FreeBSD/Linux Kernel Cross Reference
sys/i386/i386/swtch.s
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 * 4. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * $FreeBSD: releng/11.2/sys/i386/i386/swtch.s 335196 2018-06-15 13:21:37Z kib $
33 */
34
35 #include "opt_sched.h"
36
37 #include <machine/asmacros.h>
38
39 #include "assym.s"
40
41 #if defined(SMP) && defined(SCHED_ULE)
42 #define SETOP xchgl
43 #define BLOCK_SPIN(reg) \
44 movl $blocked_lock,%eax ; \
45 100: ; \
46 lock ; \
47 cmpxchgl %eax,TD_LOCK(reg) ; \
48 jne 101f ; \
49 pause ; \
50 jmp 100b ; \
51 101:
52 #else
53 #define SETOP movl
54 #define BLOCK_SPIN(reg)
55 #endif
56
57 /*****************************************************************************/
58 /* Scheduling */
59 /*****************************************************************************/
60
61 .text
62
63 /*
64 * cpu_throw()
65 *
66 * This is the second half of cpu_switch(). It is used when the current
67 * thread is either a dummy or slated to die, and we no longer care
68 * about its state. This is only a slight optimization and is probably
69 * not worth it anymore. Note that we need to clear the pm_active bits so
70 * we do need the old proc if it still exists.
71 * 0(%esp) = ret
72 * 4(%esp) = oldtd
73 * 8(%esp) = newtd
74 */
75 ENTRY(cpu_throw)
76 movl PCPU(CPUID), %esi
77 movl 4(%esp),%ecx /* Old thread */
78 testl %ecx,%ecx /* no thread? */
79 jz 1f
80 /* release bit from old pm_active */
81 movl PCPU(CURPMAP), %ebx
82 #ifdef SMP
83 lock
84 #endif
85 btrl %esi, PM_ACTIVE(%ebx) /* clear old */
86 1:
87 movl 8(%esp),%ecx /* New thread */
88 movl TD_PCB(%ecx),%edx
89 movl PCB_CR3(%edx),%eax
90 movl %eax,%cr3
91 /* set bit in new pm_active */
92 movl TD_PROC(%ecx),%eax
93 movl P_VMSPACE(%eax), %ebx
94 addl $VM_PMAP, %ebx
95 movl %ebx, PCPU(CURPMAP)
96 #ifdef SMP
97 lock
98 #endif
99 btsl %esi, PM_ACTIVE(%ebx) /* set new */
100 jmp sw1
101 END(cpu_throw)
102
103 /*
104 * cpu_switch(old, new)
105 *
106 * Save the current thread state, then select the next thread to run
107 * and load its state.
108 * 0(%esp) = ret
109 * 4(%esp) = oldtd
110 * 8(%esp) = newtd
111 * 12(%esp) = newlock
112 */
113 ENTRY(cpu_switch)
114
115 /* Switch to new thread. First, save context. */
116 movl 4(%esp),%ecx
117
118 #ifdef INVARIANTS
119 testl %ecx,%ecx /* no thread? */
120 jz badsw2 /* no, panic */
121 #endif
122
123 movl TD_PCB(%ecx),%edx
124
125 movl (%esp),%eax /* Hardware registers */
126 movl %eax,PCB_EIP(%edx)
127 movl %ebx,PCB_EBX(%edx)
128 movl %esp,PCB_ESP(%edx)
129 movl %ebp,PCB_EBP(%edx)
130 movl %esi,PCB_ESI(%edx)
131 movl %edi,PCB_EDI(%edx)
132 mov %gs,PCB_GS(%edx)
133 pushfl /* PSL */
134 popl PCB_PSL(%edx)
135 /* Test if debug registers should be saved. */
136 testl $PCB_DBREGS,PCB_FLAGS(%edx)
137 jz 1f /* no, skip over */
138 movl %dr7,%eax /* yes, do the save */
139 movl %eax,PCB_DR7(%edx)
140 andl $0x0000fc00, %eax /* disable all watchpoints */
141 movl %eax,%dr7
142 movl %dr6,%eax
143 movl %eax,PCB_DR6(%edx)
144 movl %dr3,%eax
145 movl %eax,PCB_DR3(%edx)
146 movl %dr2,%eax
147 movl %eax,PCB_DR2(%edx)
148 movl %dr1,%eax
149 movl %eax,PCB_DR1(%edx)
150 movl %dr0,%eax
151 movl %eax,PCB_DR0(%edx)
152 1:
153
154 /* have we used fp, and need a save? */
155 cmpl %ecx,PCPU(FPCURTHREAD)
