xref: /titanic_41/usr/src/cmd/mdb/intel/mdb/mdb_amd64util.c (revision 936260673937830abacea5e1c31988a86d2d9f0a)
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 /*
23  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 /*
27  * Copyright (c) 2012, Joyent, Inc.  All rights reserved.
28  * Copyright 2014 Nexenta Systems, Inc.  All rights reserved.
29  * Copyright (c) 2013 by Delphix. All rights reserved.
30  */
31 
32 #include <sys/types.h>
33 #include <sys/reg.h>
34 #include <sys/privregs.h>
35 #include <sys/stack.h>
36 #include <sys/frame.h>
37 
38 #include <mdb/mdb_target_impl.h>
39 #include <mdb/mdb_kreg_impl.h>
40 #include <mdb/mdb_debug.h>
41 #include <mdb/mdb_modapi.h>
42 #include <mdb/mdb_amd64util.h>
43 #include <mdb/mdb_ctf.h>
44 #include <mdb/mdb_err.h>
45 #include <mdb/mdb.h>
46 
47 #include <saveargs.h>
48 
49 /*
50  * This array is used by the getareg and putareg entry points, and also by our
51  * register variable discipline.
52  */
53 
54 const mdb_tgt_regdesc_t mdb_amd64_kregs[] = {
55 	{ "savfp", KREG_SAVFP, MDB_TGT_R_EXPORT },
56 	{ "savpc", KREG_SAVPC, MDB_TGT_R_EXPORT },
57 	{ "rdi", KREG_RDI, MDB_TGT_R_EXPORT },
58 	{ "edi", KREG_RDI, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
59 	{ "di",  KREG_RDI, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
60 	{ "dil", KREG_RDI, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
61 	{ "rsi", KREG_RSI, MDB_TGT_R_EXPORT },
62 	{ "esi", KREG_RSI, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
63 	{ "si",  KREG_RSI, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
64 	{ "sil", KREG_RSI, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
65 	{ "rdx", KREG_RDX, MDB_TGT_R_EXPORT },
66 	{ "edx", KREG_RDX, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
67 	{ "dx",  KREG_RDX, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
68 	{ "dh",  KREG_RDX, MDB_TGT_R_EXPORT | MDB_TGT_R_8H },
69 	{ "dl",  KREG_RDX, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
70 	{ "rcx", KREG_RCX, MDB_TGT_R_EXPORT },
71 	{ "ecx", KREG_RCX, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
72 	{ "cx",  KREG_RCX, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
73 	{ "ch",  KREG_RCX, MDB_TGT_R_EXPORT | MDB_TGT_R_8H },
74 	{ "cl",  KREG_RCX, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
75 	{ "r8", KREG_R8, MDB_TGT_R_EXPORT },
76 	{ "r8d", KREG_R8,  MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
77 	{ "r8w", KREG_R8,  MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
78 	{ "r8l", KREG_R8,  MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
79 	{ "r9", KREG_R9, MDB_TGT_R_EXPORT },
80 	{ "r9d", KREG_R8,  MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
81 	{ "r9w", KREG_R8,  MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
82 	{ "r9l", KREG_R8,  MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
83 	{ "rax", KREG_RAX, MDB_TGT_R_EXPORT },
84 	{ "eax", KREG_RAX, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
