xref: /netbsd-src/sys/arch/sparc/include/cpu.h (revision bdc22b2e01993381dcefeff2bc9b56ca75a4235c)
1 /*	$NetBSD: cpu.h,v 1.100 2018/01/16 08:23:17 mrg Exp $ */
2 
3 /*
4  * Copyright (c) 1992, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * This software was developed by the Computer Systems Engineering group
8  * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
9  * contributed to Berkeley.
10  *
11  * All advertising materials mentioning features or use of this software
12  * must display the following acknowledgement:
13  *	This product includes software developed by the University of
14  *	California, Lawrence Berkeley Laboratory.
15  *
16  * Redistribution and use in source and binary forms, with or without
17  * modification, are permitted provided that the following conditions
18  * are met:
19  * 1. Redistributions of source code must retain the above copyright
20  *    notice, this list of conditions and the following disclaimer.
21  * 2. Redistributions in binary form must reproduce the above copyright
22  *    notice, this list of conditions and the following disclaimer in the
23  *    documentation and/or other materials provided with the distribution.
24  * 3. Neither the name of the University nor the names of its contributors
25  *    may be used to endorse or promote products derived from this software
26  *    without specific prior written permission.
27  *
28  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38  * SUCH DAMAGE.
39  *
40  *	@(#)cpu.h	8.4 (Berkeley) 1/5/94
41  */
42 
43 #ifndef _CPU_H_
44 #define _CPU_H_
45 
46 /*
47  * CTL_MACHDEP definitions.
48  */
49 #define	CPU_BOOTED_KERNEL	1	/* string: booted kernel name */
50 #define	CPU_BOOTED_DEVICE	2	/* string: device booted from */
51 #define	CPU_BOOT_ARGS		3	/* string: args booted with */
52 #define	CPU_ARCH		4	/* integer: cpu architecture version */
53 #define	CPU_MAXID		5	/* number of valid machdep ids */
54 
55 /*
56  * Exported definitions unique to SPARC cpu support.
57  */
58 
59 /*
60  * Sun-4 and Sun-4c virtual address cache.
61  *
62  * Sun-4 virtual caches come in two flavors, write-through (Sun-4c)
63  * and write-back (Sun-4).  The write-back caches are much faster
64  * but require a bit more care.
65  *
66  * This is exported via sysctl so be careful changing it.
67  */
68 enum vactype { VAC_UNKNOWN, VAC_NONE, VAC_WRITETHROUGH, VAC_WRITEBACK };
69 
70 /*
71  * Cache control information.
72  *
73  * This is exported via sysctl so be careful changing it.
74  */
75 
76 struct cacheinfo {
77 	int	c_totalsize;		/* total size, in bytes */
78 					/* if split, MAX(icache,dcache) */
79 	int	c_enabled;		/* true => cache is enabled */
80 	int	c_hwflush;		/* true => have hardware flush */
81 	int	c_linesize;		/* line size, in bytes */
82 					/* if split, MIN(icache,dcache) */
83 	int	c_l2linesize;		/* log2(linesize) */
84 	int	c_nlines;		/* precomputed # of lines to flush */
85 	int	c_physical;		/* true => cache has physical
86 						   address tags */
87 	int 	c_associativity;	/* # of "buckets" in cache line */
88 	int 	c_split;		/* true => cache is split */
89 
90 	int 	ic_totalsize;		/* instruction cache */
91 	int 	ic_enabled;
92 	int 	ic_linesize;
93 	int 	ic_l2linesize;
94 	int 	ic_nlines;
95 	int 	ic_associativity;
96 
97 	int 	dc_totalsize;		/* data cache */
98 	int 	dc_enabled;
99 	int 	dc_linesize;
100 	int 	dc_l2linesize;
101 	int 	dc_nlines;
102 	int 	dc_associativity;
103 
104 	int	ec_totalsize;		/* external cache info */
105 	int 	ec_enabled;
106 	int	ec_linesize;
107 	int	ec_l2linesize;
