/*      $NetBSD: srt0.S,v 1.5 2014/08/07 13:56:57 joerg Exp $   */

/*-
* Copyright (c) 2002 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Steve C. Woodford.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/

#include <machine/asm.h>
#include <machine/psl.h>
#include <powerpc/spr.h>
#include <powerpc/oea/spr.h>

#define STACK_SIZE      8192

/*
* The main entry point when loaded by PPC-Bug.
*
* There are two possible entry conditions here:
*
*   1) We were booted in `PReP' mode, either from disk or the network.
*      In this case, we have no control over the load address so we
*      have to relocate ourselves to the appropriate place.
*      The firmware passes us the following registers:
*
*        %r1  -> Temporary stack
*        %r3  -> Residual Data
*        %r4  -> The address we were loaded to
*        %r5  -> Zero
*
*   2) We were booted over the network in Non-PReP mode. In this case,
*      the load address is usually set using PPC-Bug's "niot" command,
*      but we won't depend on it so relocation may be required. The
*      firmware passes us the following registers:
*
*        %r1  -> Temporary stack
*        %r3  -> CLUN of the network device we booted from
*        %r4  -> DLUN of the network device we booted from
*        %r5  -> Non-zero
*        %r6  -> Base address of network device
*        %r7  -> Execution address of loaded program
*        %r8  -> Address of IP-address data structure
*        %r9  -> Pointer to start of filename string
*        %r10 -> Pointer to end+1 of filename string
*        %r11 -> Pointer to start of argument string
*        %r12 -> Pointer to end+1 of argument string
*
* The obvious way to distinguish between the two boot modes is by
* checking the value of %r5.
*/
ENTRY(_start)
       bl      1f
1:      xor     %r0,%r0,%r0

       /* First, switch off Instruction and Data caches. */
       mfspr   %r13,SPR_HID0
       LDCONST(%r14, HID0_DCE|HID0_ICE)
       andc    %r13,%r13,%r14
       sync
       mtspr   SPR_HID0,%r13


       /*
        * All registers now available. Let's see if we need to relocate
        */
       LDCONST(%r13,_C_LABEL(_start))  /* Where we'd like to be */
       LDCONST(%r14,_C_LABEL(edata))   /* End of data section */
       LDCONST(%r15,0x3)
       add     %r14,%r14,%r15
       andc    %r14,%r14,%r15          /* Rounded up to the nearest 32-bits */
       sub     %r15,%r14,%r13          /* Our size, in bytes */
       mflr    %r16                    /* Get address we were loaded to */
       subi    %r16,%r16,0x4           /* Correct for branch */
       cmpw    %r13,%r16               /* Do we need to relocate? */
       beq     _ASM_LABEL(clrbss)      /* No relocation necessary */
       li      %r17,0x4
       bgt     1f                      /* Relocate using forward copy? */

       /* Nope. Need to copy in reverse in case of overlap */
       mr      %r13,%r14               /* dest -> end */
       add     %r16,%r16,%r15          /* src + size */
       subi    %r17,%r17,0x8           /* Increment is -4 */

       /*
        * Do the relocation
        *  %r13  -> dest
        *  %r15  -> number of bytes
        *  %r16  -> src
        *  %r17  -> Increment (+4 or -4)
        */
1:      srwi    %r15,%r15,0x2           /* Convert length to 32-bit words */
       mtctr   %r15                    /* Save in counter register */

2:      lwz     %r15,0(%r16)
       stw     %r15,0(%r13)
       add     %r16,%r16,%r17
       add     %r13,%r13,%r17
       bdnz    2b

       /* Now do an absolute jump to the relocated code */
       LDCONST(%r13,_ASM_LABEL(clrbss))
       mtlr    %r13
       blr

ASENTRY(clrbss)
       LDCONST(%r13,_C_LABEL(edata))   /* End of the data section */
       LDCONST(%r14,_C_LABEL(end))     /* End of BSS */
       LDCONST(%r15,0x3)
       add     %r14,%r14,%r15
       andc    %r14,%r14,%r15          /* Round-up end of BSS to 32-bits */
       sub     %r15,%r14,%r13          /* r15 == length of BSS */
       srwi    %r15,%r15,0x2
       mtctr   %r15                    /* CTR == # of 32-bit words in BSS */
1:      stw     %r0,0(%r13)             /* Clear BSS */
       addi    %r13,%r13,4
       bdnz    1b

       /* Fix up our own stack */
       LDCONST(%r1,stack)
       addi    %r1,%r1,STACK_SIZE-0x10
       LDCONST(%r13,0x0f)
       andc    %r1,%r1,%r13

       /*
        * Copy the arguments passed in from Bug into bug_bootinfo
        *
        * See bugsyscalls.h for details.
        */
       LDCONST(%r13,_C_LABEL(bug_bootinfo))
       stw     %r5,0x00(%r13)
       stw     %r3,0x04(%r13)
       stw     %r4,0x08(%r13)
       stw     %r6,0x0c(%r13)
       stw     %r7,0x10(%r13)
       stw     %r8,0x14(%r13)
       stw     %r9,0x18(%r13)
       stw     %r10,0x1c(%r13)
       stw     %r11,0x20(%r13)
       stw     %r12,0x24(%r13)

       mr      %r3,%r13
       bl      _C_LABEL(main)          /* void main(void) */
       /* FALLTHROUGH */

/*
* Return to the debugger, either because main() returned or via panic().
*/
ENTRY(_rtt)
       addi    %r10,0,0x0063
       sc
1:      nop
       b       1b

       /*
        * C code runs on this stack.
        */
       .comm   stack,STACK_SIZE,4
       .comm   errno,4,4
       .comm   debug,4,4

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