locore.s

早期freebsd实现

/*
 * Copyright (c) 1992, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Digital Equipment Corporation, Ralph Campbell, Sony Corp and
 * Kazumasa Utashiro of Software Research Associates, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * Copyright (C) 1989 Digital Equipment Corporation.
 * Permission to use, copy, modify, and distribute this software and
 * its documentation for any purpose and without fee is hereby granted,
 * provided that the above copyright notice appears in all copies.
 * Digital Equipment Corporation makes no representations about the
 * suitability of this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 *
 * from: $Header: /sprite/src/kernel/mach/ds3100.md/RCS/loMem.s,
 *	v 1.1 89/07/11 17:55:04 nelson Exp $ SPRITE (DECWRL)
 * from: $Header: /sprite/src/kernel/mach/ds3100.md/RCS/machAsm.s,
 *	v 9.2 90/01/29 18:00:39 shirriff Exp $ SPRITE (DECWRL)
 * from: $Header: /sprite/src/kernel/vm/ds3100.md/vmPmaxAsm.s,
 *	v 1.1 89/07/10 14:27:41 nelson Exp $ SPRITE (DECWRL)
 *
 *	@(#)locore.s	8.3 (Berkeley) 9/23/93
 */

/*
 *	Contains code that is the first executed at boot time plus
 *	assembly language support routines.
 */

#include <sys/errno.h>
#include <sys/syscall.h>

#include <machine/param.h>
#include <machine/psl.h>
#include <machine/reg.h>
#include <machine/machAsmDefs.h>
#include <machine/pte.h>
#include <machine/adrsmap.h>
#include "assym.h"

/* #include <machine/endian.h> */
/* common endian.h includes function declarations */
#define	LITTLE_ENDIAN	1234	/* LSB first: i386, vax */
#define	BIG_ENDIAN	4321	/* MSB first: 68000, ibm, net */
#define	PDP_ENDIAN	3412	/* LSB first in word, MSW first in long */
#define	BYTE_ORDER	BIG_ENDIAN

/*
 * Amount to take off of the stack for the benefit of the debugger.
 */
#define START_FRAME	((4 * 4) + 4 + 4)

.text
	.globl	start
start:
	.set	noreorder
	li	t1, MACH_SR_COP_1_BIT		# Enable CP1
	mtc0	t1, MACH_COP_0_STATUS_REG
	nop
	nop
	ctc1	zero, MACH_FPC_CSR		# Clear exceptions of CP1
	mtc0	zero, MACH_COP_0_STATUS_REG	# Disable interrupts
	li	t1, MACH_CACHED_MEMORY_ADDR	# invalid address
	mtc0	t1, MACH_COP_0_TLB_HI		# Mark entry high as invalid
	mtc0	zero, MACH_COP_0_TLB_LOW	# Zero out low entry.
/*
 * Clear the TLB (just to be safe).
 * Align the starting value (t1), the increment (t2) and the upper bound (t3).
 */
	move	t1, zero
	li	t2, 1 << VMMACH_TLB_INDEX_SHIFT
	li	t3, VMMACH_NUM_TLB_ENTRIES << VMMACH_TLB_INDEX_SHIFT
1:
	mtc0	t1, MACH_COP_0_TLB_INDEX	# Set the index register.
	addu	t1, t1, t2			# Increment index.
	bne	t1, t3, 1b			# NB: always executes next
	tlbwi					# Write the TLB entry.

	li	sp, MACH_CODE_START - START_FRAME
	la	gp, _gp
	sw	zero, START_FRAME - 4(sp)	# Zero out old ra for debugger
#ifdef news3400
	/*  a0: bootsw		*/
	/*  a1: boot dev	*/
	/*  a2: ??? 		*/
	/*  a3: maxmemory	*/
#endif
	jal	mach_init			# mach_init(argc, argv, envp)
	sw	zero, START_FRAME - 8(sp)	# Zero out old fp for debugger

	li	t0, MACH_SR_COP_1_BIT		# Disable interrupts and
	mtc0	t0, MACH_COP_0_STATUS_REG	#   enable the coprocessor
	li	sp, KERNELSTACK - START_FRAME	# switch to standard stack
	mfc0	t0, MACH_COP_0_PRID		# read processor ID register
	cfc1	t1, MACH_FPC_ID			# read FPU ID register
	sw	t0, cpu				# save PRID register
	sw	t1, fpu				# save FPU ID register
	jal	main				# main()
	nop

