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/* $Id: bare.S,v 1.1 2005-12-20 09:50:39 jcastillo Exp $
 * base.S:      Ugly low-level boot program entry code.  The job of this
 *              module is to parse the boot flags, try to mount the remote
 *              root filesystem and load the kernel into virtual memory.
 *
 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
 */

#include "bare.h"
#include <asm/ptrace.h>

        .data
        .globl C_LABEL(romvec)
        .globl C_LABEL(idp_ptr)

C_LABEL(romvec):
        .word 0
C_LABEL(idp_ptr):
        .word 0

        .text
        .align 8
        .globl C_LABEL(first_adr_in_text)

C_LABEL(first_adr_in_text):

        /* Grrr, boot block, scratching my head... */
        .globl C_LABEL(b_block)       /* Start of actual boot block */
        .globl C_LABEL(b_block_size)  /* In bytes */
        .globl C_LABEL(b_block_cksum) /* Checksum of boot block bytes */

        b       start_of_execution    /* XXX Hack */
        nop

        .align  8
C_LABEL(b_block):       
        .skip   (BOOTBLOCK_NENTRIES * BOOTBLOCK_ENTSIZE)

C_LABEL(b_block_size):
        .word   0

C_LABEL(b_block_cksum):
        .word   0

/* Ok, the prom has left in %o0 the PROM pointer.  We leave it here
 * for when we jump into the kernel.  So save out of this window before
 * you dick with %o0.  As far as I know we could be loaded *anywhere*, so
 * we relocate ourselves to the "linked" location.  Self modifying code rules.
 */

start_of_execution:
        sethi   %hi(C_LABEL(first_adr_in_text)), %o1            ! This is our top
        or      %o1, %lo(C_LABEL(first_adr_in_text)), %o1       ! of stack too.
        sub     %o1, REGWIN_SZ, %o1
        add     %o1, 0x7, %o1
        andn    %o1, 0x7, %o1
        save    %o1, 0x0, %sp                                   ! save is an add
here:
        call    there
        sethi   %hi(here), %o4
there:  
        sub     %o7, here-C_LABEL(first_adr_in_text), %o5
        or      %o4, %lo(here), %o4
        cmp     %o4, %o7
        be      loaded_ok
        nop

        /* Gotta relocate, compute our size sans bss segment. */
        set     C_LABEL(edata)+4, %o3
        set     C_LABEL(first_adr_in_text), %o2
        sub     %o3, %o2, %o3
rel_loop:
        ld      [%o5], %o4
        add     %o5, 0x4, %o5
        st      %o4, [%o2]
        subcc   %o3, 0x4, %o3
        bg      rel_loop
        add     %o2, 0x4, %o2

        /* Pray that we are now in a sane place in memory */
        sethi   %hi(loaded_ok), %o2
        or      %o2, %lo(loaded_ok), %o2
        jmp     %o2
        nop

loaded_ok:
        /* Save the PROM pointer */
        sethi   %hi(C_LABEL(romvec)), %o1
        or      %o1, %lo(C_LABEL(romvec)), %o1
        st      %i0, [%o1]

        /* Build a PSR we can live with */
        rd      %psr, %o1

#if 0
        andn    %o1, PSR_PIL, %o1
        sethi   %hi(SANE_PSR), %g4
        or      %g4, %lo(SANE_PSR), %g4
        or      %o1, %g4, %o1
#endif

        /* V8 book says this works to calculate num_windows */
        sethi   %hi(0xffffffff), %g2
        rd      %wim, %g3
        or      %g2, %lo(0xffffffff), %g2
        wr      %g2, 0x0, %wim
        WRITE_PAUSE

        rd      %wim, %g4
        WRITE_PAUSE

        wr      %g3, 0x0, %wim
        WRITE_PAUSE

        /* Restore old %psr */
        wr      %o1, 0x0, %psr
        WRITE_PAUSE

        or      %g0, 0x0, %g3
1:
        srl     %g4, 0x1, %g4
        subcc   %g4, 0x0, %g0
        bne     1b
        add     %g3, 0x1, %g3
        
        /* %g3 now contains nwindows */
        sethi   %hi(C_LABEL(nwindows)), %o4
        st      %g3, [%o4 + %lo(C_LABEL(nwindows))]

        /* Now zero out our bss segment, lord knows the nasty prom monster
         * didn't do it for us.
         */
        sethi   %hi(C_LABEL(end)), %g1
        or      %g1, %lo(C_LABEL(end)), %g1
        add     %g1, 0x4, %g1
        sethi   %hi(C_LABEL(edata)), %g2
        or      %g2, %lo(C_LABEL(edata)), %g2

        /* Slow, inefficient, who cares, this is messy boot code */
bzero_bss_loop:
        st      %g0, [%g2]
        add     %g2, 0x4, %g2
        cmp     %g2, %g1
        bl      bzero_bss_loop
        nop

        call    C_LABEL(init_me)        ! Fun with empirical constants and prom
        nop

        /* Dump back into the prom */
get_me_out_of_here:
        set     C_LABEL(romvec), %g2
        ld      [%g2], %g2
        ld      [%g2 + 0x74], %g2
        restore
        call    %g2
        nop