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linux/arch/powerpc/kernel/misc_64.S
David Gibson 25c8a78b1e [PATCH] powerpc: Fix handling of fpscr on 64-bit 
The recent merge of fpu.S broken the handling of fpscr for
ARCH=powerpc and CONFIG_PPC64=y.  FP registers could be corrupted,
leading to strange random application crashes.

The confusion arises, because the thread_struct has (and requires) a
64-bit area to save the fpscr, because we use load/store double
instructions to get it in to/out of the FPU.  However, only the low
32-bits are actually used, so we want to treat it as a 32-bit quantity
when manipulating its bits to avoid extra load/stores on 32-bit.  This
patch replaces the current definition with a structure of two 32-bit
quantities (pad and val), to clarify things as much as is possible.
The 'val' field is used when manipulating bits, the structure itself
is used when obtaining the address for loading/unloading the value
from the FPU.

While we're at it, consolidate the 4 (!) almost identical versions of
cvt_fd() and cvt_df() (arch/ppc/kernel/misc.S,
arch/ppc64/kernel/misc.S, arch/powerpc/kernel/misc_32.S,
arch/powerpc/kernel/misc_64.S) into a single version in fpu.S.  The
new version takes a pointer to thread_struct and applies the correct
offset itself, rather than a pointer to the fpscr field itself, again
to avoid confusion as to which is the correct field to use.

Finally, this patch makes ARCH=ppc64 also use the consolidated fpu.S
code, which it previously did not.

Built for G5 (ARCH=ppc64 and ARCH=powerpc), 32-bit powermac (ARCH=ppc
and ARCH=powerpc) and Walnut (ARCH=ppc, CONFIG_MATH_EMULATION=y).
Booted on G5 (ARCH=powerpc) and things which previously fell over no
longer do.

Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
2005-10-27 20:48:50 +10:00

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/*
* arch/powerpc/kernel/misc64.S
*
* This file contains miscellaneous low-level functions.
* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
*
* Largely rewritten by Cort Dougan (cort@cs.nmt.edu)
* and Paul Mackerras.
* Adapted for iSeries by Mike Corrigan (mikejc@us.ibm.com)
* PPC64 updates by Dave Engebretsen (engebret@us.ibm.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
*/
#include <linux/config.h>
#include <linux/sys.h>
#include <asm/unistd.h>
#include <asm/errno.h>
#include <asm/processor.h>
#include <asm/page.h>
#include <asm/cache.h>
#include <asm/ppc_asm.h>
#include <asm/asm-offsets.h>
#include <asm/cputable.h>
#include <asm/thread_info.h>
.text
/*
* Returns (address we are running at) - (address we were linked at)
* for use before the text and data are mapped to KERNELBASE.
*/
_GLOBAL(reloc_offset)
mflr r0
bl 1f
1: mflr r3
LOADADDR(r4,1b)
subf r3,r4,r3
mtlr r0
blr
/*
* add_reloc_offset(x) returns x + reloc_offset().
*/
_GLOBAL(add_reloc_offset)
mflr r0
bl 1f
1: mflr r5
LOADADDR(r4,1b)
subf r5,r4,r5
add r3,r3,r5
mtlr r0
blr
_GLOBAL(get_msr)
mfmsr r3
blr
_GLOBAL(get_dar)
mfdar r3
blr
_GLOBAL(get_srr0)
mfsrr0 r3
blr
_GLOBAL(get_srr1)
mfsrr1 r3
blr
_GLOBAL(get_sp)
mr r3,r1
blr
#ifdef CONFIG_IRQSTACKS
_GLOBAL(call_do_softirq)
mflr r0
std r0,16(r1)
stdu r1,THREAD_SIZE-112(r3)
mr r1,r3
bl .__do_softirq
ld r1,0(r1)
ld r0,16(r1)
mtlr r0
blr
_GLOBAL(call_handle_IRQ_event)
mflr r0
std r0,16(r1)
stdu r1,THREAD_SIZE-112(r6)
mr r1,r6
bl .handle_IRQ_event
ld r1,0(r1)
ld r0,16(r1)
mtlr r0
blr
#endif /* CONFIG_IRQSTACKS */
