swtch.s revision 128019 
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: head/sys/i386/i386/swtch.s 128019 2004-04-07 20:46:16Z imp $
33 */
34
35#include "opt_npx.h"
36
37#include <machine/asmacros.h>
38
39#include "assym.s"
40
41/*****************************************************************************/
42/* Scheduling                                                                */
43/*****************************************************************************/
44
45	.text
46
47/*
48 * cpu_throw()
49 *
50 * This is the second half of cpu_swtch(). It is used when the current
51 * thread is either a dummy or slated to die, and we no longer care
52 * about its state.  This is only a slight optimization and is probably
53 * not worth it anymore.  Note that we need to clear the pm_active bits so
54 * we do need the old proc if it still exists.
55 * 0(%esp) = ret
56 * 4(%esp) = oldtd
57 * 8(%esp) = newtd
58 */
59ENTRY(cpu_throw)
60	movl	PCPU(CPUID), %esi
61	movl	4(%esp),%ecx			/* Old thread */
62	testl	%ecx,%ecx			/* no thread? */
63	jz	1f
64	/* release bit from old pm_active */
65	movl	PCPU(CURPMAP), %ebx
66#ifdef SMP
67	lock
68#endif
69	btrl	%esi, PM_ACTIVE(%ebx)		/* clear old */
701:
71	movl	8(%esp),%ecx			/* New thread */
72	movl	TD_PCB(%ecx),%edx
73	movl	PCB_CR3(%edx),%eax
74	movl	%eax,%cr3			/* new address space */
75	/* set bit in new pm_active */
76	movl	TD_PROC(%ecx),%eax
77	movl	P_VMSPACE(%eax), %ebx
78	addl	$VM_PMAP, %ebx
79	movl	%ebx, PCPU(CURPMAP)
80#ifdef SMP
81	lock
82#endif
83	btsl	%esi, PM_ACTIVE(%ebx)		/* set new */
84	jmp	sw1
85
86/*
87 * cpu_switch(old, new)
88 *
89 * Save the current thread state, then select the next thread to run
90 * and load its state.
91 * 0(%esp) = ret
92 * 4(%esp) = oldtd
93 * 8(%esp) = newtd
94 */
95ENTRY(cpu_switch)
96
97	/* Switch to new thread.  First, save context. */
98	movl	4(%esp),%ecx
99
100#ifdef INVARIANTS
101	testl	%ecx,%ecx			/* no thread? */
102	jz	badsw2				/* no, panic */
103#endif
104
105	movl	TD_PCB(%ecx),%edx
106
107	movl	(%esp),%eax			/* Hardware registers */
108	movl	%eax,PCB_EIP(%edx)
109	movl	%ebx,PCB_EBX(%edx)
110	movl	%esp,PCB_ESP(%edx)
111	movl	%ebp,PCB_EBP(%edx)
112	movl	%esi,PCB_ESI(%edx)
113	movl	%edi,PCB_EDI(%edx)
114	movl	%gs,PCB_GS(%edx)
115	pushfl					/* PSL */
116	popl	PCB_PSL(%edx)
117	/* Check to see if we need to call a switchout function. */
118	movl	PCB_SWITCHOUT(%edx),%eax
119	cmpl	$0, %eax
120	je	1f
121	call	*%eax
1221:
123	/* Test if debug registers should be saved. */
124	testl	$PCB_DBREGS,PCB_FLAGS(%edx)
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 */
129	movl    %eax,%dr7
130	movl    %dr6,%eax
131	movl    %eax,PCB_DR6(%edx)
132	movl    %dr3,%eax
133	movl    %eax,PCB_DR3(%edx)
134	movl    %dr2,%eax
135	movl    %eax,PCB_DR2(%edx)
136	movl    %dr1,%eax
137	movl    %eax,PCB_DR1(%edx)
138	movl    %dr0,%eax
139	movl    %eax,PCB_DR0(%edx)
1401:
141
142#ifdef DEV_NPX