108 	int 	ec_nlines;
109 	int 	ec_associativity;
110 
111 	enum vactype	c_vactype;
112 
113 	int	c_flags;
114 #define CACHE_PAGETABLES	0x1	/* caching pagetables OK on (sun4m) */
115 #define CACHE_TRAPPAGEBUG	0x2	/* trap page can't be cached (sun4) */
116 #define CACHE_MANDATORY		0x4	/* if cache is on, don't use
117 					   uncached access */
118 };
119 
120 /* Things needed by crash or the kernel */
121 #if defined(_KERNEL) || defined(_KMEMUSER)
122 
123 #if defined(_KERNEL_OPT)
124 #include "opt_multiprocessor.h"
125 #include "opt_lockdebug.h"
126 #include "opt_sparc_arch.h"
127 #endif
128 
129 #include <sys/cpu_data.h>
130 #include <sys/evcnt.h>
131 
132 #include <machine/intr.h>
133 #include <machine/psl.h>
134 
135 #if defined(_KERNEL)
136 #include <sparc/sparc/cpuvar.h>
137 #include <sparc/sparc/intreg.h>
138 #endif
139 
140 struct trapframe;
141 
142 /*
143  * Message structure for Inter Processor Communication in MP systems
144  */
145 struct xpmsg {
146 	volatile int tag;
147 #define	XPMSG15_PAUSECPU	1
148 #define	XPMSG_FUNC		4
149 #define	XPMSG_FTRP		5
150 
151 	volatile union {
152 		/*
153 		 * Cross call: ask to run (*func)(arg0,arg1,arg2)
154 		 * or (*trap)(arg0,arg1,arg2). `trap' should be the
155 		 * address of a `fast trap' handler that executes in
156 		 * the trap window (see locore.s).
157 		 */
158 		struct xpmsg_func {
159 			void	(*func)(int, int, int);
160 			void	(*trap)(int, int, int);
161 			int	arg0;
162 			int	arg1;
163 			int	arg2;
164 		} xpmsg_func;
165 	} u;
166 	volatile int	received;
167 	volatile int	complete;
168 };
169 
170 /*
171  * The cpuinfo structure. This structure maintains information about one
172  * currently installed CPU (there may be several of these if the machine
173  * supports multiple CPUs, as on some Sun4m architectures). The information
174  * in this structure supersedes the old "cpumod", "mmumod", and similar
175  * fields.
176  */
177 
178 struct cpu_info {
179 	struct cpu_data ci_data;	/* MI per-cpu data */
180 
181 	/*
182 	 * Primary Inter-processor message area.  Keep this aligned
183 	 * to a cache line boundary if possible, as the structure
184 	 * itself is one or less (32/64 byte) cache-line.
185 	 */
186 	struct xpmsg	msg __aligned(64);
187 
188 	/* Scheduler flags */
189 	int	ci_want_ast;
190 	int	ci_want_resched;
191 
192 	/*
193 	 * SPARC cpu_info structures live at two VAs: one global
194 	 * VA (so each CPU can access any other CPU's cpu_info)
195 	 * and an alias VA CPUINFO_VA which is the same on each
196 	 * CPU and maps to that CPU's cpu_info.  Since the alias
197 	 * CPUINFO_VA is how we locate our cpu_info, we have to
198 	 * self-reference the global VA so that we can return it
199 	 * in the curcpu() macro.
200 	 */
201 	struct cpu_info * volatile ci_self;
202 
203 	int		ci_cpuid;	/* CPU index (see cpus[] array) */
204 
205 	/* Context administration */
206 	int		*ctx_tbl;	/* [4m] SRMMU-edible context table */
207 	paddr_t		ctx_tbl_pa;	/* [4m] ctx table physical address */
208 
209 	/* Cache information */
210 	struct cacheinfo	cacheinfo;	/* see above */
211 
212 	/* various flags to workaround anomalies in chips */
213 	volatile int	flags;		/* see CPUFLG_xxx, below */
214 
215 	/* Per processor counter register (sun4m only) */
216 	volatile struct counter_4m	*counterreg_4m;
217 
218 	/* Per processor interrupt mask register (sun4m only) */
219 	volatile struct icr_pi	*intreg_4m;
220 	/*
221 	 * Send a IPI to (cpi).  For Ross cpus we need to read
222 	 * the pending register to avoid a hardware bug.
