path: root/arch/powerpc/kernel/head_64.S

/*
 *  PowerPC version
 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 *
 *  Rewritten by Cort Dougan (cort@cs.nmt.edu) for PReP
 *    Copyright (C) 1996 Cort Dougan <cort@cs.nmt.edu>
 *  Adapted for Power Macintosh by Paul Mackerras.
 *  Low-level exception handlers and MMU support
 *  rewritten by Paul Mackerras.
 *    Copyright (C) 1996 Paul Mackerras.
 *
 *  Adapted for 64bit PowerPC by Dave Engebretsen, Peter Bergner, and
 *    Mike Corrigan {engebret|bergner|mikejc}@us.ibm.com
 *
 *  This file contains the entry point for the 64-bit kernel along
 *  with some early initialization code common to all 64-bit powerpc
 *  variants.
 *
 *  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/threads.h>
#include <asm/reg.h>
#include <asm/page.h>
#include <asm/mmu.h>
#include <asm/ppc_asm.h>
#include <asm/asm-offsets.h>
#include <asm/bug.h>
#include <asm/cputable.h>
#include <asm/setup.h>
#include <asm/hvcall.h>
#include <asm/iseries/lpar_map.h>
#include <asm/thread_info.h>
#include <asm/firmware.h>
#include <asm/page_64.h>
#include <asm/exception.h>
#include <asm/irqflags.h>

/* The physical memory is layed out such that the secondary processor
 * spin code sits at 0x0000...0x00ff. On server, the vectors follow
 * using the layout described in exceptions-64s.S
 */

/*
 * Entering into this code we make the following assumptions:
 *
 *  For pSeries or server processors:
 *   1. The MMU is off & open firmware is running in real mode.
 *   2. The kernel is entered at __start
 *
 *  For iSeries:
 *   1. The MMU is on (as it always is for iSeries)
 *   2. The kernel is entered at system_reset_iSeries
 *
 *  For Book3E processors:
 *   1. The MMU is on running in AS0 in a state defined in ePAPR
 *   2. The kernel is entered at __start
 */

	.text
	.globl  _stext
_stext:
_GLOBAL(__start)
	/* NOP this out unconditionally */
BEGIN_FTR_SECTION
	b	.__start_initialization_multiplatform
END_FTR_SECTION(0, 1)

	/* Catch branch to 0 in real mode */
	trap

	/* Secondary processors spin on this value until it becomes nonzero.
	 * When it does it contains the real address of the descriptor
	 * of the function that the cpu should jump to to continue
	 * initialization.
	 */
	.globl  __secondary_hold_spinloop
__secondary_hold_spinloop:
	.llong	0x0

	/* Secondary processors write this value with their cpu # */
	/* after they enter the spin loop immediately below.	  */
	.globl	__secondary_hold_acknowledge
__secondary_hold_acknowledge:
	.llong	0x0

#ifdef CONFIG_PPC_ISERIES
	/*
	 * At offset 0x20, there is a pointer to iSeries LPAR data.
	 * This is required by the hypervisor
	 */
	. = 0x20
	.llong hvReleaseData-KERNELBASE
#endif /* CONFIG_PPC_ISERIES */

#ifdef CONFIG_CRASH_DUMP
	/* This flag is set to 1 by a loader if the kernel should run
	 * at the loaded address instead of the linked address.  This
	 * is used by kexec-tools to keep the the kdump kernel in the
	 * crash_kernel region.  The loader is responsible for
	 * observing the alignment requirement.
	 */
	/* Do not move this variable as kexec-tools knows about it. */
	. = 0x5c
	.globl	__run_at_load
__run_at_load:
	.long	0x72756e30	/* "run0" -- relocate to 0 by default */
#endif

