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 * Copyright 2013 Voxer Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 #include <unistd.h>
28 #include <fcntl.h>
29 #include <dlfcn.h>
30 #include <link.h>
31 #include <sys/dtrace.h>
32
33 #include <stdarg.h>
34 #include <stdio.h>
35 #include <stdlib.h>
36 #include <string.h>
37 #include <errno.h>
38 #include <libelf.h>
39 #include <gelf.h>
40
41 /*
42 * In Solaris 10 GA, the only mechanism for communicating helper information
43 * is through the DTrace helper pseudo-device node in /devices; there is
44 * no /dev link. Because of this, USDT providers and helper actions don't
45 * work inside of non-global zones. This issue was addressed by adding
46 * the /dev and having this initialization code use that /dev link. If the
47 * /dev link doesn't exist it falls back to looking for the /devices node
48 * as this code may be embedded in a binary which runs on Solaris 10 GA.
49 *
50 * Users may set the following environment variable to affect the way
51 * helper initialization takes place:
52 *
53 * DTRACE_DOF_INIT_DEBUG enable debugging output
54 * DTRACE_DOF_INIT_DISABLE disable helper loading
55 * DTRACE_DOF_INIT_DEVNAME set the path to the helper node
56 */
57
58 static const char *devnamep = "/dev/dtrace/helper";
59 #if defined(sun)
60 static const char *olddevname = "/devices/pseudo/dtrace@0:helper";
61 #endif
62
63 static const char *modname; /* Name of this load object */
64 static int gen; /* DOF helper generation */
65 #if defined(sun)
66 extern dof_hdr_t __SUNW_dof; /* DOF defined in the .SUNW_dof section */
67 #endif
68 static boolean_t dof_init_debug = B_FALSE; /* From DTRACE_DOF_INIT_DEBUG */
69
70 static void
dprintf(int debug,const char * fmt,...)71 dprintf(int debug, const char *fmt, ...)
72 {
73 va_list ap;
74
75 if (debug && !dof_init_debug)
76 return;
77
78 va_start(ap, fmt);
79
80 if (modname == NULL)
81 (void) fprintf(stderr, "dtrace DOF: ");
82 else
83 (void) fprintf(stderr, "dtrace DOF %s: ", modname);
84
85 (void) vfprintf(stderr, fmt, ap);
86
87 if (fmt[strlen(fmt) - 1] != '\n')
88 (void) fprintf(stderr, ": %s\n", strerror(errno));
89
90 va_end(ap);
91 }
92
93 #if !defined(sun)
94 static void
fixsymbol(Elf * e,Elf_Data * data,size_t idx,int nprobes,char * buf,dof_sec_t * sec,int * fixedprobes,char * dofstrtab)95 fixsymbol(Elf *e, Elf_Data *data, size_t idx, int nprobes, char *buf,
96 dof_sec_t *sec, int *fixedprobes, char *dofstrtab)
97 {
98 GElf_Sym sym;
99 char *s;
100 unsigned char *funcname;
101 dof_probe_t *prb;
102 int j = 0;
103 int ndx;
104
105 while (gelf_getsym(data, j++, &sym) != NULL) {
106 prb = (dof_probe_t *)(void *)(buf + sec->dofs_offset);
107
108 for (ndx = nprobes; ndx; ndx--, prb += 1) {
109 funcname = dofstrtab + prb->dofpr_func;
110 s = elf_strptr(e, idx, sym.st_name);
111 if (strcmp(s, funcname) == 0) {
112 dprintf(1, "fixing %s() symbol\n", s);
113 prb->dofpr_addr = sym.st_value;
114 (*fixedprobes)++;
115 }
116 }
117 if (*fixedprobes == nprobes)
118 break;
119 }
120 }
121 #endif
122
123 #if defined(sun)
124 #pragma init(dtrace_dof_init)
125 #else
126 static void dtrace_dof_init(void) __attribute__ ((constructor));
127 #endif
128
129 static void
dtrace_dof_init(void)130 dtrace_dof_init(void)
131 {
132 #if defined(sun)
133 dof_hdr_t *dof = &__SUNW_dof;
134 #else
135 dof_hdr_t *dof = NULL;
136 #endif
137 #ifdef _LP64
138 Elf64_Ehdr *elf;
139 #else
140 Elf32_Ehdr *elf;
141 #endif