143	/* have we used fp, and need a save? */
144	cmpl	%ecx,PCPU(FPCURTHREAD)
145	jne	1f
146	addl	$PCB_SAVEFPU,%edx		/* h/w bugs make saving complicated */
147	pushl	%edx
148	call	npxsave				/* do it in a big C function */
149	popl	%eax
1501:
151#endif
152
153	/* Save is done.  Now fire up new thread. Leave old vmspace. */
154	movl	%ecx,%edi
155	movl	8(%esp),%ecx			/* New thread */
156#ifdef INVARIANTS
157	testl	%ecx,%ecx			/* no thread? */
158	jz	badsw3				/* no, panic */
159#endif
160	movl	TD_PCB(%ecx),%edx
161	movl	PCPU(CPUID), %esi
162
163	/* switch address space */
164	movl	PCB_CR3(%edx),%eax
165#ifdef PAE
166	cmpl	%eax,IdlePDPT			/* Kernel address space? */
167#else
168	cmpl	%eax,IdlePTD			/* Kernel address space? */
169#endif
170	je	sw1
171	movl	%cr3,%ebx			/* The same address space? */
172	cmpl	%ebx,%eax
173	je	sw1
174	movl	%eax,%cr3			/* new address space */
175
176	/* Release bit from old pmap->pm_active */
177	movl	PCPU(CURPMAP), %ebx
178#ifdef SMP
179	lock
180#endif
181	btrl	%esi, PM_ACTIVE(%ebx)		/* clear old */
182
183	/* Set bit in new pmap->pm_active */
184	movl	TD_PROC(%ecx),%eax		/* newproc */
185	movl	P_VMSPACE(%eax), %ebx
186	addl	$VM_PMAP, %ebx
187	movl	%ebx, PCPU(CURPMAP)
188#ifdef SMP
189	lock
190#endif
191	btsl	%esi, PM_ACTIVE(%ebx)		/* set new */
192
193sw1:
194	/*
195	 * At this point, we've switched address spaces and are ready
196	 * to load up the rest of the next context.
197	 */
198	cmpl	$0, PCB_EXT(%edx)		/* has pcb extension? */
199	je	1f				/* If not, use the default */
200	btsl	%esi, private_tss		/* mark use of private tss */
201	movl	PCB_EXT(%edx), %edi		/* new tss descriptor */
202	jmp	2f				/* Load it up */
203
2041:	/*
205	 * Use the common default TSS instead of our own.
206	 * Set our stack pointer into the TSS, it's set to just
207	 * below the PCB.  In C, common_tss.tss_esp0 = &pcb - 16;
208	 */
209	leal	-16(%edx), %ebx			/* leave space for vm86 */
210	movl	%ebx, PCPU(COMMON_TSS) + TSS_ESP0
211
212	/*
213	 * Test this CPU's  bit in the bitmap to see if this
214	 * CPU was using a private TSS.
215	 */
216	btrl	%esi, private_tss		/* Already using the common? */
217	jae	3f				/* if so, skip reloading */
218	PCPU_ADDR(COMMON_TSSD, %edi)
2192:
220	/* Move correct tss descriptor into GDT slot, then reload tr. */
221	movl	PCPU(TSS_GDT), %ebx		/* entry in GDT */
222	movl	0(%edi), %eax
223	movl	%eax, 0(%ebx)
224	movl	4(%edi), %eax
225	movl	%eax, 4(%ebx)
226	movl	$GPROC0_SEL*8, %esi		/* GSEL(entry, SEL_KPL) */
227	ltr	%si
2283:
229
230	/* Restore context. */
231	movl	PCB_EBX(%edx),%ebx
232	movl	PCB_ESP(%edx),%esp
233	movl	PCB_EBP(%edx),%ebp
234	movl	PCB_ESI(%edx),%esi
235	movl	PCB_EDI(%edx),%edi
236	movl	PCB_EIP(%edx),%eax
237	movl	%eax,(%esp)
238	pushl	PCB_PSL(%edx)
239	popfl
240
241	movl	%edx, PCPU(CURPCB)
242	movl	%ecx, PCPU(CURTHREAD)		/* into next thread */
243
244	/*
245	 * Determine the LDT to use and load it if is the default one and
246	 * that is not the current one.