	. = 0x60
/*
 * The following code is used to hold secondary processors
 * in a spin loop after they have entered the kernel, but
 * before the bulk of the kernel has been relocated.  This code
 * is relocated to physical address 0x60 before prom_init is run.
 * All of it must fit below the first exception vector at 0x100.
 * Use .globl here not _GLOBAL because we want __secondary_hold
 * to be the actual text address, not a descriptor.
 */
	.globl	__secondary_hold
__secondary_hold:
	mfmsr	r24
	ori	r24,r24,MSR_RI
	mtmsrd	r24			/* RI on */

	/* Grab our physical cpu number */
	mr	r24,r3

	/* Tell the master cpu we're here */
	/* Relocation is off & we are located at an address less */
	/* than 0x100, so only need to grab low order offset.    */
	std	r24,__secondary_hold_acknowledge-_stext(0)
	sync

	/* All secondary cpus wait here until told to start. */
100:	ld	r4,__secondary_hold_spinloop-_stext(0)
	cmpdi	0,r4,0
	beq	100b

#if defined(CONFIG_SMP) || defined(CONFIG_KEXEC)
	ld	r4,0(r4)		/* deref function descriptor */
	mtctr	r4
	mr	r3,r24
	bctr
#else
	BUG_OPCODE
#endif

/* This value is used to mark exception frames on the stack. */
	.section ".toc","aw"
exception_marker:
	.tc	ID_72656773_68657265[TC],0x7265677368657265
	.text

/*
 * On server, we include the exception vectors code here as it
 * relies on absolute addressing which is only possible within
 * this compilation unit
 */
#ifdef CONFIG_PPC_BOOK3S
#include "exceptions-64s.S"
#endif


/*
 * On pSeries and most other platforms, secondary processors spin
 * in the following code.
 * At entry, r3 = this processor's number (physical cpu id)
 */
_GLOBAL(generic_secondary_smp_init)
	mr	r24,r3
	
	/* turn on 64-bit mode */
	bl	.enable_64b_mode

	/* get the TOC pointer (real address) */
	bl	.relative_toc

	/* Set up a paca value for this processor. Since we have the
	 * physical cpu id in r24, we need to search the pacas to find
	 * which logical id maps to our physical one.
	 */
	LOAD_REG_ADDR(r13, paca)	/* Get base vaddr of paca array	 */
	li	r5,0			/* logical cpu id                */
1:	lhz	r6,PACAHWCPUID(r13)	/* Load HW procid from paca      */
	cmpw	r6,r24			/* Compare to our id             */
	beq	2f
	addi	r13,r13,PACA_SIZE	/* Loop to next PACA on miss     */
	addi	r5,r5,1
	cmpwi	r5,NR_CPUS
	blt	1b

	mr	r3,r24			/* not found, copy phys to r3	 */
	b	.kexec_wait		/* next kernel might do better	 */

2:	mtspr	SPRN_SPRG3,r13		/* Save vaddr of paca in SPRG3	 */
	/* From now on, r24 is expected to be logical cpuid */
	mr	r24,r5
3:	HMT_LOW
	lbz	r23,PACAPROCSTART(r13)	/* Test if this processor should */
					/* start.			 */

#ifndef CONFIG_SMP
	b	3b			/* Never go on non-SMP		 */
#else
	cmpwi	0,r23,0
	beq	3b			/* Loop until told to go	 */

	sync				/* order paca.run and cur_cpu_spec */

	/* See if we need to call a cpu state restore handler */
	LOAD_REG_ADDR(r23, cur_cpu_spec)
	ld	r23,0(r23)
	ld	r23,CPU_SPEC_RESTORE(r23)
	cmpdi	0,r23,0
	beq	4f
	ld	r23,0(r23)
	mtctr	r23
	bctrl

4:	/* Create a temp kernel stack for use before relocation is on.	*/
	ld	r1,PACAEMERGSP(r13)
	subi	r1,r1,STACK_FRAME_OVERHEAD

	b	__secondary_start
#endif

/*
 * Turn the MMU off.
 * Assumes we're mapped EA == RA if the MMU is on.
 */
_STATIC(__mmu_off)
	mfmsr	r3
	andi.	r0,r3,MSR_IR|MSR_DR
	beqlr
	mflr	r4
	andc	r3,r3,r0
	mtspr	SPRN_SRR0,r4
	mtspr	SPRN_SRR1,r3
	sync
	rfid
	b	.	/* prevent speculative execution */


