klib88.s

MINIX2.0操作系统源码 MINIX2.0操作系统源码

#
#include <minix/config.h>
#include <minix/const.h>
#include "const.h"
#include "sconst.h"
#include "protect.h"

! This file contains a number of assembly code utility routines needed by the
! kernel.  They are:

.define	_monitor	! exit Minix and return to the monitor
.define real2prot	! switch from real to protected mode
.define prot2real	! switch from protected to real mode
.define	_check_mem	! check a block of memory, return the valid size
.define	_cp_mess	! copies messages from source to destination
.define	_exit		! dummy for library routines
.define	__exit		! dummy for library routines
.define	___exit		! dummy for library routines
.define	.fat, .trp	! dummies for library routines
.define	_in_byte	! read a byte from a port and return it
.define	_in_word	! read a word from a port and return it
.define	_out_byte	! write a byte to a port
.define	_out_word	! write a word to a port
.define	_port_read	! transfer data from (disk controller) port to memory
.define	_port_read_byte	! likewise byte by byte
.define	_port_write	! transfer data from memory to (disk controller) port
.define	_port_write_byte ! likewise byte by byte
.define	_lock		! disable interrupts
.define	_unlock		! enable interrupts
.define	_enable_irq	! enable an irq at the 8259 controller
.define	_disable_irq	! disable an irq
.define	_phys_copy	! copy data from anywhere to anywhere in memory
.define	_mem_rdw	! copy one word from [segment:offset]
.define	_reset		! reset the system
.define	_mem_vid_copy	! copy data to video ram
.define	_vid_vid_copy	! move data in video ram
.define	_level0		! call a function at level 0
.define	klib_init_prot	! initialize klib functions for protected mode

! The routines only guarantee to preserve the registers the C compiler
! expects to be preserved (si, di, bp, sp, segment registers, and direction
! bit in the flags), though some of the older ones preserve bx, cx and dx.

#define DS_286_OFFSET	DS_286_INDEX*DESC_SIZE
#define ES_286_OFFSET	ES_286_INDEX*DESC_SIZE
#	define EM_XFER_FUNC	0x87
#define JMP_OPCODE	0xE9	/* opcode used for patching */
#define OFF_MASK	0x000F	/* offset mask for phys_b -> hclick:offset */
#define HCHIGH_MASK	0x0F	/* h/w click mask for low byte of hi word */
#define HCLOW_MASK	0xF0	/* h/w click mask for low byte of low word */

! Imported functions

.extern	p_restart
.extern	p_save
.extern	_restart
.extern	save

! Exported variables

.extern kernel_cs

! Imported variables

.extern kernel_ds
.extern _irq_use
.extern	_blank_color
.extern	_gdt
.extern	_protected_mode
.extern	_vid_seg
.extern	_vid_size
.extern	_vid_mask
.extern	_level0_func

	.text
!*===========================================================================*
!*				monitor					     *
!*===========================================================================*
! PUBLIC void monitor();
! Return to the monitor.

_monitor:
	call	prot2real		! switch to real mode
	mov	ax, _reboot_code+0	! address of new parameters
	mov	dx, _reboot_code+2
	mov	sp, _mon_sp		! restore monitor stack pointer
	mov	bx, _mon_ss		! monitor data segment
	mov	ds, bx
	mov	es, bx
	mov	ss, bx
	pop	di
	pop	si
	pop	bp
	retf				! return to the monitor


#if ENABLE_BIOS_WINI
!*===========================================================================*
!*				bios13					     *
!*===========================================================================*
! PUBLIC void bios13();
.define _bios13
_bios13:			! make a BIOS 0x13 call for disk I/O
	push	si
	push	di		! save C variable registers
	pushf			! save flags

	call	int13		! make the actual call

	popf			! restore flags
	pop	di		! restore C registers
	pop	si
	ret

! Make a BIOS 0x13 call from protected mode
p_bios13:
	push	bp
	push	si
	push	di			! save C variable registers
	pushf				! save flags
	cli				! no interruptions
	inb	INT2_CTLMASK
	movb	ah, al
	inb	INT_CTLMASK
	push	ax			! save interrupt masks
	mov	ax, _irq_use		! map of in-use IRQs
	and	ax, #~[1<<CLOCK_IRQ]	! there is a special clock handler
	outb	INT_CTLMASK		! enable all unused IRQs and vv.
	movb	al, ah
	outb	INT2_CTLMASK

	smsw	ax
	push	ax			! save machine status word
	call	prot2real		! switch to real mode

