2 * Copyright (c) 2003,2004 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
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
15 * the documentation and/or other materials provided with the
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * Copyright (c) 1990 The Regents of the University of California.
35 * All rights reserved.
37 * This code is derived from software contributed to Berkeley by
40 * Redistribution and use in source and binary forms, with or without
41 * modification, are permitted provided that the following conditions
43 * 1. Redistributions of source code must retain the above copyright
44 * notice, this list of conditions and the following disclaimer.
45 * 2. Redistributions in binary form must reproduce the above copyright
46 * notice, this list of conditions and the following disclaimer in the
47 * documentation and/or other materials provided with the distribution.
48 * 3. All advertising materials mentioning features or use of this software
49 * must display the following acknowledgement:
50 * This product includes software developed by the University of
51 * California, Berkeley and its contributors.
52 * 4. Neither the name of the University nor the names of its contributors
53 * may be used to endorse or promote products derived from this software
54 * without specific prior written permission.
56 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
57 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
58 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
59 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
60 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
61 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
62 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
63 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
64 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
65 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
68 * $FreeBSD: src/sys/i386/i386/swtch.s,v 1.89.2.10 2003/01/23 03:36:24 ps Exp $
69 * $DragonFly: src/sys/platform/pc32/i386/swtch.s,v 1.39 2005/11/02 09:14:58 dillon Exp $
74 #include <sys/rtprio.h>
76 #include <machine/asmacros.h>
77 #include <machine/segments.h>
78 #include <machine/ipl.h>
80 #include <machine/pmap.h>
81 #include <machine/smptests.h> /** GRAB_LOPRIO */
82 #include <arch/apic/apicreg.h>
83 #include <machine/lock.h>
88 #define MPLOCKED lock ;
97 #if defined(SWTCH_OPTIM_STATS)
98 .globl swtch_optim_stats, tlb_flush_count
99 swtch_optim_stats: .long 0 /* number of _swtch_optims */
100 tlb_flush_count: .long 0
107 * cpu_heavy_switch(next_thread)
109 * Switch from the current thread to a new thread. This entry
110 * is normally called via the thread->td_switch function, and will
111 * only be called when the current thread is a heavy weight process.
113 * Some instructions have been reordered to reduce pipeline stalls.
115 * YYY disable interrupts once giant is removed.
117 ENTRY(cpu_heavy_switch)
121 movl PCPU(curthread),%ecx
122 movl (%esp),%eax /* (reorder optimization) */
123 movl TD_PCB(%ecx),%edx /* EDX = PCB */
124 movl %eax,PCB_EIP(%edx) /* return PC may be modified */
125 movl %ebx,PCB_EBX(%edx)
126 movl %esp,PCB_ESP(%edx)
127 movl %ebp,PCB_EBP(%edx)
128 movl %esi,PCB_ESI(%edx)
129 movl %edi,PCB_EDI(%edx)
130 movl %gs,PCB_GS(%edx)
132 movl %ecx,%ebx /* EBX = curthread */
133 movl TD_PROC(%ecx),%ecx
134 movl PCPU(cpuid), %eax
135 movl P_VMSPACE(%ecx), %ecx /* ECX = vmspace */
136 MPLOCKED btrl %eax, VM_PMAP+PM_ACTIVE(%ecx)
139 * Push the LWKT switch restore function, which resumes a heavy
140 * weight process. Note that the LWKT switcher is based on
141 * TD_SP, while the heavy weight process switcher is based on
142 * PCB_ESP. TD_SP is usually two ints pushed relative to
143 * PCB_ESP. We push the flags for later restore by cpu_heavy_restore.
146 pushl $cpu_heavy_restore
147 movl %esp,TD_SP(%ebx)
150 * Save debug regs if necessary
152 movb PCB_FLAGS(%edx),%al
154 jz 1f /* no, skip over */
155 movl %dr7,%eax /* yes, do the save */
156 movl %eax,PCB_DR7(%edx)
157 andl $0x0000fc00, %eax /* disable all watchpoints */
160 movl %eax,PCB_DR6(%edx)
162 movl %eax,PCB_DR3(%edx)
164 movl %eax,PCB_DR2(%edx)
166 movl %eax,PCB_DR1(%edx)
168 movl %eax,PCB_DR0(%edx)
173 * Save the FP state if we have used the FP. Note that calling
174 * npxsave will NULL out PCPU(npxthread).
