2 * Copyright (c) 1990 The Regents of the University of California.
4 * LWKT threads Copyright (c) 2003 Matthew Dillon
6 * This code is derived from software contributed to Berkeley by
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. All advertising materials mentioning features or use of this software
18 * must display the following acknowledgement:
19 * This product includes software developed by the University of
20 * California, Berkeley and its contributors.
21 * 4. Neither the name of the University nor the names of its contributors
22 * may be used to endorse or promote products derived from this software
23 * without specific prior written permission.
25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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37 * $FreeBSD: src/sys/i386/i386/swtch.s,v 1.89.2.10 2003/01/23 03:36:24 ps Exp $
38 * $DragonFly: src/sys/platform/pc32/i386/swtch.s,v 1.26 2003/08/07 21:17:22 dillon Exp $
42 #include "opt_user_ldt.h"
44 #include <sys/rtprio.h>
46 #include <machine/asmacros.h>
47 #include <machine/ipl.h>
50 #include <machine/pmap.h>
51 #include <machine/smptests.h> /** GRAB_LOPRIO */
52 #include <machine/apic.h>
53 #include <machine/lock.h>
59 #define MPLOCKED lock ;
68 #if defined(SWTCH_OPTIM_STATS)
69 .globl swtch_optim_stats, tlb_flush_count
70 swtch_optim_stats: .long 0 /* number of _swtch_optims */
71 tlb_flush_count: .long 0
78 * cpu_heavy_switch(next_thread)
80 * Switch from the current thread to a new thread. This entry
81 * is normally called via the thread->td_switch function, and will
82 * only be called when the current thread is a heavy weight process.
84 * Some instructions have been reordered to reduce pipeline stalls.
86 * YYY disable interrupts once giant is removed.
88 ENTRY(cpu_heavy_switch)
92 movl PCPU(curthread),%ecx
93 movl (%esp),%eax /* (reorder optimization) */
94 movl TD_PCB(%ecx),%edx /* EDX = PCB */
95 movl %eax,PCB_EIP(%edx) /* return PC may be modified */
96 movl %ebx,PCB_EBX(%edx)
97 movl %esp,PCB_ESP(%edx)
98 movl %ebp,PCB_EBP(%edx)
99 movl %esi,PCB_ESI(%edx)
100 movl %edi,PCB_EDI(%edx)
101 movl %gs,PCB_GS(%edx)
103 movl %ecx,%ebx /* EBX = curthread */
104 movl TD_PROC(%ecx),%ecx
105 movl PCPU(cpuid), %eax
106 movl P_VMSPACE(%ecx), %ecx /* ECX = vmspace */
107 MPLOCKED btrl %eax, VM_PMAP+PM_ACTIVE(%ecx)
110 * Push the LWKT switch restore function, which resumes a heavy
111 * weight process. Note that the LWKT switcher is based on
112 * TD_SP, while the heavy weight process switcher is based on
113 * PCB_ESP. TD_SP is usually two ints pushed relative to
114 * PCB_ESP. We push the flags for later restore by cpu_heavy_restore.
117 pushl $cpu_heavy_restore
118 movl %esp,TD_SP(%ebx)
121 * Save debug regs if necessary
123 movb PCB_FLAGS(%edx),%al
125 jz 1f /* no, skip over */
126 movl %dr7,%eax /* yes, do the save */
127 movl %eax,PCB_DR7(%edx)
128 andl $0x0000fc00, %eax /* disable all watchpoints */
131 movl %eax,PCB_DR6(%edx)
133 movl %eax,PCB_DR3(%edx)
135 movl %eax,PCB_DR2(%edx)
137 movl %eax,PCB_DR1(%edx)
139 movl %eax,PCB_DR0(%edx)
143 * Save the FP state if we have used the FP. Note that calling
144 * npxsave will NULL out PCPU(npxthread).
147 cmpl %ebx,PCPU(npxthread)
149 addl $PCB_SAVEFPU,%edx
151 call npxsave /* do it in a big C function */
152 addl $4,%esp /* EAX, ECX, EDX trashed */
154 #endif /* NNPX > 0 */
157 * Switch to the next thread, which was passed as an argument
158 * to cpu_heavy_switch(). Due to the eflags and switch-restore
159 * function we pushed, the argument is at 12(%esp). Set the current
160 * thread, load the stack pointer, and 'ret' into the switch-restore
163 * The switch restore function expects the new thread to be in %eax
164 * and the old one to be in %ebx.
166 movl 12(%esp),%eax /* EAX = newtd, EBX = oldtd */
167 movl %eax,PCPU(curthread)
168 movl TD_SP(%eax),%esp
174 * The switch function is changed to this when a thread is going away
175 * for good. We have to ensure that the MMU state is not cached, and
176 * we don't bother saving the existing thread state before switching.
178 * At this point we are in a critical section and this cpu owns the
179 * thread's token, which serves as an interlock until the switchout is
182 ENTRY(cpu_exit_switch)
184 * Get us out of the vmspace
192 movl PCPU(curthread),%ebx
194 * Switch to the next thread. RET into the restore function, which
195 * expects the new thread in EAX and the old in EBX.
