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/*
* Mini-loader for the SVGM BSP.
*
* Author: Till Straumann, 10/2001 <strauman@slac.stanford.edu>
*
* Some ideas are borrowed from the powerpc/shared/bootloader
* by
* Copyright (C) 1998, 1999 Gabriel Paubert, paubert@iram.es
* Copyright (C) 1999 Eric Valette. valette@crf.canon.fr
*
* The SMON firmware is unable to load the RTEMS image below
* 0x2000 (I believe their stack is growing below 0x1000).
*
* The code provided by this file is responsible for the performing
* the following steps:
*
* 1) Save commandline parameters to an area that is
* a) not covered by the downloaded image
* b) will not be overwritten by the moved image
* nor the final BSS segment (rtems clears BSS
* before saving the command line).
* 2) Move the entire image (including this very file) to
* its final location starting at 0x0000.
* It is important to note that _NO_STACK_ is available
* during this step. Also, there is probably no return to
* SMON because relocating RTEMS will destroy vital SMON
* data (such as its stack).
* 3) Flush the cache to make sure the relocated image is actually
* in memory.
* 4) setup RTEMS environment (initial register values), most
* notably an initial STACK. The initial stack may be small and
* is used by RTEMS only at a very early stage.
* A safe place for the stack seems to be the 00..0x7f area.
* NOTE: we should respect the MAILBOX area 0x80..0xff!
* 5) switch the MMU off (because that's what RTEMS is expecting
* it to be at startup).
* 6) fire up rtems...
*
*
* Calling convention:
* R1: SMON SP
* R3: command line string start
* R4: command line string end + 1
* R5: where SMON put the image
* if R5 is 0, the preloader will use its entry point
* as the image starting address.
* See NOTE below.
* R6: end of the image (i.e. R6-R5 is the image length)
* if R6 is 0, _edata will be used as the image length
* See NOTE below.
*
* NOTE: if the symbol DONT_USE_R5_ENTRY is defined,
* R5/R6 are never used and the necessary parameters are
* determined at runtime (R5) / linkage (R6) [_edata]
*
* ASSUMPTIONS:
* The code RELIES on the assumption that the image will be
* moved DOWNWARDS in memory and that the this loader is
* prepended to the image, i.e. it is safe to do
* codemove(codemove,0,codemove_end - codemove);
* (*0)(codemove_end, codemove_end-codemove, __rtems_end-codemove_end);
* where codemove(from, to, nbytes) is defined as
* codemove(from, to, nbytes) { while (nbytes--) *(to++)=*(from++); }
* Implicit to these assumptions is the assumption that the destination
* address is cache block aligned.
* Furthermore, the byte count is assumed to be a multiple
* of four
*
*/
#if 0
#include <rtems/score/powerpc.h>
#else
#ifndef PPC_CACHE_ALIGNMENT
#define PPC_CACHE_ALIGNMENT 32
#endif
#endif
#include <rtems/score/cpu.h>
#include <rtems/asm.h>
/* Note that major modifications may be needed
* if DESTINATION_ADDR is not 0
*/
#define KERNELBASE 0x0
#define INITIAL_STACK 0x70 /* 16-byte aligned */
#define CACHE_LINE_SIZE PPC_CACHE_ALIGNMENT /* autodetect doesn't work, see below */
#define ASSUME_RTEMS_INSTALLS_VECTORS /* assume we need not load vectors */
#define DONT_USE_R5_ENTRY /* always dynamically determine the address we're running from */
/* put this into its own section which we want to
* be loaded at the very beginning. We should probably
* not use more than 255 bytes.
*/
PUBLIC_VAR(__rtems_start)
PUBLIC_VAR(__rtems_entry_point)
PUBLIC_VAR(__rtems_end)
.section .entry_point_section,"awx",@progbits
preload:
/* find out where we are */
bl here
here:
xor r0,r0,r0
mtmsr r0 /* clear MSR to known state */
mflr r5
addi r5,r5,-(here-preload)
lis r27,_edata@h
ori r27,r27,_edata@l
/* at this point the register contents are
* R3: command line start
* R4: R3 + command line length
* R5: address we are running from / loaded to
* R27: image end
*/
/* save command line start */
mr r6, r3
/* save the command line parameters if they are to be overwritten */
sub. r17, r4, r3 /* string length */
ble leaveparms /* <=0 -> no parameters */
/* copy has to be out of the way of the bss; therefore we must
* put the string out of the way of both, the current end of
* the image (without bss) AND the end of the loaded image
* (including bss):
* |......image.........| downloaded image
* |image_bss...........| loaded image with bss appended
*
* ^ safe place for string
*
* the alternative scenario looks like this:
* |..image.............| downloaded image
* |image_bss...........| loaded image with bss appended
* ^ safe place for string
*/
lis r18, __rtems_end+0x10000@h /* round up, save one instruction */
add r16, r5, r27 /* image end + 1 */
cmpw r16, r18
bge ishighenough
mr r16,r18 /* __rtems_end is higher than the image end
* (without bss)
*/
ishighenough:
cmpw r16, r3 /* destination start > current string start ? */
ble leaveparms /* string already after dst, leave it */
/* copy string from the last byte downwards */
add r6, r16, r17 /* last byte of destination + 1 */
mtctr r17
1:
lbzu r3, -1(r4)
stbu r3, -1(r6)
bdnz 1b
leaveparms:
add r7, r6, r17 /* destination + strlen */
#ifndef CACHE_LINE_SIZE
/* Oh well, SMON has inhibited the cache, so this
* nice routine doesn't work...
