sdt.c revision 289791
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 * Portions Copyright 2006-2008 John Birrell jb@freebsd.org 22 * 23 * $FreeBSD: stable/10/sys/cddl/dev/sdt/sdt.c 289791 2015-10-23 07:35:39Z avg $ 24 * 25 */ 26 27/* 28 * This file contains a reimplementation of the statically-defined tracing (SDT) 29 * framework for DTrace. Probes and SDT providers are defined using the macros 30 * in sys/sdt.h, which append all the needed structures to linker sets. When 31 * this module is loaded, it iterates over all of the loaded modules and 32 * registers probes and providers with the DTrace framework based on the 33 * contents of these linker sets. 34 * 35 * A list of SDT providers is maintained here since a provider may span multiple 36 * modules. When a kernel module is unloaded, a provider defined in that module 37 * is unregistered only if no other modules refer to it. The DTrace framework is 38 * responsible for destroying individual probes when a kernel module is 39 * unloaded; in particular, probes may not span multiple kernel modules. 40 */ 41 42#include "opt_kdtrace.h" 43 44#include <sys/cdefs.h> 45#include <sys/param.h> 46#include <sys/systm.h> 47 48#include <sys/conf.h> 49#include <sys/eventhandler.h> 50#include <sys/kernel.h> 51#include <sys/limits.h> 52#include <sys/linker.h> 53#include <sys/linker_set.h> 54#include <sys/lock.h> 55#include <sys/malloc.h> 56#include <sys/module.h> 57#include <sys/mutex.h> 58#include <sys/queue.h> 59#include <sys/sdt.h> 60 61#include <sys/dtrace.h> 62#include <sys/dtrace_bsd.h> 63 64/* DTrace methods. */ 65static void sdt_getargdesc(void *, dtrace_id_t, void *, dtrace_argdesc_t *); 66static void sdt_provide_probes(void *, dtrace_probedesc_t *); 67static void sdt_destroy(void *, dtrace_id_t, void *); 68static void sdt_enable(void *, dtrace_id_t, void *); 69static void sdt_disable(void *, dtrace_id_t, void *); 70 71static void sdt_load(void); 72static int sdt_unload(void); 73static void sdt_create_provider(struct sdt_provider *); 74static void sdt_create_probe(struct sdt_probe *); 75static void sdt_kld_load(void *, struct linker_file *); 76static void sdt_kld_unload_try(void *, struct linker_file *, int *); 77 78static MALLOC_DEFINE(M_SDT, "SDT", "DTrace SDT providers"); 79 80static dtrace_pattr_t sdt_attr = { 81{ DTRACE_STABILITY_EVOLVING, DTRACE_STABILITY_EVOLVING, DTRACE_CLASS_COMMON }, 82{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN }, 83{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_ISA }, 84{ DTRACE_STABILITY_EVOLVING, DTRACE_STABILITY_EVOLVING, DTRACE_CLASS_COMMON }, 85{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_ISA }, 86}; 87 88static dtrace_pops_t sdt_pops = { 89 sdt_provide_probes, 90 NULL, 91 sdt_enable, 92 sdt_disable, 93 NULL, 94 NULL, 95 sdt_getargdesc, 96 NULL, 97 NULL, 98 sdt_destroy, 99}; 100 101static TAILQ_HEAD(, sdt_provider) sdt_prov_list; 102 103static eventhandler_tag sdt_kld_load_tag; 104static eventhandler_tag sdt_kld_unload_try_tag; 105 106static void 107sdt_create_provider(struct sdt_provider *prov) 108{ 109 struct sdt_provider *curr, *newprov; 110 111 TAILQ_FOREACH(curr, &sdt_prov_list, prov_entry) 112 if (strcmp(prov->name, curr->name) == 0) { 113 /* The provider has already been defined. */ 114 curr->sdt_refs++; 115 return; 116 } 117 118 /* 119 * Make a copy of prov so that we don't lose fields if its module is 120 * unloaded but the provider isn't destroyed. This could happen with 121 * a provider that spans multiple modules. 