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/* $Id: bare.S,v 1.4 1996/04/23 01:53:40 davem 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
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