156 jne 1f
157 pushl PCB_SAVEFPU(%edx) /* h/w bugs make saving complicated */
158 call npxsave /* do it in a big C function */
159 popl %eax
160 1:
161
162 /* Save is done. Now fire up new thread. Leave old vmspace. */
163 movl 4(%esp),%edi
164 movl 8(%esp),%ecx /* New thread */
165 movl 12(%esp),%esi /* New lock */
166 #ifdef INVARIANTS
167 testl %ecx,%ecx /* no thread? */
168 jz badsw3 /* no, panic */
169 #endif
170 movl TD_PCB(%ecx),%edx
171
172 /* switch address space */
173 movl PCB_CR3(%edx),%eax
174 movl %cr3,%ebx /* The same address space? */
175 cmpl %ebx,%eax
176 je sw0
177 movl %eax,%cr3 /* new address space */
178 movl %esi,%eax
179 movl PCPU(CPUID),%esi
180 SETOP %eax,TD_LOCK(%edi) /* Switchout td_lock */
181
182 /* Release bit from old pmap->pm_active */
183 movl PCPU(CURPMAP), %ebx
184 #ifdef SMP
185 lock
186 #endif
187 btrl %esi, PM_ACTIVE(%ebx) /* clear old */
188
189 /* Set bit in new pmap->pm_active */
190 movl TD_PROC(%ecx),%eax /* newproc */
191 movl P_VMSPACE(%eax), %ebx
192 addl $VM_PMAP, %ebx
193 movl %ebx, PCPU(CURPMAP)
194 #ifdef SMP
195 lock
196 #endif
197 btsl %esi, PM_ACTIVE(%ebx) /* set new */
198 jmp sw1
199
200 sw0:
201 SETOP %esi,TD_LOCK(%edi) /* Switchout td_lock */
202 sw1:
203 BLOCK_SPIN(%ecx)
204 /*
205 * At this point, we've switched address spaces and are ready
206 * to load up the rest of the next context.
207 */
208 cmpl $0, PCB_EXT(%edx) /* has pcb extension? */
209 je 1f /* If not, use the default */
210 movl $1, PCPU(PRIVATE_TSS) /* mark use of private tss */
211 movl PCB_EXT(%edx), %edi /* new tss descriptor */
212 jmp 2f /* Load it up */
213
214 1: /*
215 * Use the common default TSS instead of our own.
216 * Set our stack pointer into the TSS, it's set to just
217 * below the PCB. In C, common_tss.tss_esp0 = &pcb - 16;
218 */
219 leal -16(%edx), %ebx /* leave space for vm86 */
220 movl %ebx, PCPU(COMMON_TSS) + TSS_ESP0
221
222 /*
223 * Test this CPU's bit in the bitmap to see if this
224 * CPU was using a private TSS.
225 */
226 cmpl $0, PCPU(PRIVATE_TSS) /* Already using the common? */
227 je 3f /* if so, skip reloading */
228 movl $0, PCPU(PRIVATE_TSS)
229 PCPU_ADDR(COMMON_TSSD, %edi)
230 2:
231 /* Move correct tss descriptor into GDT slot, then reload tr. */
232 movl PCPU(TSS_GDT), %ebx /* entry in GDT */
233 movl 0(%edi), %eax
234 movl 4(%edi), %esi
235 movl %eax, 0(%ebx)
236 movl %esi, 4(%ebx)
237 movl $GPROC0_SEL*8, %esi /* GSEL(GPROC0_SEL, SEL_KPL) */
238 ltr %si
239 3:
240
241 /* Copy the %fs and %gs selectors into this pcpu gdt */
242 leal PCB_FSD(%edx), %esi
243 movl PCPU(FSGS_GDT), %edi
244 movl 0(%esi), %eax /* %fs selector */
245 movl 4(%esi), %ebx
246 movl %eax, 0(%edi)
247 movl %ebx, 4(%edi)
248 movl 8(%esi), %eax /* %gs selector, comes straight after */
249 movl 12(%esi), %ebx
250 movl %eax, 8(%edi)
251 movl %ebx, 12(%edi)
252
253 /* Restore context. */
254 movl PCB_EBX(%edx),%ebx
255 movl PCB_ESP(%edx),%esp
256 movl PCB_EBP(%edx),%ebp
257 movl PCB_ESI(%edx),%esi
258 movl PCB_EDI(%edx),%edi
259 movl PCB_EIP(%edx),%eax
260 movl %eax,(%esp)
261 pushl PCB_PSL(%edx)
262 popfl
263
264 movl %edx, PCPU(CURPCB)
265 movl %ecx, PCPU(CURTHREAD) /* into next thread */
266
267 /*
268 * Determine the LDT to use and load it if is the default one and
269 * that is not the current one.
