source: branches/minix3-book/kernel/mpx386.s@ 25

Last change on this file since 25 was 4, checked in by Mattia Monga, 14 years ago

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[4]1#
2! This file, mpx386.s, is included by mpx.s when Minix is compiled for
3! 32-bit Intel CPUs. The alternative mpx88.s is compiled for 16-bit CPUs.
4
5! This file is part of the lowest layer of the MINIX kernel. (The other part
6! is "proc.c".) The lowest layer does process switching and message handling.
7! Furthermore it contains the assembler startup code for Minix and the 32-bit
8! interrupt handlers. It cooperates with the code in "start.c" to set up a
9! good environment for main().
10
11! Every transition to the kernel goes through this file. Transitions to the
12! kernel may be nested. The initial entry may be with a system call (i.e.,
13! send or receive a message), an exception or a hardware interrupt; kernel
14! reentries may only be made by hardware interrupts. The count of reentries
15! is kept in "k_reenter". It is important for deciding whether to switch to
16! the kernel stack and for protecting the message passing code in "proc.c".
17
18! For the message passing trap, most of the machine state is saved in the
19! proc table. (Some of the registers need not be saved.) Then the stack is
20! switched to "k_stack", and interrupts are reenabled. Finally, the system
21! call handler (in C) is called. When it returns, interrupts are disabled
22! again and the code falls into the restart routine, to finish off held-up
23! interrupts and run the process or task whose pointer is in "proc_ptr".
24
25! Hardware interrupt handlers do the same, except (1) The entire state must
26! be saved. (2) There are too many handlers to do this inline, so the save
27! routine is called. A few cycles are saved by pushing the address of the
28! appropiate restart routine for a return later. (3) A stack switch is
29! avoided when the stack is already switched. (4) The (master) 8259 interrupt
30! controller is reenabled centrally in save(). (5) Each interrupt handler
31! masks its interrupt line using the 8259 before enabling (other unmasked)
32! interrupts, and unmasks it after servicing the interrupt. This limits the
33! nest level to the number of lines and protects the handler from itself.
34
35! For communication with the boot monitor at startup time some constant
36! data are compiled into the beginning of the text segment. This facilitates
37! reading the data at the start of the boot process, since only the first
38! sector of the file needs to be read.
39
40! Some data storage is also allocated at the end of this file. This data
41! will be at the start of the data segment of the kernel and will be read
42! and modified by the boot monitor before the kernel starts.
43
44! sections
45
46.sect .text
47begtext:
48.sect .rom
49begrom:
50.sect .data
51begdata:
52.sect .bss
53begbss:
54
55#include <minix/config.h>
56#include <minix/const.h>
57#include <minix/com.h>
58#include <ibm/interrupt.h>
59#include "const.h"
60#include "protect.h"
61#include "sconst.h"
62
63/* Selected 386 tss offsets. */
64#define TSS3_S_SP0 4
65
66! Exported functions
67! Note: in assembly language the .define statement applied to a function name
68! is loosely equivalent to a prototype in C code -- it makes it possible to
69! link to an entity declared in the assembly code but does not create
70! the entity.
71
72.define _restart
73.define save
74
75.define _divide_error
76.define _single_step_exception
77.define _nmi
78.define _breakpoint_exception
79.define _overflow
80.define _bounds_check
81.define _inval_opcode
82.define _copr_not_available
83.define _double_fault
84.define _copr_seg_overrun
85.define _inval_tss
86.define _segment_not_present
87.define _stack_exception
88.define _general_protection
89.define _page_fault
90.define _copr_error
91
92.define _hwint00 ! handlers for hardware interrupts
93.define _hwint01
94.define _hwint02
95.define _hwint03
96.define _hwint04
97.define _hwint05
98.define _hwint06
99.define _hwint07
100.define _hwint08
101.define _hwint09
102.define _hwint10
103.define _hwint11
104.define _hwint12
105.define _hwint13
106.define _hwint14
107.define _hwint15
108
109.define _s_call
110.define _p_s_call
111.define _level0_call
112
113! Exported variables.
114.define begbss
115.define begdata
116
117.sect .text
118!*===========================================================================*
119!* MINIX *
120!*===========================================================================*
121MINIX: ! this is the entry point for the MINIX kernel
122 jmp over_flags ! skip over the next few bytes
123 .data2 CLICK_SHIFT ! for the monitor: memory granularity
124flags:
125 .data2 0x01FD ! boot monitor flags:
126 ! call in 386 mode, make bss, make stack,
127 ! load high, don't patch, will return,
128 ! uses generic INT, memory vector,
129 ! new boot code return
130 nop ! extra byte to sync up disassembler
131over_flags:
132
133! Set up a C stack frame on the monitor stack. (The monitor sets cs and ds
134! right. The ss descriptor still references the monitor data segment.)
