Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/i386/start.s
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1 /* 2 * Mach Operating System 3 * Copyright (c) 1993-1990 Carnegie Mellon University 4 * All Rights Reserved. 5 * 6 * Permission to use, copy, modify and distribute this software and its 7 * documentation is hereby granted, provided that both the copyright 8 * notice and this permission notice appear in all copies of the 9 * software, derivative works or modified versions, and any portions 10 * thereof, and that both notices appear in supporting documentation. 11 * 12 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 13 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR 14 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 15 * 16 * Carnegie Mellon requests users of this software to return to 17 * 18 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 19 * School of Computer Science 20 * Carnegie Mellon University 21 * Pittsburgh PA 15213-3890 22 * 23 * any improvements or extensions that they make and grant Carnegie Mellon 24 * the rights to redistribute these changes. 25 */ 26 /* 27 * HISTORY 28 * $Log: start.s,v $ 29 * Revision 2.18 93/05/10 17:46:38 rvb 30 * Use C comments 31 * [93/05/04 17:17:00 rvb] 32 * 33 * Revision 2.17 93/02/04 07:58:02 danner 34 * Replace lost ps2 asm_startup include. 35 * 36 * Revision 2.16 93/01/14 17:29:39 danner 37 * Boot_info changed. 38 * [92/12/10 17:43:44 af] 39 * 40 * Revision 2.15 92/04/04 11:51:04 rpd 41 * Changed #-style comments to /-style, for ANSI preprocessors. 42 * 43 * Revision 2.14 92/01/03 20:08:53 dbg 44 * Move symbol table and bootstrap image out of BSS. 45 * [91/08/02 dbg] 46 * 47 * Revision 2.13 91/07/31 17:40:55 dbg 48 * Add pointers to interrupt stack (for uniprocessor). 49 * [91/07/30 16:57:13 dbg] 50 * 51 * Revision 2.12 91/06/19 11:55:39 rvb 52 * cputypes.h->platforms.h 53 * [91/06/12 13:45:27 rvb] 54 * 55 * Revision 2.11 91/05/14 16:16:59 mrt 56 * Correcting copyright 57 * 58 * Revision 2.10 91/05/08 12:42:43 dbg 59 * Put parentheses around substituted immediate expressions, so 60 * that they will pass through the GNU preprocessor. 61 * 62 * Moved model-specific code to machine-dependent directories. 63 * Added startup code for multiple CPUs. 64 * [91/04/26 14:38:55 dbg] 65 * 66 * Revision 2.9 91/02/05 17:14:50 mrt 67 * Changed to new Mach copyright 68 * [91/02/01 17:38:15 mrt] 69 * 70 * Revision 2.8 90/12/20 16:37:02 jeffreyh 71 * Changes for __STDC__ 72 * [90/12/07 15:43:21 jeffreyh] 73 * 74 * 75 * Revision 2.7 90/12/04 14:46:38 jsb 76 * iPSC2 -> iPSC386; ipsc2_foo -> ipsc_foo; 77 * changes for merged intel/pmap.{c,h}. 78 * [90/12/04 11:20:35 jsb] 79 * 80 * Revision 2.6 90/11/24 15:14:56 jsb 81 * Added AT386 conditional around "BIOS/DOS hack". 82 * [90/11/24 11:44:47 jsb] 83 * 84 * Revision 2.5 90/11/05 14:27:51 rpd 85 * Since we steal pages after esym for page tables, use first_avail 86 * to record the last page +1 that we stole. 87 * Tell bios to warm boot on reboot. 88 * [90/09/05 rvb] 89 * 90 * Revision 2.4 90/09/23 17:45:20 jsb 91 * Added support for iPSC386. 92 * [90/09/21 16:42:34 jsb] 93 * 94 * Revision 2.3 90/08/27 21:58:29 dbg 95 * Change fix_desc to match new fake_descriptor format. 