/*
* To be called by C code which needs to do some operations with MMU
* disabled. Note that interrupts have to be disabled by the caller
* prior to calling us. The code called _MUST_ be in the RMO of course
* and part of the linear mapping as we don't attempt to translate the
* stack pointer at all. The function is called with the stack switched
* to this CPU emergency stack
*
* prototype is void *call_with_mmu_off(void *func, void *data);
*
* the called function is expected to be of the form
*
* void *called(void *data);
*/
_GLOBAL(call_with_mmu_off)
mflr r0 /* get link, save it on stackframe */
std r0,16(r1)
mr r1,r5 /* save old stack ptr */
ld r1,PACAEMERGSP(r13) /* get emerg. stack */
subi r1,r1,STACK_FRAME_OVERHEAD
std r0,16(r1) /* save link on emerg. stack */
std r5,0(r1) /* save old stack ptr in backchain */
ld r3,0(r3) /* get to real function ptr (assume same TOC) */
bl 2f /* we need LR to return, continue at label 2 */
ld r0,16(r1) /* we return here from the call, get LR and */
ld r1,0(r1) /* .. old stack ptr */
mtspr SPRN_SRR0,r0 /* and get back to virtual mode with these */
mfmsr r4
ori r4,r4,MSR_IR|MSR_DR
mtspr SPRN_SRR1,r4
rfid
2: mtspr SPRN_SRR0,r3 /* coming from above, enter real mode */
mr r3,r4 /* get parameter */
mfmsr r0
ori r0,r0,MSR_IR|MSR_DR
xori r0,r0,MSR_IR|MSR_DR
mtspr SPRN_SRR1,r0
rfid
.section ".toc","aw"
PPC64_CACHES:
.tc ppc64_caches[TC],ppc64_caches
.section ".text"
/*
* Write any modified data cache blocks out to memory
* and invalidate the corresponding instruction cache blocks.
*
* flush_icache_range(unsigned long start, unsigned long stop)
*
* flush all bytes from start through stop-1 inclusive
*/
_KPROBE(__flush_icache_range)
/*
* Flush the data cache to memory
*
* Different systems have different cache line sizes
* and in some cases i-cache and d-cache line sizes differ from
* each other.
*/
ld r10,PPC64_CACHES@toc(r2)
lwz r7,DCACHEL1LINESIZE(r10)/* Get cache line size */
addi r5,r7,-1
andc r6,r3,r5 /* round low to line bdy */
subf r8,r6,r4 /* compute length */
add r8,r8,r5 /* ensure we get enough */
lwz r9,DCACHEL1LOGLINESIZE(r10) /* Get log-2 of cache line size */
srw. r8,r8,r9 /* compute line count */
beqlr /* nothing to do? */
mtctr r8
1: dcbst 0,r6
add r6,r6,r7
bdnz 1b
sync
/* Now invalidate the instruction cache */
lwz r7,ICACHEL1LINESIZE(r10) /* Get Icache line size */
addi r5,r7,-1
andc r6,r3,r5 /* round low to line bdy */
subf r8,r6,r4 /* compute length */
add r8,r8,r5
lwz r9,ICACHEL1LOGLINESIZE(r10) /* Get log-2 of Icache line size */
srw. r8,r8,r9 /* compute line count */
beqlr /* nothing to do? */
mtctr r8
2: icbi 0,r6
add r6,r6,r7
bdnz 2b
isync
blr
.previous .text
/*
* Like above, but only do the D-cache.
*
* flush_dcache_range(unsigned long start, unsigned long stop)
*
* flush all bytes from start to stop-1 inclusive
*/
_GLOBAL(flush_dcache_range)
/*
* Flush the data cache to memory
*
* Different systems have different cache line sizes
*/
ld r10,PPC64_CACHES@toc(r2)
lwz r7,DCACHEL1LINESIZE(r10) /* Get dcache line size */
addi r5,r7,-1
andc r6,r3,r5 /* round low to line bdy */
subf r8,r6,r4 /* compute length */
add r8,r8,r5 /* ensure we get enough */
lwz r9,DCACHEL1LOGLINESIZE(r10) /* Get log-2 of dcache line size */
srw. r8,r8,r9 /* compute line count */
beqlr /* nothing to do? */
mtctr r8
0: dcbst 0,r6
add r6,r6,r7
bdnz 0b
sync
blr
/*
* Like above, but works on non-mapped physical addresses.
