xref: /illumos-gate/usr/src/cmd/mdb/sparc/mdb/kvm_v7dep.c (revision 0597f6f3)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 /*
22  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
23  * Use is subject to license terms.
24  *
25  * Copyright 2018 Joyent, Inc.
26  */
27 
28 /*
29  * Libkvm Kernel Target SPARC v7 component
30  *
31  * This file provides the ISA-dependent portion of the libkvm kernel target.
32  * For more details on the implementation refer to mdb_kvm.c.
33  */
34 
35 #include <sys/types.h>
36 #include <sys/machtypes.h>
37 #include <sys/regset.h>
38 #include <sys/frame.h>
39 #include <sys/stack.h>
40 #include <sys/sysmacros.h>
41 #include <sys/panic.h>
42 #include <strings.h>
43 
44 #include <mdb/mdb_target_impl.h>
45 #include <mdb/mdb_disasm.h>
46 #include <mdb/mdb_modapi.h>
47 #include <mdb/mdb_conf.h>
48 #include <mdb/mdb_kreg.h>
49 #include <mdb/mdb_kvm.h>
50 #include <mdb/mdb_err.h>
51 #include <mdb/mdb_debug.h>
52 #include <mdb/mdb.h>
53 
54 /*
55  * The mdb_tgt_gregset type is opaque to callers of the target interface
56  * and to our own target common code.  We now can define it explicitly.
57  */
58 struct mdb_tgt_gregset {
59 	kreg_t kregs[KREG_NGREG];
60 };
61 
62 /*
63  * We also define an array of register names and their corresponding
64  * array indices.  This is used by the getareg and putareg entry points,
65  * and also by our register variable discipline.
66  */
67 static const mdb_tgt_regdesc_t kt_sparcv7_regs[] = {
68 	{ "g0", KREG_G0, MDB_TGT_R_EXPORT },
69 	{ "g1", KREG_G1, MDB_TGT_R_EXPORT },
70 	{ "g2", KREG_G2, MDB_TGT_R_EXPORT },
71 	{ "g3", KREG_G3, MDB_TGT_R_EXPORT },
72 	{ "g4", KREG_G4, MDB_TGT_R_EXPORT },
73 	{ "g5", KREG_G5, MDB_TGT_R_EXPORT },
74 	{ "g6", KREG_G6, MDB_TGT_R_EXPORT },
75 	{ "g7", KREG_G7, MDB_TGT_R_EXPORT },
76 	{ "o0", KREG_O0, MDB_TGT_R_EXPORT },
77 	{ "o1", KREG_O1, MDB_TGT_R_EXPORT },
78 	{ "o2", KREG_O2, MDB_TGT_R_EXPORT },
79 	{ "o3", KREG_O3, MDB_TGT_R_EXPORT },
80 	{ "o4", KREG_O4, MDB_TGT_R_EXPORT },
81 	{ "o5", KREG_O5, MDB_TGT_R_EXPORT },
82 	{ "o6", KREG_O6, MDB_TGT_R_EXPORT },
83 	{ "o7", KREG_O7, MDB_TGT_R_EXPORT },
84 	{ "l0", KREG_L0, MDB_TGT_R_EXPORT },
85 	{ "l1", KREG_L1, MDB_TGT_R_EXPORT },
86 	{ "l2", KREG_L2, MDB_TGT_R_EXPORT },
87 	{ "l3", KREG_L3, MDB_TGT_R_EXPORT },
88 	{ "l4", KREG_L4, MDB_TGT_R_EXPORT },
89 	{ "l5", KREG_L5, MDB_TGT_R_EXPORT },
90 	{ "l6", KREG_L6, MDB_TGT_R_EXPORT },
91 	{ "l7", KREG_L7, MDB_TGT_R_EXPORT },
92 	{ "i0", KREG_I0, MDB_TGT_R_EXPORT },
93 	{ "i1", KREG_I1, MDB_TGT_R_EXPORT },
