Minix2.0/src/kernel/mpx386.s
#
! This file contains the assembler startup code for Minix and the 32-bit
! interrupt handlers. It cooperates with start.c to set up a good
! environment for main().
! This file is part of the lowest layer of the MINIX kernel. The other part
! is "proc.c". The lowest layer does process switching and message handling.
! Every transition to the kernel goes through this file. Transitions are
! caused by sending/receiving messages and by most interrupts. (RS232
! interrupts may be handled in the file "rs2.s" and then they rarely enter
! the kernel.)
! Transitions to the kernel may be nested. The initial entry may be with a
! system call, exception or hardware interrupt; reentries may only be made
! by hardware interrupts. The count of reentries is kept in "k_reenter".
! It is important for deciding whether to switch to the kernel stack and
! for protecting the message passing code in "proc.c".
! For the message passing trap, most of the machine state is saved in the
! proc table. (Some of the registers need not be saved.) Then the stack is
! switched to "k_stack", and interrupts are reenabled. Finally, the system
! call handler (in C) is called. When it returns, interrupts are disabled
! again and the code falls into the restart routine, to finish off held-up
! interrupts and run the process or task whose pointer is in "proc_ptr".
! Hardware interrupt handlers do the same, except (1) The entire state must
! be saved. (2) There are too many handlers to do this inline, so the save
! routine is called. A few cycles are saved by pushing the address of the
! appropiate restart routine for a return later. (3) A stack switch is
! avoided when the stack is already switched. (4) The (master) 8259 interrupt
! controller is reenabled centrally in save(). (5) Each interrupt handler
! masks its interrupt line using the 8259 before enabling (other unmasked)
! interrupts, and unmasks it after servicing the interrupt. This limits the
! nest level to the number of lines and protects the handler from itself.
! For communication with the boot monitor at startup time some constant
! data are compiled into the beginning of the text segment. This facilitates
! reading the data at the start of the boot process, since only the first
! sector of the file needs to be read.
! Some data storage is also allocated at the end of this file. This data
! will be at the start of the data segment of the kernel and will be read
! and modified by the boot monitor before the kernel starts.
! sections
.sect .text
begtext:
.sect .rom
begrom:
.sect .data
begdata:
.sect .bss
begbss:
#include <minix/config.h>
#include <minix/const.h>
#include <minix/com.h>
#include "const.h"
#include "protect.h"
#include "sconst.h"
/* Selected 386 tss offsets. */
#define TSS3_S_SP0 4
! Exported functions
! Note: in assembly language the .define statement applied to a function name
! is loosely equivalent to a prototype in C code -- it makes it possible to
! link to an entity declared in the assembly code but does not create
! the entity.
.define _idle_task
.define _restart
.define save
.define _divide_error
.define _single_step_exception
.define _nmi
.define _breakpoint_exception
.define _overflow
.define _bounds_check
.define _inval_opcode
.define _copr_not_available
.define _double_fault
.define _copr_seg_overrun
.define _inval_tss
.define _segment_not_present
.define _stack_exception
.define _general_protection
.define _page_fault
.define _copr_error
.define _hwint00 ! handlers for hardware interrupts
.define _hwint01
.define _hwint02
.define _hwint03
.define _hwint04
.define _hwint05
.define _hwint06
.define _hwint07
.define _hwint08
.define _hwint09
.define _hwint10
.define _hwint11
.define _hwint12
.define _hwint13
.define _hwint14
.define _hwint15
.define _s_call
.define _p_s_call
.define _level0_call
! Imported functions.
.extern _cstart
.extern _main
.extern _exception
.extern _interrupt
.extern _sys_call
.extern _unhold
! Exported variables.
! Note: when used with a variable the .define does not reserve storage,
! it makes the name externally visible so it may be linked to.
.define begbss
.define begdata
.define _sizes
! Imported variables.