*/
/* figure out the cache line size */
li r16, 0x80
cmpw r5, r16 /* 'from' must be > 0x80 */
blt panic
1: /* store some arbitrary, nonzero stuff in 0..0x7c */
stwu r16,-4(r16)
cmpwi r16,0
bne 1b
dcbz 0,r16 /* zero out one cache line */
subi r16,r16,4
2: lwzu r0,4(r16) /* search for a non-zero word */
cmpwi r0,0
beq 2b
/* OK, r16 now hold the size of a cache line in bytes */
#else
li r16,CACHE_LINE_SIZE
#endif
lis r3,preload@h
ori r3,r3,preload@l
mr r4,r5 /* from-addr */
li r5,_preload_size/* this is never > 16k */
/* now move ourselves to the link address ('preload').
* We set up the LR, so domove() 'returns' to the
* relocated copy
*/
lis r0,return_here@h
ori r0,r0,return_here@l
mtlr r0
b domove /* move the preloader itself */
return_here:
/* now we move the entire rest of the image */
#ifdef ASSUME_RTEMS_INSTALLS_VECTORS
lis r3,__rtems_start@h
ori r3,r3,__rtems_start@l
lis r0,preload@h /* calculate/adjust from address */
ori r0,r0,preload@l
sub r0,r3,r0
add r4,r4,r0
sub r5,r27,r3
#else
add r3,r3,r5 /* add preloader size to destination */
add r4,r4,r5 /* and source addresses */
sub r5,r27,r5 /* length of the remaining rest */
#endif
bl domove
/* OK, now everything should be in place.
* we are ready to start...
*/
/* setup initial stack for rtems early boot */
li r1,INITIAL_STACK
/* tag TOS with a NULL pointer (for stack trace) */
li r0, 0
stw r0, 0(r1)
/* disable the MMU and fire up rtems */
mfmsr r0
ori r0,r0,MSR_IR|MSR_DR|MSR_IP|MSR_ME
xori r0,r0,MSR_IR|MSR_DR
mtsrr1 r0
lis r0,__rtems_entry_point@h
ori r0,r0,__rtems_entry_point@l
mtsrr0 r0
/* R6: start of command line */
/* R7: end of command line +1 */
rfi
/* domove(to, from, nbytes):
*
* move a R5 bytes from R4 to R3 and flush
* the caches for the destination memory
* region. R16 provides the cache line size.
* DESTROYS: R0, R17, R18, CTR, CR
*/
domove:
addi r0,r5,3 /* convert to word count */
srwi. r0,r0,2
beq 3f /* nothing to do */
cmpw r3,r4 /* from == to ? */
beq 3f
mtctr r0
la r18,-4(r4)
la r17,-4(r3)
1: lwzu r0,4(r18)
stwu r0,4(r17)
bdnz 1b /* move data */
/* now, we must flush the destination cache region */
#ifndef CACHE_LINE_SIZE
cmpwi r16,0
beq 3f /* nothing to do */
#endif
#if defined(CACHE_LINE_SIZE) && CACHE_LINE_SIZE > 0
add r17,r3,r5 /* target end pointer */
subi r0,r16,1
add r17,r17,r0
andc r17,r17,r0 /* cache aligned target end pointer */
mr r18,r3
2: cmpw r18,r17
dcbst 0,r18 /* write out data cache line */
icbi 0,r18 /* invalidate corresponding i-cache line */
add r18,r18,r16
blt 2b
sync /* make sure data is written back */
isync /* invalidate possibly preloaded instructions */
#endif
3:
blr
#if !defined(CACHE_LINE_SIZE)
panic:
li r10,0x63
mfmsr r0
ori r0,r0,MSR_IP
mtmsr r0
sc
#endif
/* DONT PUT ANY CODE BELOW HERE */
_preload_size = . - preload
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