FreeBSD/Linux Kernel Cross Reference
sys/dev/ksyms/ksyms.c
1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2008-2009, Stacey Son <sson@freebsd.org>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 *
28 * $FreeBSD$
29 */
30
31 #include <sys/param.h>
32 #include <sys/systm.h>
33 #include <sys/kernel.h>
34
35 #include <sys/conf.h>
36 #include <sys/elf.h>
37 #include <sys/linker.h>
38 #include <sys/malloc.h>
39 #include <sys/mman.h>
40 #include <sys/module.h>
41 #include <sys/proc.h>
42 #include <sys/queue.h>
43 #include <sys/resourcevar.h>
44 #include <sys/rwlock.h>
45 #include <sys/stat.h>
46 #include <sys/sx.h>
47 #include <sys/uio.h>
48
49 #include <machine/elf.h>
50
51 #include <vm/pmap.h>
52 #include <vm/vm.h>
53 #include <vm/vm_extern.h>
54 #include <vm/vm_object.h>
55 #include <vm/vm_page.h>
56 #include <vm/vm_pager.h>
57
58 #include "linker_if.h"
59
60 #define SHDR_NULL 0
61 #define SHDR_SYMTAB 1
62 #define SHDR_STRTAB 2
63 #define SHDR_SHSTRTAB 3
64
65 #define SHDR_NUM 4
66
67 #define STR_SYMTAB ".symtab"
68 #define STR_STRTAB ".strtab"
69 #define STR_SHSTRTAB ".shstrtab"
70
71 #define KSYMS_DNAME "ksyms"
72
73 static d_open_t ksyms_open;
74 static d_read_t ksyms_read;
75 static d_mmap_single_t ksyms_mmap_single;
76
77 static struct cdevsw ksyms_cdevsw = {
78 .d_version = D_VERSION,
79 .d_flags = 0,
80 .d_open = ksyms_open,
81 .d_read = ksyms_read,
82 .d_mmap_single = ksyms_mmap_single,
83 .d_name = KSYMS_DNAME
84 };
85
86 struct ksyms_softc {
87 LIST_ENTRY(ksyms_softc) sc_list;
88 vm_offset_t sc_uaddr;
89 size_t sc_usize;
90 vm_object_t sc_obj;
91 vm_size_t sc_objsz;
92 struct proc *sc_proc;
93 };
94
95 static struct sx ksyms_mtx;
96 static struct cdev *ksyms_dev;
97 static LIST_HEAD(, ksyms_softc) ksyms_list = LIST_HEAD_INITIALIZER(ksyms_list);
98
99 static const char ksyms_shstrtab[] =
100 "\0" STR_SYMTAB "\0" STR_STRTAB "\0" STR_SHSTRTAB "\0";
101
102 struct ksyms_hdr {
103 Elf_Ehdr kh_ehdr;
104 Elf_Phdr kh_txtphdr;
105 Elf_Phdr kh_datphdr;
106 Elf_Shdr kh_shdr[SHDR_NUM];
107 char kh_shstrtab[sizeof(ksyms_shstrtab)];
108 };
109
110 struct tsizes {
111 size_t ts_symsz;
112 size_t ts_strsz;
113 };
114
115 struct toffsets {
116 struct ksyms_softc *to_sc;
117 vm_offset_t to_symoff;
118 vm_offset_t to_stroff;
119 unsigned to_stridx;
120 size_t to_resid;
121 };
122
123 static MALLOC_DEFINE(M_KSYMS, "KSYMS", "Kernel Symbol Table");
124
125 /*
126 * Get the symbol and string table sizes for a kernel module. Add it to the
127 * running total.
128 */
129 static int
130 ksyms_size_permod(linker_file_t lf, void *arg)
131 {
132 struct tsizes *ts;
133 const Elf_Sym *symtab;
134 caddr_t strtab;
135 long syms;
136
137 ts = arg;
138
139 syms = LINKER_SYMTAB_GET(lf, &symtab);
140 ts->ts_symsz += syms * sizeof(Elf_Sym);
141 ts->ts_strsz += LINKER_STRTAB_GET(lf, &strtab);
142
143 return (0);
144 }
145
146 /*
147 * For kernel module get the symbol and string table sizes, returning the
148 * totals in *ts.