/*
 * Here is our main kernel entry point. We support currently 2 kind of entries
 * depending on the value of r5.
 *
 *   r5 != NULL -> OF entry, we go to prom_init, "legacy" parameter content
 *                 in r3...r7
 *   
 *   r5 == NULL -> kexec style entry. r3 is a physical pointer to the
 *                 DT block, r4 is a physical pointer to the kernel itself
 *
 */
_GLOBAL(__start_initialization_multiplatform)
	/* Make sure we are running in 64 bits mode */
	bl	.enable_64b_mode

	/* Get TOC pointer (current runtime address) */
	bl	.relative_toc

	/* find out where we are now */
	bcl	20,31,$+4
0:	mflr	r26			/* r26 = runtime addr here */
	addis	r26,r26,(_stext - 0b)@ha
	addi	r26,r26,(_stext - 0b)@l	/* current runtime base addr */

	/*
	 * Are we booted from a PROM Of-type client-interface ?
	 */
	cmpldi	cr0,r5,0
	beq	1f
	b	.__boot_from_prom		/* yes -> prom */
1:
	/* Save parameters */
	mr	r31,r3
	mr	r30,r4

	/* Setup some critical 970 SPRs before switching MMU off */
	mfspr	r0,SPRN_PVR
	srwi	r0,r0,16
	cmpwi	r0,0x39		/* 970 */
	beq	1f
	cmpwi	r0,0x3c		/* 970FX */
	beq	1f
	cmpwi	r0,0x44		/* 970MP */
	beq	1f
	cmpwi	r0,0x45		/* 970GX */
	bne	2f
1:	bl	.__cpu_preinit_ppc970
2:

	/* Switch off MMU if not already off */
	bl	.__mmu_off
	b	.__after_prom_start

_INIT_STATIC(__boot_from_prom)
#ifdef CONFIG_PPC_OF_BOOT_TRAMPOLINE
	/* Save parameters */
	mr	r31,r3
	mr	r30,r4
	mr	r29,r5
	mr	r28,r6
	mr	r27,r7

	/*
	 * Align the stack to 16-byte boundary
	 * Depending on the size and layout of the ELF sections in the initial
	 * boot binary, the stack pointer may be unaligned on PowerMac
	 */
	rldicr	r1,r1,0,59

#ifdef CONFIG_RELOCATABLE
	/* Relocate code for where we are now */
	mr	r3,r26
	bl	.relocate
#endif

	/* Restore parameters */
	mr	r3,r31
	mr	r4,r30
	mr	r5,r29
	mr	r6,r28
	mr	r7,r27

	/* Do all of the interaction with OF client interface */
	mr	r8,r26
	bl	.prom_init
#endif /* #CONFIG_PPC_OF_BOOT_TRAMPOLINE */

	/* We never return. We also hit that trap if trying to boot
	 * from OF while CONFIG_PPC_OF_BOOT_TRAMPOLINE isn't selected */
	trap

_STATIC(__after_prom_start)
#ifdef CONFIG_RELOCATABLE
	/* process relocations for the final address of the kernel */
	lis	r25,PAGE_OFFSET@highest	/* compute virtual base of kernel */
	sldi	r25,r25,32
#ifdef CONFIG_CRASH_DUMP
	lwz	r7,__run_at_load-_stext(r26)
	cmplwi	cr0,r7,1	/* kdump kernel ? - stay where we are */
	bne	1f
	add	r25,r25,r26
#endif
1:	mr	r3,r25
	bl	.relocate
#endif

/*
 * We need to run with _stext at physical address PHYSICAL_START.
 * This will leave some code in the first 256B of
 * real memory, which are reserve