176 cmpl %ebx,PCPU(npxthread)
178 pushl TD_SAVEFPU(%ebx)
179 call npxsave /* do it in a big C function */
180 addl $4,%esp /* EAX, ECX, EDX trashed */
182 #endif /* NNPX > 0 */
185 * Switch to the next thread, which was passed as an argument
186 * to cpu_heavy_switch(). Due to the eflags and switch-restore
187 * function we pushed, the argument is at 12(%esp). Set the current
188 * thread, load the stack pointer, and 'ret' into the switch-restore
191 * The switch restore function expects the new thread to be in %eax
192 * and the old one to be in %ebx.
194 * There is a one-instruction window where curthread is the new
195 * thread but %esp still points to the old thread's stack, but
196 * we are protected by a critical section so it is ok.
198 movl 12(%esp),%eax /* EAX = newtd, EBX = oldtd */
199 movl %eax,PCPU(curthread)
200 movl TD_SP(%eax),%esp
206 * The switch function is changed to this when a thread is going away
207 * for good. We have to ensure that the MMU state is not cached, and
208 * we don't bother saving the existing thread state before switching.
210 * At this point we are in a critical section and this cpu owns the
211 * thread's token, which serves as an interlock until the switchout is
214 ENTRY(cpu_exit_switch)
216 * Get us out of the vmspace
224 movl PCPU(curthread),%ebx
226 * Switch to the next thread. RET into the restore function, which
227 * expects the new thread in EAX and the old in EBX.
229 * There is a one-instruction window where curthread is the new
230 * thread but %esp still points to the old thread's stack, but
231 * we are protected by a critical section so it is ok.
234 movl %eax,PCPU(curthread)
235 movl TD_SP(%eax),%esp
239 * cpu_heavy_restore() (current thread in %eax on entry)
241 * Restore the thread after an LWKT switch. This entry is normally
242 * called via the LWKT switch restore function, which was pulled
243 * off the thread stack and jumped to.
245 * This entry is only called if the thread was previously saved
246 * using cpu_heavy_switch() (the heavy weight process thread switcher),
247 * or when a new process is initially scheduled. The first thing we
248 * do is clear the TDF_RUNNING bit in the old thread and set it in the
251 * NOTE: The process may be in any state, not necessarily SRUN, because
252 * a preemption switch may interrupt the process and then return via
255 * YYY theoretically we do not have to restore everything here, a lot
256 * of this junk can wait until we return to usermode. But for now
257 * we restore everything.
259 * YYY the PCB crap is really crap, it makes startup a bitch because
260 * we can't switch away.
262 * YYY note: spl check is done in mi_switch when it splx()'s.
265 ENTRY(cpu_heavy_restore)
267 movl TD_PCB(%eax),%edx /* EDX = PCB */
268 movl TD_PROC(%eax),%ecx
270 #if defined(SWTCH_OPTIM_STATS)
271 incl _swtch_optim_stats
274 * Tell the pmap that our cpu is using the VMSPACE now. We cannot
275 * safely test/reload %cr3 until after we have set the bit in the
276 * pmap (remember, we do not hold the MP lock in the switch code).
278 movl P_VMSPACE(%ecx), %ecx /* ECX = vmspace */
279 movl PCPU(cpuid), %esi
280 MPLOCKED btsl %esi, VM_PMAP+PM_ACTIVE(%ecx)
283 * Restore the MMU address space. If it is the same as the last
284 * thread we don't have to invalidate the tlb (i.e. reload cr3).
285 * YYY which naturally also means that the PM_ACTIVE bit had better
286 * already have been set before we set it above, check? YYY
289 movl PCB_CR3(%edx),%ecx
292 #if defined(SWTCH_OPTIM_STATS)
293 decl _swtch_optim_stats
294 incl _tlb_flush_count
299 * Clear TDF_RUNNING flag in old thread only after cleaning up
300 * %cr3. The target thread is already protected by being TDF_RUNQ
301 * so setting TDF_RUNNING isn't as big a deal.
