Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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sys/i386/i386/swtch.s
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1 /*- 2 * Copyright (c) 1990 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * William Jolitz. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * $FreeBSD: src/sys/i386/i386/swtch.s,v 1.41.2.1 1999/09/05 08:11:17 peter Exp $ 37 */ 38 39 #include "apm.h" 40 #include "npx.h" 41 #include "opt_user_ldt.h" 42 43 #include <sys/rtprio.h> 44 45 #include <machine/asmacros.h> 46 #include <machine/spl.h> 47 48 #include "assym.s" 49 50 51 /*****************************************************************************/ 52 /* Scheduling */ 53 /*****************************************************************************/ 54 55 /* 56 * The following primitives manipulate the run queues. 57 * _whichqs tells which of the 32 queues _qs 58 * have processes in them. setrunqueue puts processes into queues, Remrq 59 * removes them from queues. The running process is on no queue, 60 * other processes are on a queue related to p->p_priority, divided by 4 61 * actually to shrink the 0-127 range of priorities into the 32 available 62 * queues. 63 */ 64 .data 65 .globl _curpcb 66 _curpcb: .long 0 /* pointer to curproc's PCB area */ 67 _whichqs: .long 0 /* which run queues have data */ 68 _whichrtqs: .long 0 /* which realtime run queues have data */ 69 _whichidqs: .long 0 /* which idletime run queues have data */ 70 71 .globl _qs,_cnt,_panic 72 73 .globl _want_resched 74 _want_resched: .long 0 /* we need to re-run the scheduler */ 75 76 .text 77 /* 78 * setrunqueue(p) 79 * 80 * Call should be made at spl6(), and p->p_stat should be SRUN 81 */ 82 ENTRY(setrunqueue) 83 movl 4(%esp),%eax 84 #ifdef DIAGNOSTIC 85 cmpb $SRUN,P_STAT(%eax) 86 je set1 87 pushl $set2 88 call _panic 89 set1: 90 #endif 91 cmpw $RTP_PRIO_NORMAL,P_RTPRIO_TYPE(%eax) /* normal priority process? */ 92 je set_nort 93 94 movzwl P_RTPRIO_PRIO(%eax),%edx 95 96 cmpw $RTP_PRIO_REALTIME,P_RTPRIO_TYPE(%eax) /* realtime priority? */ 97 jne set_id /* must be idle priority */ 98 99 set_rt: 100 btsl %edx,_whichrtqs /* set q full bit */ 101 shll $3,%edx 102 addl $_rtqs,%edx /* locate q hdr */ 103 movl %edx,P_FORW(%eax) /* link process on tail of q */ 104 movl P_BACK(%edx),%ecx 105 movl %ecx,P_BACK(%eax) 106 movl %eax,P_BACK(%edx) 107 movl %eax,P_FORW(%ecx) 108 ret 109 110 set_id: 111 btsl %edx,_whichidqs /* set q full bit */ 112 shll $3,%edx 113 addl $_idqs,%edx /* locate q hdr */ 114 movl %edx,P_FORW(%eax) /* link process on tail of q */ 115 movl P_BACK(%edx),%ecx 116 movl %ecx,P_BACK(%eax) 117 movl %eax,P_BACK(%edx) 118 movl %eax,P_FORW(%ecx) 119 ret 120 121 set_nort: /* Normal (RTOFF) code */ 122 movzbl P_PRI(%eax),%edx 123 shrl $2,%edx 124 btsl %edx,_whichqs /* set q full bit */ 125 shll $3,%edx 126 addl $_qs,%edx /* locate q hdr */ 127 movl %edx,P_FORW(%eax) /* link process on tail of q */ 128 movl P_BACK(%edx),%ecx 129 movl %ecx,P_BACK(%eax) 130 movl %eax,P_BACK(%edx) 131 movl %eax,P_FORW(%ecx) 132 ret 133 134 set2: .asciz "setrunqueue" 135 136 /* 137 * Remrq(p) 138 * 139 * Call should be made at spl6(). 