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 * 3. 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 * $FreeBSD$
33 */
34
35 #include "opt_sched.h"
36
37 #include <machine/asmacros.h>
38
39 #include "assym.inc"
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 /* release bit from old pm_active */
78 movl PCPU(CURPMAP), %ebx
79 #ifdef SMP
80 lock
81 #endif
82 btrl %esi, PM_ACTIVE(%ebx) /* clear old */
83 movl 8(%esp),%ecx /* New thread */
84 movl TD_PCB(%ecx),%edx
85 /* set bit in new pm_active */
86 movl TD_PROC(%ecx),%eax
87 movl P_VMSPACE(%eax), %ebx
88 addl $VM_PMAP, %ebx
89 movl %ebx, PCPU(CURPMAP)
90 #ifdef SMP
91 lock
92 #endif
93 btsl %esi, PM_ACTIVE(%ebx) /* set new */
94 jmp sw1
95 END(cpu_throw)
96
97 /*
98 * cpu_switch(old, new)
99 *
100 * Save the current thread state, then select the next thread to run
101 * and load its state.
102 * 0(%esp) = ret
103 * 4(%esp) = oldtd
104 * 8(%esp) = newtd
105 * 12(%esp) = newlock
106 */
107 ENTRY(cpu_switch)
108
109 /* Switch to new thread. First, save context. */
110 movl 4(%esp),%ecx
111
112 #ifdef INVARIANTS
113 testl %ecx,%ecx /* no thread? */
114 jz badsw2 /* no, panic */
115 #endif
116
117 movl TD_PCB(%ecx),%edx
118
119 movl (%esp),%eax /* Hardware registers */
120 movl %eax,PCB_EIP(%edx)
121 movl %ebx,PCB_EBX(%edx)
122 movl %esp,PCB_ESP(%edx)
123 movl %ebp,PCB_EBP(%edx)
124 movl %esi,PCB_ESI(%edx)
125 movl %edi,PCB_EDI(%edx)
126 mov %gs,PCB_GS(%edx)
127 /* Test if debug registers should be saved. */
128 testl $PCB_DBREGS,PCB_FLAGS(%edx)
129 jz 1f /* no, skip over */
130 movl %dr7,%eax /* yes, do the save */
131 movl %eax,PCB_DR7(%edx)
132 andl $0x0000fc00, %eax /* disable all watchpoints */
133 movl %eax,%dr7
134 movl %dr6,%eax
135 movl %eax,PCB_DR6(%edx)
136 movl %dr3,%eax
137 movl %eax,PCB_DR3(%edx)
138 movl %dr2,%eax
139 movl %eax,PCB_DR2(%edx)
140 movl %dr1,%eax
141 movl %eax,PCB_DR1(%edx)
142 movl %dr0,%eax
143 movl %eax,PCB_DR0(%edx)
144 1:
145
146 /* have we used fp, and need a save? */
147 cmpl %ecx,PCPU(FPCURTHREAD)
148 jne 1f
149 pushl PCB_SAVEFPU(%edx) /* h/w bugs make saving complicated */
150 call npxsave /* do it in a big C function */
151 popl %eax
152 1:
153
154 /* Save is done. Now fire up new thread. */
155 movl 4(%esp),%edi
156 movl 8(%esp),%ecx /* New thread */
157 movl 12(%esp),%esi /* New lock */
158 #ifdef INVARIANTS
159 testl %ecx,%ecx /* no thread? */
160 jz badsw3 /* no, panic */
161 #endif
162 movl TD_PCB(%ecx),%edx
163
164 /* Switchout td_lock */
165 movl %esi,%eax
166 movl PCPU(CPUID),%esi
167 SETOP %eax,TD_LOCK(%edi)
168
169 /* Release bit from old pmap->pm_active */
170 movl PCPU(CURPMAP), %ebx
171 #ifdef SMP
172 lock
173 #endif
174 btrl %esi, PM_ACTIVE(%ebx) /* clear old */
175
176 /* Set bit in new pmap->pm_active */
177 movl TD_PROC(%ecx),%eax /* newproc */
178 movl P_VMSPACE(%eax), %ebx
179 addl $VM_PMAP, %ebx
180 movl %ebx, PCPU(CURPMAP)
181 #ifdef SMP
182 lock
183 #endif
184 btsl %esi, PM_ACTIVE(%ebx) /* set new */
185 sw1:
186 BLOCK_SPIN(%ecx)
187 /*
188 * At this point, we have managed thread locks and are ready
189 * to load up the rest of the next context.
190 */
191
192 /* Load a pointer to the thread kernel stack into PCPU. */
193 leal -VM86_STACK_SPACE(%edx), %eax /* leave space for vm86 */
194 movl %eax, PCPU(KESP0)
195
196 cmpl $0, PCB_EXT(%edx) /* has pcb extension? */
197 je 1f /* If not, use the default */
198 movl $1, PCPU(PRIVATE_TSS) /* mark use of private tss */
199 movl PCB_EXT(%edx), %edi /* new tss descriptor */
200 movl PCPU(TRAMPSTK), %ebx
201 movl %ebx, PCB_EXT_TSS+TSS_ESP0(%edi)
202 jmp 2f /* Load it up */
203
204 1: /*
205 * Use the common default TSS instead of our own.