303 andl $~TDF_RUNNING,TD_FLAGS(%ebx)
304 orl $TDF_RUNNING,TD_FLAGS(%eax)
307 * Deal with the PCB extension, restore the private tss
309 movl PCB_EXT(%edx),%edi /* check for a PCB extension */
310 movl $1,%ebx /* maybe mark use of a private tss */
315 * Going back to the common_tss. We may need to update TSS_ESP0
316 * which sets the top of the supervisor stack when entering from
317 * usermode. The PCB is at the top of the stack but we need another
318 * 16 bytes to take vm86 into account.
321 movl %ebx, PCPU(common_tss) + TSS_ESP0
323 cmpl $0,PCPU(private_tss) /* don't have to reload if */
324 je 3f /* already using the common TSS */
326 subl %ebx,%ebx /* unmark use of private tss */
329 * Get the address of the common TSS descriptor for the ltr.
330 * There is no way to get the address of a segment-accessed variable
331 * so we store a self-referential pointer at the base of the per-cpu
332 * data area and add the appropriate offset.
334 movl $gd_common_tssd, %edi
338 * Move the correct TSS descriptor into the GDT slot, then reload
342 movl %ebx,PCPU(private_tss) /* mark/unmark private tss */
343 movl PCPU(tss_gdt), %ebx /* entry in GDT */
348 movl $GPROC0_SEL*8, %esi /* GSEL(entry, SEL_KPL) */
353 * Restore general registers.
355 movl PCB_EBX(%edx),%ebx
356 movl PCB_ESP(%edx),%esp
357 movl PCB_EBP(%edx),%ebp
358 movl PCB_ESI(%edx),%esi
359 movl PCB_EDI(%edx),%edi
360 movl PCB_EIP(%edx),%eax
364 * Restore the user LDT if we have one
366 cmpl $0, PCB_USERLDT(%edx)
368 movl _default_ldt,%eax
369 cmpl PCPU(currentldt),%eax
372 movl %eax,PCPU(currentldt)
379 * Restore the user TLS if we have one
385 * Restore the %gs segment register, which must be done after
386 * loading the user LDT. Since user processes can modify the
387 * register via procfs, this may result in a fault which is
388 * detected by checking the fault address against cpu_switch_load_gs
389 * in i386/i386/trap.c
391 .globl cpu_switch_load_gs
393 movl PCB_GS(%edx),%gs
396 * Restore the DEBUG register state if necessary.
398 movb PCB_FLAGS(%edx),%al
400 jz 1f /* no, skip over */
401 movl PCB_DR6(%edx),%eax /* yes, do the restore */
403 movl PCB_DR3(%edx),%eax
405 movl PCB_DR2(%edx),%eax
407 movl PCB_DR1(%edx),%eax
409 movl PCB_DR0(%edx),%eax
411 movl %dr7,%eax /* load dr7 so as not to disturb */
412 andl $0x0000fc00,%eax /* reserved bits */
414 movl PCB_DR7(%edx),%ebx
415 andl $~0x0000fc00,%ebx
426 * Update pcb, saving current processor state.
432 /* caller's return address - child won't execute this routine */
434 movl %eax,PCB_EIP(%ecx)
437 movl %eax,PCB_CR3(%ecx)
439 movl %ebx,PCB_EBX(%ecx)
440 movl %esp,PCB_ESP(%ecx)
441 movl %ebp,PCB_EBP(%ecx)
442 movl %esi,PCB_ESI(%ecx)
443 movl %edi,PCB_EDI(%ecx)
444 movl %gs,PCB_GS(%ecx)
448 * If npxthread == NULL, then the npx h/w state is irrelevant and the
449 * state had better already be in the pcb. This is true for forks
450 * but not for dumps (the old book-keeping with FP flags in the pcb
451 * always lost for dumps because the dump pcb has 0 flags).
453 * If npxthread != NULL, then we have to save the npx h/w state to
454 * npxthread's pcb and copy it to the requested pcb, or save to the
455 * requested pcb and reload. Copying is easier because we would
456 * have to handle h/w bugs for reloading. We used to lose the
457 * parent's npx state for forks by forgetting to reload.