* Use only for non-LPAR setups ! It also assumes real mode
* is cacheable. Used for flushing out the DART before using
* it as uncacheable memory
*
* flush_dcache_phys_range(unsigned long start, unsigned long stop)
*
* flush all bytes from start to stop-1 inclusive
*/
_GLOBAL(flush_dcache_phys_range)
ld r10,PPC64_CACHES@toc(r2)
lwz r7,DCACHEL1LINESIZE(r10) /* Get dcache line size */
addi r5,r7,-1
andc r6,r3,r5 /* round low to line bdy */
subf r8,r6,r4 /* compute length */
add r8,r8,r5 /* ensure we get enough */
lwz r9,DCACHEL1LOGLINESIZE(r10) /* Get log-2 of dcache line size */
srw. r8,r8,r9 /* compute line count */
beqlr /* nothing to do? */
mfmsr r5 /* Disable MMU Data Relocation */
ori r0,r5,MSR_DR
xori r0,r0,MSR_DR
sync
mtmsr r0
sync
isync
mtctr r8
0: dcbst 0,r6
add r6,r6,r7
bdnz 0b
sync
isync
mtmsr r5 /* Re-enable MMU Data Relocation */
sync
isync
blr
_GLOBAL(flush_inval_dcache_range)
ld r10,PPC64_CACHES@toc(r2)
lwz r7,DCACHEL1LINESIZE(r10) /* Get dcache line size */
addi r5,r7,-1
andc r6,r3,r5 /* round low to line bdy */
subf r8,r6,r4 /* compute length */
add r8,r8,r5 /* ensure we get enough */
lwz r9,DCACHEL1LOGLINESIZE(r10)/* Get log-2 of dcache line size */
srw. r8,r8,r9 /* compute line count */
beqlr /* nothing to do? */
sync
isync
mtctr r8
0: dcbf 0,r6
add r6,r6,r7
bdnz 0b
sync
isync
blr
/*
* Flush a particular page from the data cache to RAM.
* Note: this is necessary because the instruction cache does *not*
* snoop from the data cache.
*
* void __flush_dcache_icache(void *page)
*/
_GLOBAL(__flush_dcache_icache)
/*
* Flush the data cache to memory
*
* Different systems have different cache line sizes
*/
/* Flush the dcache */
ld r7,PPC64_CACHES@toc(r2)
clrrdi r3,r3,PAGE_SHIFT /* Page align */
lwz r4,DCACHEL1LINESPERPAGE(r7) /* Get # dcache lines per page */
lwz r5,DCACHEL1LINESIZE(r7) /* Get dcache line size */
mr r6,r3
mtctr r4
0: dcbst 0,r6
add r6,r6,r5
bdnz 0b
sync
/* Now invalidate the icache */
lwz r4,ICACHEL1LINESPERPAGE(r7) /* Get # icache lines per page */
lwz r5,ICACHEL1LINESIZE(r7) /* Get icache line size */
mtctr r4
1: icbi 0,r3
add r3,r3,r5
bdnz 1b
isync
blr
/*
* I/O string operations
*
* insb(port, buf, len)
* outsb(port, buf, len)
* insw(port, buf, len)
* outsw(port, buf, len)
* insl(port, buf, len)
* outsl(port, buf, len)
* insw_ns(port, buf, len)
* outsw_ns(port, buf, len)
* insl_ns(port, buf, len)
* outsl_ns(port, buf, len)
*
* The *_ns versions don't do byte-swapping.