/* proc[1] == /etc/init now running here; run icode */
	li	v0, PSL_USERSET
	mtc0	v0, MACH_COP_0_STATUS_REG	# switch to user mode
	li	v0, VM_MIN_ADDRESS
	j	v0				# jump to icode
	rfe
	.set	reorder

/*
 * GCC2 seems to want to call __main in main() for some reason.
 */
LEAF(__main)
	j	ra
END(__main)

/*
 * This code is copied to user data space as the first program to run.
 * Basically, it just calls execve();
 */
	.globl	icode
icode:
	.set	noreorder
	li	a1, VM_MIN_ADDRESS + (9 * 4)	# address of 'icode_argv'
	addu	a0, a1, (3 * 4)		# address of 'icode_fname'
	move	a2, zero		# no environment
	li	v0, SYS_execve		# code for execve system call
	syscall
	li	v0, SYS_exit		# code for exit system call
	syscall				# execve failed: call exit()
1:	b	1b			# loop if exit returns
	nop
	.set	reorder
icode_argv:
	.word	VM_MIN_ADDRESS + (12 * 4)	# address of 'icode_fname'
	.word	VM_MIN_ADDRESS + (15 * 4)	# address of 'icodeEnd'
	.word	0
icode_fname:
	.asciiz	"/sbin/init"		# occupies 3 words
	.align	2
	.globl	icodeEnd
icodeEnd:

	.sdata
	.align	2
	.globl	szicode
szicode:
	.word	(9 + 3 + 3) * 4		# compute icodeEnd - icode
	.text

/*
 * This code is copied the user's stack for returning from signal handlers
 * (see sendsig() and sigreturn()). We have to compute the address
 * of the sigcontext struct for the sigreturn call.
 */
	.globl	sigcode
sigcode:
	addu	a0, sp, 16		# address of sigcontext 
	li	v0, SYS_sigreturn	# sigreturn(scp)
	syscall
	break	0			# just in case sigreturn fails
	.globl	esigcode
esigcode:

/*
 * Primitives
 */

/*
 * This table is indexed by u.u_pcb.pcb_onfault in trap().
 * The reason for using this table rather than storing an address in
 * u.u_pcb.pcb_onfault is simply to make the code faster.
 */
	.globl	onfault_table
	.data	
	.align	2
onfault_table:
	.word	0		# invalid index number
#define BADERR		1
	.word	baderr
#define COPYERR		2
	.word	copyerr
#define FSWBERR		3
	.word	fswberr
#define FSWINTRBERR	4
	.word	fswintrberr
#ifdef KADB
#define KADBERR		5
	.word	kadberr
#endif
	.text

/*
 * See if access to addr with a len type instruction causes a machine check.
 * len is length of access (1=byte, 2=short, 4=long)
 *
 * badaddr(addr, len)
 *	char *addr;
 *	int len;
 */
LEAF(badaddr)
	li	v0, BADERR
	sw	v0, UADDR+U_PCB_ONFAULT
	sw	zero, badaddr_flag
	bne	a1, 1, 2f
	lbu	v0, (a0)
	b	5f
2:
	bne	a1, 2, 4f
	lhu	v0, (a0)
	b	5f
4:
	lw	v0, (a0)
5:
	sw	zero, UADDR+U_PCB_ONFAULT
	lw	v0, badaddr_flag	# set by interrupt handler
	j	ra
	/*
	 * This onfault table entry is not necessary for single processor
	 * machine.  But dual processor machine causes exception when
	 * data is loaded from bad address.  Onfault table index is also
	 * used to determine if the access is occured during bad address
	 * check.  This should be changed to better way.  K.U.
	 */
baderr:
	li	v0, 1			# trap sends us here
	j	ra
END(badaddr)