85 	{ "ax",  KREG_RAX, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
86 	{ "ah",  KREG_RAX, MDB_TGT_R_EXPORT | MDB_TGT_R_8H },
87 	{ "al",  KREG_RAX, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
88 	{ "rbx", KREG_RBX, MDB_TGT_R_EXPORT },
89 	{ "ebx", KREG_RBX, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
90 	{ "bx",  KREG_RBX, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
91 	{ "bh",  KREG_RBX, MDB_TGT_R_EXPORT | MDB_TGT_R_8H },
92 	{ "bl",  KREG_RBX, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
93 	{ "rbp", KREG_RBP, MDB_TGT_R_EXPORT },
94 	{ "ebp", KREG_RBP, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
95 	{ "bp",  KREG_RBP, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
96 	{ "bpl", KREG_RBP, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
97 	{ "r10", KREG_R10, MDB_TGT_R_EXPORT },
98 	{ "r10d", KREG_R10, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
99 	{ "r10w", KREG_R10, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
100 	{ "r10l", KREG_R10, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
101 	{ "r11", KREG_R11, MDB_TGT_R_EXPORT },
102 	{ "r11d", KREG_R11, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
103 	{ "r11w", KREG_R11, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
104 	{ "r11l", KREG_R11, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
105 	{ "r12", KREG_R12, MDB_TGT_R_EXPORT },
106 	{ "r12d", KREG_R12, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
107 	{ "r12w", KREG_R12, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
108 	{ "r12l", KREG_R12, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
109 	{ "r13", KREG_R13, MDB_TGT_R_EXPORT },
110 	{ "r13d", KREG_R13, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
111 	{ "r13w", KREG_R13, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
112 	{ "r13l", KREG_R13, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
113 	{ "r14", KREG_R14, MDB_TGT_R_EXPORT },
114 	{ "r14d", KREG_R14, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
115 	{ "r14w", KREG_R14, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
116 	{ "r14l", KREG_R14, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
117 	{ "r15", KREG_R15, MDB_TGT_R_EXPORT },
118 	{ "r15d", KREG_R15, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
119 	{ "r15w", KREG_R15, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
120 	{ "r15l", KREG_R15, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
121 	{ "ds", KREG_DS, MDB_TGT_R_EXPORT },
122 	{ "es", KREG_ES, MDB_TGT_R_EXPORT },
123 	{ "fs", KREG_FS, MDB_TGT_R_EXPORT },
124 	{ "gs", KREG_GS, MDB_TGT_R_EXPORT },
125 	{ "trapno", KREG_TRAPNO, MDB_TGT_R_EXPORT | MDB_TGT_R_PRIV },
126 	{ "err", KREG_ERR, MDB_TGT_R_EXPORT | MDB_TGT_R_PRIV },
127 	{ "rip", KREG_RIP, MDB_TGT_R_EXPORT },
128 	{ "cs", KREG_CS, MDB_TGT_R_EXPORT },
129 	{ "rflags", KREG_RFLAGS, MDB_TGT_R_EXPORT },
130 	{ "eflags", KREG_RFLAGS, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
131 	{ "rsp", KREG_RSP, MDB_TGT_R_EXPORT },