198 movl %eax,PCPU(curthread)
199 movl TD_SP(%eax),%esp
203 * cpu_heavy_restore() (current thread in %eax on entry)
205 * Restore the thread after an LWKT switch. This entry is normally
206 * called via the LWKT switch restore function, which was pulled
207 * off the thread stack and jumped to.
209 * This entry is only called if the thread was previously saved
210 * using cpu_heavy_switch() (the heavy weight process thread switcher),
211 * or when a new process is initially scheduled. The first thing we
212 * do is clear the TDF_RUNNING bit in the old thread and set it in the
215 * YYY theoretically we do not have to restore everything here, a lot
216 * of this junk can wait until we return to usermode. But for now
217 * we restore everything.
219 * YYY the PCB crap is really crap, it makes startup a bitch because
220 * we can't switch away.
222 * YYY note: spl check is done in mi_switch when it splx()'s.
225 ENTRY(cpu_heavy_restore)
227 movl TD_PCB(%eax),%edx /* EDX = PCB */
228 movl TD_PROC(%eax),%ecx
230 cmpb $SRUN,P_STAT(%ecx)
234 #if defined(SWTCH_OPTIM_STATS)
235 incl _swtch_optim_stats
238 * Tell the pmap that our cpu is using the VMSPACE now. We cannot
239 * safely test/reload %cr3 until after we have set the bit in the
240 * pmap (remember, we do not hold the MP lock in the switch code).
242 movl P_VMSPACE(%ecx), %ecx /* ECX = vmspace */
243 movl PCPU(cpuid), %esi
244 MPLOCKED btsl %esi, VM_PMAP+PM_ACTIVE(%ecx)
247 * Restore the MMU address space. If it is the same as the last
248 * thread we don't have to invalidate the tlb (i.e. reload cr3).
249 * YYY which naturally also means that the PM_ACTIVE bit had better
250 * already have been set before we set it above, check? YYY
253 movl PCB_CR3(%edx),%ecx
256 #if defined(SWTCH_OPTIM_STATS)
257 decl _swtch_optim_stats
258 incl _tlb_flush_count
263 * Clear TDF_RUNNING flag in old thread only after cleaning up
264 * %cr3. The target thread is already protected by being TDF_RUNQ
265 * so setting TDF_RUNNING isn't as big a deal.
267 andl $~TDF_RUNNING,TD_FLAGS(%ebx)
268 orl $TDF_RUNNING,TD_FLAGS(%eax)
271 * Deal with the PCB extension, restore the private tss
273 movl PCB_EXT(%edx),%edi /* check for a PCB extension */
274 movl $1,%ebx /* maybe mark use of a private tss */
279 * Going back to the common_tss. We may need to update TSS_ESP0
280 * which sets the top of the supervisor stack when entering from
281 * usermode. The PCB is at the top of the stack but we need another
282 * 16 bytes to take vm86 into account.
285 movl %ebx, PCPU(common_tss) + TSS_ESP0
287 cmpl $0,PCPU(private_tss) /* don't have to reload if */
288 je 3f /* already using the common TSS */
290 subl %ebx,%ebx /* unmark use of private tss */
293 * Get the address of the common TSS descriptor for the ltr.
294 * There is no way to get the address of a segment-accessed variable
295 * so we store a self-referential pointer at the base of the per-cpu
296 * data area and add the appropriate offset.
298 movl $gd_common_tssd, %edi
302 * Move the correct TSS descriptor into the GDT slot, then reload
306 movl %ebx,PCPU(private_tss) /* mark/unmark private tss */
307 movl PCPU(tss_gdt), %ebx /* entry in GDT */
312 movl $GPROC0_SEL*8, %esi /* GSEL(entry, SEL_KPL) */
317 * Restore general registers.
319 movl PCB_EBX(%edx),%ebx
320 movl PCB_ESP(%edx),%esp
321 movl PCB_EBP(%edx),%ebp
322 movl PCB_ESI(%edx),%esi
323 movl PCB_EDI(%edx),%edi
324 movl PCB_EIP(%edx),%eax
328 * Restore the user LDT if we have one
331 cmpl $0, PCB_USERLDT(%edx)
333 movl _default_ldt,%eax
334 cmpl PCPU(currentldt),%eax
337 movl %eax,PCPU(currentldt)
345 * Restore the %gs segment register, which must be done after
346 * loading the user LDT. Since user processes can modify the
347 * register via procfs, this may result in a fault which is
348 * detected by checking the fault address against cpu_switch_load_gs
349 * in i386/i386/trap.c
351 .globl cpu_switch_load_gs
353 movl PCB_GS(%edx),%gs
356 * Restore the DEBUG register state if necessary.