122 */ 123 newprov = malloc(sizeof(*newprov), M_SDT, M_WAITOK | M_ZERO); 124 newprov->name = strdup(prov->name, M_SDT); 125 prov->sdt_refs = newprov->sdt_refs = 1; 126 127 TAILQ_INSERT_TAIL(&sdt_prov_list, newprov, prov_entry); 128 129 (void)dtrace_register(newprov->name, &sdt_attr, DTRACE_PRIV_USER, NULL, 130 &sdt_pops, NULL, (dtrace_provider_id_t *)&newprov->id); 131 prov->id = newprov->id; 132} 133 134static void 135sdt_create_probe(struct sdt_probe *probe) 136{ 137 struct sdt_provider *prov; 138 char mod[DTRACE_MODNAMELEN]; 139 char func[DTRACE_FUNCNAMELEN]; 140 char name[DTRACE_NAMELEN]; 141 const char *from; 142 char *to; 143 size_t len; 144 145 TAILQ_FOREACH(prov, &sdt_prov_list, prov_entry) 146 if (strcmp(prov->name, probe->prov->name) == 0) 147 break; 148 149 KASSERT(prov != NULL, ("probe defined without a provider")); 150 151 /* If no module name was specified, use the module filename. */ 152 if (*probe->mod == 0) { 153 len = strlcpy(mod, probe->sdtp_lf->filename, sizeof(mod)); 154 if (len > 3 && strcmp(mod + len - 3, ".ko") == 0) 155 mod[len - 3] = '\0'; 156 } else 157 strlcpy(mod, probe->mod, sizeof(mod)); 158 159 /* 160 * Unfortunately this is necessary because the Solaris DTrace 161 * code mixes consts and non-consts with casts to override 162 * the incompatibilies. On FreeBSD, we use strict warnings 163 * in the C compiler, so we have to respect const vs non-const. 164 */ 165 strlcpy(func, probe->func, sizeof(func)); 166 167 from = probe->name; 168 to = name; 169 for (len = 0; len < (sizeof(name) - 1) && *from != '\0'; 170 len++, from++, to++) { 171 if (from[0] == '_' && from[1] == '_') { 172 *to = '-'; 173 from++; 174 } else 175 *to = *from; 176 } 177 *to = '\0'; 178 179 if (dtrace_probe_lookup(prov->id, mod, func, name) != DTRACE_IDNONE) 180 return; 181 182 (void)dtrace_probe_create(prov->id, mod, func, name, 1, probe); 183} 184 185/* 186 * Probes are created through the SDT module load/unload hook, so this function 187 * has nothing to do. It only exists because the DTrace provider framework 188 * requires one of provide_probes and provide_module to be defined. 189 */ 190static void 191sdt_provide_probes(void *arg, dtrace_probedesc_t *desc) 192{ 193} 194 195static void 196sdt_enable(void *arg __unused, dtrace_id_t id, void *parg) 197{ 198 struct sdt_probe *probe = parg; 199 200 probe->id = id; 201 probe->sdtp_lf->nenabled++; 202} 203 204static void 205sdt_disable(void *arg __unused, dtrace_id_t id, void *parg) 206{ 207 struct sdt_probe *probe = parg; 208 209 KASSERT(probe->sdtp_lf->nenabled > 0, ("no probes enabled")); 210 211 probe->id = 0; 212 probe->sdtp_lf->nenabled--; 213} 214 215static void 216sdt_getargdesc(void *arg, dtrace_id_t id, void *parg, dtrace_argdesc_t *desc) 217{ 218 struct sdt_argtype *argtype; 219 struct sdt_probe *probe = parg; 220 221 if (desc->dtargd_ndx >= probe->n_args) { 222 desc->dtargd_ndx = DTRACE_ARGNONE; 223 return; 224 } 225 226 TAILQ_FOREACH(argtype, &probe->argtype_list, argtype_entry) { 227 if (desc->dtargd_ndx == argtype->ndx) { 228 desc->dtargd_mapping = desc->dtargd_ndx; 229 if (argtype->type == NULL) { 230 desc->dtargd_native[0] = '\0'; 231 desc->dtargd_xlate[0] = '\0'; 232 continue; 233 } 234 strlcpy(desc->dtargd_native, argtype->type, 235 sizeof(desc->dtargd_native)); 236 if (argtype->xtype != NULL) 237 strlcpy(desc->dtargd_xlate, argtype->xtype, 238 sizeof(desc->dtargd_xlate)); 239 } 240 } 241} 242 243static void 244sdt_destroy(void *arg, dtrace_id_t id, void *parg) 245{ 246} 247 248/* 249 * Called from the kernel linker when a module is loaded, before 250 * dtrace_module_loaded() is called. This is done so that it's possible to 251 * register new providers when modules are loaded. The DTrace framework 252 * explicitly disallows calling into the framework from the provide_module 253 * provider method, so we cannot do this there. 