132 	{ "esp", KREG_RSP, MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
133 	{ "sp",  KREG_RSP, MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
134 	{ "spl", KREG_RSP, MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
135 	{ "ss", KREG_SS, MDB_TGT_R_EXPORT },
136 	{ NULL, 0, 0 }
137 };
138 
139 void
140 mdb_amd64_printregs(const mdb_tgt_gregset_t *gregs)
141 {
142 	const kreg_t *kregs = &gregs->kregs[0];
143 	kreg_t rflags = kregs[KREG_RFLAGS];
144 
145 #define	GETREG2(x) ((uintptr_t)kregs[(x)]), ((uintptr_t)kregs[(x)])
146 
147 	mdb_printf("%%rax = 0x%0?p %15A %%r9  = 0x%0?p %A\n",
148 	    GETREG2(KREG_RAX), GETREG2(KREG_R9));
149 	mdb_printf("%%rbx = 0x%0?p %15A %%r10 = 0x%0?p %A\n",
150 	    GETREG2(KREG_RBX), GETREG2(KREG_R10));
151 	mdb_printf("%%rcx = 0x%0?p %15A %%r11 = 0x%0?p %A\n",
152 	    GETREG2(KREG_RCX), GETREG2(KREG_R11));
153 	mdb_printf("%%rdx = 0x%0?p %15A %%r12 = 0x%0?p %A\n",
154 	    GETREG2(KREG_RDX), GETREG2(KREG_R12));
155 	mdb_printf("%%rsi = 0x%0?p %15A %%r13 = 0x%0?p %A\n",
156 	    GETREG2(KREG_RSI), GETREG2(KREG_R13));
157 	mdb_printf("%%rdi = 0x%0?p %15A %%r14 = 0x%0?p %A\n",
158 	    GETREG2(KREG_RDI), GETREG2(KREG_R14));
159 	mdb_printf("%%r8  = 0x%0?p %15A %%r15 = 0x%0?p %A\n\n",
160 	    GETREG2(KREG_R8), GETREG2(KREG_R15));
161 
162 	mdb_printf("%%rip = 0x%0?p %A\n", GETREG2(KREG_RIP));
163 	mdb_printf("%%rbp = 0x%0?p\n", kregs[KREG_RBP]);
164 	mdb_printf("%%rsp = 0x%0?p\n", kregs[KREG_RSP]);
165 
166 	mdb_printf("%%rflags = 0x%08x\n", rflags);
167 
168 	mdb_printf("  id=%u vip=%u vif=%u ac=%u vm=%u rf=%u nt=%u iopl=0x%x\n",
169 	    (rflags & KREG_EFLAGS_ID_MASK) >> KREG_EFLAGS_ID_SHIFT,
170 	    (rflags & KREG_EFLAGS_VIP_MASK) >> KREG_EFLAGS_VIP_SHIFT,
171 	    (rflags & KREG_EFLAGS_VIF_MASK) >> KREG_EFLAGS_VIF_SHIFT,
172 	    (rflags & KREG_EFLAGS_AC_MASK) >> KREG_EFLAGS_AC_SHIFT,
173 	    (rflags & KREG_EFLAGS_VM_MASK) >> KREG_EFLAGS_VM_SHIFT,
174 	    (rflags & KREG_EFLAGS_RF_MASK) >> KREG_EFLAGS_RF_SHIFT,
175 	    (rflags & KREG_EFLAGS_NT_MASK) >> KREG_EFLAGS_NT_SHIFT,
176 	    (rflags & KREG_EFLAGS_IOPL_MASK) >> KREG_EFLAGS_IOPL_SHIFT);
177 
178 	mdb_printf("  status=<%s,%s,%s,%s,%s,%s,%s,%s,%s>\n\n",
179 	    (rflags & KREG_EFLAGS_OF_MASK) ? "OF" : "of",
180 	    (rflags & KREG_EFLAGS_DF_MASK) ? "DF" : "df",
181 	    (rflags & KREG_EFLAGS_IF_MASK) ? "IF" : "if",
182 	    (rflags & KREG_EFLAGS_TF_MASK) ? "TF" : "tf",
183 	    (rflags & KREG_EFLAGS_SF_MASK) ? "SF" : "sf",
184 	    (rflags & KREG_EFLAGS_ZF_MASK) ? "ZF" : "zf",
185 	    (rflags & KREG_EFLAGS_AF_MASK) ? "AF" : "af",
186 	    (rflags & KREG_EFLAGS_PF_MASK) ? "PF" : "pf",
187 	    (rflags & KREG_EFLAGS_CF_MASK) ? "CF" : "cf");
188 
189 	mdb_printf("%24s%%cs = 0x%04x\t%%ds = 0x%04x\t%%es = 0x%04x\n",
190 	    " ", kregs[KREG_CS], kregs[KREG_DS], kregs[KREG_ES]);
191 
192 	mdb_printf("%%trapno = 0x%x\t\t%%fs = 0x%04x\t%%gs = 0x%04x\n",
193 	    kregs[KREG_TRAPNO], (kregs[KREG_FS] & 0xffff),
194 	    (kregs[KREG_GS] & 0xffff));