96 * [90/07/25 dbg] 97 * 98 * Revision 2.2 90/05/03 15:37:40 dbg 99 * Created. 100 * [90/02/14 dbg] 101 * 102 */ 103 104 #include <platforms.h> 105 #include <cpus.h> 106 #include <mach_kdb.h> 107 108 #include <i386/asm.h> 109 #include <i386/proc_reg.h> 110 #include <assym.s> 111 112 #if NCPUS > 1 113 114 #ifdef SYMMETRY 115 #include <sqt/asm_macros.h> 116 #endif 117 118 #endif NCPUS > 1 119 120 /* 121 * GAS won't handle an intersegment jump with a relocatable offset. 122 */ 123 #define LJMP(segment,address) \ 124 .byte 0xea ;\ 125 .long address ;\ 126 .word segment 127 128 129 #define KVTOPHYS (-KERNELBASE) 130 #define KVTOLINEAR (0) 131 132 #define PA(addr) (addr)+KVTOPHYS 133 #define VA(addr) (addr)-KVTOPHYS 134 135 .data 136 /* 137 * interrupt and bootup stack for initial processor. 138 */ 139 .align 4 140 .globl _intstack 141 _intstack: 142 .set ., .+4096 143 .globl _eintstack 144 _eintstack: 145 146 #if NCPUS == 1 147 .globl _int_stack_high /* all interrupt stacks */ 148 _int_stack_high: /* must lie below this */ 149 .long _eintstack /* address */ 150 151 .globl _int_stack_top /* top of interrupt stack */ 152 _int_stack_top: 153 .long _eintstack 154 155 #endif 156 157 /* 158 * Pointers to GDT and IDT. These contain linear addresses. 159 */ 160 .align 8 161 .globl EXT(gdtptr) 162 LEXT(gdtptr) 163 .word Times(8,GDTSZ)-1 164 .long EXT(gdt)+KVTOLINEAR 165 166 .align 8 167 .globl EXT(idtptr) 168 LEXT(idtptr) 169 .word Times(8,IDTSZ)-1 170 .long EXT(idt)+KVTOLINEAR 171 172 #if NCPUS > 1 173 .data 174 .globl _start_lock 175 .align 2 176 _start_lock: 177 .long 0 /* lock for 'upyet' */ 178 .globl _upyet 179 _upyet: 180 .long 0 /* 1 when OK for other processors */ 181 /* to start */ 182 .globl _mp_boot_pde 183 _mp_boot_pde: 184 .long 0 185 #endif NCPUS > 1 186 187 /* 188 * All CPUs start here. 189 * 190 * Environment: 191 * protected mode, no paging, flat 32-bit address space. 192 * (Code/data/stack segments have base == 0, limit == 4G) 193 */ 194 .text 195 .align 2 196 .globl EXT(pstart) 197 LEXT(pstart) 198 mov $0,%ax /* fs, gs must be zeroed; */ 199 mov %ax,%fs /* some bootstrappers don`t do this */ 200 mov %ax,%gs /* for us */ 201 202 #if NCPUS > 1 203 jmp 1f 204 0: cmpl $0,PA(_start_lock) 205 jne 0b 206 1: movl $1,%eax 207 xchgl %eax,PA(_start_lock) /* locked */ 208 testl %eax,%eax 209 jnz 0b 210 211 cmpl $0,PA(_upyet) /* are we first? */ 212 jne _slave_start /* no -- system already up. */ 213 #endif NCPUS > 1 214 215 /* 216 * Move symbol table out of the way of BSS. 217 * 218 * When kernel is loaded, at the start of BSS we have a struct boot_info: 219 * _edata: 220 * .long magic_number 221 * .long sym_size 222 * .long boot_size 223 * .long load_info_size 224 * sym_start: 225 * kernel symbols 226 * .align 2 227 * boot_start: 228 * bootstrap image 229 * .align 2 230 * load_info_start: 231 * bootstrap load information 232 * 233 * all of which must be moved somewhere else, since it 234 * is sitting in the kernel BSS. In addition, the bootstrap 235 * image must be moved to a machine page boundary, so that we get: 236 * 237 * _edata: 238 * BSS 239 * _end: <- kern_sym_start (VA) 240 * kernel symbols . 241 * .align 2 . (kern_sym_size) 242 * . 