135 movzx esp, sp ! monitor stack is a 16 bit stack
136 push ebp
137 mov ebp, esp
138 push esi
139 push edi
140 cmp 4(ebp), 0 ! monitor return vector is
141 jz noret ! nonzero if return possible
142 inc (_mon_return)
143noret: mov (_mon_sp), esp ! save stack pointer for later return
144
145! Copy the monitor global descriptor table to the address space of kernel and
146! switch over to it. Prot_init() can then update it with immediate effect.
147
148 sgdt (_gdt+GDT_SELECTOR) ! get the monitor gdtr
149 mov esi, (_gdt+GDT_SELECTOR+2) ! absolute address of GDT
150 mov ebx, _gdt ! address of kernel GDT
151 mov ecx, 8*8 ! copying eight descriptors
152copygdt:
153 eseg movb al, (esi)
154 movb (ebx), al
155 inc esi
156 inc ebx
157 loop copygdt
158 mov eax, (_gdt+DS_SELECTOR+2) ! base of kernel data
159 and eax, 0x00FFFFFF ! only 24 bits
160 add eax, _gdt ! eax = vir2phys(gdt)
161 mov (_gdt+GDT_SELECTOR+2), eax ! set base of GDT
162 lgdt (_gdt+GDT_SELECTOR) ! switch over to kernel GDT
163
164! Locate boot parameters, set up kernel segment registers and stack.
165 mov ebx, 8(ebp) ! boot parameters offset
166 mov edx, 12(ebp) ! boot parameters length
167 mov eax, 16(ebp) ! address of a.out headers
168 mov (_aout), eax
169 mov ax, ds ! kernel data
170 mov es, ax
171 mov fs, ax
172 mov gs, ax
173 mov ss, ax
174 mov esp, k_stktop ! set sp to point to the top of kernel stack
175
176! Call C startup code to set up a proper environment to run main().
177 push edx
178 push ebx
179 push SS_SELECTOR
180 push DS_SELECTOR
181 push CS_SELECTOR
182 call _cstart ! cstart(cs, ds, mds, parmoff, parmlen)
183 add esp, 5*4
184
185! Reload gdtr, idtr and the segment registers to global descriptor table set
186! up by prot_init().
187
188 lgdt (_gdt+GDT_SELECTOR)
189 lidt (_gdt+IDT_SELECTOR)
190
191 jmpf CS_SELECTOR:csinit
192csinit:
193 o16 mov ax, DS_SELECTOR
194 mov ds, ax
195 mov es, ax
196 mov fs, ax
197 mov gs, ax
198 mov ss, ax
199 o16 mov ax, TSS_SELECTOR ! no other TSS is used
200 ltr ax
201 push 0 ! set flags to known good state
202 popf ! esp, clear nested task and int enable
203
204 jmp _main ! main()
205
206
207!*===========================================================================*
208!* interrupt handlers *
209!* interrupt handlers for 386 32-bit protected mode *
210!*===========================================================================*
211
212!*===========================================================================*
213!* hwint00 - 07 *
214!*===========================================================================*
215! Note this is a macro, it just looks like a subroutine.
216#define hwint_master(irq) \
217 call save /* save interrupted process state */;\
218 push (_irq_handlers+4*irq) /* irq_handlers[irq] */;\
219 call _intr_handle /* intr_handle(irq_handlers[irq]) */;\
220 pop ecx ;\
221 cmp (_irq_actids+4*irq), 0 /* interrupt still active? */;\
222 jz 0f ;\
223 inb INT_CTLMASK /* get current mask */ ;\
224 orb al, [1<<irq] /* mask irq */ ;\
225 outb INT_CTLMASK /* disable the irq */;\
2260: movb al, END_OF_INT ;\
227 outb INT_CTL /* reenable master 8259 */;\
228 ret /* restart (another) process */
229
230! Each of these entry points is an expansion of the hwint_master macro
231 .align 16
232_hwint00: ! Interrupt routine for irq 0 (the clock).
233 hwint_master(0)
234
235 .align 16
236_hwint01: ! Interrupt routine for irq 1 (keyboard)
237 hwint_master(1)
238
239 .align 16
240_hwint02: ! Interrupt routine for irq 2 (cascade!)
