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author | Till Straumann <strauman@slac.stanford.edu> | 2007-12-11 07:49:00 +0000 |
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committer | Till Straumann <strauman@slac.stanford.edu> | 2007-12-11 07:49:00 +0000 |
commit | c9f79e6da6b8b2e9ee804634668dad05637db2b9 (patch) | |
tree | d6e0f0168dc50e041d54c4f87e4ff9bf94264cf6 /c/src/lib/libbsp/powerpc/shared/start/preload.S | |
parent | 2007-12-10 Till Straumann <strauman@slac.stanford.edu> (diff) | |
download | rtems-c9f79e6da6b8b2e9ee804634668dad05637db2b9.tar.bz2 |
2007-12-10 Till Straumann <strauman@slac.stanford.edu>
* Makefile.am, start/preload.S: moved preload.S
to ../shared/start.
Diffstat (limited to 'c/src/lib/libbsp/powerpc/shared/start/preload.S')
-rw-r--r-- | c/src/lib/libbsp/powerpc/shared/start/preload.S | 277 |
1 files changed, 277 insertions, 0 deletions
diff --git a/c/src/lib/libbsp/powerpc/shared/start/preload.S b/c/src/lib/libbsp/powerpc/shared/start/preload.S new file mode 100644 index 0000000000..9da4b1ca7d --- /dev/null +++ b/c/src/lib/libbsp/powerpc/shared/start/preload.S @@ -0,0 +1,277 @@ +/* + * Mini-loader for the SVGM BSP. + * + * $Id$ + * + * 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 0x78 /* 8-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 + /* 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 |