243 * .align VAX_PAGE_SIZE 244 * <- boot_start (VA) 245 * bootstrap image 246 * <- load_info_start (VA) 247 * load information 248 * <- %ebx (PA) 249 * 250 */ 251 252 lea PA(_edata),%esi /* point to symbol size word */ 253 movl BI_SYM_SIZE(%esi),%edx /* get symbol size */ 254 255 lea PA(_end)+NBPG-1(%edx),%edi 256 /* point after BSS, add symbol */ 257 /* size, and round up to */ 258 andl $-NBPG,%edi /* machine page boundary */ 259 260 lea -KVTOPHYS(%edi),%eax /* save virtual address */ 261 movl %eax,PA(_boot_start) /* of start of bootstrap */ 262 movl BI_BOOT_SIZE(%esi),%ecx /* get size of bootstrap */ 263 movl %ecx,PA(_boot_size) /* save size of bootstrap */ 264 lea -KVTOPHYS(%edi,%ecx),%eax 265 movl %eax,PA(_load_info_start) 266 /* save virtual address */ 267 /* of start of loader info */ 268 movl BI_LOAD_INFO_SIZE(%esi),%eax /* get size of loader info */ 269 movl %eax,PA(_load_info_size) 270 /* save size of loader info */ 271 addl %eax,%ecx /* get total size to move */ 272 273 leal BI_SIZE(%esi,%edx),%esi /* point to start of boot image - source */ 274 275 leal (%edi,%ecx),%ebx /* point to new location of */ 276 /* end of bootstrap - next */ 277 /* available physical address */ 278 279 lea -4(%esi,%ecx),%esi /* point to end of src - 4 */ 280 lea -4(%edi,%ecx),%edi /* point to end of dst - 4 */ 281 shrl $2,%ecx /* move by longs */ 282 std /* move backwards */ 283 rep 284 movsl /* move bootstrap and loader_info */ 285 286 movl $_end,PA(_kern_sym_start) 287 /* save virtual address */ 288 /* of start of symbols */ 289 movl %edx,PA(_kern_sym_size) /* save symbol table size */ 290 testl %edx,%edx /* any symbols? */ 291 jz 0f /* if so: */ 292 293 /* %esi already points to start of boot-4 */ 294 /* == end of symbol table (source) - 4 */ 295 leal PA(_end)-4(%edx),%edi /* point to end of dst - 4 */ 296 movl %edx,%ecx /* copy size */ 297 shrl $2,%ecx /* move by longs */ 298 std /* move backwards */ 299 rep 300 movsl /* move symbols */ 301 0: 302 cld /* reset direction flag */ 303 304 /* 305 * Get startup parameters. 306 */ 307 308 #ifdef SYMMETRY 309 #include <sqt/asm_startup.h> 310 #endif 311 #ifdef AT386 312 #include <i386at/asm_startup.h> 313 #endif 314 #ifdef iPSC386 315 #include <i386ipsc/asm_startup.h> 316 #endif 317 #ifdef PS2 318 #include <i386ps2/asm_startup.h> 319 #endif 320 321 /* 322 * Build initial page table directory and page tables. 323 * %ebx holds first available physical address. 324 */ 325 326 addl $(NBPG-1),%ebx /* round first avail physical addr */ 327 andl $(-NBPG),%ebx /* to machine page size */ 328 leal -KVTOPHYS(%ebx),%eax /* convert to virtual address */ 329 movl %eax,PA(_kpde) /* save as kernel page table directory */ 330 movl %ebx,%cr3 /* set physical address in CR3 now */ 331 332 movl %ebx,%edi /* clear page table directory */ 333 movl $(PTES_PER_PAGE),%ecx /* one page of ptes */ 334 xorl %eax,%eax 335 cld 336 rep 337 stosl /* edi now points to next page */ 338 339 /* 340 * Use next few pages for page tables. 341 */ 342 addl $(KERNELBASEPDE),%ebx /* point to pde for kernel base */ 343 movl %edi,%esi /* point to end of current pte page */ 344 345 /* 346 * Enter 1-1 mappings for kernel and for kernel page tables. 