241 hwint_master(2)
242
243 .align 16
244_hwint03: ! Interrupt routine for irq 3 (second serial)
245 hwint_master(3)
246
247 .align 16
248_hwint04: ! Interrupt routine for irq 4 (first serial)
249 hwint_master(4)
250
251 .align 16
252_hwint05: ! Interrupt routine for irq 5 (XT winchester)
253 hwint_master(5)
254
255 .align 16
256_hwint06: ! Interrupt routine for irq 6 (floppy)
257 hwint_master(6)
258
259 .align 16
260_hwint07: ! Interrupt routine for irq 7 (printer)
261 hwint_master(7)
262
263!*===========================================================================*
264!* hwint08 - 15 *
265!*===========================================================================*
266! Note this is a macro, it just looks like a subroutine.
267#define hwint_slave(irq) \
268 call save /* save interrupted process state */;\
269 push (_irq_handlers+4*irq) /* irq_handlers[irq] */;\
270 call _intr_handle /* intr_handle(irq_handlers[irq]) */;\
271 pop ecx ;\
272 cmp (_irq_actids+4*irq), 0 /* interrupt still active? */;\
273 jz 0f ;\
274 inb INT2_CTLMASK ;\
275 orb al, [1<<[irq-8]] ;\
276 outb INT2_CTLMASK /* disable the irq */;\
2770: movb al, END_OF_INT ;\
278 outb INT_CTL /* reenable master 8259 */;\
279 outb INT2_CTL /* reenable slave 8259 */;\
280 ret /* restart (another) process */
281
282! Each of these entry points is an expansion of the hwint_slave macro
283 .align 16
284_hwint08: ! Interrupt routine for irq 8 (realtime clock)
285 hwint_slave(8)
286
287 .align 16
288_hwint09: ! Interrupt routine for irq 9 (irq 2 redirected)
289 hwint_slave(9)
290
291 .align 16
292_hwint10: ! Interrupt routine for irq 10
293 hwint_slave(10)
294
295 .align 16
296_hwint11: ! Interrupt routine for irq 11
297 hwint_slave(11)
298
299 .align 16
300_hwint12: ! Interrupt routine for irq 12
301 hwint_slave(12)
302
303 .align 16
304_hwint13: ! Interrupt routine for irq 13 (FPU exception)
305 hwint_slave(13)
306
307 .align 16
308_hwint14: ! Interrupt routine for irq 14 (AT winchester)
309 hwint_slave(14)
310
311 .align 16
312_hwint15: ! Interrupt routine for irq 15
313 hwint_slave(15)
314
315!*===========================================================================*
316!* save *
317!*===========================================================================*
318! Save for protected mode.
319! This is much simpler than for 8086 mode, because the stack already points
320! into the process table, or has already been switched to the kernel stack.
321
322 .align 16
323save:
324 cld ! set direction flag to a known value
325 pushad ! save "general" registers
326 o16 push ds ! save ds
327 o16 push es ! save es
328 o16 push fs ! save fs
329 o16 push gs ! save gs
330 mov dx, ss ! ss is kernel data segment
331 mov ds, dx ! load rest of kernel segments
332 mov es, dx ! kernel does not use fs, gs
333 mov eax, esp ! prepare to return
334 incb (_k_reenter) ! from -1 if not reentering
335 jnz set_restart1 ! stack is already kernel stack
336 mov esp, k_stktop
337 push _restart ! build return address for int handler
338 xor ebp, ebp ! for stacktrace
339 jmp RETADR-P_STACKBASE(eax)
340
341 .align 4
342set_restart1:
343 push restart1
344 jmp RETADR-P_STACKBASE(eax)
345
346!*===========================================================================*
347!* _s_call *
348!*===========================================================================*
349 .align 16
350_s_call:
351_p_s_call:
352 cld ! set direction flag to a known value
353 sub esp, 6*4 ! skip RETADR, eax, ecx, edx, ebx, est
354 push ebp ! stack already points into proc table
355 push esi
356 push edi
357 o16 push ds
358 o16 push es
359 o16 push fs
360 o16 push gs
361 mov dx, ss
362 mov ds, dx
363 mov es, dx
364 incb (_k_reenter)
365 mov esi, esp ! assumes P_STACKBASE == 0
366 mov esp, k_stktop
367 xor ebp, ebp ! for stacktrace
368 ! end of inline save
369 ! now set up parameters for sys_call()
370 push ebx ! pointer to user message
371 push eax ! src/dest
372 push ecx ! SEND/RECEIVE/BOTH
373 call _sys_call ! sys_call(function, src_dest, m_ptr)
374 ! caller is now explicitly in proc_ptr
375 mov AXREG(esi), eax ! sys_call MUST PRESERVE si
376
377! Fall into code to restart proc/task running.