223 	 */
224 #define raise_ipi(cpi,lvl)	do {			\
225 	volatile int x;						\
226 	(cpi)->intreg_4m->pi_set = PINTR_SINTRLEV(lvl);	\
227 	x = (cpi)->intreg_4m->pi_pend; __USE(x);	\
228 } while (0)
229 
230 	int		sun4_mmu3l;	/* [4]: 3-level MMU present */
231 #if defined(SUN4_MMU3L)
232 #define HASSUN4_MMU3L	(cpuinfo.sun4_mmu3l)
233 #else
234 #define HASSUN4_MMU3L	(0)
235 #endif
236 	int		ci_idepth;		/* Interrupt depth */
237 
238 	/*
239 	 * The following pointers point to processes that are somehow
240 	 * associated with this CPU--running on it, using its FPU,
241 	 * etc.
242 	 */
243 	struct	lwp	*ci_curlwp;		/* CPU owner */
244 	struct	lwp 	*fplwp;			/* FPU owner */
245 
246 	int		ci_mtx_count;
247 	int		ci_mtx_oldspl;
248 
249 	/*
250 	 * Idle PCB and Interrupt stack;
251 	 */
252 	void		*eintstack;		/* End of interrupt stack */
253 #define INT_STACK_SIZE	(128 * 128)		/* 128 128-byte stack frames */
254 	void		*redzone;		/* DEBUG: stack red zone */
255 #define REDSIZE		(8*96)			/* some room for bouncing */
256 
257 	struct	pcb	*curpcb;		/* CPU's PCB & kernel stack */
258 
259 	/* locore defined: */
260 	void	(*get_syncflt)(void);		/* Not C-callable */
261 	int	(*get_asyncflt)(u_int *, u_int *);
262 
263 	/* Synchronous Fault Status; temporary storage */
264 	struct {
265 		int	sfsr;
266 		int	sfva;
267 	} syncfltdump;
268 
269 	/*
270 	 * Cache handling functions.
271 	 * Most cache flush function come in two flavours: one that
272 	 * acts only on the CPU it executes on, and another that
273 	 * uses inter-processor signals to flush the cache on
274 	 * all processor modules.
275 	 * The `ft_' versions are fast trap cache flush handlers.
276 	 */
277 	void	(*cache_flush)(void *, u_int);
278 	void	(*vcache_flush_page)(int, int);
279 	void	(*sp_vcache_flush_page)(int, int);
280 	void	(*ft_vcache_flush_page)(int, int);
281 	void	(*vcache_flush_segment)(int, int, int);
282 	void	(*sp_vcache_flush_segment)(int, int, int);
283 	void	(*ft_vcache_flush_segment)(int, int, int);
284 	void	(*vcache_flush_region)(int, int);
285 	void	(*sp_vcache_flush_region)(int, int);
286 	void	(*ft_vcache_flush_region)(int, int);
287 	void	(*vcache_flush_context)(int);
288 	void	(*sp_vcache_flush_context)(int);
289 	void	(*ft_vcache_flush_context)(int);
290 
291 	/* The are helpers for (*cache_flush)() */
292 	void	(*sp_vcache_flush_range)(int, int, int);
293 	void	(*ft_vcache_flush_range)(int, int, int);
294 
295 	void	(*pcache_flush_page)(paddr_t, int);
296 	void	(*pure_vcache_flush)(void);
297 	void	(*cache_flush_all)(void);
298 
299 	/* Support for hardware-assisted page clear/copy */
300 	void	(*zero_page)(paddr_t);
301 	void	(*copy_page)(paddr_t, paddr_t);
302 
303 	/* Virtual addresses for use in pmap copy_page/zero_page */
304 	void *	vpage[2];
305 	int	*vpage_pte[2];		/* pte location of vpage[] */
306 