270 */
271 movl TD_PROC(%ecx),%eax
272 cmpl $0,P_MD+MD_LDT(%eax)
273 jnz 1f
274 movl _default_ldt,%eax
275 cmpl PCPU(CURRENTLDT),%eax
276 je 2f
277 lldt _default_ldt
278 movl %eax,PCPU(CURRENTLDT)
279 jmp 2f
280 1:
281 /* Load the LDT when it is not the default one. */
282 pushl %edx /* Preserve pointer to pcb. */
283 addl $P_MD,%eax /* Pointer to mdproc is arg. */
284 pushl %eax
285 /*
286 * Holding dt_lock prevents context switches, so dt_lock cannot
287 * be held now and set_user_ldt() will not deadlock acquiring it.
288 */
289 call set_user_ldt
290 addl $4,%esp
291 popl %edx
292 2:
293
294 /* This must be done after loading the user LDT. */
295 .globl cpu_switch_load_gs
296 cpu_switch_load_gs:
297 mov PCB_GS(%edx),%gs
298
299 pushl %edx
300 pushl PCPU(CURTHREAD)
301 call npxswitch
302 popl %edx
303 popl %edx
304
305 /* Test if debug registers should be restored. */
306 testl $PCB_DBREGS,PCB_FLAGS(%edx)
307 jz 1f
308
309 /*
310 * Restore debug registers. The special code for dr7 is to
311 * preserve the current values of its reserved bits.
312 */
313 movl PCB_DR6(%edx),%eax
314 movl %eax,%dr6
315 movl PCB_DR3(%edx),%eax
316 movl %eax,%dr3
317 movl PCB_DR2(%edx),%eax
318 movl %eax,%dr2
319 movl PCB_DR1(%edx),%eax
320 movl %eax,%dr1
321 movl PCB_DR0(%edx),%eax
322 movl %eax,%dr0
323 movl %dr7,%eax
324 andl $0x0000fc00,%eax
325 movl PCB_DR7(%edx),%ecx
326 andl $~0x0000fc00,%ecx
327 orl %ecx,%eax
328 movl %eax,%dr7
329 1:
330 ret
331
332 #ifdef INVARIANTS
333 badsw1:
334 pushal
335 pushl $sw0_1
336 call panic
337 sw0_1: .asciz "cpu_throw: no newthread supplied"
338
339 badsw2:
340 pushal
341 pushl $sw0_2
342 call panic
343 sw0_2: .asciz "cpu_switch: no curthread supplied"
344
345 badsw3:
346 pushal
347 pushl $sw0_3
348 call panic
349 sw0_3: .asciz "cpu_switch: no newthread supplied"
350 #endif
351 END(cpu_switch)
352
353 /*
354 * savectx(pcb)
355 * Update pcb, saving current processor state.