*/
_GLOBAL(_insb)
cmpwi 0,r5,0
mtctr r5
subi r4,r4,1
blelr-
00: lbz r5,0(r3)
eieio
stbu r5,1(r4)
bdnz 00b
twi 0,r5,0
isync
blr
_GLOBAL(_outsb)
cmpwi 0,r5,0
mtctr r5
subi r4,r4,1
blelr-
00: lbzu r5,1(r4)
stb r5,0(r3)
bdnz 00b
sync
blr
_GLOBAL(_insw)
cmpwi 0,r5,0
mtctr r5
subi r4,r4,2
blelr-
00: lhbrx r5,0,r3
eieio
sthu r5,2(r4)
bdnz 00b
twi 0,r5,0
isync
blr
_GLOBAL(_outsw)
cmpwi 0,r5,0
mtctr r5
subi r4,r4,2
blelr-
00: lhzu r5,2(r4)
sthbrx r5,0,r3
bdnz 00b
sync
blr
_GLOBAL(_insl)
cmpwi 0,r5,0
mtctr r5
subi r4,r4,4
blelr-
00: lwbrx r5,0,r3
eieio
stwu r5,4(r4)
bdnz 00b
twi 0,r5,0
isync
blr
_GLOBAL(_outsl)
cmpwi 0,r5,0
mtctr r5
subi r4,r4,4
blelr-
00: lwzu r5,4(r4)
stwbrx r5,0,r3
bdnz 00b
sync
blr
/* _GLOBAL(ide_insw) now in drivers/ide/ide-iops.c */
_GLOBAL(_insw_ns)
cmpwi 0,r5,0
mtctr r5
subi r4,r4,2
blelr-
00: lhz r5,0(r3)
eieio
sthu r5,2(r4)
bdnz 00b
twi 0,r5,0
isync
blr
/* _GLOBAL(ide_outsw) now in drivers/ide/ide-iops.c */
_GLOBAL(_outsw_ns)
cmpwi 0,r5,0
mtctr r5
subi r4,r4,2
blelr-
00: lhzu r5,2(r4)
sth r5,0(r3)
bdnz 00b
sync
blr
_GLOBAL(_insl_ns)
cmpwi 0,r5,0
mtctr r5
subi r4,r4,4
blelr-
00: lwz r5,0(r3)
eieio
stwu r5,4(r4)
bdnz 00b
twi 0,r5,0
isync
blr
_GLOBAL(_outsl_ns)
cmpwi 0,r5,0
mtctr r5
subi r4,r4,4
blelr-
00: lwzu r5,4(r4)
stw r5,0(r3)
bdnz 00b
sync
blr
/*
* identify_cpu and calls setup_cpu
* In: r3 = base of the cpu_specs array
* r4 = address of cur_cpu_spec
* r5 = relocation offset
*/
_GLOBAL(identify_cpu)
mfpvr r7
1:
lwz r8,CPU_SPEC_PVR_MASK(r3)
and r8,r8,r7
lwz r9,CPU_SPEC_PVR_VALUE(r3)
cmplw 0,r9,r8
beq 1f
addi r3,r3,CPU_SPEC_ENTRY_SIZE
b 1b
1:
sub r0,r3,r5
std r0,0(r4)
ld r4,CPU_SPEC_SETUP(r3)
add r4,r4,r5
ld r4,0(r4)
add r4,r4,r5
mtctr r4
/* Calling convention for cpu setup is r3=offset, r4=cur_cpu_spec */
mr r4,r3
mr r3,r5
bctr
/*
* do_cpu_ftr_fixups - goes through the list of CPU feature fixups
* and writes nop's over sections of code that don't apply for this cpu.
* r3 = data offset (not changed)
*/
_GLOBAL(do_cpu_ftr_fixups)
/* Get CPU 0 features */
LOADADDR(r6,cur_cpu_spec)
sub r6,r6,r3
ld r4,0(r6)
sub r4,r4,r3
ld r4,CPU_SPEC_FEATURES(r4)
/* Get the fixup table */
LOADADDR(r6,__start___ftr_fixup)
sub r6,r6,r3
LOADADDR(r7,__stop___ftr_fixup)
sub r7,r7,r3
/* Do the fixup */
1: cmpld r6,r7
bgelr
addi r6,r6,32
ld r8,-32(r6) /* mask */
and r8,r8,r4
ld r9,-24(r6) /* value */
cmpld r8,r9
beq 1b
ld r8,-16(r6) /* section begin */
ld r9,-8(r6) /* section end */
subf. r9,r8,r9
beq 1b
/* write nops over the section of code */
/* todo: if large section, add a branch at the start of it */
srwi r9,r9,2
mtctr r9
sub r8,r8,r3
lis r0,0x60000000@h /* nop */
3: stw r0,0(r8)
andi. r10,r4,CPU_FTR_SPLIT_ID_CACHE@l
beq 2f
dcbst 0,r8 /* suboptimal, but simpler */
sync
icbi 0,r8
2: addi r8,r8,4
bdnz 3b
sync /* additional sync needed on g4 */
isync
b 1b
#if defined(CONFIG_PPC_PMAC) || defined(CONFIG_PPC_MAPLE)
/*
