head-nommu.s

linux 内核源代码

/*
 *  linux/arch/arm/kernel/head-nommu.S
 *
 *  Copyright (C) 1994-2002 Russell King
 *  Copyright (C) 2003-2006 Hyok S. Choi
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  Common kernel startup code (non-paged MM)
 *
 */
#include <linux/linkage.h>
#include <linux/init.h>

#include <asm/assembler.h>
#include <asm/mach-types.h>
#include <asm/ptrace.h>
#include <asm/asm-offsets.h>
#include <asm/thread_info.h>
#include <asm/system.h>

/*
 * Kernel startup entry point.
 * ---------------------------
 *
 * This is normally called from the decompressor code.  The requirements
 * are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
 * r1 = machine nr.
 *
 * See linux/arch/arm/tools/mach-types for the complete list of machine
 * numbers for r1.
 *
 */
	.section ".text.head", "ax"
	.type	stext, %function
ENTRY(stext)
	msr	cpsr_c, #PSR_F_BIT | PSR_I_BIT | SVC_MODE @ ensure svc mode
						@ and irqs disabled
#ifndef CONFIG_CPU_CP15
	ldr	r9, =CONFIG_PROCESSOR_ID
#else
	mrc	p15, 0, r9, c0, c0		@ get processor id
#endif
	bl	__lookup_processor_type		@ r5=procinfo r9=cpuid
	movs	r10, r5				@ invalid processor (r5=0)?
	beq	__error_p				@ yes, error 'p'
	bl	__lookup_machine_type		@ r5=machinfo
	movs	r8, r5				@ invalid machine (r5=0)?
	beq	__error_a			@ yes, error 'a'

	ldr	r13, __switch_data		@ address to jump to after
						@ the initialization is done
	adr	lr, __after_proc_init		@ return (PIC) address
	add	pc, r10, #PROCINFO_INITFUNC

/*
 * Set the Control Register and Read the process ID.
 */
	.type	__after_proc_init, %function
__after_proc_init:
#ifdef CONFIG_CPU_CP15
	mrc	p15, 0, r0, c1, c0, 0		@ read control reg
#ifdef CONFIG_ALIGNMENT_TRAP
	orr	r0, r0, #CR_A
#else
	bic	r0, r0, #CR_A
#endif
#ifdef CONFIG_CPU_DCACHE_DISABLE
	bic	r0, r0, #CR_C
#endif
#ifdef CONFIG_CPU_BPREDICT_DISABLE
	bic	r0, r0, #CR_Z
#endif
#ifdef CONFIG_CPU_ICACHE_DISABLE
	bic	r0, r0, #CR_I
#endif
#ifdef CONFIG_CPU_HIGH_VECTOR
	orr	r0, r0, #CR_V
#else
	bic	r0, r0, #CR_V
#endif
	mcr	p15, 0, r0, c1, c0, 0		@ write control reg
#endif /* CONFIG_CPU_CP15 */

	mov	pc, r13				@ clear the BSS and jump
						@ to start_kernel
	.ltorg

#include "head-common.S"