94 	{ "i2", KREG_I2, MDB_TGT_R_EXPORT },
95 	{ "i3", KREG_I3, MDB_TGT_R_EXPORT },
96 	{ "i4", KREG_I4, MDB_TGT_R_EXPORT },
97 	{ "i5", KREG_I5, MDB_TGT_R_EXPORT },
98 	{ "i6", KREG_I6, MDB_TGT_R_EXPORT },
99 	{ "i7", KREG_I7, MDB_TGT_R_EXPORT },
100 	{ "psr", KREG_PSR, MDB_TGT_R_EXPORT },
101 	{ "pc", KREG_PC, MDB_TGT_R_EXPORT },
102 	{ "npc", KREG_NPC, MDB_TGT_R_EXPORT },
103 	{ "y", KREG_Y, 0 },
104 	{ "wim", KREG_WIM, MDB_TGT_R_EXPORT | MDB_TGT_R_PRIV },
105 	{ "tbr", KREG_TBR, MDB_TGT_R_EXPORT | MDB_TGT_R_PRIV },
106 	{ "sp", KREG_SP, MDB_TGT_R_EXPORT | MDB_TGT_R_ALIAS },
107 	{ "fp", KREG_FP, MDB_TGT_R_EXPORT | MDB_TGT_R_ALIAS },
108 	{ NULL, 0, 0 }
109 };
110 
111 static int
kt_getareg(mdb_tgt_t * t,mdb_tgt_tid_t tid,const char * rname,mdb_tgt_reg_t * rp)112 kt_getareg(mdb_tgt_t *t, mdb_tgt_tid_t tid,
113     const char *rname, mdb_tgt_reg_t *rp)
114 {
115 	const mdb_tgt_regdesc_t *rdp;
116 	kt_data_t *kt = t->t_data;
117 
118 	if (tid != kt->k_tid)
119 		return (set_errno(EMDB_NOREGS));
120 
121 	for (rdp = kt->k_rds; rdp->rd_name != NULL; rdp++) {
122 		if (strcmp(rname, rdp->rd_name) == 0) {
123 			*rp = kt->k_regs->kregs[rdp->rd_num];
124 			return (0);
125 		}
126 	}
127 
128 	return (set_errno(EMDB_BADREG));
129 }
130 
131 static int
kt_putareg(mdb_tgt_t * t,mdb_tgt_tid_t tid,const char * rname,mdb_tgt_reg_t r)132 kt_putareg(mdb_tgt_t *t, mdb_tgt_tid_t tid, const char *rname, mdb_tgt_reg_t r)
133 {
134 	const mdb_tgt_regdesc_t *rdp;
135 	kt_data_t *kt = t->t_data;
136 
137 	if (tid != kt->k_tid)
138 		return (set_errno(EMDB_NOREGS));
139 
140 	for (rdp = kt->k_rds; rdp->rd_name != NULL; rdp++) {
141 		if (strcmp(rname, rdp->rd_name) == 0) {
142 			kt->k_regs->kregs[rdp->rd_num] = r;
143 			return (0);
144 		}
145 	}
146 
147 	return (set_errno(EMDB_BADREG));
148 }
149 
150 static int
kt_stack_iter(mdb_tgt_t * t,const mdb_tgt_gregset_t * gsp,mdb_tgt_stack_f * func,void * arg)151 kt_stack_iter(mdb_tgt_t *t, const mdb_tgt_gregset_t *gsp,
152     mdb_tgt_stack_f *func, void *arg)
153 {
154 	mdb_tgt_gregset_t gregs;
155 	kreg_t *kregs = &gregs.kregs[0];
156 	int got_pc = (gsp->kregs[KREG_PC] != 0);
157 
158 	struct rwindow rwin;
159 	uintptr_t sp;
160 	long argv[6];
161 	int i;
162 
163 	bcopy(gsp, &gregs, sizeof (gregs));
164 
165 	for (;;) {
166 		for (i = 0; i < 6; i++)
167 			argv[i] = kregs[KREG_I0 + i];
168 
169 		if (got_pc && func(arg, kregs[KREG_PC], 6, argv, &gregs) != 0)
170 			break;
171 
172 		kregs[KREG_PC] = kregs[KREG_I7];
173 		kregs[KREG_NPC] = kregs[KREG_PC] + 4;
174 