.extern _gdt
.extern _code_base
.extern _data_base
.extern _held_head
.extern _k_reenter
.extern _pc_at
.extern _proc_ptr
.extern _ps_mca
.extern _tss
.extern _level0_func
.extern _mon_sp
.extern _mon_return
.extern _reboot_code
.sect .text
!*===========================================================================*
!* MINIX *
!*===========================================================================*
MINIX: ! this is the entry point for the MINIX kernel
jmp over_flags ! skip over the next few bytes
.data2 CLICK_SHIFT ! for the monitor: memory granularity
flags:
.data2 0x002D ! boot monitor flags:
! call in 386 mode, make stack,
! load high, will return
nop ! extra byte to sync up disassembler
over_flags:
! Set up a C stack frame on the monitor stack. (The monitor sets cs and ds
! right. The ss descriptor still references the monitor data segment.)
movzx esp, sp ! monitor stack is a 16 bit stack
push ebp
mov ebp, esp
push esi
push edi
cmp 4(ebp), 0 ! nonzero if return possible
jz noret
inc (_mon_return)
noret: mov (_mon_sp), esp ! save stack pointer for later return
! Copy the monitor global descriptor table to the address space of kernel and
! switch over to it. Prot_init() can then update it with immediate effect.
sgdt (_gdt+GDT_SELECTOR) ! get the monitor gdtr
mov esi, (_gdt+GDT_SELECTOR+2) ! absolute address of GDT
mov ebx, _gdt ! address of kernel GDT
mov ecx, 8*8 ! copying eight descriptors
copygdt:
eseg movb al, (esi)
movb (ebx), al
inc esi
inc ebx
loop copygdt
mov eax, (_gdt+DS_SELECTOR+2) ! base of kernel data
and eax, 0x00FFFFFF ! only 24 bits
add eax, _gdt ! eax = vir2phys(gdt)
mov (_gdt+GDT_SELECTOR+2), eax ! set base of GDT
lgdt (_gdt+GDT_SELECTOR) ! switch over to kernel GDT
! Locate boot parameters, set up kernel segment registers and stack.
mov ebx, 8(ebp) ! boot parameters offset
mov edx, 12(ebp) ! boot parameters length
mov ax, ds ! kernel data
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
mov esp, k_stktop ! set sp to point to the top of kernel stack
! Call C startup code to set up a proper environment to run main().
push edx
push ebx
push SS_SELECTOR
push MON_CS_SELECTOR
push DS_SELECTOR
push CS_SELECTOR
call _cstart ! cstart(cs, ds, mcs, mds, parmoff, parmlen)
add esp, 6*4
! Reload gdtr, idtr and the segment registers to global descriptor table set
! up by prot_init().
lgdt (_gdt+GDT_SELECTOR)
lidt (_gdt+IDT_SELECTOR)
jmpf CS_SELECTOR:csinit
csinit:
o16 mov ax, DS_SELECTOR
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
o16 mov ax, TSS_SELECTOR ! no other TSS is used
ltr ax
push 0 ! set flags to known good state
popf ! esp, clear nested task and int enable
jmp _main ! main()
!*===========================================================================*
!* interrupt handlers *
!* interrupt handlers for 386 32-bit protected mode *
!*===========================================================================*
!*===========================================================================*
!* hwint00 - 07 *
!*===========================================================================*
! Note this is a macro, it looks like a subroutine.
#define hwint_master(irq) \
call save /* save interrupted process state */;\
inb INT_CTLMASK ;\
orb al, [1<<irq] ;\
outb INT_CTLMASK /* disable the irq */;\
movb al, ENABLE ;\
outb INT_CTL /* reenable master 8259 */;\
sti /* enable interrupts */;\
push irq /* irq */;\
call (_irq_table + 4*irq) /* eax = (*irq_table[irq])(irq) */;\
pop ecx ;\
cli /* disable interrupts */;\
test eax, eax /* need to reenable irq? */;\
jz 0f ;\
inb INT_CTLMASK ;\
andb al, ~[1<<irq] ;\
outb INT_CTLMASK /* enable the irq */;\
0: ret /* restart (another) process */
! Each of these entry points is an expansion of the hwint_master macro
.align 16
_hwint00: ! Interrupt routine for irq 0 (the clock).
hwint_master(0)
.align 16
_hwint01: ! Interrupt routine for irq 1 (keyboard)
hwint_master(1)
.align 16
_hwint02: ! Interrupt routine for irq 2 (cascade!)
hwint_master(2)
.align 16
_hwint03: ! Interrupt routine for irq 3 (second serial)
hwint_master(3)
.align 16
_hwint04: ! Interrupt routine for irq 4 (first serial)
hwint_master(4)
.align 16
_hwint05: ! Interrupt routine for irq 5 (XT winchester)
hwint_master(5)
.align 16
_hwint06: ! Interrupt routine for irq 6 (floppy)
hwint_master(6)
.align 16
_hwint07: ! Interrupt routine for irq 7 (printer)
hwint_master(7)
!*===========================================================================*
!* hwint08 - 15 *
!*===========================================================================*
! Note this is a macro, it looks like a subroutine.