307 	void	(*cache_enable)(void);
308 
309 	int	cpu_type;	/* Type: see CPUTYP_xxx below */
310 
311 	/* Inter-processor message area (high priority but used infrequently) */
312 	struct xpmsg	msg_lev15;
313 
314 	/* CPU information */
315 	int		node;		/* PROM node for this CPU */
316 	int		mid;		/* Module ID for MP systems */
317 	int		mbus;		/* 1 if CPU is on MBus */
318 	int		mxcc;		/* 1 if a MBus-level MXCC is present */
319 	const char	*cpu_longname;	/* CPU model */
320 	int		cpu_impl;	/* CPU implementation code */
321 	int		cpu_vers;	/* CPU version code */
322 	int		mmu_impl;	/* MMU implementation code */
323 	int		mmu_vers;	/* MMU version code */
324 	int		master;		/* 1 if this is bootup CPU */
325 
326 	vaddr_t		mailbox;	/* VA of CPU's mailbox */
327 
328 	int		mmu_ncontext;	/* Number of contexts supported */
329 	int		mmu_nregion; 	/* Number of regions supported */
330 	int		mmu_nsegment;	/* [4/4c] Segments */
331 	int		mmu_npmeg;	/* [4/4c] Pmegs */
332 
333 /* XXX - we currently don't actually use the following */
334 	int		arch;		/* Architecture: CPU_SUN4x */
335 	int		class;		/* Class: SuperSPARC, microSPARC... */
336 	int		classlvl;	/* Iteration in class: 1, 2, etc. */
337 	int		classsublvl;	/* stepping in class (version) */
338 
339 	int		hz;		/* Clock speed */
340 
341 	/* FPU information */
342 	int		fpupresent;	/* true if FPU is present */
343 	int		fpuvers;	/* FPU revision */
344 	const char	*fpu_name;	/* FPU model */
345 	char		fpu_namebuf[32];/* Buffer for FPU name, if necessary */
346 
347 	/* XXX */
348 	volatile void	*ci_ddb_regs;		/* DDB regs */
349 
350 	/*
351 	 * The following are function pointers to do interesting CPU-dependent
352 	 * things without having to do type-tests all the time
353 	 */
354 
355 	/* bootup things: access to physical memory */
356 	u_int	(*read_physmem)(u_int addr, int space);
357 	void	(*write_physmem)(u_int addr, u_int data);
358 	void	(*cache_tablewalks)(void);
359 	void	(*mmu_enable)(void);
360 	void	(*hotfix)(struct cpu_info *);
361 
362 
363 #if 0
364 	/* hardware-assisted block operation routines */
365 	void		(*hwbcopy)(const void *from, void *to, size_t len);
366 	void		(*hwbzero)(void *buf, size_t len);
367 
368 	/* routine to clear mbus-sbus buffers */
369 	void		(*mbusflush)(void);
370 #endif
371 
372 	/*
373 	 * Memory error handler; parity errors, unhandled NMIs and other
374 	 * unrecoverable faults end up here.
375 	 */
376 	void		(*memerr)(unsigned, u_int, u_int, struct trapframe *);
377 	void		(*idlespin)(struct cpu_info *);
378 	/* Module Control Registers */
379 	/*bus_space_handle_t*/ long ci_mbusport;
380 	/*bus_space_handle_t*/ long ci_mxccregs;
381 
382 	u_int	ci_tt;			/* Last trap (if tracing) */
383 
384 	/*
385 	 * Start/End VA's of this cpu_info region; we upload the other pages
386 	 * in this region that aren't part of the cpu_info to uvm.