175 		bcopy(&kregs[KREG_I0], &kregs[KREG_O0], 8 * sizeof (kreg_t));
176 		got_pc |= (kregs[KREG_PC] != 0);
177 
178 		if ((sp = kregs[KREG_FP]) == 0)
179 			break; /* Stop if we're at the end of the stack */
180 
181 		if (sp & (STACK_ALIGN - 1))
182 			return (set_errno(EMDB_STKALIGN));
183 
184 		if (mdb_tgt_vread(t, &rwin, sizeof (rwin), sp) != sizeof (rwin))
185 			return (-1); /* Failed to read frame */
186 
187 		for (i = 0; i < 8; i++)
188 			kregs[KREG_L0 + i] = (uintptr_t)rwin.rw_local[i];
189 		for (i = 0; i < 8; i++)
190 			kregs[KREG_I0 + i] = (uintptr_t)rwin.rw_in[i];
191 	}
192 
193 	return (0);
194 }
195 
196 /*ARGSUSED*/
197 static int
kt_regs(uintptr_t addr,uint_t flags,int argc,const mdb_arg_t * argv)198 kt_regs(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
199 {
200 	mdb_tgt_gregset_t *k_regs = (mdb_tgt_gregset_t *)addr;
201 	const kreg_t *kregs = &k_regs->kregs[0];
202 
203 	if (argc != 0 || (flags & DCMD_ADDRSPEC))
204 		return (DCMD_USAGE);
205 
206 #define	GETREG2(x) ((uintptr_t)kregs[(x)]), ((uintptr_t)kregs[(x)])
207 
208 	mdb_printf("%%g0 = 0x%0?p %15A %%l0 = 0x%0?p %A\n",
209 	    GETREG2(KREG_G0), GETREG2(KREG_L0));
210 
211 	mdb_printf("%%g1 = 0x%0?p %15A %%l1 = 0x%0?p %A\n",
212 	    GETREG2(KREG_G1), GETREG2(KREG_L1));
213 
214 	mdb_printf("%%g2 = 0x%0?p %15A %%l2 = 0x%0?p %A\n",
215 	    GETREG2(KREG_G2), GETREG2(KREG_L2));
216 
217 	mdb_printf("%%g3 = 0x%0?p %15A %%l3 = 0x%0?p %A\n",
218 	    GETREG2(KREG_G3), GETREG2(KREG_L3));
219 
220 	mdb_printf("%%g4 = 0x%0?p %15A %%l4 = 0x%0?p %A\n",
221 	    GETREG2(KREG_G4), GETREG2(KREG_L4));
222 
223 	mdb_printf("%%g5 = 0x%0?p %15A %%l5 = 0x%0?p %A\n",
224 	    GETREG2(KREG_G5), GETREG2(KREG_L5));
225 
226 	mdb_printf("%%g6 = 0x%0?p %15A %%l6 = 0x%0?p %A\n",
227 	    GETREG2(KREG_G6), GETREG2(KREG_L6));
228 
229 	mdb_printf("%%g7 = 0x%0?p %15A %%l7 = 0x%0?p %A\n\n",
230 	    GETREG2(KREG_G7), GETREG2(KREG_L7));
231 
232 	mdb_printf("%%o0 = 0x%0?p %15A %%i0 = 0x%0?p %A\n",
233 	    GETREG2(KREG_O0), GETREG2(KREG_I0));
234 
235 	mdb_printf("%%o1 = 0x%0?p %15A %%i1 = 0x%0?p %A\n",
236 	    GETREG2(KREG_O1), GETREG2(KREG_I1));
237 
238 	mdb_printf("%%o2 = 0x%0?p %15A %%i2 = 0x%0?p %A\n",
239 	    GETREG2(KREG_O2), GETREG2(KREG_I2));
240 
241 	mdb_printf("%%o3 = 0x%0?p %15A %%i3 = 0x%0?p %A\n",
242 	    GETREG2(KREG_O3), GETREG2(KREG_I3));
243 
244 	mdb_printf("%%o4 = 0x%0?p %15A %%i4 = 0x%0?p %A\n",
245 	    GETREG2(KREG_O4), GETREG2(KREG_I4));
246 
247 	mdb_printf("%%o5 = 0x%0?p %15A %%i5 = 0x%0?p %A\n",
248 	    GETREG2(KREG_O5), GETREG2(KREG_I5));