254 */ 255static void 256sdt_kld_load(void *arg __unused, struct linker_file *lf) 257{ 258 struct sdt_provider **prov, **begin, **end; 259 struct sdt_probe **probe, **p_begin, **p_end; 260 struct sdt_argtype **argtype, **a_begin, **a_end; 261 262 if (linker_file_lookup_set(lf, "sdt_providers_set", &begin, &end, 263 NULL) == 0) { 264 for (prov = begin; prov < end; prov++) 265 sdt_create_provider(*prov); 266 } 267 268 if (linker_file_lookup_set(lf, "sdt_probes_set", &p_begin, &p_end, 269 NULL) == 0) { 270 for (probe = p_begin; probe < p_end; probe++) { 271 (*probe)->sdtp_lf = lf; 272 sdt_create_probe(*probe); 273 TAILQ_INIT(&(*probe)->argtype_list); 274 } 275 } 276 277 if (linker_file_lookup_set(lf, "sdt_argtypes_set", &a_begin, &a_end, 278 NULL) == 0) { 279 for (argtype = a_begin; argtype < a_end; argtype++) { 280 (*argtype)->probe->n_args++; 281 TAILQ_INSERT_TAIL(&(*argtype)->probe->argtype_list, 282 *argtype, argtype_entry); 283 } 284 } 285} 286 287static void 288sdt_kld_unload_try(void *arg __unused, struct linker_file *lf, int *error) 289{ 290 struct sdt_provider *prov, **curr, **begin, **end, *tmp; 291 292 if (*error != 0) 293 /* We already have an error, so don't do anything. */ 294 return; 295 else if (linker_file_lookup_set(lf, "sdt_providers_set", &begin, &end, 296 NULL)) 297 /* No DTrace providers are declared in this file. */ 298 return; 299 300 /* 301 * Go through all the providers declared in this linker file and 302 * unregister any that aren't declared in another loaded file. 303 */ 304 for (curr = begin; curr < end; curr++) { 305 TAILQ_FOREACH_SAFE(prov, &sdt_prov_list, prov_entry, tmp) { 306 if (strcmp(prov->name, (*curr)->name) != 0) 307 continue; 308 309 if (prov->sdt_refs == 1) { 310 if (dtrace_unregister(prov->id) != 0) { 311 *error = 1; 312 return; 313 } 314 TAILQ_REMOVE(&sdt_prov_list, prov, prov_entry); 315 free(prov->name, M_SDT); 316 free(prov, M_SDT); 317 } else 318 prov->sdt_refs--; 319 break; 320 } 321 } 322} 323 324static int 325sdt_linker_file_cb(linker_file_t lf, void *arg __unused) 326{ 327 328 sdt_kld_load(NULL, lf); 329 330 return (0); 331} 332 333static void 334sdt_load() 335{ 336 337 TAILQ_INIT(&sdt_prov_list); 338 339 sdt_probe_func = dtrace_probe; 340 341 sdt_kld_load_tag = EVENTHANDLER_REGISTER(kld_load, sdt_kld_load, NULL, 342 EVENTHANDLER_PRI_ANY); 343 sdt_kld_unload_try_tag = EVENTHANDLER_REGISTER(kld_unload_try, 344 sdt_kld_unload_try, NULL, EVENTHANDLER_PRI_ANY); 345 346 /* Pick up probes from the kernel and already-loaded linker files. */ 347 linker_file_foreach(sdt_linker_file_cb, NULL); 348} 349 350static int 351sdt_unload() 352{ 353 struct sdt_provider *prov, *tmp; 354 int ret; 355 356 EVENTHANDLER_DEREGISTER(kld_load, sdt_kld_load_tag); 357 EVENTHANDLER_DEREGISTER(kld_unload_try, sdt_kld_unload_try_tag); 358 359 sdt_probe_func = sdt_probe_stub; 360 361 TAILQ_FOREACH_SAFE(prov, &sdt_prov_list, prov_entry, tmp) { 362 ret = dtrace_unregister(prov->id); 363 if (ret != 0) 364 return (ret); 365 TAILQ_REMOVE(&sdt_prov_list, prov, prov_entry); 366 free(prov->name, M_SDT); 367 free(prov, M_SDT); 368 } 369 370 return (0); 371} 372 373static int 374sdt_modevent(module_t mod __unused, int type, void *data __unused) 375{ 376 int error = 0; 377 378 switch (type) { 379 case MOD_LOAD: 380 sdt_load(); 381 break; 382 383 case MOD_UNLOAD: 384 error = sdt_unload(); 385 break; 386 387 case MOD_SHUTDOWN: 388 break; 389 390 default: 391 error = EOPNOTSUPP; 392 break; 393 } 394 395 return (error); 396} 397 398DEV_MODULE(sdt, sdt_modevent, NULL); 399MODULE_VERSION(sdt, 1); 400MODULE_DEPEND(sdt, dtrace, 1, 1, 1); 401