387 	 */
388 	vaddr_t	ci_free_sva1, ci_free_eva1, ci_free_sva2, ci_free_eva2;
389 
390 	struct evcnt ci_savefpstate;
391 	struct evcnt ci_savefpstate_null;
392 	struct evcnt ci_xpmsg_mutex_fail;
393 	struct evcnt ci_xpmsg_mutex_fail_call;
394 	struct evcnt ci_xpmsg_mutex_not_held;
395 	struct evcnt ci_xpmsg_bogus;
396 	struct evcnt ci_intrcnt[16];
397 	struct evcnt ci_sintrcnt[16];
398 };
399 
400 /*
401  * definitions of cpu-dependent requirements
402  * referenced in generic code
403  */
404 #define	cpuinfo			(*(struct cpu_info *)CPUINFO_VA)
405 #define	curcpu()		(cpuinfo.ci_self)
406 #define	curlwp			(cpuinfo.ci_curlwp)
407 #define	CPU_IS_PRIMARY(ci)	((ci)->master)
408 
409 #define	cpu_number()		(cpuinfo.ci_cpuid)
410 
411 #endif /* _KERNEL || _KMEMUSER */
412 
413 /* Kernel only things. */
414 #if defined(_KERNEL)
415 void	cpu_proc_fork(struct proc *, struct proc *);
416 
417 #if defined(MULTIPROCESSOR)
418 void	cpu_boot_secondary_processors(void);
419 #endif
420 
421 /*
422  * Arguments to hardclock, softclock and statclock encapsulate the
423  * previous machine state in an opaque clockframe.  The ipl is here
424  * as well for strayintr (see locore.s:interrupt and intr.c:strayintr).
425  * Note that CLKF_INTR is valid only if CLKF_USERMODE is false.
426  */
427 struct clockframe {
428 	u_int	psr;		/* psr before interrupt, excluding PSR_ET */
429 	u_int	pc;		/* pc at interrupt */
430 	u_int	npc;		/* npc at interrupt */
431 	u_int	ipl;		/* actual interrupt priority level */
432 	u_int	fp;		/* %fp at interrupt */
433 };
434 typedef struct clockframe clockframe;
435 
436 extern int eintstack[];
437 
438 #define	CLKF_USERMODE(framep)	(((framep)->psr & PSR_PS) == 0)
439 #define	CLKF_LOPRI(framep,n)	(((framep)->psr & PSR_PIL) < (n) << 8)
440 #define	CLKF_PC(framep)		((framep)->pc)
441 #if defined(MULTIPROCESSOR)
442 #define	CLKF_INTR(framep)						\
443 	((framep)->fp > (u_int)cpuinfo.eintstack - INT_STACK_SIZE &&	\
444 	 (framep)->fp < (u_int)cpuinfo.eintstack)
445 #else
446 #define	CLKF_INTR(framep)	((framep)->fp < (u_int)eintstack)
447 #endif
448 
449 void	sparc_softintr_init(void);
450 
451 /*
452  * Preempt the current process on the target CPU if in interrupt from
453  * user mode, or after the current trap/syscall if in system mode.
454  */
455 #define cpu_need_resched(ci, flags) do {				\
456 	__USE(flags);							\
457 	(ci)->ci_want_resched = 1;					\
458 	(ci)->ci_want_ast = 1;						\
459 									\
460 	/* Just interrupt the target CPU, so it can notice its AST */	\
461 	if (((flags) & RESCHED_IMMED) || (ci)->ci_cpuid != cpu_number()) \
462 		XCALL0(sparc_noop, 1U << (ci)->ci_cpuid);		\
463 } while (/*CONSTCOND*/0)
464 
465 /*
466  * Give a profiling tick to the current process when the user profiling
467  * buffer pages are invalid.  On the sparc, request an ast to send us
468  * through trap(), marking the proc as needing a profiling tick.
469  */
470 #define	cpu_need_proftick(l)	((l)->l_pflag |= LP_OWEUPC, cpuinfo.ci_want_ast = 1)
471 
472 /*
473  * Notify the current process (p) that it has a signal pending,
474  * process as soon as possible.
475  */
476 #define cpu_signotify(l) do {						\
477 	(l)->l_cpu->ci_want_ast = 1;					\
478 									\
479 	/* Just interrupt the target CPU, so it can notice its AST */	\
480 	if ((l)->l_cpu->ci_cpuid != cpu_number())			\
481 		XCALL0(sparc_noop, 1U << (l)->l_cpu->ci_cpuid);		\
482 } while (/*CONSTCOND*/0)
483 
484 /* CPU architecture version */
485 extern int cpu_arch;
486 
487 /* Number of CPUs in the system */
488 extern int sparc_ncpus;
489 
490 /* Provide %pc of a lwp */
491 #define LWP_PC(l)       ((l)->l_md.md_tf->tf_pc)
492 
493 /*
494  * Interrupt handler chains.  Interrupt handlers should return 0 for
495  * ``not me'' or 1 (``I took care of it'').  intr_establish() inserts a
496  * handler into the list.  The handler is called with its (single)
497  * argument, or with a pointer to a clockframe if ih_arg is NULL.