249 
250 	mdb_printf("%%o6 = 0x%0?p %15A %%i6 = 0x%0?p %A\n",
251 	    GETREG2(KREG_O6), GETREG2(KREG_I6));
252 
253 	mdb_printf("%%o7 = 0x%0?p %15A %%i7 = 0x%0?p %A\n\n",
254 	    GETREG2(KREG_O7), GETREG2(KREG_I7));
255 
256 	mdb_printf(" %%psr = 0x%08x impl=0x%x ver=0x%x icc=%c%c%c%c\n"
257 	    "                   ec=%u ef=%u pil=%u s=%u ps=%u et=%u cwp=0x%x\n",
258 	    kregs[KREG_PSR],
259 	    (kregs[KREG_PSR] & KREG_PSR_IMPL_MASK) >> KREG_PSR_IMPL_SHIFT,
260 	    (kregs[KREG_PSR] & KREG_PSR_VER_MASK) >> KREG_PSR_VER_SHIFT,
261 	    (kregs[KREG_PSR] & KREG_PSR_ICC_N_MASK) ? 'N' : 'n',
262 	    (kregs[KREG_PSR] & KREG_PSR_ICC_Z_MASK) ? 'Z' : 'z',
263 	    (kregs[KREG_PSR] & KREG_PSR_ICC_V_MASK) ? 'V' : 'v',
264 	    (kregs[KREG_PSR] & KREG_PSR_ICC_C_MASK) ? 'C' : 'c',
265 	    kregs[KREG_PSR] & KREG_PSR_EC_MASK,
266 	    kregs[KREG_PSR] & KREG_PSR_EF_MASK,
267 	    (kregs[KREG_PSR] & KREG_PSR_PIL_MASK) >> KREG_PSR_PIL_SHIFT,
268 	    kregs[KREG_PSR] & KREG_PSR_S_MASK,
269 	    kregs[KREG_PSR] & KREG_PSR_PS_MASK,
270 	    kregs[KREG_PSR] & KREG_PSR_ET_MASK,
271 	    (kregs[KREG_PSR] & KREG_PSR_CWP_MASK) >> KREG_PSR_CWP_SHIFT);
272 
273 	mdb_printf("   %%y = 0x%0?p\n", kregs[KREG_Y]);
274 
275 	mdb_printf("  %%pc = 0x%0?p %A\n", GETREG2(KREG_PC));
276 	mdb_printf(" %%npc = 0x%0?p %A\n", GETREG2(KREG_NPC));
277 
278 	mdb_printf("  %%sp = 0x%0?p\n", kregs[KREG_SP]);
279 	mdb_printf("  %%fp = 0x%0?p\n\n", kregs[KREG_FP]);
280 
281 	mdb_printf(" %%wim = 0x%08lx\n", kregs[KREG_WIM]);
282 	mdb_printf(" %%tbr = 0x%08lx\n", kregs[KREG_TBR]);
283 
284 	return (DCMD_OK);
285 }
286 
287 /*ARGSUSED*/
288 static int
kt_frame(void * arglim,uintptr_t pc,uint_t argc,const long * argv,const mdb_tgt_gregset_t * gregs)289 kt_frame(void *arglim, uintptr_t pc, uint_t argc, const long *argv,
290     const mdb_tgt_gregset_t *gregs)
291 {
292 	argc = MIN(argc, (uint_t)arglim);
293 	mdb_printf("%a(", pc);
294 
295 	if (argc != 0) {
296 		mdb_printf("%lr", *argv++);
297 		for (argc--; argc != 0; argc--)
298 			mdb_printf(", %lr", *argv++);
299 	}
300 
301 	mdb_printf(")\n");
302 	return (0);
303 }
304 
305 static int
kt_framev(void * arglim,uintptr_t pc,uint_t argc,const long * argv,const mdb_tgt_gregset_t * gregs)306 kt_framev(void *arglim, uintptr_t pc, uint_t argc, const long *argv,
307     const mdb_tgt_gregset_t *gregs)
308 {
309 	argc = MIN(argc, (uint_t)arglim);
310 	mdb_printf("%0?lr %a(", gregs->kregs[KREG_SP], pc);
311 
312 	if (argc != 0) {
313 		mdb_printf("%lr", *argv++);
314 		for (argc--; argc != 0; argc--)