347 */ 348 movl $(INTEL_PTE_KERNEL),%eax /* set up pte prototype */ 349 0: 350 cmpl %esi,%edi /* at end of pte page? */ 351 jb 1f /* if so: */ 352 movl %edi,%edx /* get pte address (physical) */ 353 andl $(-NBPG),%edx /* mask out offset in page */ 354 orl $(INTEL_PTE_KERNEL),%edx /* add pte bits */ 355 movl %edx,(%ebx) /* set pde */ 356 addl $4,%ebx /* point to next pde */ 357 movl %edi,%esi /* point to */ 358 addl $(NBPG),%esi /* end of new pte page */ 359 1: 360 movl %eax,(%edi) /* set pte */ 361 addl $4,%edi /* advance to next pte */ 362 addl $(NBPG),%eax /* advance to next phys page */ 363 cmpl %edi,%eax /* have we mapped this pte page yet? */ 364 jb 0b /* loop if not */ 365 366 /* 367 * Zero rest of last pte page. 368 */ 369 xor %eax,%eax /* don`t map yet */ 370 2: cmpl %esi,%edi /* at end of pte page? */ 371 jae 3f 372 movl %eax,(%edi) /* zero mapping */ 373 addl $4,%edi 374 jmp 2b 375 3: 376 377 #if NCPUS > 1 378 /* 379 * Grab (waste?) another page for a bootstrap page directory 380 * for the other CPUs. We don't want the running CPUs to see 381 * addresses 0..3fffff mapped 1-1. 382 */ 383 movl %edi,PA(_mp_boot_pde) /* save its physical address */ 384 movl $(PTES_PER_PAGE),%ecx /* and clear it */ 385 rep 386 stosl 387 #endif NCPUS > 1 388 movl %edi,PA(_first_avail) /* save first available phys addr */ 389 390 /* 391 * pmap_bootstrap will enter rest of mappings. 392 */ 393 394 /* 395 * Fix initial descriptor tables. 396 */ 397 lea PA(_idt),%esi /* fix IDT */ 398 movl $(IDTSZ),%ecx 399 movl $(PA(fix_idt_ret)),%ebx 400 jmp fix_desc /* (cannot use stack) */ 401 fix_idt_ret: 402 403 lea PA(_gdt),%esi /* fix GDT */ 404 movl $(GDTSZ),%ecx 405 movl $(PA(fix_gdt_ret)),%ebx 406 jmp fix_desc /* (cannot use stack) */ 407 fix_gdt_ret: 408 409 lea PA(_ldt),%esi /* fix LDT */ 410 movl $(LDTSZ),%ecx 411 movl $(PA(fix_ldt_ret)),%ebx 412 jmp fix_desc /* (cannot use stack) */ 413 fix_ldt_ret: 414 415 /* 416 * Turn on paging. 417 */ 418 movl %cr3,%eax /* retrieve kernel PDE phys address */ 419 movl KERNELBASEPDE(%eax),%ecx 420 /* point to pte for KERNELBASE */ 421 movl %ecx,(%eax) /* set it also as pte for location */ 422 /* 0..3fffff, so that the code */ 423 /* that enters paged mode is mapped */ 424 /* to identical addresses after */ 425 /* paged mode is enabled */ 426 427 movl $_pag_start,%ebx /* first paged code address */ 428 429 movl %cr0,%eax 430 orl $(CR0_PG),%eax /* set PG bit in CR0 */ 431 movl %eax,%cr0 /* to enable paging */ 432 433 jmp *%ebx /* flush prefetch queue */ 434 435 /* 436 * We are now paging, and can run with correct addresses. 437 */ 438 _pag_start: 439 lgdt EXT(gdtptr) /* load GDT */ 440 lidt EXT(idtptr) /* load IDT */ 441 LJMP(KERNEL_CS,_vstart) /* switch to kernel code segment */ 442 443 /* 444 * Master is now running with correct addresses. 445 */ 446 _vstart: 447 mov $(KERNEL_DS),%ax /* set kernel data segment */ 448 mov %ax,%ds 449 mov %ax,%es 450 mov %ax,%ss 451 mov %ax,EXT(ktss)+TSS_SS0 /* set kernel stack segment */ 452 /* for traps to kernel */ 453 454 movw $(KERNEL_LDT),%ax /* get LDT segment */ 455 lldt %ax /* load LDT */ 456 movw $(KERNEL_TSS),%ax 457 ltr %ax /* set up KTSS */ 458 459 lea EXT(eintstack),%esp /* switch to the bootup stack */ 460 call EXT(machine_startup) /* run C code */ 461 /*NOTREACHED*/ 462 hlt 463 464 #if NCPUS > 1 465 /* 466 * We aren't the first. Call