498  *
499  * realfun/realarg are used to chain callers, usually with the
500  * biglock wrapper.
501  */
502 extern struct intrhand {
503 	int	(*ih_fun)(void *);
504 	void	*ih_arg;
505 	struct	intrhand *ih_next;
506 	int	ih_classipl;
507 	int	(*ih_realfun)(void *);
508 	void	*ih_realarg;
509 } *intrhand[15];
510 
511 void	intr_establish(int, int, struct intrhand *, void (*)(void), bool);
512 void	intr_disestablish(int, struct intrhand *);
513 
514 void	intr_lock_kernel(void);
515 void	intr_unlock_kernel(void);
516 
517 /* disksubr.c */
518 struct dkbad;
519 int isbad(struct dkbad *, int, int, int);
520 
521 /* machdep.c */
522 int	ldcontrolb(void *);
523 void *	reserve_dumppages(void *);
524 void	wcopy(const void *, void *, u_int);
525 void	wzero(void *, u_int);
526 
527 /* clock.c */
528 struct timeval;
529 void	lo_microtime(struct timeval *);
530 void	schedintr(void *);
531 
532 /* locore.s */
533 struct fpstate;
534 void	ipi_savefpstate(struct fpstate *);
535 void	savefpstate(struct fpstate *);
536 void	loadfpstate(struct fpstate *);
537 int	probeget(void *, int);
538 void	write_all_windows(void);
539 void	write_user_windows(void);
540 void 	lwp_trampoline(void);
541 struct pcb;
542 void	snapshot(struct pcb *);
543 struct frame *getfp(void);
544 int	xldcontrolb(void *, struct pcb *);
545 void	copywords(const void *, void *, size_t);
546 void	qcopy(const void *, void *, size_t);
547 void	qzero(void *, size_t);
548 
549 /* trap.c */
550 void	cpu_vmspace_exec(struct lwp *, vaddr_t, vaddr_t);
551 int	rwindow_save(struct lwp *);
552 
553 /* cons.c */
554 int	cnrom(void);
555 
556 /* zs.c */
557 void zsconsole(struct tty *, int, int, void (**)(struct tty *, int));
558 #ifdef KGDB
559 void zs_kgdb_init(void);
560 #endif
561 
562 /* fb.c */
563 void	fb_unblank(void);
564 
565 /* kgdb_stub.c */
566 #ifdef KGDB
567 void kgdb_attach(int (*)(void *), void (*)(void *, int), void *);
568 void kgdb_connect(int);
569 void kgdb_panic(void);
570 #endif
571 
572 /* emul.c */
573 struct trapframe;
574 int fixalign(struct lwp *, struct trapframe *, void **);
575 int emulinstr(int, struct trapframe *);
576 
577 /* cpu.c */
578 void mp_pause_cpus(void);
579 void mp_resume_cpus(void);
580 void mp_halt_cpus(void);
581 #ifdef DDB
582 void mp_pause_cpus_ddb(void);
583 void mp_resume_cpus_ddb(void);
584 #endif
585 
586 /* intr.c */
587 u_int setitr(u_int);
588 u_int getitr(void);
589 
590 
591 /*
592  *
593  * The SPARC has a Trap Base Register (TBR) which holds the upper 20 bits
594  * of the trap vector table.  The next eight bits are supplied by the
595  * hardware when the trap occurs, and the bottom four bits are always
596  * zero (so that we can shove up to 16 bytes of executable code---exactly
597  * four instructions---into each trap vector).
598  *
599  * The hardware allocates half the trap vectors to hardware and half to
600  * software.
601  *
602  * Traps have priorities assigned (lower number => higher priority).
603  */
604 
605 struct trapvec {
606 	int	tv_instr[4];		/* the four instructions */
607 };
608 
609 extern struct trapvec *trapbase;	/* the 256 vectors */
610 
611 #endif /* _KERNEL */
612 #endif /* _CPU_H_ */
613