xref: /netbsd-src/sys/arch/sparc/include/cpu.h (revision 627f7eb200a4419d89b531d55fccd2ee3ffdcde0)
1 /*	$NetBSD: cpu.h,v 1.109 2021/01/24 07:36:54 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 
54 /*
55  * Exported definitions unique to SPARC cpu support.
56  */
57 
58 /*
59  * Sun-4 and Sun-4c virtual address cache.
60  *
61  * Sun-4 virtual caches come in two flavors, write-through (Sun-4c)
62  * and write-back (Sun-4).  The write-back caches are much faster
63  * but require a bit more care.
64  *
65  * This is exported via sysctl so be careful changing it.
66  */
67 enum vactype { VAC_UNKNOWN, VAC_NONE, VAC_WRITETHROUGH, VAC_WRITEBACK };
68 
69 /*
70  * Cache control information.
71  *
72  * This is exported via sysctl so be careful changing it.
73  */
74 
75 struct cacheinfo {
76 	int	c_totalsize;		/* total size, in bytes */
77 					/* if split, MAX(icache,dcache) */
78 	int	c_enabled;		/* true => cache is enabled */
79 	int	c_hwflush;		/* true => have hardware flush */
80 	int	c_linesize;		/* line size, in bytes */
81 					/* if split, MIN(icache,dcache) */
82 	int	c_l2linesize;		/* log2(linesize) */
83 	int	c_nlines;		/* precomputed # of lines to flush */
84 	int	c_physical;		/* true => cache has physical
85 						   address tags */
86 	int 	c_associativity;	/* # of "buckets" in cache line */
87 	int 	c_split;		/* true => cache is split */
88 
89 	int 	ic_totalsize;		/* instruction cache */
90 	int 	ic_enabled;
91 	int 	ic_linesize;
92 	int 	ic_l2linesize;
93 	int 	ic_nlines;
94 	int 	ic_associativity;
95 
96 	int 	dc_totalsize;		/* data cache */
97 	int 	dc_enabled;
98 	int 	dc_linesize;
99 	int 	dc_l2linesize;
100 	int 	dc_nlines;
101 	int 	dc_associativity;
102 
103 	int	ec_totalsize;		/* external cache info */
104 	int 	ec_enabled;
105 	int	ec_linesize;
106 	int	ec_l2linesize;
107 	int 	ec_nlines;
108 	int 	ec_associativity;
109 
110 	enum vactype	c_vactype;
111 
112 	int	c_flags;
113 #define CACHE_PAGETABLES	0x1	/* caching pagetables OK on (sun4m) */
114 #define CACHE_TRAPPAGEBUG	0x2	/* trap page can't be cached (sun4) */
115 #define CACHE_MANDATORY		0x4	/* if cache is on, don't use
116 					   uncached access */
117 };
118 
119 /* Things needed by crash or the kernel */
120 #if defined(_KERNEL) || defined(_KMEMUSER)
121 
122 #if defined(_KERNEL_OPT)
123 #include "opt_multiprocessor.h"
124 #include "opt_lockdebug.h"
125 #include "opt_sparc_arch.h"
126 #endif
127 
128 #include <sys/cpu_data.h>
129 #include <sys/evcnt.h>
130 
131 #include <machine/intr.h>
132 #include <machine/psl.h>
133 
134 #if defined(_KERNEL)
135 #include <sparc/sparc/cpuvar.h>
136 #include <sparc/sparc/intreg.h>
137 #endif
138 
139 struct trapframe;
140 
141 /*
142  * Message structure for Inter Processor Communication in MP systems
143  */
144 struct xpmsg {
145 	volatile int tag;
146 #define	XPMSG15_PAUSECPU	1
147 #define	XPMSG_FUNC		4
148 #define	XPMSG_FTRP		5
149 
150 	volatile union {
151 		/*
152 		 * Cross call: ask to run (*func)(arg0,arg1,arg2)
153 		 * or (*trap)(arg0,arg1,arg2). `trap' should be the
154 		 * address of a `fast trap' handler that executes in
155 		 * the trap window (see locore.s).