* Do an IO access in real mode
*/
_GLOBAL(real_readb)
mfmsr r7
ori r0,r7,MSR_DR
xori r0,r0,MSR_DR
sync
mtmsrd r0
sync
isync
mfspr r6,SPRN_HID4
rldicl r5,r6,32,0
ori r5,r5,0x100
rldicl r5,r5,32,0
sync
mtspr SPRN_HID4,r5
isync
slbia
isync
lbz r3,0(r3)
sync
mtspr SPRN_HID4,r6
isync
slbia
isync
mtmsrd r7
sync
isync
blr
/*
* Do an IO access in real mode
*/
_GLOBAL(real_writeb)
mfmsr r7
ori r0,r7,MSR_DR
xori r0,r0,MSR_DR
sync
mtmsrd r0
sync
isync
mfspr r6,SPRN_HID4
rldicl r5,r6,32,0
ori r5,r5,0x100
rldicl r5,r5,32,0
sync
mtspr SPRN_HID4,r5
isync
slbia
isync
stb r3,0(r4)
sync
mtspr SPRN_HID4,r6
isync
slbia
isync
mtmsrd r7
sync
isync
blr
#endif /* defined(CONFIG_PPC_PMAC) || defined(CONFIG_PPC_MAPLE) */
/*
* Create a kernel thread
* kernel_thread(fn, arg, flags)
*/
_GLOBAL(kernel_thread)
std r29,-24(r1)
std r30,-16(r1)
stdu r1,-STACK_FRAME_OVERHEAD(r1)
mr r29,r3
mr r30,r4
ori r3,r5,CLONE_VM /* flags */
oris r3,r3,(CLONE_UNTRACED>>16)
li r4,0 /* new sp (unused) */
li r0,__NR_clone
sc
cmpdi 0,r3,0 /* parent or child? */
bne 1f /* return if parent */
li r0,0
stdu r0,-STACK_FRAME_OVERHEAD(r1)
ld r2,8(r29)
ld r29,0(r29)
mtlr r29 /* fn addr in lr */
mr r3,r30 /* load arg and call fn */
blrl
li r0,__NR_exit /* exit after child exits */
li r3,0
sc
1: addi r1,r1,STACK_FRAME_OVERHEAD
ld r29,-24(r1)
ld r30,-16(r1)
blr
/*
* disable_kernel_fp()
* Disable the FPU.
*/
_GLOBAL(disable_kernel_fp)
mfmsr r3
rldicl r0,r3,(63-MSR_FP_LG),1
rldicl r3,r0,(MSR_FP_LG+1),0
mtmsrd r3 /* disable use of fpu now */
isync
blr
#ifdef CONFIG_ALTIVEC
#if 0 /* this has no callers for now */
/*
* disable_kernel_altivec()
* Disable the VMX.
*/
_GLOBAL(disable_kernel_altivec)
mfmsr r3
rldicl r0,r3,(63-MSR_VEC_LG),1
rldicl r3,r0,(MSR_VEC_LG+1),0
mtmsrd r3 /* disable use of VMX now */
isync
blr
#endif /* 0 */
/*
* giveup_altivec(tsk)
* Disable VMX for the task given as the argument,
* and save the vector registers in its thread_struct.
* Enables the VMX for use in the kernel on return.
*/
_GLOBAL(giveup_altivec)
mfmsr r5
oris r5,r5,MSR_VEC@h
mtmsrd r5 /* enable use of VMX now */
isync
cmpdi 0,r3,0
beqlr- /* if no previous owner, done */
addi r3,r3,THREAD /* want THREAD of task */
ld r5,PT_REGS(r3)
cmpdi 0,r5,0
SAVE_32VRS(0,r4,r3)
mfvscr vr0
li r4,THREAD_VSCR
stvx vr0,r4,r3
beq 1f
ld r4,_MSR-STACK_FRAME_OVERHEAD(r5)
lis r3,MSR_VEC@h
andc r4,r4,r3 /* disable FP for previous task */
std r4,_MSR-STACK_FRAME_OVERHEAD(r5)
1:
#ifndef CONFIG_SMP
li r5,0
ld r4,last_task_used_altivec@got(r2)
std r5,0(r4)
#endif /* CONFIG_SMP */
blr
#endif /* CONFIG_ALTIVEC */
_GLOBAL(__setup_cpu_power3)
blr
_GLOBAL(execve)
li r0,__NR_execve
sc
bnslr
neg r3,r3
blr
/* kexec_wait(phys_cpu)
*
* wait for the flag to change, indicating this kernel is going away but
* the slave code for the next one is at addresses 0 to 100.
*
* This is used by all slaves.
*
* Physical (hardware) cpu id should be in r3.