#if BYTE_ORDER == LITTLE_ENDIAN
/*
 * netorder = htonl(hostorder)
 * hostorder = ntohl(netorder)
 */
LEAF(htonl)				# a0 = 0x11223344, return 0x44332211
ALEAF(ntohl)
	srl	v1, a0, 24		# v1 = 0x00000011
	sll	v0, a0, 24		# v0 = 0x44000000
	or	v0, v0, v1
	and	v1, a0, 0xff00
	sll	v1, v1, 8		# v1 = 0x00330000
	or	v0, v0, v1
	srl	v1, a0, 8
	and	v1, v1, 0xff00		# v1 = 0x00002200
	or	v0, v0, v1
	j	ra
END(htonl)

/*
 * netorder = htons(hostorder)
 * hostorder = ntohs(netorder)
 */
LEAF(htons)
ALEAF(ntohs)
	srl	v0, a0, 8
	and	v0, v0, 0xff
	sll	v1, a0, 8
	and	v1, v1, 0xff00
	or	v0, v0, v1
	j	ra
END(htons)
#endif

/*
 * bit = ffs(value)
 */
#ifdef NOTDEF
LEAF(ffs)
	move	v0, zero
	beq	a0, zero, 2f
1:
	and	v1, a0, 1		# bit set?
	addu	v0, v0, 1
	srl	a0, a0, 1
	beq	v1, zero, 1b		# no, continue
2:
	j	ra
END(ffs)
#endif /* NOTDEF */

/*
 * strlen(str)
 */
LEAF(strlen)
	addu	v1, a0, 1
1:
	lb	v0, 0(a0)		# get byte from string
	addu	a0, a0, 1		# increment pointer
	bne	v0, zero, 1b		# continue if not end
	subu	v0, a0, v1		# compute length - 1 for '\0' char
	j	ra
END(strlen)

/*
 * strcmp(s1, s2)
 * NOTE: this version assumes unsigned chars in order to be "8 bit clean".
 */
LEAF(strcmp)
1:
	lbu	t0, 0(a0)		# get two bytes and compare them
	lbu	t1, 0(a1)
	beq	t0, zero, LessOrEq	# end of first string?
	bne	t0, t1, NotEq
	lbu	t0, 1(a0)		# unroll loop
	lbu	t1, 1(a1)
	add	a0, a0, 2
	beq	t0, zero, LessOrEq	# end of first string?
	add	a1, a1, 2
	beq	t0, t1, 1b
NotEq:
	subu	v0, t0, t1
	j	ra
LessOrEq:
	subu	v0, zero, t1
	j	ra
END(strcmp)

/*
 * strcmp(s1, s2, length)
 * NOTE: this version assumes unsigned chars in order to be "8 bit clean".
 */
LEAF(strncmp)
1:
	beq	a2, zero, 3f		# end of len
	lbu	t0, 0(a0)		# get two bytes and compare them
	lbu	t1, 0(a1)
	beq	t0, zero, 2f		# end of first string?
	bne	t0, t1, 1f
	sub	a2, a2, 1
	beq	a2, zero, 3f		# end of len
	lbu	t0, 1(a0)		# unroll loop
	lbu	t1, 1(a1)
	add	a0, a0, 2
	beq	t0, zero, 2f		# end of first string?
	add	a1, a1, 2
	sub	a2, a2, 1
	beq	t0, t1, 1b
1:					# NotEq
	subu	v0, t0, t1
	j	ra
2:					# LessOrEq
	subu	v0, zero, t1
	j	ra
3:					# Eq
	move	v0, zero
	j	ra
END(strcmp)

#if BYTE_ORDER == LITTLE_ENDIAN
#	define	LWHI	lwr
#	define	LWLO	lwl
#	define	SWHI	swr
#	define	SWLO	swl
#endif
#if BYTE_ORDER == BIG_ENDIAN
#	define	LWHI	lwl
#	define	LWLO	lwr
#	define	SWHI	swl
#	define	SWLO	swr
#endif