156 		 */
157 		struct xpmsg_func {
158 			void	(*func)(int, int, int);
159 			void	(*trap)(int, int, int);
160 			int	arg0;
161 			int	arg1;
162 			int	arg2;
163 		} xpmsg_func;
164 	} u;
165 	volatile int	received;
166 	volatile int	complete;
167 };
168 
169 /*
170  * The cpuinfo structure. This structure maintains information about one
171  * currently installed CPU (there may be several of these if the machine
172  * supports multiple CPUs, as on some Sun4m architectures). The information
173  * in this structure supersedes the old "cpumod", "mmumod", and similar
174  * fields.
175  */
176 
177 struct cpu_info {
178 	/*
179 	 * Primary Inter-processor message area.  Keep this aligned
180 	 * to a cache line boundary if possible, as the structure
181 	 * itself is one or less (32/64 byte) cache-line.
182 	 */
183 	struct xpmsg	msg __aligned(64);
184 
185 	/* Scheduler flags */
186 	int	ci_want_ast;
187 	int	ci_want_resched;
188 
189 	/*
190 	 * SPARC cpu_info structures live at two VAs: one global
191 	 * VA (so each CPU can access any other CPU's cpu_info)
192 	 * and an alias VA CPUINFO_VA which is the same on each
193 	 * CPU and maps to that CPU's cpu_info.  Since the alias
194 	 * CPUINFO_VA is how we locate our cpu_info, we have to
195 	 * self-reference the global VA so that we can return it
196 	 * in the curcpu() macro.
197 	 */
198 	struct cpu_info * volatile ci_self;
199 
200 	int		ci_cpuid;	/* CPU index (see cpus[] array) */
201 
202 	/* Context administration */
203 	int		*ctx_tbl;	/* [4m] SRMMU-edible context table */
204 	paddr_t		ctx_tbl_pa;	/* [4m] ctx table physical address */
205 
206 	/* Cache information */
207 	struct cacheinfo	cacheinfo;	/* see above */
208 
209 	/* various flags to workaround anomalies in chips */
210 	volatile int	flags;		/* see CPUFLG_xxx, below */
211 
212 	/* Per processor counter register (sun4m only) */
213 	volatile struct counter_4m	*counterreg_4m;
214 
215 	/* Per processor interrupt mask register (sun4m only) */
216 	volatile struct icr_pi	*intreg_4m;
217 	/*
218 	 * Send a IPI to (cpi).  For Ross cpus we need to read
219 	 * the pending register to avoid a hardware bug.
220 	 */
221 #define raise_ipi(cpi,lvl)	do {			\
222 	volatile int x;						\
223 	(cpi)->intreg_4m->pi_set = PINTR_SINTRLEV(lvl);	\
224 	x = (cpi)->intreg_4m->pi_pend; __USE(x);	\
225 } while (0)
226 
227 	int		sun4_mmu3l;	/* [4]: 3-level MMU present */
228 #if defined(SUN4_MMU3L)
229 #define HASSUN4_MMU3L	(cpuinfo.sun4_mmu3l)
230 #else
231 #define HASSUN4_MMU3L	(0)
232 #endif
233 	int		ci_idepth;		/* Interrupt depth */
234 
235 	/*
236 	 * The following pointers point to processes that are somehow
237 	 * associated with this CPU--running on it, using its FPU,
238 	 * etc.
239 	 */
240 	struct	lwp	*ci_curlwp;		/* CPU owner */
241 	struct	lwp	*ci_onproc;		/* current user LWP / kthread */
242 	struct	lwp 	*fplwp;			/* FPU owner */
243 
244 	int		ci_mtx_count;
245 	int		ci_mtx_oldspl;
246 
247 	/*
248 	 * Idle PCB and Interrupt stack;
249 	 */
250 	void		*eintstack;		/* End of interrupt stack */
251 #define INT_STACK_SIZE	(128 * 128)		/* 128 128-byte stack frames */
252 	void		*redzone;		/* DEBUG: stack red zone */
253 #define REDSIZE		(8*96)			/* some room for bouncing */
254 
255 	struct	pcb	*curpcb;		/* CPU's PCB & kernel stack */
256 
257 	/* locore defined: */
258 	void	(*get_syncflt)(void);		/* Not C-callable */
259 	int	(*get_asyncflt)(u_int *, u_int *);
260 
261 	/* Synchronous Fault Status; temporary storage */
262 	struct {
263 		int	sfsr;
264 		int	sfva;
265 	} syncfltdump;
266 
267 	/*
268 	 * Cache handling functions.
269 	 * Most cache flush function come in two flavours: one that
270 	 * acts only on the CPU it executes on, and another that
271 	 * uses inter-processor signals to flush the cache on
272 	 * all processor modules.