140 */ 141 ENTRY(remrq) 142 movl 4(%esp),%eax 143 cmpw $RTP_PRIO_NORMAL,P_RTPRIO_TYPE(%eax) /* normal priority process? */ 144 je rem_nort 145 146 movzwl P_RTPRIO_PRIO(%eax),%edx 147 148 cmpw $RTP_PRIO_REALTIME,P_RTPRIO_TYPE(%eax) /* normal priority process? */ 149 jne rem_id 150 151 btrl %edx,_whichrtqs /* clear full bit, panic if clear already */ 152 jb rem1rt 153 pushl $rem3rt 154 call _panic 155 rem1rt: 156 pushl %edx 157 movl P_FORW(%eax),%ecx /* unlink process */ 158 movl P_BACK(%eax),%edx 159 movl %edx,P_BACK(%ecx) 160 movl P_BACK(%eax),%ecx 161 movl P_FORW(%eax),%edx 162 movl %edx,P_FORW(%ecx) 163 popl %edx 164 movl $_rtqs,%ecx 165 shll $3,%edx 166 addl %edx,%ecx 167 cmpl P_FORW(%ecx),%ecx /* q still has something? */ 168 je rem2rt 169 shrl $3,%edx /* yes, set bit as still full */ 170 btsl %edx,_whichrtqs 171 rem2rt: 172 ret 173 rem_id: 174 btrl %edx,_whichidqs /* clear full bit, panic if clear already */ 175 jb rem1id 176 pushl $rem3id 177 call _panic 178 rem1id: 179 pushl %edx 180 movl P_FORW(%eax),%ecx /* unlink process */ 181 movl P_BACK(%eax),%edx 182 movl %edx,P_BACK(%ecx) 183 movl P_BACK(%eax),%ecx 184 movl P_FORW(%eax),%edx 185 movl %edx,P_FORW(%ecx) 186 popl %edx 187 movl $_idqs,%ecx 188 shll $3,%edx 189 addl %edx,%ecx 190 cmpl P_FORW(%ecx),%ecx /* q still has something? */ 191 je rem2id 192 shrl $3,%edx /* yes, set bit as still full */ 193 btsl %edx,_whichidqs 194 rem2id: 195 ret 196 197 rem_nort: 198 movzbl P_PRI(%eax),%edx 199 shrl $2,%edx 200 btrl %edx,_whichqs /* clear full bit, panic if clear already */ 201 jb rem1 202 pushl $rem3 203 call _panic 204 rem1: 205 pushl %edx 206 movl P_FORW(%eax),%ecx /* unlink process */ 207 movl P_BACK(%eax),%edx 208 movl %edx,P_BACK(%ecx) 209 movl P_BACK(%eax),%ecx 210 movl P_FORW(%eax),%edx 211 movl %edx,P_FORW(%ecx) 212 popl %edx 213 movl $_qs,%ecx 214 shll $3,%edx 215 addl %edx,%ecx 216 cmpl P_FORW(%ecx),%ecx /* q still has something? */ 217 je rem2 218 shrl $3,%edx /* yes, set bit as still full */ 219 btsl %edx,_whichqs 220 rem2: 221 ret 222 223 rem3: .asciz "remrq" 224 rem3rt: .asciz "remrq.rt" 225 rem3id: .asciz "remrq.id" 226 227 /* 228 * When no processes are on the runq, cpu_switch() branches to _idle 229 * to wait for something to come ready. 230 */ 231 ALIGN_TEXT 232 _idle: 233 xorl %ebp,%ebp 234 movl $tmpstk,%esp 235 movl _IdlePTD,%ecx 236 movl %ecx,%cr3 237 sti 238 239 /* 240 * XXX callers of cpu_switch() do a bogus splclock(). Locking should 241 * be left to cpu_switch(). 