358 movb PCB_FLAGS(%edx),%al
360 jz 1f /* no, skip over */
361 movl PCB_DR6(%edx),%eax /* yes, do the restore */
363 movl PCB_DR3(%edx),%eax
365 movl PCB_DR2(%edx),%eax
367 movl PCB_DR1(%edx),%eax
369 movl PCB_DR0(%edx),%eax
371 movl %dr7,%eax /* load dr7 so as not to disturb */
372 andl $0x0000fc00,%eax /* reserved bits */
374 movl PCB_DR7(%edx),%ebx
375 andl $~0x0000fc00,%ebx
387 sw0_2: .asciz "cpu_switch: not SRUN"
391 * Update pcb, saving current processor state.
397 /* caller's return address - child won't execute this routine */
399 movl %eax,PCB_EIP(%ecx)
402 movl %eax,PCB_CR3(%ecx)
404 movl %ebx,PCB_EBX(%ecx)
405 movl %esp,PCB_ESP(%ecx)
406 movl %ebp,PCB_EBP(%ecx)
407 movl %esi,PCB_ESI(%ecx)
408 movl %edi,PCB_EDI(%ecx)
409 movl %gs,PCB_GS(%ecx)
413 * If npxthread == NULL, then the npx h/w state is irrelevant and the
414 * state had better already be in the pcb. This is true for forks
415 * but not for dumps (the old book-keeping with FP flags in the pcb
416 * always lost for dumps because the dump pcb has 0 flags).
418 * If npxthread != NULL, then we have to save the npx h/w state to
419 * npxthread's pcb and copy it to the requested pcb, or save to the
420 * requested pcb and reload. Copying is easier because we would
421 * have to handle h/w bugs for reloading. We used to lose the
422 * parent's npx state for forks by forgetting to reload.
424 movl PCPU(npxthread),%eax
429 movl TD_PCB(%eax),%eax
430 leal PCB_SAVEFPU(%eax),%eax
438 pushl $PCB_SAVEFPU_SIZE
439 leal PCB_SAVEFPU(%ecx),%ecx
444 #endif /* NNPX > 0 */
450 * cpu_idle_restore() (current thread in %eax on entry) (one-time execution)
452 * Don't bother setting up any regs other then %ebp so backtraces
453 * don't die. This restore function is used to bootstrap into the
454 * cpu_idle() LWKT only, after that cpu_lwkt_*() will be used for
457 * Clear TDF_RUNNING in old thread only after we've cleaned up %cr3.
459 * If we are an AP we have to call ap_init() before jumping to
460 * cpu_idle(). ap_init() will synchronize with the BP and finish
461 * setting up various ncpu-dependant globaldata fields. This may
462 * happen on UP as well as SMP if we happen to be simulating multiple
465 ENTRY(cpu_idle_restore)
471 andl $~TDF_RUNNING,TD_FLAGS(%ebx)
472 orl $TDF_RUNNING,TD_FLAGS(%eax)
483 * cpu_kthread_restore() (current thread is %eax on entry) (one-time execution)
485 * Don't bother setting up any regs other then %ebp so backtraces
486 * don't die. This restore function is used to bootstrap into an
487 * LWKT based kernel thread only. cpu_lwkt_switch() will be used
490 * Since all of our context is on the stack we are reentrant and
491 * we can release our critical section and enable interrupts early.
493 ENTRY(cpu_kthread_restore)
496 movl TD_PCB(%eax),%edx
499 andl $~TDF_RUNNING,TD_FLAGS(%ebx)
500 orl $TDF_RUNNING,TD_FLAGS(%eax)
501 subl $TDPRI_CRIT,TD_PRI(%eax)
502 popl %eax /* kthread exit function */
503 pushl PCB_EBX(%edx) /* argument to ESI function */
504 pushl %eax /* set exit func as return address */
505 movl PCB_ESI(%edx),%eax
511 * Standard LWKT switching function. Only non-scratch registers are
512 * saved and we don't bother with the MMU state or anything else.
514 * This function is always called while in a critical section.
518 ENTRY(cpu_lwkt_switch)
525 movl PCPU(curthread),%ebx
526 pushl $cpu_lwkt_restore
527 movl %esp,TD_SP(%ebx)
528 movl %eax,PCPU(curthread)
529 movl TD_SP(%eax),%esp
532 * eax contains new thread, ebx contains old thread.
537 * cpu_lwkt_restore() (current thread in %eax on entry)
539 * Standard LWKT restore function. This function is always called
540 * while in a critical section.
542 * Warning: due to preemption the restore function can be used to
543 * 'return' to the original thread. Interrupt disablement must be
544 * protected through the switch so we cannot run splz here.
546 * YYY we theoretically do not need to load IdlePTD into cr3, but if
547 * so we need a way to detect when the PTD we are using is being
548 * deleted due to a process exiting.
550 ENTRY(cpu_lwkt_restore)
551 movl IdlePTD,%ecx /* YYY borrow but beware desched/cpuchg/exit */
557 andl $~TDF_RUNNING,TD_FLAGS(%ebx)
558 orl $TDF_RUNNING,TD_FLAGS(%eax)