273 	 * The `ft_' versions are fast trap cache flush handlers.
274 	 */
275 	void	(*cache_flush)(void *, u_int);
276 	void	(*vcache_flush_page)(int, int);
277 	void	(*sp_vcache_flush_page)(int, int);
278 	void	(*ft_vcache_flush_page)(int, int);
279 	void	(*vcache_flush_segment)(int, int, int);
280 	void	(*sp_vcache_flush_segment)(int, int, int);
281 	void	(*ft_vcache_flush_segment)(int, int, int);
282 	void	(*vcache_flush_region)(int, int);
283 	void	(*sp_vcache_flush_region)(int, int);
284 	void	(*ft_vcache_flush_region)(int, int);
285 	void	(*vcache_flush_context)(int);
286 	void	(*sp_vcache_flush_context)(int);
287 	void	(*ft_vcache_flush_context)(int);
288 
289 	/* The are helpers for (*cache_flush)() */
290 	void	(*sp_vcache_flush_range)(int, int, int);
291 	void	(*ft_vcache_flush_range)(int, int, int);
292 
293 	void	(*pcache_flush_page)(paddr_t, int);
294 	void	(*pure_vcache_flush)(void);
295 	void	(*cache_flush_all)(void);
296 
297 	/* Support for hardware-assisted page clear/copy */
298 	void	(*zero_page)(paddr_t);
299 	void	(*copy_page)(paddr_t, paddr_t);
300 
301 	/* Virtual addresses for use in pmap copy_page/zero_page */
302 	void *	vpage[2];
303 	int	*vpage_pte[2];		/* pte location of vpage[] */
304 
305 	void	(*cache_enable)(void);
306 
307 	int	cpu_type;	/* Type: see CPUTYP_xxx below */
308 
309 	/* Inter-processor message area (high priority but used infrequently) */
310 	struct xpmsg	msg_lev15;
311 
312 	/* CPU information */
313 	int		node;		/* PROM node for this CPU */
314 	int		mid;		/* Module ID for MP systems */
315 	int		mbus;		/* 1 if CPU is on MBus */
316 	int		mxcc;		/* 1 if a MBus-level MXCC is present */
317 	const char	*cpu_longname;	/* CPU model */
318 	int		cpu_impl;	/* CPU implementation code */
319 	int		cpu_vers;	/* CPU version code */
320 	int		mmu_impl;	/* MMU implementation code */
321 	int		mmu_vers;	/* MMU version code */
322 	int		master;		/* 1 if this is bootup CPU */
323 
324 	vaddr_t		mailbox;	/* VA of CPU's mailbox */
325 
326 	int		mmu_ncontext;	/* Number of contexts supported */
327 	int		mmu_nregion; 	/* Number of regions supported */
328 	int		mmu_nsegment;	/* [4/4c] Segments */
329 	int		mmu_npmeg;	/* [4/4c] Pmegs */
330 
331 /* XXX - we currently don't actually use the following */
332 	int		arch;		/* Architecture: CPU_SUN4x */
333 	int		class;		/* Class: SuperSPARC, microSPARC... */
334 	int		classlvl;	/* Iteration in class: 1, 2, etc. */
335 	int		classsublvl;	/* stepping in class (version) */
336 
337 	int		hz;		/* Clock speed */
338 
339 	/* FPU information */
340 	int		fpupresent;	/* true if FPU is present */
341 	int		fpuvers;	/* FPU revision */
342 	const char	*fpu_name;	/* FPU model */
343 	char		fpu_namebuf[32];/* Buffer for FPU name, if necessary */
344 
345 	/* XXX */
346 	volatile void	*ci_ddb_regs;		/* DDB regs */
347 
348 	/*
349 	 * The following are function pointers to do interesting CPU-dependent
350 	 * things without having to do type-tests all the time
351 	 */
352 
353 	/* bootup things: access to physical memory */
354 	u_int	(*read_physmem)(u_int addr, int space);
355 	void	(*write_physmem)(u_int addr, u_int data);
356 	void	(*cache_tablewalks)(void);
357 	void	(*mmu_enable)(void);
358 	void	(*hotfix)(struct cpu_info *);
359 
360 
361 #if 0
362 	/* hardware-assisted block operation routines */
363 	void		(*hwbcopy)(const void *from, void *to, size_t len);
364 	void		(*hwbzero)(void *buf, size_t len);
365 
366 	/* routine to clear mbus-sbus buffers */
367 	void		(*mbusflush)(void);
368 #endif
369 
370 	/*
371 	 * Memory error handler; parity errors, unhandled NMIs and other
372 	 * unrecoverable faults end up here.