195 	mdb_printf("   %%err = 0x%x\n", kregs[KREG_ERR]);
196 }
197 
198 int
199 mdb_amd64_kvm_stack_iter(mdb_tgt_t *t, const mdb_tgt_gregset_t *gsp,
200     mdb_tgt_stack_f *func, void *arg)
201 {
202 	mdb_tgt_gregset_t gregs;
203 	kreg_t *kregs = &gregs.kregs[0];
204 	int got_pc = (gsp->kregs[KREG_RIP] != 0);
205 	uint_t argc, reg_argc;
206 	long fr_argv[32];
207 	int start_index; /* index to save_instr where to start comparison */
208 	int err;
209 	int i;
210 
211 	struct {
212 		uintptr_t fr_savfp;
213 		uintptr_t fr_savpc;
214 	} fr;
215 
216 	uintptr_t fp = gsp->kregs[KREG_RBP];
217 	uintptr_t pc = gsp->kregs[KREG_RIP];
218 	uintptr_t lastfp = 0;
219 
220 	ssize_t size;
221 	ssize_t insnsize;
222 	uint8_t ins[SAVEARGS_INSN_SEQ_LEN];
223 
224 	GElf_Sym s;
225 	mdb_syminfo_t sip;
226 	mdb_ctf_funcinfo_t mfp;
227 	int xpv_panic = 0;
228 #ifndef	_KMDB
229 	int xp;
230 
231 	if ((mdb_readsym(&xp, sizeof (xp), "xpv_panicking") != -1) && (xp > 0))
232 		xpv_panic = 1;
233 #endif
234 
235 	bcopy(gsp, &gregs, sizeof (gregs));
236 
237 	while (fp != 0) {
238 		int args_style = 0;
239 
240 		/*
241 		 * Ensure progress (increasing fp), and prevent
242 		 * endless loop with the same FP.
243 		 */
244 		if (fp <= lastfp) {
245 			err = EMDB_STKFRAME;
246 			goto badfp;
247 		}
248 		if (mdb_tgt_vread(t, &fr, sizeof (fr), fp) != sizeof (fr)) {
249 			err = EMDB_NOMAP;
250 			goto badfp;
251 		}
252 
253 		if ((mdb_tgt_lookup_by_addr(t, pc, MDB_TGT_SYM_FUZZY,
254 		    NULL, 0, &s, &sip) == 0) &&
255 		    (mdb_ctf_func_info(&s, &sip, &mfp) == 0)) {
256 			int return_type = mdb_ctf_type_kind(mfp.mtf_return);
257 			mdb_ctf_id_t args_types[5];
258 
259 			argc = mfp.mtf_argc;
260 
261 			/*
262 			 * If the function returns a structure or union
263 			 * greater than 16 bytes in size %rdi contains the
264 			 * address in which to store the return value rather
265 			 * than for an argument.
266 			 */
267 			if ((return_type == CTF_K_STRUCT ||
268 			    return_type == CTF_K_UNION) &&
269 			    mdb_ctf_type_size(mfp.mtf_return) > 16)
270 				start_index = 1;
271 			else
272 				start_index = 0;
273 
274 			/*
275 			 * If any of the first 5 arguments are a structure
276 			 * less than 16 bytes in size, it will be passed
277 			 * spread across two argument registers, and we will
278 			 * not cope.
279 			 */
280 			if (mdb_ctf_func_args(&mfp, 5, args_types) == CTF_ERR)
281 				argc = 0;
282 
283 			for (i = 0; i < MIN(5, argc); i++) {
284 				int t = mdb_ctf_type_kind(args_types[i]);
285 
286 				if (((t == CTF_K_STRUCT) ||
287 				    (t == CTF_K_UNION)) &&
288 				    mdb_ctf_type_size(args_types[i]) <= 16) {
289 					argc = 0;
290 					break;
291 				}
292 			}
293 		} else {
294 			argc = 0;
295 		}
296 
297 		/*
298 		 * The number of instructions to search for argument saving is
299 		 * limited such that only instructions prior to %pc are
300 		 * considered such that we never read arguments from a
301 		 * function where the saving code has not in fact yet
302 		 * executed.