slave_main to initialize the processor 467 * and get Mach going on it. 468 */ 469 .align 2 470 .globl EXT(slave_start) 471 LEXT(slave_start) 472 cli /* disable interrupts, so we don`t */ 473 /* need IDT for a while */ 474 movl PA(_kpde),%ebx /* get PDE virtual address */ 475 addl $(KVTOPHYS),%ebx /* convert to physical address */ 476 477 movl PA(_mp_boot_pde),%edx /* point to the bootstrap PDE */ 478 movl KERNELBASEPDE(%ebx),%eax 479 /* point to pte for KERNELBASE */ 480 movl %eax,KERNELBASEPDE(%edx) 481 /* set in bootstrap PDE */ 482 movl %eax,(%edx) /* set it also as pte for location */ 483 /* 0..3fffff, so that the code */ 484 /* that enters paged mode is mapped */ 485 /* to identical addresses after */ 486 /* paged mode is enabled */ 487 movl %edx,%cr3 /* use bootstrap PDE to enable paging */ 488 489 movl $_spag_start,%edx /* first paged code address */ 490 491 movl %cr0,%eax 492 orl $(CR0_PG),%eax /* set PG bit in CR0 */ 493 movl %eax,%cr0 /* to enable paging */ 494 495 jmp *%edx /* flush prefetch queue. */ 496 497 /* 498 * We are now paging, and can run with correct addresses. 499 */ 500 _spag_start: 501 movl %ebx,%cr3 /* switch to the real kernel PDE */ 502 503 lgdt EXT(gdtptr) /* load GDT */ 504 lidt EXT(idtptr) /* load IDT */ 505 LJMP(KERNEL_CS,_svstart) /* switch to kernel code segment */ 506 507 /* 508 * Slave is now running with correct addresses. 509 */ 510 _svstart: 511 mov $(KERNEL_DS),%ax /* set kernel data segment */ 512 mov %ax,%ds 513 mov %ax,%es 514 mov %ax,%ss 515 516 CPU_NUMBER(%eax) /* get CPU number */ 517 movl EXT(interrupt_stack)(,%eax,4),%esp 518 /* get stack */ 519 addl $(INTSTACK_SIZE),%esp /* point to top */ 520 xorl %ebp,%ebp /* for completeness */ 521 522 movl $0,%ecx /* unlock start_lock */ 523 xchgl %ecx,_start_lock /* since we are no longer using */ 524 /* bootstrap stack */ 525 526 /* 527 * switch to the per-cpu descriptor tables 528 */ 529 pushl %eax /* pass CPU number */ 530 call _mp_desc_init /* set up local table */ 531 /* pointer returned in %eax */ 532 subl $4,%esp /* get space to build pseudo-descriptors */ 533 534 movw $(GDTSZ*8-1),0(%esp) /* set GDT size in GDT descriptor */ 535 lea MP_GDT+KVTOLINEAR(%eax),%edx 536 movl %edx,2(%esp) /* point to local GDT (linear address) */ 537 lgdt 0(%esp) /* load new GDT */ 538 539 movw $(IDTSZ*8-1),0(%esp) /* set IDT size in IDT descriptor */ 540 lea MP_IDT+KVTOLINEAR(%eax),%edx 541 movl %edx,2(%esp) /* point to local IDT (linear address) */ 542 lidt 0(%esp) /* load new IDT */ 543 544 movw $(KERNEL_LDT),%ax 545 lldt %ax /* load new LDT */ 546 547 movw $(KERNEL_TSS),%ax 548 ltr %ax /* load new KTSS */ 549 550 call _slave_main /* start MACH */ 551 /*NOTREACHED*/ 552 hlt 553 #endif NCPUS > 1 554 555 /* 556 * Convert a descriptor from fake to real format. 