373 	 */
374 	void		(*memerr)(unsigned, u_int, u_int, struct trapframe *);
375 	void		(*idlespin)(void);
376 	/* Module Control Registers */
377 	/*bus_space_handle_t*/ long ci_mbusport;
378 	/*bus_space_handle_t*/ long ci_mxccregs;
379 
380 	u_int	ci_tt;			/* Last trap (if tracing) */
381 
382 	/*
383 	 * Start/End VA's of this cpu_info region; we upload the other pages
384 	 * in this region that aren't part of the cpu_info to uvm.
385 	 */
386 	vaddr_t	ci_free_sva1, ci_free_eva1, ci_free_sva2, ci_free_eva2;
387 
388 	struct evcnt ci_savefpstate;
389 	struct evcnt ci_savefpstate_null;
390 	struct evcnt ci_xpmsg_mutex_fail;
391 	struct evcnt ci_xpmsg_mutex_fail_call;
392 	struct evcnt ci_xpmsg_mutex_not_held;
393 	struct evcnt ci_xpmsg_bogus;
394 	struct evcnt ci_intrcnt[16];
395 	struct evcnt ci_sintrcnt[16];
396 
397 	struct cpu_data ci_data;	/* MI per-cpu data */
398 };
399 
400 #endif /* _KERNEL || _KMEMUSER */
401 
402 /* Kernel only things. */
403 #if defined(_KERNEL)
404 
405 /*
406  * definitions of cpu-dependent requirements
407  * referenced in generic code
408  */
409 #define	cpuinfo			(*(struct cpu_info *)CPUINFO_VA)
410 #define	curcpu()		(cpuinfo.ci_self)
411 #define	curlwp			(cpuinfo.ci_curlwp)
412 #define	CPU_IS_PRIMARY(ci)	((ci)->master)
413 
414 #define	cpu_number()		(cpuinfo.ci_cpuid)
415 
416 void	cpu_proc_fork(struct proc *, struct proc *);
417 
418 #if defined(MULTIPROCESSOR)
419 void	cpu_boot_secondary_processors(void);
420 #endif
421 
422 /*
423  * Arguments to hardclock, softclock and statclock encapsulate the
424  * previous machine state in an opaque clockframe.  The ipl is here
425  * as well for strayintr (see locore.s:interrupt and intr.c:strayintr).
426  * Note that CLKF_INTR is valid only if CLKF_USERMODE is false.
427  */
428 struct clockframe {
429 	u_int	psr;		/* psr before interrupt, excluding PSR_ET */
430 	u_int	pc;		/* pc at interrupt */
431 	u_int	npc;		/* npc at interrupt */
432 	u_int	ipl;		/* actual interrupt priority level */
433 	u_int	fp;		/* %fp at interrupt */
434 };
435 typedef struct clockframe clockframe;
436 
437 extern int eintstack[];
438 
439 #define	CLKF_USERMODE(framep)	(((framep)->psr & PSR_PS) == 0)
440 #define	CLKF_LOPRI(framep,n)	(((framep)->psr & PSR_PIL) < (n) << 8)
441 #define	CLKF_PC(framep)		((framep)->pc)
442 #if defined(MULTIPROCESSOR)
443 #define	CLKF_INTR(framep)						\
444 	((framep)->fp > (u_int)cpuinfo.eintstack - INT_STACK_SIZE &&	\
445 	 (framep)->fp < (u_int)cpuinfo.eintstack)
446 #else
447 #define	CLKF_INTR(framep)	((framep)->fp < (u_int)eintstack)
448 #endif
449 
450 void	sparc_softintr_init(void);
451 
452 /*
453  * Preempt the current process on the target CPU if in interrupt from
454  * user mode, or after the current trap/syscall if in system mode.