#define hwint_slave(irq) \
call save /* save interrupted process state */;\
inb INT2_CTLMASK ;\
orb al, [1<<[irq-8]] ;\
outb INT2_CTLMASK /* disable the irq */;\
movb al, ENABLE ;\
outb INT_CTL /* reenable master 8259 */;\
jmp .+2 /* delay */;\
outb INT2_CTL /* reenable slave 8259 */;\
sti /* enable interrupts */;\
push irq /* irq */;\
call (_irq_table + 4*irq) /* eax = (*irq_table[irq])(irq) */;\
pop ecx ;\
cli /* disable interrupts */;\
test eax, eax /* need to reenable irq? */;\
jz 0f ;\
inb INT2_CTLMASK ;\
andb al, ~[1<<[irq-8]] ;\
outb INT2_CTLMASK /* enable the irq */;\
0: ret /* restart (another) process */
! Each of these entry points is an expansion of the hwint_slave macro
.align 16
_hwint08: ! Interrupt routine for irq 8 (realtime clock)
hwint_slave(8)
.align 16
_hwint09: ! Interrupt routine for irq 9 (irq 2 redirected)
hwint_slave(9)
.align 16
_hwint10: ! Interrupt routine for irq 10
hwint_slave(10)
.align 16
_hwint11: ! Interrupt routine for irq 11
hwint_slave(11)
.align 16
_hwint12: ! Interrupt routine for irq 12
hwint_slave(12)
.align 16
_hwint13: ! Interrupt routine for irq 13 (FPU exception)
hwint_slave(13)
.align 16
_hwint14: ! Interrupt routine for irq 14 (AT winchester)
hwint_slave(14)
.align 16
_hwint15: ! Interrupt routine for irq 15
hwint_slave(15)
!*===========================================================================*
!* save *
!*===========================================================================*
! Save for protected mode.
! This is much simpler than for 8086 mode, because the stack already points
! into the process table, or has already been switched to the kernel stack.
.align 16
save:
cld ! set direction flag to a known value
pushad ! save "general" registers
o16 push ds ! save ds
o16 push es ! save es
o16 push fs ! save fs
o16 push gs ! save gs
mov dx, ss ! ss is kernel data segment
mov ds, dx ! load rest of kernel segments
mov es, dx ! kernel does not use fs, gs
mov eax, esp ! prepare to return
incb (_k_reenter) ! from -1 if not reentering
jnz set_restart1 ! stack is already kernel stack
mov esp, k_stktop
push _restart ! build return address for int handler
xor ebp, ebp ! for stacktrace
jmp RETADR-P_STACKBASE(eax)
.align 4
set_restart1:
push restart1
jmp RETADR-P_STACKBASE(eax)
!*===========================================================================*
!* _s_call *
!*===========================================================================*
.align 16
_s_call:
_p_s_call:
cld ! set direction flag to a known value
sub esp, 6*4 ! skip RETADR, eax, ecx, edx, ebx, est
push ebp ! stack already points into proc table
push esi
push edi
o16 push ds
o16 push es
o16 push fs
o16 push gs
mov dx, ss
mov ds, dx
mov es, dx
incb (_k_reenter)
mov esi, esp ! assumes P_STACKBASE == 0
mov esp, k_stktop
xor ebp, ebp ! for stacktrace
! end of inline save
sti ! allow SWITCHER to be interrupted
! now set up parameters for sys_call()
push ebx ! pointer to user message
push eax ! src/dest
push ecx ! SEND/RECEIVE/BOTH
call _sys_call ! sys_call(function, src_dest, m_ptr)
! caller is now explicitly in proc_ptr
mov AXREG(esi), eax ! sys_call MUST PRESERVE si
cli ! disable interrupts
! Fall into code to restart proc/task running.
!*===========================================================================*
!* restart *
!*===========================================================================*
_restart:
! Flush any held-up interrupts.
! This reenables interrupts, so the current interrupt handler may reenter.