315 			mdb_printf(", %lr", *argv++);
316 	}
317 
318 	mdb_printf(")\n");
319 	return (0);
320 }
321 
322 static int
kt_stack_common(uintptr_t addr,uint_t flags,int argc,const mdb_arg_t * argv,mdb_tgt_stack_f * func)323 kt_stack_common(uintptr_t addr, uint_t flags, int argc,
324     const mdb_arg_t *argv, mdb_tgt_stack_f *func)
325 {
326 	kt_data_t *kt = mdb.m_target->t_data;
327 	void *arg = (void *)mdb.m_nargs;
328 	mdb_tgt_gregset_t gregs, *grp;
329 
330 	if (flags & DCMD_ADDRSPEC) {
331 		bzero(&gregs, sizeof (gregs));
332 		gregs.kregs[KREG_FP] = addr;
333 		grp = &gregs;
334 	} else
335 		grp = kt->k_regs;
336 
337 	if (argc != 0) {
338 		if (argv->a_type == MDB_TYPE_CHAR || argc > 1)
339 			return (DCMD_USAGE);
340 
341 		if (argv->a_type == MDB_TYPE_STRING)
342 			arg = (void *)(uint_t)mdb_strtoull(argv->a_un.a_str);
343 		else
344 			arg = (void *)(uint_t)argv->a_un.a_val;
345 	}
346 
347 	(void) kt_stack_iter(mdb.m_target, grp, func, arg);
348 	return (DCMD_OK);
349 }
350 
351 static int
kt_stack(uintptr_t addr,uint_t flags,int argc,const mdb_arg_t * argv)352 kt_stack(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
353 {
354 	return (kt_stack_common(addr, flags, argc, argv, kt_frame));
355 }
356 
357 static int
kt_stackv(uintptr_t addr,uint_t flags,int argc,const mdb_arg_t * argv)358 kt_stackv(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
359 {
360 	return (kt_stack_common(addr, flags, argc, argv, kt_framev));
361 }
362 
363 /*ARGSUSED*/
364 static int
kt_notsup(uintptr_t addr,uint_t flags,int argc,const mdb_arg_t * argv)365 kt_notsup(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
366 {
367 	errno = EMDB_TGTNOTSUP;
368 	return (DCMD_ERR);
369 }
370 
371 const mdb_tgt_ops_t kt_sparcv7_ops = {
372 	kt_setflags,				/* t_setflags */
373 	kt_setcontext,				/* t_setcontext */
374 	kt_activate,				/* t_activate */
375 	kt_deactivate,				/* t_deactivate */
376 	(void (*)())(uintptr_t)mdb_tgt_nop,	/* t_periodic */
377 	kt_destroy,				/* t_destroy */
378 	kt_name,				/* t_name */
379 	(const char *(*)())mdb_conf_isa,	/* t_isa */
380 	kt_platform,				/* t_platform */
381 	kt_uname,				/* t_uname */
382 	kt_dmodel,				/* t_dmodel */
383 	kt_aread,				/* t_aread */
384 	kt_awrite,				/* t_awrite */
385 	kt_vread,				/* t_vread */
386 	kt_vwrite,				/* t_vwrite */
387 	kt_pread,				/* t_pread */
388 	kt_pwrite,				/* t_pwrite */
389 	kt_fread,				/* t_fread */
390 	kt_fwrite,				/* t_fwrite */
391 	(ssize_t (*)())mdb_tgt_notsup,		/* t_ioread */
392 	(ssize_t (*)())mdb_tgt_notsup,		/* t_iowrite */