378
379!*===========================================================================*
380!* restart *
381!*===========================================================================*
382_restart:
383
384! Restart the current process or the next process if it is set.
385
386 cmp (_next_ptr), 0 ! see if another process is scheduled
387 jz 0f
388 mov eax, (_next_ptr)
389 mov (_proc_ptr), eax ! schedule new process
390 mov (_next_ptr), 0
3910: mov esp, (_proc_ptr) ! will assume P_STACKBASE == 0
392 lldt P_LDT_SEL(esp) ! enable process' segment descriptors
393 lea eax, P_STACKTOP(esp) ! arrange for next interrupt
394 mov (_tss+TSS3_S_SP0), eax ! to save state in process table
395restart1:
396 decb (_k_reenter)
397 o16 pop gs
398 o16 pop fs
399 o16 pop es
400 o16 pop ds
401 popad
402 add esp, 4 ! skip return adr
403 iretd ! continue process
404
405!*===========================================================================*
406!* exception handlers *
407!*===========================================================================*
408_divide_error:
409 push DIVIDE_VECTOR
410 jmp exception
411
412_single_step_exception:
413 push DEBUG_VECTOR
414 jmp exception
415
416_nmi:
417 push NMI_VECTOR
418 jmp exception
419
420_breakpoint_exception:
421 push BREAKPOINT_VECTOR
422 jmp exception
423
424_overflow:
425 push OVERFLOW_VECTOR
426 jmp exception
427
428_bounds_check:
429 push BOUNDS_VECTOR
430 jmp exception
431
432_inval_opcode:
433 push INVAL_OP_VECTOR
434 jmp exception
435
436_copr_not_available:
437 push COPROC_NOT_VECTOR
438 jmp exception
439
440_double_fault:
441 push DOUBLE_FAULT_VECTOR
442 jmp errexception
443
444_copr_seg_overrun:
445 push COPROC_SEG_VECTOR
446 jmp exception
447
448_inval_tss:
449 push INVAL_TSS_VECTOR
450 jmp errexception
451
452_segment_not_present:
453 push SEG_NOT_VECTOR
454 jmp errexception
455
456_stack_exception:
457 push STACK_FAULT_VECTOR
458 jmp errexception
459
460_general_protection:
461 push PROTECTION_VECTOR
462 jmp errexception
463
464_page_fault:
465 push PAGE_FAULT_VECTOR
466 jmp errexception
467
468_copr_error:
469 push COPROC_ERR_VECTOR
470 jmp exception
471
472!*===========================================================================*
473!* exception *
474!*===========================================================================*
475! This is called for all exceptions which do not push an error code.
476
477 .align 16
478exception:
479 sseg mov (trap_errno), 0 ! clear trap_errno
480 sseg pop (ex_number)
481 jmp exception1
482
483!*===========================================================================*
484!* errexception *
485!*===========================================================================*
486! This is called for all exceptions which push an error code.
487
488 .align 16
489errexception:
490 sseg pop (ex_number)
491 sseg pop (trap_errno)
492exception1: ! Common for all exceptions.
493 push eax ! eax is scratch register
494 mov eax, 0+4(esp) ! old eip
495 sseg mov (old_eip), eax
496 movzx eax, 4+4(esp) ! old cs
497 sseg mov (old_cs), eax
498 mov eax, 8+4(esp) ! old eflags
499 sseg mov (old_eflags), eax
500 pop eax
501 call save
502 push (old_eflags)
503 push (old_cs)
504 push (old_eip)
505 push (trap_errno)
506 push (ex_number)
507 call _exception ! (ex_number, trap_errno, old_eip,
508 ! old_cs, old_eflags)
509 add esp, 5*4
510 ret
511
512!*===========================================================================*
513!* level0_call *
514!*===========================================================================*
515_level0_call:
516 call save
517 jmp (_level0_func)
518
519!*===========================================================================*
520!* data *
521!*===========================================================================*
522
523.sect .rom ! Before the string table please
524 .data2 0x526F ! this must be the first data entry (magic #)
525
526.sect .bss
527k_stack:
528 .space K_STACK_BYTES ! kernel stack
529k_stktop: ! top of kernel stack
530 .comm ex_number, 4
531 .comm trap_errno, 4
532 .comm old_eip, 4
533 .comm old_cs, 4
534 .comm old_eflags, 4
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