242 */ 243 movl $SWI_AST_MASK,_cpl 244 testl $~SWI_AST_MASK,_ipending 245 je idle_loop 246 call _splz 247 248 ALIGN_TEXT 249 idle_loop: 250 cli 251 movb $1,_intr_nesting_level /* charge Intr if we leave */ 252 cmpl $0,_whichrtqs /* real-time queue */ 253 CROSSJUMP(jne, sw1a, je) 254 cmpl $0,_whichqs /* normal queue */ 255 CROSSJUMP(jne, nortqr, je) 256 cmpl $0,_whichidqs /* 'idle' queue */ 257 CROSSJUMP(jne, idqr, je) 258 movb $0,_intr_nesting_level /* charge Idle for this loop */ 259 call _vm_page_zero_idle 260 testl %eax, %eax 261 jnz idle_loop 262 sti 263 #if NAPM > 0 && defined(APM_IDLE_CPU) 264 call _apm_cpu_idle 265 call _apm_cpu_busy 266 #else 267 hlt /* wait for interrupt */ 268 #endif 269 jmp idle_loop 270 271 CROSSJUMPTARGET(_idle) 272 273 /* 274 * cpu_switch() 275 */ 276 ENTRY(cpu_switch) 277 /* switch to new process. first, save context as needed */ 278 movl _curproc,%ecx 279 280 /* if no process to save, don't bother */ 281 testl %ecx,%ecx 282 je sw1 283 284 movl P_ADDR(%ecx),%ecx 285 286 movl (%esp),%eax /* Hardware registers */ 287 movl %eax,PCB_EIP(%ecx) 288 movl %ebx,PCB_EBX(%ecx) 289 movl %esp,PCB_ESP(%ecx) 290 movl %ebp,PCB_EBP(%ecx) 291 movl %esi,PCB_ESI(%ecx) 292 movl %edi,PCB_EDI(%ecx) 293 294 #if NNPX > 0 295 /* have we used fp, and need a save? */ 296 mov _curproc,%eax 297 cmp %eax,_npxproc 298 jne 1f 299 addl $PCB_SAVEFPU,%ecx /* h/w bugs make saving complicated */ 300 pushl %ecx 301 call _npxsave /* do it in a big C function */ 302 popl %eax 303 1: 304 #endif /* NNPX > 0 */ 305 306 movb $1,_intr_nesting_level /* charge Intr, not Sys/Idle */ 307 308 movl $0,_curproc /* out of process */ 309 310 /* save is done, now choose a new process or idle */ 311 sw1: 312 cli 313 sw1a: 314 movl _whichrtqs,%edi /* pick next p. from rtqs */ 315 testl %edi,%edi 316 jz nortqr /* no realtime procs */ 317 318 /* XXX - bsf is sloow */ 319 bsfl %edi,%ebx /* find a full q */ 320 jz nortqr /* no proc on rt q - try normal ... */ 321 322 /* XX update whichqs? */ 323 btrl %ebx,%edi /* clear q full status */ 324 leal _rtqs(,%ebx,8),%eax /* select q */ 325 movl %eax,%esi 326 327 movl P_FORW(%eax),%ecx /* unlink from front of process q */ 328 movl P_FORW(%ecx),%edx 329 movl %edx,P_FORW(%eax) 330 movl P_BACK(%ecx),%eax 331 movl %eax,P_BACK(%edx) 332 333 cmpl P_FORW(%ecx),%esi /* q empty */ 334 je rt3 335 btsl %ebx,%edi /* nope, set to indicate not empty */ 336 rt3: 337 movl %edi,_whichrtqs /* update q status */ 338 jmp swtch_com 339 340 /* old sw1a */ 341 /* Normal process priority's */ 342 nortqr: 343 movl _whichqs,%edi 344 2: 345 /* XXX - bsf is sloow */ 346 bsfl %edi,%ebx /* find a full q */ 347 jz idqr /* if none, idle */ 348 349 /* XX update whichqs? */ 350 btrl %ebx,%edi /* clear q full status */ 351 leal _qs(,%ebx,8),%eax /* select q */ 352 movl %eax,%esi 353 354 movl P_FORW(%eax),%ecx /* unlink from front of process q */ 355 movl P_FORW(%ecx),%edx 356 movl %edx,P_FORW(%eax) 357 movl P_BACK(%ecx),%eax 358 movl %eax,P_BACK(%edx) 359 360 cmpl P_FORW(%ecx),%esi /* q empty */ 361 je 3f 362 btsl %ebx,%edi /* nope, set to indicate not empty */ 363 3: 364 movl %edi,_whichqs /* update q status */ 365 jmp swtch_com 366 367 idqr: /* was sw1a */ 368 movl _whichidqs,%edi /* pick next p. from idqs */ 369 370 /* XXX - bsf is sloow */ 371 bsfl %edi,%ebx /* find a full q */ 372 CROSSJUMP(je, _idle, jne) /* if no proc, idle */ 373 374 /* XX update whichqs? */ 375 btrl %ebx,%edi /* clear q full status */ 