393 	kt_vtop,				/* t_vtop */
394 	kt_lookup_by_name,			/* t_lookup_by_name */
395 	kt_lookup_by_addr,			/* t_lookup_by_addr */
396 	kt_symbol_iter,				/* t_symbol_iter */
397 	kt_mapping_iter,			/* t_mapping_iter */
398 	kt_object_iter,				/* t_object_iter */
399 	kt_addr_to_map,				/* t_addr_to_map */
400 	kt_name_to_map,				/* t_name_to_map */
401 	kt_addr_to_ctf,				/* t_addr_to_ctf */
402 	kt_name_to_ctf,				/* t_name_to_ctf */
403 	kt_status,				/* t_status */
404 	(int (*)())mdb_tgt_notsup,		/* t_run */
405 	(int (*)())mdb_tgt_notsup,		/* t_step */
406 	(int (*)())mdb_tgt_notsup,		/* t_step_out */
407 	(int (*)())mdb_tgt_notsup,		/* t_next */
408 	(int (*)())mdb_tgt_notsup,		/* t_cont */
409 	(int (*)())mdb_tgt_notsup,		/* t_signal */
410 	(int (*)())(uintptr_t)mdb_tgt_null,	/* t_add_vbrkpt */
411 	(int (*)())(uintptr_t)mdb_tgt_null,	/* t_add_sbrkpt */
412 	(int (*)())(uintptr_t)mdb_tgt_null,	/* t_add_pwapt */
413 	(int (*)())(uintptr_t)mdb_tgt_null,	/* t_add_vwapt */
414 	(int (*)())(uintptr_t)mdb_tgt_null,	/* t_add_iowapt */
415 	(int (*)())(uintptr_t)mdb_tgt_null,	/* t_add_sysenter */
416 	(int (*)())(uintptr_t)mdb_tgt_null,	/* t_add_sysexit */
417 	(int (*)())(uintptr_t)mdb_tgt_null,	/* t_add_signal */
418 	(int (*)())(uintptr_t)mdb_tgt_null,	/* t_add_fault */
419 	kt_getareg,				/* t_getareg */
420 	kt_putareg,				/* t_putareg */
421 	kt_stack_iter,				/* t_stack_iter */
422 	(int (*)())mdb_tgt_notsup		/* t_auxv */
423 };
424 
425 void
kt_sparcv7_init(mdb_tgt_t * t)426 kt_sparcv7_init(mdb_tgt_t *t)
427 {
428 	kt_data_t *kt = t->t_data;
429 
430 	struct rwindow rwin;
431 	panic_data_t pd;
432 	label_t label;
433 	kreg_t *kregs;
434 
435 	/*
436 	 * Initialize the machine-dependent parts of the kernel target
437 	 * structure.  Once this is complete and we fill in the ops
438 	 * vector, the target is now fully constructed and we can use
439 	 * the target API itself to perform the rest of our initialization.
440 	 */
441 	kt->k_rds = kt_sparcv7_regs;
442 	kt->k_regs = mdb_zalloc(sizeof (mdb_tgt_gregset_t), UM_SLEEP);
443 	kt->k_regsize = sizeof (mdb_tgt_gregset_t);
444 	kt->k_dcmd_regs = kt_regs;
445 	kt->k_dcmd_stack = kt_stack;
446 	kt->k_dcmd_stackv = kt_stackv;
447 	kt->k_dcmd_stackr = kt_stackv;
448 	kt->k_dcmd_cpustack = kt_notsup;
449 	kt->k_dcmd_cpuregs = kt_notsup;
450 
451 	t->t_ops = &kt_sparcv7_ops;
452 	kregs = kt->k_regs->kregs;
453 
454 	(void) mdb_dis_select("v8");
455 
456 	/*
457 	 * Don't attempt to load any thread or register information if
458 	 * we're examining the live operating system.