356 */
357 ENTRY(savectx)
358 /* Fetch PCB. */
359 movl 4(%esp),%ecx
360
361 /* Save caller's return address. Child won't execute this routine. */
362 movl (%esp),%eax
363 movl %eax,PCB_EIP(%ecx)
364
365 movl %cr3,%eax
366 movl %eax,PCB_CR3(%ecx)
367
368 movl %ebx,PCB_EBX(%ecx)
369 movl %esp,PCB_ESP(%ecx)
370 movl %ebp,PCB_EBP(%ecx)
371 movl %esi,PCB_ESI(%ecx)
372 movl %edi,PCB_EDI(%ecx)
373 mov %gs,PCB_GS(%ecx)
374 pushfl
375 popl PCB_PSL(%ecx)
376
377 movl %cr0,%eax
378 movl %eax,PCB_CR0(%ecx)
379 movl %cr2,%eax
380 movl %eax,PCB_CR2(%ecx)
381 movl %cr4,%eax
382 movl %eax,PCB_CR4(%ecx)
383
384 movl %dr0,%eax
385 movl %eax,PCB_DR0(%ecx)
386 movl %dr1,%eax
387 movl %eax,PCB_DR1(%ecx)
388 movl %dr2,%eax
389 movl %eax,PCB_DR2(%ecx)
390 movl %dr3,%eax
391 movl %eax,PCB_DR3(%ecx)
392 movl %dr6,%eax
393 movl %eax,PCB_DR6(%ecx)
394 movl %dr7,%eax
395 movl %eax,PCB_DR7(%ecx)
396
397 mov %ds,PCB_DS(%ecx)
398 mov %es,PCB_ES(%ecx)
399 mov %fs,PCB_FS(%ecx)
400 mov %ss,PCB_SS(%ecx)
401
402 sgdt PCB_GDT(%ecx)
403 sidt PCB_IDT(%ecx)
404 sldt PCB_LDT(%ecx)
405 str PCB_TR(%ecx)
406
407 movl $1,%eax
408 ret
409 END(savectx)
410
411 /*
412 * resumectx(pcb) __fastcall
413 * Resuming processor state from pcb.
414 */
415 ENTRY(resumectx)
416 /* Restore GDT. */
417 lgdt PCB_GDT(%ecx)
418
419 /* Restore segment registers */
420 movzwl PCB_DS(%ecx),%eax
421 mov %ax,%ds
422 movzwl PCB_ES(%ecx),%eax
423 mov %ax,%es
424 movzwl PCB_FS(%ecx),%eax
425 mov %ax,%fs
426 movzwl PCB_GS(%ecx),%eax
427 movw %ax,%gs
428 movzwl PCB_SS(%ecx),%eax
429 mov %ax,%ss
430
431 /* Restore CR2, CR4, CR3 and CR0 */
432 movl PCB_CR2(%ecx),%eax
433 movl %eax,%cr2
434 movl PCB_CR4(%ecx),%eax
435 movl %eax,%cr4
436 movl PCB_CR3(%ecx),%eax
437 movl %eax,%cr3
438 movl PCB_CR0(%ecx),%eax
439 movl %eax,%cr0
440 jmp 1f
441 1:
442
443 /* Restore descriptor tables */
444 lidt PCB_IDT(%ecx)
445 lldt PCB_LDT(%ecx)
446
447 #define SDT_SYS386TSS 9
448 #define SDT_SYS386BSY 11
449 /* Clear "task busy" bit and reload TR */
450 movl PCPU(TSS_GDT),%eax
451 andb $(~SDT_SYS386BSY | SDT_SYS386TSS),5(%eax)
452 movzwl PCB_TR(%ecx),%eax
453 ltr %ax
454 #undef SDT_SYS386TSS
455 #undef SDT_SYS386BSY
456
457 /* Restore debug registers */
458 movl PCB_DR0(%ecx),%eax
459 movl %eax,%dr0
460 movl PCB_DR1(%ecx),%eax
461 movl %eax,%dr1
462 movl PCB_DR2(%ecx),%eax
463 movl %eax,%dr2
464 movl PCB_DR3(%ecx),%eax
465 movl %eax,%dr3
466 movl PCB_DR6(%ecx),%eax
467 movl %eax,%dr6
468 movl PCB_DR7(%ecx),%eax
469 movl %eax,%dr7
470
471 /* Restore other registers */
472 movl PCB_EDI(%ecx),%edi
473 movl PCB_ESI(%ecx),%esi
474 movl PCB_EBP(%ecx),%ebp
475 movl PCB_ESP(%ecx),%esp
476 movl PCB_EBX(%ecx),%ebx
477
478 /* reload code selector by turning return into intersegmental return */
479 pushl PCB_EIP(%ecx)
480 movl $KCSEL,4(%esp)
481 xorl %eax,%eax
482 lret
483 END(resumectx)
Cache object: 4872b0327cfff1755e58c9a69c3ddfac
|