*/
_GLOBAL(kexec_wait)
bl 1f
1: mflr r5
addi r5,r5,kexec_flag-1b
99: HMT_LOW
#ifdef CONFIG_KEXEC /* use no memory without kexec */
lwz r4,0(r5)
cmpwi 0,r4,0
bnea 0x60
#endif
b 99b
/* this can be in text because we won't change it until we are
* running in real anyways
*/
kexec_flag:
.long 0
#ifdef CONFIG_KEXEC
/* kexec_smp_wait(void)
*
* call with interrupts off
* note: this is a terminal routine, it does not save lr
*
* get phys id from paca
* set paca id to -1 to say we got here
* switch to real mode
* join other cpus in kexec_wait(phys_id)
*/
_GLOBAL(kexec_smp_wait)
lhz r3,PACAHWCPUID(r13)
li r4,-1
sth r4,PACAHWCPUID(r13) /* let others know we left */
bl real_mode
b .kexec_wait
/*
* switch to real mode (turn mmu off)
* we use the early kernel trick that the hardware ignores bits
* 0 and 1 (big endian) of the effective address in real mode
*
* don't overwrite r3 here, it is live for kexec_wait above.
*/
real_mode: /* assume normal blr return */
1: li r9,MSR_RI
li r10,MSR_DR|MSR_IR
mflr r11 /* return address to SRR0 */
mfmsr r12
andc r9,r12,r9
andc r10,r12,r10
mtmsrd r9,1
mtspr SPRN_SRR1,r10
mtspr SPRN_SRR0,r11
rfid
/*
* kexec_sequence(newstack, start, image, control, clear_all())
*
* does the grungy work with stack switching and real mode switches
* also does simple calls to other code
*/
_GLOBAL(kexec_sequence)
mflr r0
std r0,16(r1)
/* switch stacks to newstack -- &kexec_stack.stack */
stdu r1,THREAD_SIZE-112(r3)
mr r1,r3
li r0,0
std r0,16(r1)
/* save regs for local vars on new stack.
* yes, we won't go back, but ...
*/
std r31,-8(r1)
std r30,-16(r1)
std r29,-24(r1)
std r28,-32(r1)
std r27,-40(r1)
std r26,-48(r1)
std r25,-56(r1)
stdu r1,-112-64(r1)
/* save args into preserved regs */
mr r31,r3 /* newstack (both) */
mr r30,r4 /* start (real) */
mr r29,r5 /* image (virt) */
mr r28,r6 /* control, unused */
mr r27,r7 /* clear_all() fn desc */
mr r26,r8 /* spare */
lhz r25,PACAHWCPUID(r13) /* get our phys cpu from paca */
/* disable interrupts, we are overwriting kernel data next */
mfmsr r3
rlwinm r3,r3,0,17,15
mtmsrd r3,1
/* copy dest pages, flush whole dest image */
mr r3,r29
bl .kexec_copy_flush /* (image) */
/* turn off mmu */
bl real_mode
/* clear out hardware hash page table and tlb */
ld r5,0(r27) /* deref function descriptor */
mtctr r5
bctrl /* ppc_md.hash_clear_all(void); */
/*
* kexec image calling is:
* the first 0x100 bytes of the entry point are copied to 0
*
* all slaves branch to slave = 0x60 (absolute)
* slave(phys_cpu_id);
*
* master goes to start = entry point
* start(phys_cpu_id, start, 0);
*
*
* a wrapper is needed to call existing kernels, here is an approximate
* description of one method:
*
* v2: (2.6.10)
* start will be near the boot_block (maybe 0x100 bytes before it?)
* it will have a 0x60, which will b to boot_block, where it will wait
* and 0 will store phys into struct boot-block and load r3 from there,
* copy kernel 0-0x100 and tell slaves to back down to 0x60 again
*
* v1: (2.6.9)
* boot block will have all cpus scanning device tree to see if they
* are the boot cpu ?????
* other device tree differences (prop sizes, va vs pa, etc)...
*/
/* copy 0x100 bytes starting at start to 0 */
li r3,0
mr r4,r30
li r5,0x100
li r6,0
bl .copy_and_flush /* (dest, src, copy limit, start offset) */
1: /* assume normal blr return */
/* release other cpus to the new kernel secondary start at 0x60 */
mflr r5
li r6,1
stw r6,kexec_flag-1b(5)
mr r3,r25 # my phys cpu
mr r4,r30 # start, aka phys mem offset
mtlr 4
li r5,0
blr /* image->start(physid, image->start, 0); */
#endif /* CONFIG_KEXEC */
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