shll2   r0
    mov.l   @(r0,r2),r3
    mov.l   r3,@(r0,r1)

    /* Move the UserBreak vector as well (12) */
    mov     #12,r0
    shll2   r0
    mov.l   @(r0,r2),r3
    mov.l   r3,@(r0,r1)

    /* Move the breakpoint trap vector (32) */
    mov     #32,r0
    shll2   r0
    mov.l   @(r0,r2),r3
    mov.l   r3,@(r0,r1)

    /* Move the IO trap vector (33) */
    mov     #33,r0
    shll2   r0
    mov.l   @(r0,r2),r3
    mov.l   r3,@(r0,r1)

    /* Move the serial Rx interrupt vector (105) */
    mov     #105,r0
    shll2   r0
    mov.l   @(r0,r2),r3
    mov.l   r3,@(r0,r1)

    /* Move the single step trap vector (127) */
    mov     #127,r0
    shll2   r0
    mov.l   @(r0,r2),r3
    mov.l   r3,@(r0,r1)
#endif /* DEBUG */
    ldc     r1,vbr

    mov     #0,r0
    ldc     r0,gbr

    /* zero out .ibss */
    mov.l   .iedata_k,r0
    mov.l   .iend_k,r1
    bra     .iedatastart
    mov     #0,r2
.iedataloop: /* backwards is faster and shorter */
    mov.l   r2,@-r1
.iedatastart:
    cmp/hi  r0,r1
    bt      .iedataloop

    /* copy the .iram section */
    mov.l   .iramcopy_k,r0
    mov.l   .iram_k,r1
    mov.l   .iramend_k,r2
    /* Note: We cannot put a PC relative load into the delay slot of a 'bra'
       instruction (the offset would be wrong), but there is nothing else to
       do before the loop, so the delay slot would be 'nop'. The cmp / bf
       sequence is the same length, but more efficient. */
    cmp/hi  r1,r2
    bf      .noiramcopy
.iramloop:
    mov.l   @r0+,r3
    mov.l   r3,@r1
    add     #4,r1
    cmp/hi  r1,r2
    bt      .iramloop
.noiramcopy:

    /* zero out bss */
    mov.l   .edata_k,r0
    mov.l   .end_k,r1
    bra     .edatastart
    mov     #0,r2
.edataloop: /* backwards is faster and shorter */
    mov.l   r2,@-r1
.edatastart:
    cmp/hi  r0,r1
    bt      .edataloop

    /* copy the .data section, for rombased execution */
    mov.l   .datacopy_k,r0
    mov.l   .data_k,r1
    cmp/eq  r0,r1
    bt      .nodatacopy   /* Don't copy if src and dest are equal */
    mov.l   .dataend_k,r2
    cmp/hi  r1,r2
    bf      .nodatacopy
.dataloop:
    mov.l   @r0+,r3
    mov.l   r3,@r1
    add     #4,r1
    cmp/hi  r1,r2
    bt      .dataloop
.nodatacopy:

    /* Munge the main thread stack */
    mov.l   .stackbegin_k,r0
    mov.l   .stackend_k,r1
    mov     r1,r15
    mov.l   .deadbeef_k,r2
.mungeloop: /* backwards is faster and shorter */
    mov.l   r2,@-r1
    cmp/hi  r0,r1
    bt      .mungeloop

    /* call the mainline */
    mov.l   .main_k,r0
    jsr     @r0
    nop
.hoo:
    bra     .hoo
    nop

    .align  2
.vbr_k:
    .long   vectors
#ifdef DEBUG
.orig_vbr_k:
    .long   0x09000000
#endif
.iedata_k:
    .long   _iedata
.iend_k:
    .long   _iend
.iramcopy_k:
    .long   _iramcopy
.iram_k:
    .long   _iramstart
.iramend_k:
    .long   _iramend
.edata_k:
    .long   _edata
.end_k:
    .long   _end
.datacopy_k:
    .long   _datacopy
.data_k:
    .long   _datastart
.dataend_k:
    .long   _dataend
.stackbegin_k:
    .long   _stackbegin
.stackend_k:
    .long   _stackend
.deadbeef_k:
    .long   0xdeadbeef
.main_k:
    .long   _main

    .section .resetvectors
vectors:
    .long   start
    .long   _stackend
    .long   start
    .long   _stackend
#endif