context.s

ecos为实时嵌入式操作系统

// #=============================================================================
// #
// #	context.S
// #
// #	PowerPC context switch code
// #
// #=============================================================================
// ####COPYRIGHTBEGIN####
// 
//  -------------------------------------------
//  The contents of this file are subject to the Cygnus eCos Public License
//  Version 1.0 (the "License"); you may not use this file except in
//  compliance with the License.  You may obtain a copy of the License at
//  http://sourceware.cygnus.com/ecos
//  
//  Software distributed under the License is distributed on an "AS IS"
//  basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See the
//  License for the specific language governing rights and limitations under
//  the License.
//  
//  The Original Code is eCos - Embedded Cygnus Operating System, released
//  September 30, 1998.
//  
//  The Initial Developer of the Original Code is Cygnus.  Portions created
//  by Cygnus are Copyright (C) 1998,1999 Cygnus Solutions.  All Rights Reserved.
//  -------------------------------------------
// 
// ####COPYRIGHTEND####
// #=============================================================================
// ######DESCRIPTIONBEGIN####
// #
// # Author(s): 	nickg, gthomas
// # Contributors:	nickg, gthomas
// # Date:	1998-09-15
// # Purpose:	ARM context switch code
// # Description:	This file contains implementations of the thread context 
// #		switch routines. It also contains the longjmp() and setjmp()
// #              routines.
// #
// #####DESCRIPTIONEND####
// #
// #=============================================================================

#include <pkgconf/hal.h>

#include "arm.inc"

	.text

// ------------------------------------------------------------------------------
//  function declaration macro
		
#define FUNC_START(name) \
        .globl name; \
name:	
		
// ------------------------------------------------------------------------------
//  hal_thread_switch_context
//  Switch thread contexts
//  R0 = address of sp of next thread to execute
//  R1 = address of sp save location of current thread

// Need to save/restore R4..R12, R13 (sp), R14 (lr)

// Note: this is a little wasteful since r0..r3 don't need to be saved.
// They are saved here though so that the information can match the HAL_SavedRegisters
	
FUNC_START(hal_thread_switch_context)
	mov	ip,sp			// saved stack pointer
	sub	sp,sp,#ARMREG_SIZE	// make space for saved registers
	stmea	sp,{r0-r10,fp,ip,lr,pc}
	mrs	r2,cpsr
	str	r2,[sp,#armreg_cpsr]
	str	sp,[r1]			// return new stack pointer

	# Now load the destination thread by dropping through
	# to hal_thread_load_context
	
// ------------------------------------------------------------------------------
//  hal_thread_load_context
//  Load thread context
//  R0 = address of sp of next thread to execute
//  Note that this function is also the second half of hal_thread_switch_context
//  and is simply dropped into from it.
	
FUNC_START(hal_thread_load_context)
	ldr	fp,[r0]			// get context to restore
	mrs	r0,cpsr			// disable IRQ's
	orr	r0,r0,#CPSR_IRQ_DISABLE
	msr	cpsr,r0
	ldr	r0,[fp,#armreg_cpsr]
	msr	spsr,r0
	ldmfd	fp,{r0-r10,fp,sp,lr}	// also restores saved PSR
	movs	pc,lr

// ------------------------------------------------------------------------------
//  HAL longjmp, setjmp implementations
//  hal_setjmp saves only to callee save registers 4-14
//  and lr into buffer supplied in r0[arg0]

FUNC_START(hal_setjmp)
	stmea	r0,{r4-r14}
	mov	r0,#0
	mov	pc,lr;		# return

//  hal_longjmp loads state from r0[arg0] and returns
	
FUNC_START(hal_longjmp)
	ldmfd	r0,{r4-r14}
	mov	r0,r1;		# return [arg1]
	mov	pc,lr

// ------------------------------------------------------------------------------
//  end of context.S