142 dof_helper_t dh;
143 Link_map *lmp;
144 #if defined(sun)
145 Lmid_t lmid;
146 #else
147 u_long lmid = 0;
148 dof_sec_t *sec, *secstart, *dofstrtab, *dofprobes;
149 dof_provider_t *dofprovider;
150 size_t i;
151 #endif
152 int fd;
153 const char *p;
154 #if !defined(sun)
155 Elf *e;
156 Elf_Scn *scn = NULL;
157 Elf_Data *symtabdata = NULL, *dynsymdata = NULL, *dofdata = NULL;
158 dof_hdr_t *dof_next = NULL;
159 GElf_Shdr shdr;
160 int efd, nprobes;
161 char *s;
162 char *dofstrtabraw;
163 size_t shstridx, symtabidx = 0, dynsymidx = 0;
164 unsigned char *buf;
165 int fixedprobes;
166 uint64_t aligned_filesz;
167 #endif
168
169 if (getenv("DTRACE_DOF_INIT_DISABLE") != NULL)
170 return;
171
172 if (getenv("DTRACE_DOF_INIT_DEBUG") != NULL)
173 dof_init_debug = B_TRUE;
174
175 if (dlinfo(RTLD_SELF, RTLD_DI_LINKMAP, &lmp) == -1 || lmp == NULL) {
176 dprintf(1, "couldn't discover module name or address\n");
177 return;
178 }
179
180 #if defined(sun)
181 if (dlinfo(RTLD_SELF, RTLD_DI_LMID, &lmid) == -1) {
182 dprintf(1, "couldn't discover link map ID\n");
183 return;
184 }
185 #endif
186
187
188 if ((modname = strrchr(lmp->l_name, '/')) == NULL)
189 modname = lmp->l_name;
190 else
191 modname++;
192 #if !defined(sun)
193 elf_version(EV_CURRENT);
194 if ((efd = open(lmp->l_name, O_RDONLY, 0)) < 0) {
195 dprintf(1, "couldn't open file for reading\n");
196 return;
197 }
198 if ((e = elf_begin(efd, ELF_C_READ, NULL)) == NULL) {
199 dprintf(1, "elf_begin failed\n");
200 close(efd);
201 return;
202 }
203 elf_getshdrstrndx(e, &shstridx);
204 dof = NULL;
205 while ((scn = elf_nextscn(e, scn)) != NULL) {
206 gelf_getshdr(scn, &shdr);
207 if (shdr.sh_type == SHT_SYMTAB) {
208 symtabidx = shdr.sh_link;
209 symtabdata = elf_getdata(scn, NULL);
210 } else if (shdr.sh_type == SHT_DYNSYM) {
211 dynsymidx = shdr.sh_link;
212 dynsymdata = elf_getdata(scn, NULL);
213 } else if (shdr.sh_type == SHT_PROGBITS) {
214 s = elf_strptr(e, shstridx, shdr.sh_name);
215 if (s && strcmp(s, ".SUNW_dof") == 0) {
216 dofdata = elf_getdata(scn, NULL);
217 dof = dofdata->d_buf;
218 }
219 }
220 }
221 if (dof == NULL) {
222 dprintf(1, "SUNW_dof section not found\n");
223 elf_end(e);
224 close(efd);
225 return;
226 }
227
228 while ((char *) dof < (char *) dofdata->d_buf + dofdata->d_size) {
229 fixedprobes = 0;
230 aligned_filesz = (shdr.sh_addralign == 0 ? dof->dofh_filesz :
231 roundup2(dof->dofh_filesz, shdr.sh_addralign));
232 dof_next = (void *) ((char *) dof + aligned_filesz);
233 #endif
234
235 if (dof->dofh_ident[DOF_ID_MAG0] != DOF_MAG_MAG0 ||
236 dof->dofh_ident[DOF_ID_MAG1] != DOF_MAG_MAG1 ||
237 dof->dofh_ident[DOF_ID_MAG2] != DOF_MAG_MAG2 ||
238 dof->dofh_ident[DOF_ID_MAG3] != DOF_MAG_MAG3) {
239 dprintf(0, ".SUNW_dof section corrupt\n");
240 return;
241 }
242
243 elf = (void *)lmp->l_addr;
244
245 dh.dofhp_dof = (uintptr_t)dof;
246 dh.dofhp_addr = elf->e_type == ET_DYN ? (uintptr_t) lmp->l_addr : 0;
247
248 if (lmid == 0) {
249 (void) snprintf(dh.dofhp_mod, sizeof (dh.dofhp_mod),
250 "%s", modname);
251 } else {
252 (void) snprintf(dh.dofhp_mod, sizeof (dh.dofhp_mod),
253 "LM%lu`%s", lmid, modname);
254 }
255
256 if ((p = getenv("DTRACE_DOF_INIT_DEVNAME")) != NULL)
257 devnamep = p;
258
259 if ((fd = open64(devnamep, O_RDWR)) < 0) {
260 dprintf(1, "failed to open helper device %s", devnamep);
261 #if defined(sun)
262 /*
263 * If the device path wasn't explicitly set, try again with
264 * the old device path.