557 * 558 * Calls from assembly code: 559 * %ebx = return address (physical) CANNOT USE STACK 560 * %esi = descriptor table address (physical) 561 * %ecx = number of descriptors 562 * 563 * Calls from C: 564 * 0(%esp) = return address 565 * 4(%esp) = descriptor table address (physical) 566 * 8(%esp) = number of descriptors 567 * 568 * Fake descriptor format: 569 * bytes 0..3 base 31..0 570 * bytes 4..5 limit 15..0 571 * byte 6 access byte 2 | limit 19..16 572 * byte 7 access byte 1 573 * 574 * Real descriptor format: 575 * bytes 0..1 limit 15..0 576 * bytes 2..3 base 15..0 577 * byte 4 base 23..16 578 * byte 5 access byte 1 579 * byte 6 access byte 2 | limit 19..16 580 * byte 7 base 31..24 581 * 582 * Fake gate format: 583 * bytes 0..3 offset 584 * bytes 4..5 selector 585 * byte 6 word count << 4 (to match fake descriptor) 586 * byte 7 access byte 1 587 * 588 * Real gate format: 589 * bytes 0..1 offset 15..0 590 * bytes 2..3 selector 591 * byte 4 word count 592 * byte 5 access byte 1 593 * bytes 6..7 offset 31..16 594 */ 595 .globl EXT(fix_desc) 596 LEXT(fix_desc) 597 pushl %ebp /* set up */ 598 movl %esp,%ebp /* stack frame */ 599 pushl %esi /* save registers */ 600 pushl %ebx 601 movl B_ARG0,%esi /* point to first descriptor */ 602 movl B_ARG1,%ecx /* get number of descriptors */ 603 lea 0f,%ebx /* get return address */ 604 jmp fix_desc /* call internal routine */ 605 0: popl %ebx /* restore registers */ 606 popl %esi 607 leave /* pop stack frame */ 608 ret /* return */ 609 610 fix_desc: 611 0: 612 movw 6(%esi),%dx /* get access byte */ 613 movb %dh,%al 614 andb $0x14,%al 615 cmpb $0x04,%al /* gate or descriptor? */ 616 je 1f 617 618 /* descriptor */ 619 movl 0(%esi),%eax /* get base in eax */ 620 rol $16,%eax /* swap 15..0 with 31..16 */ 621 /* (15..0 in correct place) */ 622 movb %al,%dl /* combine bits 23..16 with ACC1 */ 623 /* in dh/dl */ 624 movb %ah,7(%esi) /* store bits 31..24 in correct place */ 625 movw 4(%esi),%ax /* move limit bits 0..15 to word 0 */ 626 movl %eax,0(%esi) /* store (bytes 0..3 correct) */ 627 movw %dx,4(%esi) /* store bytes 4..5 */ 628 jmp 2f 629 630 /* gate */ 631 1: 632 movw 4(%esi),%ax /* get selector */ 633 shrb $4,%dl /* shift word count to proper place */ 634 movw %dx,4(%esi) /* store word count / ACC1 */ 635 movw 2(%esi),%dx /* get offset 16..31 */ 636 movw %dx,6(%esi) /* store in correct place */ 637 movw %ax,2(%esi) /* store selector in correct place */ 638 2: 639 addl $8,%esi /* bump to next descriptor */ 640 loop 0b /* repeat */ 641 jmp *%ebx /* all done */ 642 643 /* 644 * put arg in kbd leds and spin a while 645 * eats eax, ecx, edx 646 */ 647 #define K_RDWR 0x60 648 #define K_CMD_LEDS 0xed 649 #define K_STATUS 0x64 650 #define K_IBUF_FULL 0x02 /* input (to kbd) buffer full */ 651 #define K_OBUF_FULL 0x01 /* output (from kbd) buffer full */ 652 653 ENTRY(set_kbd_leds) 654 mov S_ARG0,%cl /* save led value */ 655 656 0: inb $(K_STATUS),%al /* get kbd status */ 657 testb $(K_IBUF_FULL),%al /* input busy? */ 658 jne 0b /* loop until not */ 659 660 mov $(K_CMD_LEDS),%al /* K_CMD_LEDS */ 661 outb %al,$(K_RDWR) /* to kbd */ 662 663 0: inb $(K_STATUS),%al /* get kbd status */ 664 testb $(K_OBUF_FULL),%al /* output present? */ 665 je 0b /* loop if not */ 666 667 inb $(K_RDWR),%al /* read status (and discard) */ 668 669 0: inb $(K_STATUS),%al /* get kbd status */ 670 testb $(K_IBUF_FULL),%al /* input busy? */ 671 jne 0b /* loop until not */ 672 673 mov %cl,%al /* move led value */ 674 outb %al,$(K_RDWR) /* to kbd */ 675 676 movl $10000000,%ecx /* spin */ 677 0: nop 678 nop 679 loop 0b /* a while */ 680 681 ret 682
Cache object: 769df3da2e1cbd5ce823e07a9647c0a8
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