455  */
456 #define cpu_need_resched(ci, l, flags) do {				\
457 	__USE(flags);							\
458 	(ci)->ci_want_ast = 1;						\
459 									\
460 	/* Just interrupt the target CPU, so it can notice its AST */	\
461 	if ((flags & RESCHED_REMOTE) != 0)				\
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 /* Hardware cross-call mutex */
494 extern kmutex_t xpmsg_mutex;
495 
496 /*
497  * Interrupt handler chains.  Interrupt handlers should return 0 for
498  * ``not me'' or 1 (``I took care of it'').  intr_establish() inserts a
499  * handler into the list.  The handler is called with its (single)
500  * argument, or with a pointer to a clockframe if ih_arg is NULL.
501  *
502  * realfun/realarg are used to chain callers, usually with the
503  * biglock wrapper.
504  */
505 extern struct intrhand {
506 	int	(*ih_fun)(void *);
507 	void	*ih_arg;
508 	struct	intrhand *ih_next;
509 	int	ih_classipl;
510 	int	(*ih_realfun)(void *);
511 	void	*ih_realarg;
512 } *intrhand[15];
513 
514 void	intr_establish(int, int, struct intrhand *, void (*)(void), bool);
515 void	intr_disestablish(int, struct intrhand *);
516 
517 void	intr_lock_kernel(void);
518 void	intr_unlock_kernel(void);
519 
520 /* disksubr.c */
521 struct dkbad;
522 int isbad(struct dkbad *, int, int, int);
523 
524 /* machdep.c */
525 int	ldcontrolb(void *);
526 void *	reserve_dumppages(void *);
527 void	wcopy(const void *, void *, u_int);
528 void	wzero(void *, u_int);
529 
530 /* clock.c */
531 struct timeval;
532 void	lo_microtime(struct timeval *);
533 void	schedintr(void *);
534 
535 /* locore.s */
536 struct fpstate;
537 void	ipi_savefpstate(struct fpstate *);
538 void	savefpstate(struct fpstate *);
539 void	loadfpstate(struct fpstate *);
540 int	probeget(void *, int);
541 void	write_all_windows(void);
542 void	write_user_windows(void);
543 void 	lwp_trampoline(void);
544 struct pcb;
545 void	snapshot(struct pcb *);
546 struct frame *getfp(void);
547 int	xldcontrolb(void *, struct pcb *);
548 void	copywords(const void *, void *, size_t);
549 void	qcopy(const void *, void *, size_t);
550 void	qzero(void *, size_t);
551 
552 /* trap.c */
553 void	cpu_vmspace_exec(struct lwp *, vaddr_t, vaddr_t);
554 int	rwindow_save(struct lwp *);
555 
556 /* cons.c */
557 int	cnrom(void);
558 
559 /* zs.c */
560 void zsconsole(struct tty *, int, int, void (**)(struct tty *, int));
561 #ifdef KGDB
562 void zs_kgdb_init(void);
563 #endif
564 
565 /* fb.c */
566 void	fb_unblank(void);
567 
568 /* kgdb_stub.c */
569 #ifdef KGDB
570 void kgdb_attach(int (*)(void *), void (*)(void *, int), void *);
571 void kgdb_connect(int);
572 void kgdb_panic(void);
573 #endif
574 
575 /* emul.c */
576 struct trapframe;
577 int fixalign(struct lwp *, struct trapframe *, void **);
578 int emulinstr(int, struct trapframe *);
579 
580 /* cpu.c */
581 void mp_pause_cpus(void);
582 void mp_resume_cpus(void);
583 void mp_halt_cpus(void);
584 #ifdef DDB
585 void mp_pause_cpus_ddb(void);
586 void mp_resume_cpus_ddb(void);
587 #endif
588 
589 /* intr.c */
590 u_int setitr(u_int);
591 u_int getitr(void);
592 
593 
594 /*
595  *
596  * The SPARC has a Trap Base Register (TBR) which holds the upper 20 bits
597  * of the trap vector table.  The next eight bits are supplied by the
598  * hardware when the trap occurs, and the bottom four bits are always
599  * zero (so that we can shove up to 16 bytes of executable code---exactly
600  * four instructions---into each trap vector).
601  *
602  * The hardware allocates half the trap vectors to hardware and half to
603  * software.
604  *
605  * Traps have priorities assigned (lower number => higher priority).
606  */
607 
608 struct trapvec {
609 	int	tv_instr[4];		/* the four instructions */
610 };
611 
612 extern struct trapvec *trapbase;	/* the 256 vectors */
613 
614 #endif /* _KERNEL */
615 #endif /* _CPU_H_ */
616