303 		 */
304 		insnsize = MIN(MIN(s.st_size, SAVEARGS_INSN_SEQ_LEN),
305 		    pc - s.st_value);
306 
307 		if (mdb_tgt_vread(t, ins, insnsize, s.st_value) != insnsize)
308 			argc = 0;
309 
310 		if ((argc != 0) &&
311 		    ((args_style = saveargs_has_args(ins, insnsize, argc,
312 		    start_index)) != SAVEARGS_NO_ARGS)) {
313 			/* Up to 6 arguments are passed via registers */
314 			reg_argc = MIN((6 - start_index), mfp.mtf_argc);
315 			size = reg_argc * sizeof (long);
316 
317 			/*
318 			 * If Studio pushed a structure return address as an
319 			 * argument, we need to read one more argument than
320 			 * actually exists (the addr) to make everything line
321 			 * up.
322 			 */
323 			if (args_style == SAVEARGS_STRUCT_ARGS)
324 				size += sizeof (long);
325 
326 			if (mdb_tgt_vread(t, fr_argv, size, (fp - size))
327 			    != size)
328 				return (-1);	/* errno has been set for us */
329 
330 			/*
331 			 * Arrange the arguments in the right order for
332 			 * printing.
333 			 */
334 			for (i = 0; i < (reg_argc / 2); i++) {
335 				long t = fr_argv[i];
336 
337 				fr_argv[i] = fr_argv[reg_argc - i - 1];
338 				fr_argv[reg_argc - i - 1] = t;
339 			}
340 
341 			if (argc > reg_argc) {
342 				size = MIN((argc - reg_argc) * sizeof (long),
343 				    sizeof (fr_argv) -
344 				    (reg_argc * sizeof (long)));
345 
346 				if (mdb_tgt_vread(t, &fr_argv[reg_argc], size,
347 				    fp + sizeof (fr)) != size)
348 					return (-1); /* errno has been set */
349 			}
350 		} else {
351 			argc = 0;
352 		}
353 
354 		if (got_pc && func(arg, pc, argc, fr_argv, &gregs) != 0)
355 			break;
356 
357 		kregs[KREG_RSP] = kregs[KREG_RBP];
358 
359 		lastfp = fp;
360 		fp = fr.fr_savfp;
361 		/*
362 		 * The Xen hypervisor marks a stack frame as belonging to
363 		 * an exception by inverting the bits of the pointer to
364 		 * that frame.  We attempt to identify these frames by
365 		 * inverting the pointer and seeing if it is within 0xfff
366 		 * bytes of the last frame.
367 		 */
368 		if (xpv_panic)
369 			if ((fp != 0) && (fp < lastfp) &&
370 			    ((lastfp ^ ~fp) < 0xfff))
371 				fp = ~fp;
372 
373 		kregs[KREG_RBP] = fp;
374 		kregs[KREG_RIP] = pc = fr.fr_savpc;
375 
376 		got_pc = (pc != 0);
377 	}
378 
379 	return (0);
380 
381 badfp:
382 	mdb_printf("%p [%s]", fp, mdb_strerror(err));
383 	return (set_errno(err));
384 }
385 
386 /*
387  * Determine the return address for the current frame.  Typically this is the
388  * fr_savpc value from the current frame, but we also perform some special
389  * handling to see if we are stopped on one of the first two instructions of
390  * a typical function prologue, in which case %rbp will not be set up yet.