206 * Stack pointer in the common TSS points to the trampoline stack
207 * already and should be not changed.
208 *
209 * Test this CPU's flag to see if this CPU was using a private TSS.
210 */
211 cmpl $0, PCPU(PRIVATE_TSS) /* Already using the common? */
212 je 3f /* if so, skip reloading */
213 movl $0, PCPU(PRIVATE_TSS)
214 PCPU_ADDR(COMMON_TSSD, %edi)
215 2:
216 /* Move correct tss descriptor into GDT slot, then reload tr. */
217 movl PCPU(TSS_GDT), %ebx /* entry in GDT */
218 movl 0(%edi), %eax
219 movl 4(%edi), %esi
220 movl %eax, 0(%ebx)
221 movl %esi, 4(%ebx)
222 movl $GPROC0_SEL*8, %esi /* GSEL(GPROC0_SEL, SEL_KPL) */
223 ltr %si
224 3:
225
226 /* Copy the %fs and %gs selectors into this pcpu gdt */
227 leal PCB_FSD(%edx), %esi
228 movl PCPU(FSGS_GDT), %edi
229 movl 0(%esi), %eax /* %fs selector */
230 movl 4(%esi), %ebx
231 movl %eax, 0(%edi)
232 movl %ebx, 4(%edi)
233 movl 8(%esi), %eax /* %gs selector, comes straight after */
234 movl 12(%esi), %ebx
235 movl %eax, 8(%edi)
236 movl %ebx, 12(%edi)
237
238 /* Restore context. */
239 movl PCB_EBX(%edx),%ebx
240 movl PCB_ESP(%edx),%esp
241 movl PCB_EBP(%edx),%ebp
242 movl PCB_ESI(%edx),%esi
243 movl PCB_EDI(%edx),%edi
244 movl PCB_EIP(%edx),%eax
245 movl %eax,(%esp)
246
247 movl %edx, PCPU(CURPCB)
248 movl %ecx, PCPU(CURTHREAD) /* into next thread */
249
250 /*
251 * Determine the LDT to use and load it if is the default one and
252 * that is not the current one.
253 */
254 movl TD_PROC(%ecx),%eax
255 cmpl $0,P_MD+MD_LDT(%eax)
256 jnz 1f
257 movl _default_ldt,%eax
258 cmpl PCPU(CURRENTLDT),%eax
259 je 2f
260 lldt _default_ldt
261 movl %eax,PCPU(CURRENTLDT)
262 jmp 2f
263 1:
264 /* Load the LDT when it is not the default one. */
265 pushl %edx /* Preserve pointer to pcb. */
266 addl $P_MD,%eax /* Pointer to mdproc is arg. */
267 pushl %eax
268 /*
269 * Holding dt_lock prevents context switches, so dt_lock cannot
270 * be held now and set_user_ldt() will not deadlock acquiring it.
271 */
272 call set_user_ldt
273 addl $4,%esp
274 popl %edx
275 2:
276
277 /* This must be done after loading the user LDT. */
278 .globl cpu_switch_load_gs
279 cpu_switch_load_gs:
280 mov PCB_GS(%edx),%gs
281
282 pushl %edx
283 pushl PCPU(CURTHREAD)
284 call npxswitch
285 popl %edx
286 popl %edx
287
288 /* Test if debug registers should be restored. */
289 testl $PCB_DBREGS,PCB_FLAGS(%edx)
290 jz 1f
291
292 /*
293 * Restore debug registers. The special code for dr7 is to
294 * preserve the current values of its reserved bits.
295 */
296 movl PCB_DR6(%edx),%eax
297 movl %eax,%dr6
298 movl PCB_DR3(%edx),%eax
299 movl %eax,%dr3
300 movl PCB_DR2(%edx),%eax
301 movl %eax,%dr2
302 movl PCB_DR1(%edx),%eax
303 movl %eax,%dr1
304 movl PCB_DR0(%edx),%eax
305 movl %eax,%dr0
306 movl %dr7,%eax
307 andl $0x0000fc00,%eax
308 movl PCB_DR7(%edx),%ecx
309 andl $~0x0000fc00,%ecx
310 orl %ecx,%eax
311 movl %eax,%dr7
312 1:
313 ret
314
315 #ifdef INVARIANTS
316 badsw1:
317 pushal
318 pushl $sw0_1
319 call panic
320 sw0_1: .asciz "cpu_throw: no newthread supplied"
321
322 badsw2:
323 pushal
324 pushl $sw0_2
325 call panic
326 sw0_2: .asciz "cpu_switch: no curthread supplied"
327
328 badsw3:
329 pushal
330 pushl $sw0_3
331 call panic
332 sw0_3: .asciz "cpu_switch: no newthread supplied"
333 #endif
334 END(cpu_switch)
335
336 /*
337 * savectx(pcb)
338 * Update pcb, saving current processor state.