! This does not matter, because the current handler is about to exit and no
! other handlers can reenter since flushing is only done when k_reenter == 0.
cmp (_held_head), 0 ! do fast test to usually avoid function call
jz over_call_unhold
call _unhold ! this is rare so overhead acceptable
over_call_unhold:
mov esp, (_proc_ptr) ! will assume P_STACKBASE == 0
lldt P_LDT_SEL(esp) ! enable segment descriptors for task
lea eax, P_STACKTOP(esp) ! arrange for next interrupt
mov (_tss+TSS3_S_SP0), eax ! to save state in process table
restart1:
decb (_k_reenter)
o16 pop gs
o16 pop fs
o16 pop es
o16 pop ds
popad
add esp, 4 ! skip return adr
iretd ! continue process
!*===========================================================================*
!* exception handlers *
!*===========================================================================*
_divide_error:
push DIVIDE_VECTOR
jmp exception
_single_step_exception:
push DEBUG_VECTOR
jmp exception
_nmi:
push NMI_VECTOR
jmp exception
_breakpoint_exception:
push BREAKPOINT_VECTOR
jmp exception
_overflow:
push OVERFLOW_VECTOR
jmp exception
_bounds_check:
push BOUNDS_VECTOR
jmp exception
_inval_opcode:
push INVAL_OP_VECTOR
jmp exception
_copr_not_available:
push COPROC_NOT_VECTOR
jmp exception
_double_fault:
push DOUBLE_FAULT_VECTOR
jmp errexception
_copr_seg_overrun:
push COPROC_SEG_VECTOR
jmp exception
_inval_tss:
push INVAL_TSS_VECTOR
jmp errexception
_segment_not_present:
push SEG_NOT_VECTOR
jmp errexception
_stack_exception:
push STACK_FAULT_VECTOR
jmp errexception
_general_protection:
push PROTECTION_VECTOR
jmp errexception
_page_fault:
push PAGE_FAULT_VECTOR
jmp errexception
_copr_error:
push COPROC_ERR_VECTOR
jmp exception
!*===========================================================================*
!* exception *
!*===========================================================================*
! This is called for all exceptions which do not push an error code.
.align 16
exception:
sseg mov (trap_errno), 0 ! clear trap_errno
sseg pop (ex_number)
jmp exception1
!*===========================================================================*
!* errexception *
!*===========================================================================*
! This is called for all exceptions which push an error code.
.align 16
errexception:
sseg pop (ex_number)
sseg pop (trap_errno)
exception1: ! Common for all exceptions.
push eax ! eax is scratch register
mov eax, 0+4(esp) ! old eip
sseg mov (old_eip), eax
movzx eax, 4+4(esp) ! old cs
sseg mov (old_cs), eax
mov eax, 8+4(esp) ! old eflags
sseg mov (old_eflags), eax
pop eax
call save
push (old_eflags)
push (old_cs)
push (old_eip)
push (trap_errno)
push (ex_number)
call _exception ! (ex_number, trap_errno, old_eip,
! old_cs, old_eflags)
add esp, 5*4
cli
ret
!*===========================================================================*
!* level0_call *
!*===========================================================================*
_level0_call:
call save
jmp (_level0_func)
!*===========================================================================*
!* idle_task *
!*===========================================================================*
_idle_task: ! executed when there is no work
jmp _idle_task ! a "hlt" before this fails in protected mode
!*===========================================================================*
!* data *
!*===========================================================================*
! These declarations assure that storage will be allocated at the very
! beginning of the kernel data section, so the boot monitor can be easily
! told how to patch these locations. Note that the magic number is put
! here by the compiler, but will be read by, and then overwritten by,
! the boot monitor. When the kernel starts the sizes array will be
! found here, as if it had been initialized by the compiler.
.sect .rom ! Before the string table please
_sizes: ! sizes of kernel, mm, fs filled in by boot
.data2 0x526F ! this must be the first data entry (magic #)
.space 16*2*2-2 ! monitor uses previous word and this space
! extra space allows for additional servers
.sect .bss
k_stack:
.space K_STACK_BYTES ! kernel stack
k_stktop: ! top of kernel stack
.comm ex_number, 4
.comm trap_errno, 4
.comm old_eip, 4
.comm old_cs, 4
.comm old_eflags, 4