459 movl PCPU(npxthread),%eax
463 pushl %ecx /* target pcb */
464 movl TD_SAVEFPU(%eax),%eax /* originating savefpu area */
474 pushl $PCB_SAVEFPU_SIZE
475 leal PCB_SAVEFPU(%ecx),%ecx
480 #endif /* NNPX > 0 */
486 * cpu_idle_restore() (current thread in %eax on entry) (one-time execution)
488 * Don't bother setting up any regs other then %ebp so backtraces
489 * don't die. This restore function is used to bootstrap into the
490 * cpu_idle() LWKT only, after that cpu_lwkt_*() will be used for
493 * Clear TDF_RUNNING in old thread only after we've cleaned up %cr3.
495 * If we are an AP we have to call ap_init() before jumping to
496 * cpu_idle(). ap_init() will synchronize with the BP and finish
497 * setting up various ncpu-dependant globaldata fields. This may
498 * happen on UP as well as SMP if we happen to be simulating multiple
501 ENTRY(cpu_idle_restore)
507 andl $~TDF_RUNNING,TD_FLAGS(%ebx)
508 orl $TDF_RUNNING,TD_FLAGS(%eax)
519 * cpu_kthread_restore() (current thread is %eax on entry) (one-time execution)
521 * Don't bother setting up any regs other then %ebp so backtraces
522 * don't die. This restore function is used to bootstrap into an
523 * LWKT based kernel thread only. cpu_lwkt_switch() will be used
526 * Since all of our context is on the stack we are reentrant and
527 * we can release our critical section and enable interrupts early.
529 ENTRY(cpu_kthread_restore)
532 movl TD_PCB(%eax),%edx
535 andl $~TDF_RUNNING,TD_FLAGS(%ebx)
536 orl $TDF_RUNNING,TD_FLAGS(%eax)
537 subl $TDPRI_CRIT,TD_PRI(%eax)
538 popl %eax /* kthread exit function */
539 pushl PCB_EBX(%edx) /* argument to ESI function */
540 pushl %eax /* set exit func as return address */
541 movl PCB_ESI(%edx),%eax
547 * Standard LWKT switching function. Only non-scratch registers are
548 * saved and we don't bother with the MMU state or anything else.
550 * This function is always called while in a critical section.
552 * There is a one-instruction window where curthread is the new
553 * thread but %esp still points to the old thread's stack, but
554 * we are protected by a critical section so it is ok.
558 ENTRY(cpu_lwkt_switch)
559 pushl %ebp /* note: GDB hacked to locate ebp relative to td_sp */
561 movl PCPU(curthread),%ebx
565 /* warning: adjust movl into %eax below if you change the pushes */
569 * Save the FP state if we have used the FP. Note that calling
570 * npxsave will NULL out PCPU(npxthread).
572 * We have to deal with the FP state for LWKT threads in case they
573 * happen to get preempted or block while doing an optimized
574 * bzero/bcopy/memcpy.
576 cmpl %ebx,PCPU(npxthread)
578 pushl TD_SAVEFPU(%ebx)
579 call npxsave /* do it in a big C function */
580 addl $4,%esp /* EAX, ECX, EDX trashed */
582 #endif /* NNPX > 0 */
584 movl 4+20(%esp),%eax /* switch to this thread */
585 pushl $cpu_lwkt_restore
586 movl %esp,TD_SP(%ebx)
587 movl %eax,PCPU(curthread)
588 movl TD_SP(%eax),%esp
591 * eax contains new thread, ebx contains old thread.
596 * cpu_lwkt_restore() (current thread in %eax on entry)
598 * Standard LWKT restore function. This function is always called
599 * while in a critical section.
601 * Warning: due to preemption the restore function can be used to
602 * 'return' to the original thread. Interrupt disablement must be
603 * protected through the switch so we cannot run splz here.
605 * YYY we theoretically do not need to load IdlePTD into cr3, but if
606 * so we need a way to detect when the PTD we are using is being
607 * deleted due to a process exiting.
609 ENTRY(cpu_lwkt_restore)
610 movl IdlePTD,%ecx /* YYY borrow but beware desched/cpuchg/exit */
616 andl $~TDF_RUNNING,TD_FLAGS(%ebx)
617 orl $TDF_RUNNING,TD_FLAGS(%eax)