459 	 */
460 	if (strcmp(kt->k_symfile, "/dev/ksyms") == 0)
461 		return;
462 
463 	/*
464 	 * If the panicbuf symbol is present and we can consume a panicbuf
465 	 * header of the appropriate version from this address, then
466 	 * we can initialize our current register set based on its contents:
467 	 */
468 	if (mdb_tgt_readsym(t, MDB_TGT_AS_VIRT, &pd, sizeof (pd),
469 	    MDB_TGT_OBJ_EXEC, "panicbuf") == sizeof (pd) &&
470 	    pd.pd_version == PANICBUFVERS) {
471 
472 		size_t pd_size = MIN(PANICBUFSIZE, pd.pd_msgoff);
473 		panic_data_t *pdp = mdb_zalloc(pd_size, UM_SLEEP);
474 		uint_t i, n;
475 
476 		(void) mdb_tgt_readsym(t, MDB_TGT_AS_VIRT, pdp, pd_size,
477 		    MDB_TGT_OBJ_EXEC, "panicbuf");
478 
479 		n = (pd_size - (sizeof (panic_data_t) -
480 		    sizeof (panic_nv_t))) / sizeof (panic_nv_t);
481 
482 		for (i = 0; i < n; i++) {
483 			(void) kt_putareg(t, kt->k_tid,
484 			    pdp->pd_nvdata[i].pnv_name,
485 			    pdp->pd_nvdata[i].pnv_value);
486 		}
487 
488 		mdb_free(pdp, pd_size);
489 	}
490 
491 	/*
492 	 * Prior to the re-structuring of panicbuf, our only register data
493 	 * was the panic_regs label_t, into which a setjmp() was performed.
494 	 */
495 	if (kregs[KREG_PC] == 0 && kregs[KREG_SP] == 0 &&
496 	    mdb_tgt_readsym(t, MDB_TGT_AS_VIRT, &label, sizeof (label),
497 	    MDB_TGT_OBJ_EXEC, "panic_regs") == sizeof (label)) {
498 
499 		kregs[KREG_PC] = label.val[0];
500 		kregs[KREG_SP] = label.val[1];
501 	}
502 
503 	/*
504 	 * If we can read a saved register window from the stack at %sp,
505 	 * we can also fill in the locals and inputs.
506 	 */
507 	if (kregs[KREG_SP] != 0 && mdb_tgt_vread(t, &rwin, sizeof (rwin),
508 	    kregs[KREG_SP]) == sizeof (rwin)) {
509 
510 		kregs[KREG_L0] = rwin.rw_local[0];
511 		kregs[KREG_L1] = rwin.rw_local[1];
512 		kregs[KREG_L2] = rwin.rw_local[2];
513 		kregs[KREG_L3] = rwin.rw_local[3];
514 		kregs[KREG_L4] = rwin.rw_local[4];
515 		kregs[KREG_L5] = rwin.rw_local[5];
516 		kregs[KREG_L6] = rwin.rw_local[6];
517 		kregs[KREG_L7] = rwin.rw_local[7];
518 
519 		kregs[KREG_I0] = rwin.rw_in[0];
520 		kregs[KREG_I1] = rwin.rw_in[1];
521 		kregs[KREG_I2] = rwin.rw_in[2];
522 		kregs[KREG_I3] = rwin.rw_in[3];
523 		kregs[KREG_I4] = rwin.rw_in[4];
524 		kregs[KREG_I5] = rwin.rw_in[5];
525 		kregs[KREG_I6] = rwin.rw_in[6];
526 		kregs[KREG_I7] = rwin.rw_in[7];
527 
528 	} else if (kregs[KREG_SP] != 0) {
529 		warn("failed to read rwindow at %p -- current "
530 		    "frame inputs will be unavailable\n",
531 		    (void *)kregs[KREG_SP]);
532 	}
533 }
534