247	 */
248	movl	TD_PROC(%ecx),%eax
249	cmpl    $0,P_MD+MD_LDT(%eax)
250	jnz	1f
251	movl	_default_ldt,%eax
252	cmpl	PCPU(CURRENTLDT),%eax
253	je	2f
254	lldt	_default_ldt
255	movl	%eax,PCPU(CURRENTLDT)
256	jmp	2f
2571:
258	/* Load the LDT when it is not the default one. */
259	pushl	%edx				/* Preserve pointer to pcb. */
260	addl	$P_MD,%eax			/* Pointer to mdproc is arg. */
261	pushl	%eax
262	call	set_user_ldt
263	addl	$4,%esp
264	popl	%edx
2652:
266
267	/* This must be done after loading the user LDT. */
268	.globl	cpu_switch_load_gs
269cpu_switch_load_gs:
270	movl	PCB_GS(%edx),%gs
271
272	/* Test if debug registers should be restored. */
273	testl	$PCB_DBREGS,PCB_FLAGS(%edx)
274	jz      1f
275
276	/*
277	 * Restore debug registers.  The special code for dr7 is to
278	 * preserve the current values of its reserved bits.
279	 */
280	movl    PCB_DR6(%edx),%eax
281	movl    %eax,%dr6
282	movl    PCB_DR3(%edx),%eax
283	movl    %eax,%dr3
284	movl    PCB_DR2(%edx),%eax
285	movl    %eax,%dr2
286	movl    PCB_DR1(%edx),%eax
287	movl    %eax,%dr1
288	movl    PCB_DR0(%edx),%eax
289	movl    %eax,%dr0
290	movl	%dr7,%eax
291	andl    $0x0000fc00,%eax
292	movl    PCB_DR7(%edx),%ecx
293	andl	$~0x0000fc00,%ecx
294	orl     %ecx,%eax
295	movl    %eax,%dr7
2961:
297	ret
298
299#ifdef INVARIANTS
300badsw1:
301	pushal
302	pushl	$0
303	pushl	$0
304	pushl	$sw0_1
305	call	__panic
306sw0_1:	.asciz	"cpu_throw: no newthread supplied"
307
308badsw2:
309	pushal
310	pushl	$0
311	pushl	$0
312	pushl	$sw0_2
313	call	__panic
314sw0_2:	.asciz	"cpu_switch: no curthread supplied"
315
316badsw3:
317	pushal
318	pushl	$0
319	pushl	$0
320	pushl	$sw0_3
321	call	__panic
322sw0_3:	.asciz	"cpu_switch: no newthread supplied"
323#endif
324
325/*
326 * savectx(pcb)
327 * Update pcb, saving current processor state.
328 */
329ENTRY(savectx)
330	/* Fetch PCB. */
331	movl	4(%esp),%ecx
332
333	/* Save caller's return address.  Child won't execute this routine. */
334	movl	(%esp),%eax
335	movl	%eax,PCB_EIP(%ecx)
336
337	movl	%cr3,%eax
338	movl	%eax,PCB_CR3(%ecx)
339
340	movl	%ebx,PCB_EBX(%ecx)
341	movl	%esp,PCB_ESP(%ecx)
342	movl	%ebp,PCB_EBP(%ecx)
343	movl	%esi,PCB_ESI(%ecx)
344	movl	%edi,PCB_EDI(%ecx)
345	movl	%gs,PCB_GS(%ecx)
346	pushfl
347	popl	PCB_PSL(%ecx)
348
349#ifdef DEV_NPX
350	/*
351	 * If fpcurthread == NULL, then the npx h/w state is irrelevant and the
352	 * state had better already be in the pcb.  This is true for forks
353	 * but not for dumps (the old book-keeping with FP flags in the pcb
354	 * always lost for dumps because the dump pcb has 0 flags).
355	 *
356	 * If fpcurthread != NULL, then we have to save the npx h/w state to
357	 * fpcurthread's pcb and copy it to the requested pcb, or save to the
358	 * requested pcb and reload.  Copying is easier because we would
359	 * have to handle h/w bugs for reloading.  We used to lose the
360	 * parent's npx state for forks by forgetting to reload.
361	 */
362	pushfl
363	cli
364	movl	PCPU(FPCURTHREAD),%eax
365	testl	%eax,%eax
366	je	1f
367
368	pushl	%ecx
369	movl	TD_PCB(%eax),%eax
370	leal	PCB_SAVEFPU(%eax),%eax
371	pushl	%eax
372	pushl	%eax
373	call	npxsave
374	addl	$4,%esp
375	popl	%eax
376	popl	%ecx
377
378	pushl	$PCB_SAVEFPU_SIZE
379	leal	PCB_SAVEFPU(%ecx),%ecx
380	pushl	%ecx
381	pushl	%eax
382	call	bcopy
383	addl	$12,%esp
3841:
385	popfl
386#endif	/* DEV_NPX */
387
388	ret
389