265 */
266 if (p != NULL)
267 return;
268
269 devnamep = olddevname;
270
271 if ((fd = open64(devnamep, O_RDWR)) < 0) {
272 dprintf(1, "failed to open helper device %s", devnamep);
273 return;
274 }
275 #else
276 return;
277 #endif
278 }
279 #if !defined(sun)
280 /*
281 * We need to fix the base address of each probe since this wasn't
282 * done by ld(1). (ld(1) needs to grow support for parsing the
283 * SUNW_dof section).
284 *
285 * The complexity of this is not that great. The first for loop
286 * iterates over the sections inside the DOF file. There are usually
287 * 10 sections here. We asume the STRTAB section comes first and the
288 * PROBES section comes after. Since we are only interested in fixing
289 * data inside the PROBES section we quit the for loop after processing
290 * the PROBES section. It's usually the case that the first section
291 * is the STRTAB section and the second section is the PROBES section,
292 * so this for loop is not meaningful when doing complexity analysis.
293 *
294 * After finding the probes section, we iterate over the symbols
295 * in the symtab section. When we find a symbol name that matches
296 * the probe function name, we fix it. If we have fixed all the
297 * probes, we exit all the loops and we are done.
298 * The number of probes is given by the variable 'nprobes' and this
299 * depends entirely on the user, but some optimizations were done.
300 *
301 * We are assuming the number of probes is less than the number of
302 * symbols (libc can have 4k symbols, for example).
303 */
304 secstart = sec = (dof_sec_t *)(dof + 1);
305 buf = (char *)dof;
306 for (i = 0; i < dof->dofh_secnum; i++, sec++) {
307 if (sec->dofs_type != DOF_SECT_PROVIDER)
308 continue;
309
310 dofprovider = (void *) (buf + sec->dofs_offset);
311 dofstrtab = secstart + dofprovider->dofpv_strtab;
312 dofprobes = secstart + dofprovider->dofpv_probes;
313
314 if (dofstrtab->dofs_type != DOF_SECT_STRTAB) {
315 fprintf(stderr, "WARNING: expected STRTAB section, but got %d\n",
316 dofstrtab->dofs_type);
317 break;
318 }
319 if (dofprobes->dofs_type != DOF_SECT_PROBES) {
320 fprintf(stderr, "WARNING: expected PROBES section, but got %d\n",
321 dofprobes->dofs_type);
322 break;
323 }
324
325 dprintf(1, "found provider %p\n", dofprovider);
326 dofstrtabraw = (char *)(buf + dofstrtab->dofs_offset);
327 nprobes = dofprobes->dofs_size / dofprobes->dofs_entsize;
328 fixsymbol(e, symtabdata, symtabidx, nprobes, buf, dofprobes, &fixedprobes,
329 dofstrtabraw);
330 if (fixedprobes != nprobes) {
331 /*
332 * If we haven't fixed all the probes using the
333 * symtab section, look inside the dynsym
334 * section.
335 */
336 fixsymbol(e, dynsymdata, dynsymidx, nprobes, buf, dofprobes,
337 &fixedprobes, dofstrtabraw);
338 }
339 if (fixedprobes != nprobes) {
340 fprintf(stderr, "WARNING: number of probes "
341 "fixed does not match the number of "
342 "defined probes (%d != %d, "
343 "respectively)\n", fixedprobes, nprobes);
344 fprintf(stderr, "WARNING: some probes might "
345 "not fire or your program might crash\n");
346 }
347 }
348 #endif
349 if ((gen = ioctl(fd, DTRACEHIOC_ADDDOF, &dh)) == -1)
350 dprintf(1, "DTrace ioctl failed for DOF at %p", dof);
351 else {
352 dprintf(1, "DTrace ioctl succeeded for DOF at %p\n", dof);
353 #if !defined(sun)
354 gen = dh.gen;
355 #endif
356 }
357
358 (void) close(fd);
359
360 #if !defined(sun)
361 /* End of while loop */
362 dof = dof_next;
363 }
364
365 elf_end(e);
366 (void) close(efd);
367 #endif
368 }
369
370 #if defined(sun)
371 #pragma fini(dtrace_dof_fini)
372 #else
373 static void dtrace_dof_fini(void) __attribute__ ((destructor));
374 #endif
375
376 static void
dtrace_dof_fini(void)377 dtrace_dof_fini(void)
378 {
379 int fd;
380
381 if ((fd = open64(devnamep, O_RDWR)) < 0) {
382 dprintf(1, "failed to open helper device %s", devnamep);
383 return;
384 }
385
386 if ((gen = ioctl(fd, DTRACEHIOC_REMOVE, &gen)) == -1)
387 dprintf(1, "DTrace ioctl failed to remove DOF (%d)\n", gen);
388 else
389 dprintf(1, "DTrace ioctl removed DOF (%d)\n", gen);
390
391 (void) close(fd);
392 }
393