	call	int13			! make the actual call

	call	real2prot		! back to protected mode
	pop	ax
	lmsw	ax			! restore msw

	pop	ax			! restore interrupt masks
	outb	INT_CTLMASK
	movb	al, ah
	outb	INT2_CTLMASK
	popf				! restore flags
	pop	di
	pop	si
	pop	bp			! restore C variable registers
	ret

int13:
	mov	ax, _Ax		! load parameters
	mov	bx, _Bx
	mov	cx, _Cx
	mov	dx, _Dx
	mov	es, _Es
	sti			! enable interrupts
	int	0x13		! make the BIOS call
	cli			! disable interrupts
	mov	_Ax, ax		! save results
	mov	_Bx, bx
	mov	_Cx, cx
	mov	_Dx, dx
	mov	_Es, es
	mov	ax, ds
	mov	es, ax		! restore es
	ret

.bss
.define	_Ax, _Bx, _Cx, _Dx, _Es		! 8086 register variables
.comm	_Ax, 2
.comm	_Bx, 2
.comm	_Cx, 2
.comm	_Dx, 2
.comm	_Es, 2
.text
#endif /* ENABLE_BIOS_WINI */


!*===========================================================================*
!*				real2prot				     *
!*===========================================================================*
! Switch from real to protected mode.
real2prot:
	lgdt	_gdt+GDT_SELECTOR	! set global descriptor table
	smsw	ax
	mov	msw, ax			! save real mode msw
	orb	al, #0x01		! set PE (protection enable) bit
	lmsw	ax			! set msw, enabling protected mode

	jmpf	csinit, CS_SELECTOR	! set code segment selector
csinit:
	mov	ax, #DS_SELECTOR	! set data selectors
	mov	ds, ax
	mov	es, ax
	mov	ss, ax
	lidt    _gdt+IDT_SELECTOR	! set interrupt vectors
	andb	_gdt+TSS_SELECTOR+DESC_ACCESS, #~0x02  ! clear TSS busy bit
	mov	ax, #TSS_SELECTOR
	ltr	ax			! set TSS register

	movb	ah, #0xDF
	jmp	gate_A20		! enable the A20 address line


!*===========================================================================*
!*				prot2real				     *
!*===========================================================================*
! Switch from protected to real mode.
prot2real:
	mov	save_sp, sp		! save stack pointer
	cmp	_processor, #386	! is this a 386?
	jae	p2r386
p2r286:
	mov	_gdt+ES_286_OFFSET+DESC_BASE, #0x0400
	movb	_gdt+ES_286_OFFSET+DESC_BASE_MIDDLE, #0x00
	mov	ax, #ES_286_SELECTOR
	mov	es, ax			! BIOS data segment
  eseg	mov	0x0067, #real		! set return from shutdown address
  cseg	mov	ax, kernel_cs
  eseg	mov	0x0069, ax
	movb	al, #0x8F
	outb	0x70			! select CMOS byte 0x0F (disable NMI)
	jmp	.+2
	movb	al, #0x0A
	outb	0x71			! set shutdown code to 0x0A "jump far"
	jmp	p_reset			! cause a processor shutdown
p2r386:
	lidt	idt_vectors		! real mode interrupt vectors
	push	_gdt+CS_SELECTOR+0
	push	_gdt+DS_SELECTOR+0	! save CS and DS limits
	mov	_gdt+CS_SELECTOR+0, #0xFFFF
	mov	_gdt+DS_SELECTOR+0, #0xFFFF ! set 64k limits
	jmpf	cs64k, CS_SELECTOR	! reload selectors
cs64k:	mov	ax, #DS_SELECTOR
	mov	ds, ax
	mov	es, ax
	mov	ss, ax
	pop	_gdt+DS_SELECTOR+0
	pop	_gdt+CS_SELECTOR+0	! restore CS and DS limits
	.data1	0x0F,0x20,0xC0		! mov	eax, cr0
	mov	ax, msw			! restore real mode (16 bits) msw
	.data1	0x0F,0x22,0xC0		! mov	cr0, eax
	.data1	0xEA			! jmpf real, "kernel_cs"
	.data2	real
kernel_cs:
	.data2	0
real:
  cseg	mov	ax, kernel_ds		! reload data segment registers
	mov	ds, ax
	mov	es, ax
	mov	ss, ax
	mov	sp, save_sp		! restore stack

	movb	ah, #0xDD
	!jmp	gate_A20		! disable the A20 address line

! Enable (ah = 0xDF) or disable (ah = 0xDD) the A20 address line.
gate_A20:
	call	kb_wait
	movb	al, #0xD1	! Tell keyboard that a command is coming
	outb	0x64
	call	kb_wait
	movb	al, ah		! Enable or disable code
	outb	0x60
	call	kb_wait
	mov	ax, #25		! 25 microsec delay for slow keyboard chip
0:	out	0xED		! Write to an unused port (1us)
	dec	ax
	jne	0b
	ret
kb_wait:
	inb	0x64
	testb	al, #0x02	! Keyboard input buffer full?
	jnz	kb_wait		! If so, wait
	ret


!*===========================================================================*
!*				check_mem				     *
!*===========================================================================*
! PUBLIC phys_bytes check_mem(phys_bytes base, phys_bytes size);
! Check a block of memory, return the amount valid.
! Only every 16th byte is checked.
! This only works in protected mode.
! An initial size of 0 means everything.
! This really should do some alias checks.