339 */
340 ENTRY(savectx)
341 /* Fetch PCB. */
342 movl 4(%esp),%ecx
343
344 /* Save caller's return address. Child won't execute this routine. */
345 movl (%esp),%eax
346 movl %eax,PCB_EIP(%ecx)
347
348 movl %cr3,%eax
349 movl %eax,PCB_CR3(%ecx)
350
351 movl %ebx,PCB_EBX(%ecx)
352 movl %esp,PCB_ESP(%ecx)
353 movl %ebp,PCB_EBP(%ecx)
354 movl %esi,PCB_ESI(%ecx)
355 movl %edi,PCB_EDI(%ecx)
356 mov %gs,PCB_GS(%ecx)
357
358 movl %cr0,%eax
359 movl %eax,PCB_CR0(%ecx)
360 movl %cr2,%eax
361 movl %eax,PCB_CR2(%ecx)
362 movl %cr4,%eax
363 movl %eax,PCB_CR4(%ecx)
364
365 movl %dr0,%eax
366 movl %eax,PCB_DR0(%ecx)
367 movl %dr1,%eax
368 movl %eax,PCB_DR1(%ecx)
369 movl %dr2,%eax
370 movl %eax,PCB_DR2(%ecx)
371 movl %dr3,%eax
372 movl %eax,PCB_DR3(%ecx)
373 movl %dr6,%eax
374 movl %eax,PCB_DR6(%ecx)
375 movl %dr7,%eax
376 movl %eax,PCB_DR7(%ecx)
377
378 mov %ds,PCB_DS(%ecx)
379 mov %es,PCB_ES(%ecx)
380 mov %fs,PCB_FS(%ecx)
381 mov %ss,PCB_SS(%ecx)
382
383 sgdt PCB_GDT(%ecx)
384 sidt PCB_IDT(%ecx)
385 sldt PCB_LDT(%ecx)
386 str PCB_TR(%ecx)
387
388 movl $1,%eax
389 ret
390 END(savectx)
391
392 /*
393 * resumectx(pcb) __fastcall
394 * Resuming processor state from pcb.
395 */
396 ENTRY(resumectx)
397 /* Restore GDT. */
398 lgdt PCB_GDT(%ecx)
399
400 /* Restore segment registers */
401 movzwl PCB_DS(%ecx),%eax
402 mov %ax,%ds
403 movzwl PCB_ES(%ecx),%eax
404 mov %ax,%es
405 movzwl PCB_FS(%ecx),%eax
406 mov %ax,%fs
407 movzwl PCB_GS(%ecx),%eax
408 movw %ax,%gs
409 movzwl PCB_SS(%ecx),%eax
410 mov %ax,%ss
411
412 /* Restore CR2, CR4, CR3 and CR0 */
413 movl PCB_CR2(%ecx),%eax
414 movl %eax,%cr2
415 movl PCB_CR4(%ecx),%eax
416 movl %eax,%cr4
417 movl PCB_CR3(%ecx),%eax
418 movl %eax,%cr3
419 movl PCB_CR0(%ecx),%eax
420 movl %eax,%cr0
421 jmp 1f
422 1:
423
424 /* Restore descriptor tables */
425 lidt PCB_IDT(%ecx)
426 lldt PCB_LDT(%ecx)
427
428 #define SDT_SYS386TSS 9
429 #define SDT_SYS386BSY 11
430 /* Clear "task busy" bit and reload TR */
431 movl PCPU(TSS_GDT),%eax
432 andb $(~SDT_SYS386BSY | SDT_SYS386TSS),5(%eax)
433 movzwl PCB_TR(%ecx),%eax
434 ltr %ax
435 #undef SDT_SYS386TSS
436 #undef SDT_SYS386BSY
437
438 /* Restore debug registers */
439 movl PCB_DR0(%ecx),%eax
440 movl %eax,%dr0
441 movl PCB_DR1(%ecx),%eax
442 movl %eax,%dr1
443 movl PCB_DR2(%ecx),%eax
444 movl %eax,%dr2
445 movl PCB_DR3(%ecx),%eax
446 movl %eax,%dr3
447 movl PCB_DR6(%ecx),%eax
448 movl %eax,%dr6
449 movl PCB_DR7(%ecx),%eax
450 movl %eax,%dr7
451
452 /* Restore other registers */
453 movl PCB_EDI(%ecx),%edi
454 movl PCB_ESI(%ecx),%esi
455 movl PCB_EBP(%ecx),%ebp
456 movl PCB_ESP(%ecx),%esp
457 movl PCB_EBX(%ecx),%ebx
458
459 /* reload code selector by turning return into intersegmental return */
460 pushl PCB_EIP(%ecx)
461 movl $KCSEL,4(%esp)
462 xorl %eax,%eax
463 lret
464 END(resumectx)
Cache object: ebbdf5daa59506ee3e306dc275cf8168
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