/*
 * bzero(s1, n)
 */
LEAF(bzero)
ALEAF(blkclr)
	.set	noreorder
	blt	a1, 12, smallclr	# small amount to clear?
	subu	a3, zero, a0		# compute # bytes to word align address
	and	a3, a3, 3
	beq	a3, zero, 1f		# skip if word aligned
	subu	a1, a1, a3		# subtract from remaining count
	SWHI	zero, 0(a0)		# clear 1, 2, or 3 bytes to align
	addu	a0, a0, a3
1:
	and	v0, a1, 3		# compute number of words left
	subu	a3, a1, v0
	move	a1, v0
	addu	a3, a3, a0		# compute ending address
2:
	addu	a0, a0, 4		# clear words
	bne	a0, a3, 2b		#   unrolling loop doesn't help
	sw	zero, -4(a0)		#   since we're limited by memory speed
smallclr:
	ble	a1, zero, 2f
	addu	a3, a1, a0		# compute ending address
1:
	addu	a0, a0, 1		# clear bytes
	bne	a0, a3, 1b
	sb	zero, -1(a0)
2:
	j	ra
	nop
	.set	reorder
END(bzero)

/*
 * bcmp(s1, s2, n)
 */
LEAF(bcmp)
	.set	noreorder
	blt	a2, 16, smallcmp	# is it worth any trouble?
	xor	v0, a0, a1		# compare low two bits of addresses
	and	v0, v0, 3
	subu	a3, zero, a1		# compute # bytes to word align address
	bne	v0, zero, unalignedcmp	# not possible to align addresses
	and	a3, a3, 3

	beq	a3, zero, 1f
	subu	a2, a2, a3		# subtract from remaining count
	move	v0, v1			# init v0,v1 so unmodified bytes match
	LWHI	v0, 0(a0)		# read 1, 2, or 3 bytes
	LWHI	v1, 0(a1)
	addu	a1, a1, a3
	bne	v0, v1, nomatch
	addu	a0, a0, a3
1:
	and	a3, a2, ~3		# compute number of whole words left
	subu	a2, a2, a3		#   which has to be >= (16-3) & ~3
	addu	a3, a3, a0		# compute ending address
2:
	lw	v0, 0(a0)		# compare words
	lw	v1, 0(a1)
	addu	a0, a0, 4
	bne	v0, v1, nomatch
	addu	a1, a1, 4
	bne	a0, a3, 2b
	nop
	b	smallcmp		# finish remainder
	nop
unalignedcmp:
	beq	a3, zero, 2f
	subu	a2, a2, a3		# subtract from remaining count
	addu	a3, a3, a0		# compute ending address
1:
	lbu	v0, 0(a0)		# compare bytes until a1 word aligned
	lbu	v1, 0(a1)
	addu	a0, a0, 1
	bne	v0, v1, nomatch
	addu	a1, a1, 1
	bne	a0, a3, 1b
	nop
2:
	and	a3, a2, ~3		# compute number of whole words left
	subu	a2, a2, a3		#   which has to be >= (16-3) & ~3
	addu	a3, a3, a0		# compute ending address
3:
	LWHI	v0, 0(a0)		# compare words a0 unaligned, a1 aligned
	LWLO	v0, 3(a0)
	lw	v1, 0(a1)
	addu	a0, a0, 4
	bne	v0, v1, nomatch
	addu	a1, a1, 4
	bne	a0, a3, 3b
	nop
smallcmp:
	ble	a2, zero, match
	addu	a3, a2, a0		# compute ending address
1:
	lbu	v0, 0(a0)
	lbu	v1, 0(a1)
	addu	a0, a0, 1
	bne	v0, v1, nomatch
	addu	a1, a1, 1
	bne	a0, a3, 1b
	nop
match:
	j	ra
	move	v0, zero
nomatch:
	j	ra
	li	v0, 1