PCM_DENSITY	=	256	! resolution of check
				! the shift logic depends on this being 256
TEST1PATTERN	=	0x55	! memory test pattern 1
TEST2PATTERN	=	0xAA	! memory test pattern 2

_check_mem:
	pop	bx
	pop	_gdt+DS_286_OFFSET+DESC_BASE
	pop	ax		! pop base into base of source descriptor
	movb	_gdt+DS_286_OFFSET+DESC_BASE_MIDDLE,al
	pop	cx		! byte count in dx:cx
	pop	dx
	sub	sp,#4+4
	push	bx
	push	ds

	sub	ax,ax		! prepare for early exit
	test	dx,#0xFF00
	jnz	cm_1exit	! cannot handle bases above 16M
	movb	cl,ch		! divide size by 256 and discard high byte
	movb	ch,dl
	push	cx		! save divided size
	sub	bx,bx		! test bytes at bases of segments
cm_loop:
	mov	ax,#DS_286_SELECTOR
	mov	ds,ax
	movb	dl,#TEST1PATTERN
	xchgb	dl,(bx)		! write test pattern, remember original value
	xchgb	dl,(bx)		! restore original value, read test pattern
	cmpb	dl,#TEST1PATTERN	! must agree if good real memory
	jnz	cm_exit		! if different, memory is unusable
	movb	dl,#TEST2PATTERN
	xchgb	dl,(bx)
	xchgb	dl,(bx)
	cmpb	dl,#TEST2PATTERN
	jnz	cm_exit
				! next segment, test for wraparound at 16M
				! assuming es == old ds
  eseg	add	_gdt+DS_286_OFFSET+DESC_BASE,#PCM_DENSITY
  eseg	adcb	_gdt+DS_286_OFFSET+DESC_BASE_MIDDLE,#0
	loopnz	cm_loop

cm_exit:
	pop	ax
	sub	ax,cx		! verified size in multiples of PCM_DENSITY
cm_1exit:
	movb	dl,ah		! convert to phys_bytes in dx:ax
	subb	dh,dh
	movb	ah,al
	movb	al,dh
	pop	ds
	ret


!*===========================================================================*
!*				cp_mess					     *
!*===========================================================================*
! PUBLIC void cp_mess(int src, phys_clicks src_clicks, vir_bytes src_offset,
!		      phys_clicks dst_clicks, vir_bytes dst_offset);
! This routine makes a fast copy of a message from anywhere in the address
! space to anywhere else.  It also copies the source address provided as a
! parameter to the call into the first word of the destination message.
!
! Note that the message size, "Msize" is in WORDS (not bytes) and must be set
! correctly.  Changing the definition of message in the type file and not
! changing it here will lead to total disaster.

_cp_mess:
	cld
	push es			! save es
	push ds			! save ds
	mov bx,sp		! index off bx because machine cannot use sp
	push si			! save si
	push di			! save di

	mov	ax,12(bx)	! destination click
#if HCLICK_SHIFT > CLICK_SHIFT
#error /* Small click sizes are not supported (right shift will lose bits). */
#endif
#if HCLICK_SHIFT < CLICK_SHIFT
	movb	cl,#CLICK_SHIFT-HCLICK_SHIFT
	shl	ax,cl		! destination segment
#endif
	mov	es,ax
	mov	di,14(bx)	! offset of destination message

! Be careful not to destroy ds before we are finished with the bx pointer.
! We are using bx and not the more natural bp to save pushing bp.

	mov	ax,6(bx)	! process number of sender
	mov	si,10(bx)	! offset of source message
	mov	bx,8(bx)	! source click (finished with bx as a pointer)
#if HCLICK_SHIFT < CLICK_SHIFT
	shl	bx,cl		! source segment
#endif
	mov	ds,bx

	stos			! copy process number of sender to dest message
	add si,*2		! do not copy first word
	mov cx,*Msize-1		! remember, first word does not count
	rep			! iterate cx times to copy 11 words