376 leal _idqs(,%ebx,8),%eax /* select q */ 377 movl %eax,%esi 378 379 movl P_FORW(%eax),%ecx /* unlink from front of process q */ 380 movl P_FORW(%ecx),%edx 381 movl %edx,P_FORW(%eax) 382 movl P_BACK(%ecx),%eax 383 movl %eax,P_BACK(%edx) 384 385 cmpl P_FORW(%ecx),%esi /* q empty */ 386 je id3 387 btsl %ebx,%edi /* nope, set to indicate not empty */ 388 id3: 389 movl %edi,_whichidqs /* update q status */ 390 391 swtch_com: 392 movl $0,%eax 393 movl %eax,_want_resched 394 395 #ifdef DIAGNOSTIC 396 cmpl %eax,P_WCHAN(%ecx) 397 jne badsw 398 cmpb $SRUN,P_STAT(%ecx) 399 jne badsw 400 #endif 401 402 movl %eax,P_BACK(%ecx) /* isolate process to run */ 403 movl P_ADDR(%ecx),%edx 404 movl PCB_CR3(%edx),%ebx 405 406 /* switch address space */ 407 movl %ebx,%cr3 408 409 /* restore context */ 410 movl PCB_EBX(%edx),%ebx 411 movl PCB_ESP(%edx),%esp 412 movl PCB_EBP(%edx),%ebp 413 movl PCB_ESI(%edx),%esi 414 movl PCB_EDI(%edx),%edi 415 movl PCB_EIP(%edx),%eax 416 movl %eax,(%esp) 417 418 movl %edx,_curpcb 419 movl %ecx,_curproc /* into next process */ 420 movb $0,_intr_nesting_level 421 422 #ifdef USER_LDT 423 cmpl $0, PCB_USERLDT(%edx) 424 jnz 1f 425 movl __default_ldt,%eax 426 cmpl _currentldt,%eax 427 je 2f 428 lldt __default_ldt 429 movl %eax,_currentldt 430 jmp 2f 431 1: pushl %edx 432 call _set_user_ldt 433 popl %edx 434 2: 435 #endif 436 437 sti 438 ret 439 440 CROSSJUMPTARGET(idqr) 441 CROSSJUMPTARGET(nortqr) 442 CROSSJUMPTARGET(sw1a) 443 444 badsw: 445 pushl $sw0 446 call _panic 447 448 sw0: .asciz "cpu_switch" 449 450 /* 451 * savectx(pcb) 452 * Update pcb, saving current processor state. 453 */ 454 ENTRY(savectx) 455 /* fetch PCB */ 456 movl 4(%esp),%ecx 457 458 /* caller's return address - child won't execute this routine */ 459 movl (%esp),%eax 460 movl %eax,PCB_EIP(%ecx) 461 462 movl %ebx,PCB_EBX(%ecx) 463 movl %esp,PCB_ESP(%ecx) 464 movl %ebp,PCB_EBP(%ecx) 465 movl %esi,PCB_ESI(%ecx) 466 movl %edi,PCB_EDI(%ecx) 467 468 #if NNPX > 0 469 /* 470 * If npxproc == NULL, then the npx h/w state is irrelevant and the 471 * state had better already be in the pcb. This is true for forks 472 * but not for dumps (the old book-keeping with FP flags in the pcb 473 * always lost for dumps because the dump pcb has 0 flags). 474 * 475 * If npxproc != NULL, then we have to save the npx h/w state to 476 * npxproc's pcb and copy it to the requested pcb, or save to the 477 * requested pcb and reload. Copying is easier because we would 478 * have to handle h/w bugs for reloading. We used to lose the 479 * parent's npx state for forks by forgetting to reload. 480 */ 481 mov _npxproc,%eax 482 testl %eax,%eax 483 je 1f 484 485 pushl %ecx 486 movl P_ADDR(%eax),%eax 487 leal PCB_SAVEFPU(%eax),%eax 488 pushl %eax 489 pushl %eax 490 call _npxsave 491 addl $4,%esp 492 popl %eax 493 popl %ecx 494 495 pushl $PCB_SAVEFPU_SIZE 496 leal PCB_SAVEFPU(%ecx),%ecx 497 pushl %ecx 498 pushl %eax 499 call _bcopy 500 addl $12,%esp 501 #endif /* NNPX > 0 */ 502 503 1: 504 ret
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