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* arch/ppc/boot/simple/relocate.S
* This is the common part of the loader relocation and initialization
* process. All of the board/processor specific initialization is
* done before we get here.
* Author: Tom Rini
* Derived from arch/ppc/boot/prep/head.S (Cort Dougan, many others).
* 2001-2004 (c) MontaVista, Software, Inc. This file is licensed under
* the terms of the GNU General Public License version 2. This program
* is licensed "as is" without any warranty of any kind, whether express
* or implied.
#include <linux/config.h>
#include <asm/cache.h>
#include <asm/ppc_asm.h>
#define GETSYM(reg, sym) \
lis reg, sym@h; ori reg, reg, sym@l
/* We get called from the early initialization code.
* Register 3 has the address where we were loaded,
* Register 4 contains any residual data passed from the
* boot rom.
.globl relocate
/* Save r3, r4 for later.
* The r8/r11 are legacy registers so I don't have to
* rewrite the code below :-).
mr r8, r3
mr r11, r4
/* compute the size of the whole image in words. */
addi r5,r5,3 /* round up */
sub r5,r5,r4 /* end - start */
srwi r5,r5,2
mr r7,r5 /* Save for later use. */
* Check if we need to relocate ourselves to the link addr or were
* we loaded there to begin with.
cmpw cr0,r3,r4
beq start_ldr /* If 0, we don't need to relocate */
/* Move this code somewhere safe. This is max(load + size, end)
* r8 == load address
GETSYM(r4, start)
GETSYM(r5, end)
sub r6,r5,r4
add r6,r8,r6 /* r6 == phys(load + size) */
cmpw r5,r6
bgt 1f
b 2f
mr r6, r5
/* dest is in r6 */
/* Ensure alignment --- this code is precautionary */
addi r6,r6,4
li r5,0x0003
andc r6,r6,r5
/* Find physical address and size of do_relocate */
GETSYM(r5, __relocate_start)
GETSYM(r4, __relocate_end)
GETSYM(r3, start)
/* Size to copy */
sub r4,r4,r5
srwi r4,r4,2
/* Src addr to copy (= __relocate_start - start + where_loaded) */
sub r3,r5,r3
add r5,r8,r3
/* Save dest */
mr r3, r6
/* Do the copy */
mtctr r4
3: lwz r4,0(r5)
stw r4,0(r3)
addi r3,r3,4
addi r5,r5,4
bdnz 3b
GETSYM(r4, __relocate_start)
GETSYM(r5, do_relocate)
sub r4,r5,r4 /* Get entry point for do_relocate in */
add r6,r6,r4 /* relocated section */
/* This will return to the relocated do_relocate */
mtlr r6
b flush_instruction_cache
.section ".relocate_code","xa"
/* We have 2 cases --- start < load, or start > load
* This determines whether we copy from the end, or the start.
* Its easier to have 2 loops than to have paramaterised
* loops. Sigh.
li r6,0 /* Clear checksum */
mtctr r7 /* Setup for a loop */
GETSYM(r4, start)
mr r3,r8 /* Get the load addr */
cmpw cr0,r4,r3 /* If we need to copy from the end, do so */
bgt do_relocate_from_end
1: lwz r5,0(r3) /* Load and decrement */
stw r5,0(r4) /* Store and decrement */
addi r3,r3,4
addi r4,r4,4
xor r6,r6,r5 /* Update checksum */
bdnz 1b /* Are we done? */
b do_relocate_out /* Finished */
GETSYM(r3, end)
slwi r4,r7,2
add r4,r8,r4 /* Get the physical end */
1: lwzu r5,-4(r4)
stwu r5, -4(r3)
xor r6,r6,r5
bdnz 1b
mtlr r3 /* Easiest way to do an absolute jump */
/* Some boards don't boot up with the I-cache enabled. Do that
* now because the decompress runs much faster that way.
* As a side effect, we have to ensure the data cache is not enabled
* so we can access the serial I/O without trouble.
b flush_instruction_cache
/* Clear all of BSS and set up stack for C calls */
lis r3,edata@h
ori r3,r3,edata@l
lis r4,end@h
ori r4,r4,end@l
subi r3,r3,4
subi r4,r4,4
li r0,0
50: stwu r0,4(r3)
cmpw cr0,r3,r4
bne 50b
90: mr r9,r1 /* Save old stack pointer (in case it matters) */
lis r1,.stack@h
ori r1,r1,.stack@l
addi r1,r1,4096*2
subi r1,r1,256
li r2,0x000F /* Mask pointer to 16-byte boundary */
andc r1,r1,r2
* Exec kernel loader
mr r3,r8 /* Load point */
mr r4,r7 /* Program length */
mr r5,r6 /* Checksum */
mr r6,r11 /* Residual data */
mr r7,r25 /* Validated OFW interface */
bl load_kernel
* Make sure the kernel knows we don't have things set in
* registers. -- Tom
li r4,0
li r5,0
li r6,0
* Start at the begining.
li r9,0xc
mtlr r9
/* tell kernel we're prep, by putting 0xdeadc0de at KERNELLOAD,
* and tell the kernel to start on the 4th instruction since we
* overwrite the first 3 sometimes (which are 'nop').
lis r10,0xdeadc0de@h
ori r10,r10,0xdeadc0de@l
li r9,0
stw r10,0(r9)
li r9,0
mtlr r9
.comm .stack,4096*2,4