391  */
392 int
393 mdb_amd64_step_out(mdb_tgt_t *t, uintptr_t *p, kreg_t pc, kreg_t fp, kreg_t sp,
394     mdb_instr_t curinstr)
395 {
396 	struct frame fr;
397 	GElf_Sym s;
398 	char buf[1];
399 
400 	enum {
401 		M_PUSHQ_RBP	= 0x55,	/* pushq %rbp */
402 		M_REX_W		= 0x48, /* REX prefix with only W set */
403 		M_MOVL_RBP	= 0x8b	/* movq %rsp, %rbp with prefix */
404 	};
405 
406 	if (mdb_tgt_lookup_by_addr(t, pc, MDB_TGT_SYM_FUZZY,
407 	    buf, 0, &s, NULL) == 0) {
408 		if (pc == s.st_value && curinstr == M_PUSHQ_RBP)
409 			fp = sp - 8;
410 		else if (pc == s.st_value + 1 && curinstr == M_REX_W) {
411 			if (mdb_tgt_vread(t, &curinstr, sizeof (curinstr),
412 			    pc + 1) == sizeof (curinstr) && curinstr ==
413 			    M_MOVL_RBP)
414 				fp = sp;
415 		}
416 	}
417 
418 	if (mdb_tgt_vread(t, &fr, sizeof (fr), fp) == sizeof (fr)) {
419 		*p = fr.fr_savpc;
420 		return (0);
421 	}
422 
423 	return (-1); /* errno is set for us */
424 }
425 
426 /*ARGSUSED*/
427 int
428 mdb_amd64_next(mdb_tgt_t *t, uintptr_t *p, kreg_t pc, mdb_instr_t curinstr)
429 {
430 	mdb_tgt_addr_t npc;
431 	mdb_tgt_addr_t callpc;
432 
433 	enum {
434 		M_CALL_REL = 0xe8, /* call near with relative displacement */
435 		M_CALL_REG = 0xff, /* call near indirect or call far register */
436 
437 		M_REX_LO = 0x40,
438 		M_REX_HI = 0x4f
439 	};
440 
441 	/*
442 	 * If the opcode is a near call with relative displacement, assume the
443 	 * displacement is a rel32 from the next instruction.
444 	 */
445 	if (curinstr == M_CALL_REL) {
446 		*p = pc + sizeof (mdb_instr_t) + sizeof (uint32_t);
447 		return (0);
448 	}
449 
450 	/* Skip the rex prefix, if any */
451 	callpc = pc;
452 	while (curinstr >= M_REX_LO && curinstr <= M_REX_HI) {
453 		if (mdb_tgt_vread(t, &curinstr, sizeof (curinstr), ++callpc) !=
454 		    sizeof (curinstr))
455 			return (-1); /* errno is set for us */
456 	}
457 
458 	if (curinstr != M_CALL_REG) {
459 		/* It's not a call */
460 		return (set_errno(EAGAIN));
461 	}
462 
463 	if ((npc = mdb_dis_nextins(mdb.m_disasm, t, MDB_TGT_AS_VIRT, pc)) == pc)
464 		return (-1); /* errno is set for us */
465 
466 	*p = npc;
467 	return (0);
468 }
469 
470 /*ARGSUSED*/
471 int
472 mdb_amd64_kvm_frame(void *arglim, uintptr_t pc, uint_t argc, const long *argv,
473     const mdb_tgt_gregset_t *gregs)
474 {
475 	argc = MIN(argc, (uintptr_t)arglim);
476 	mdb_printf("%a(", pc);
477 
478 	if (argc != 0) {
479 		mdb_printf("%lr", *argv++);
480 		for (argc--; argc != 0; argc--)
481 			mdb_printf(", %lr", *argv++);
482 	}
483 
484 	mdb_printf(")\n");
485 	return (0);
486 }
487 
488 int
489 mdb_amd64_kvm_framev(void *arglim, uintptr_t pc, uint_t argc, const long *argv,
490     const mdb_tgt_gregset_t *gregs)
491 {
492 	/*
493 	 * Historically adb limited stack trace argument display to a fixed-
494 	 * size number of arguments since no symbolic debugging info existed.
495 	 * On amd64 we can detect the true number of saved arguments so only
496 	 * respect an arglim of zero; otherwise display the entire argv[].
497 	 */
498 	if (arglim == 0)
499 		argc = 0;
500 
501 	mdb_printf("%0?lr %a(", gregs->kregs[KREG_RBP], pc);
502 
503 	if (argc != 0) {
504 		mdb_printf("%lr", *argv++);
505 		for (argc--; argc != 0; argc--)
506 			mdb_printf(", %lr", *argv++);
507 	}
508 
509 	mdb_printf(")\n");
510 	return (0);
511 }
512