149 */
150 static void
151 ksyms_size_calc(struct tsizes *ts)
152 {
153
154 ts->ts_symsz = 0;
155 ts->ts_strsz = 0;
156
157 (void)linker_file_foreach(ksyms_size_permod, ts);
158 }
159
160 static int
161 ksyms_emit(struct ksyms_softc *sc, void *buf, off_t off, size_t sz)
162 {
163 struct iovec iov;
164 struct uio uio;
165
166 iov.iov_base = buf;
167 iov.iov_len = sz;
168 uio.uio_iov = &iov;
169 uio.uio_iovcnt = 1;
170 uio.uio_offset = off;
171 uio.uio_resid = (ssize_t)sz;
172 uio.uio_segflg = UIO_SYSSPACE;
173 uio.uio_rw = UIO_WRITE;
174 uio.uio_td = curthread;
175
176 return (uiomove_object(sc->sc_obj, sc->sc_objsz, &uio));
177 }
178
179 #define SYMBLKSZ (256 * sizeof(Elf_Sym))
180
181 /*
182 * For a kernel module, add the symbol and string tables into the
183 * snapshot buffer. Fix up the offsets in the tables.
184 */
185 static int
186 ksyms_add(linker_file_t lf, void *arg)
187 {
188 char *buf;
189 struct ksyms_softc *sc;
190 struct toffsets *to;
191 const Elf_Sym *symtab;
192 Elf_Sym *symp;
193 caddr_t strtab;
194 size_t len, numsyms, strsz, symsz;
195 linker_symval_t symval;
196 int error, i, nsyms;
197 bool fixup;
198
199 buf = malloc(SYMBLKSZ, M_KSYMS, M_WAITOK);
200 to = arg;
201 sc = to->to_sc;
202
203 MOD_SLOCK;
204 numsyms = LINKER_SYMTAB_GET(lf, &symtab);
205 strsz = LINKER_STRTAB_GET(lf, &strtab);
206 symsz = numsyms * sizeof(Elf_Sym);
207
208 #ifdef RELOCATABLE_KERNEL
209 fixup = true;
210 #else
211 fixup = lf->id > 1;
212 #endif
213
214 while (symsz > 0) {
215 len = min(SYMBLKSZ, symsz);
216 bcopy(symtab, buf, len);
217
218 /*
219 * Fix up symbol table for kernel modules:
220 * string offsets need adjusted
221 * symbol values made absolute
222 */
223 symp = (Elf_Sym *) buf;
224 nsyms = len / sizeof(Elf_Sym);
225 for (i = 0; i < nsyms; i++) {
226 symp[i].st_name += to->to_stridx;
227 if (fixup && LINKER_SYMBOL_VALUES(lf,
228 (c_linker_sym_t)&symtab[i], &symval) == 0) {
229 symp[i].st_value = (uintptr_t)symval.value;
230 }
231 }
232
233 if (len > to->to_resid) {
234 MOD_SUNLOCK;
235 free(buf, M_KSYMS);
236 return (ENXIO);
237 }
238 to->to_resid -= len;
239 error = ksyms_emit(sc, buf, to->to_symoff, len);
240 to->to_symoff += len;
241 if (error != 0) {
242 MOD_SUNLOCK;
243 free(buf, M_KSYMS);
244 return (error);
245 }
246
247 symtab += nsyms;
248 symsz -= len;
249 }
250 free(buf, M_KSYMS);
251 MOD_SUNLOCK;
252
253 if (strsz > to->to_resid)
254 return (ENXIO);
255 to->to_resid -= strsz;
256 error = ksyms_emit(sc, strtab, to->to_stroff, strsz);
257 to->to_stroff += strsz;
258 to->to_stridx += strsz;
259
260 return (error);
261 }
262
263 /*
264 * Create a single ELF symbol table for the kernel and kernel modules loaded
265 * at this time. Write this snapshot out in the process address space. Return
266 * 0 on success, otherwise error.
267 */
268 static int
269 ksyms_snapshot(struct ksyms_softc *sc, struct tsizes *ts)
270 {
271 struct toffsets to;
272 struct ksyms_hdr *hdr;
273 int error;
274
275 hdr = malloc(sizeof(*hdr), M_KSYMS, M_WAITOK | M_ZERO);
276
277 /*
278 * Create the ELF header.
279 */
280 hdr->kh_ehdr.e_ident[EI_PAD] = 0;
281 hdr->kh_ehdr.e_ident[EI_MAG0] = ELFMAG0;
282 hdr->kh_ehdr.e_ident[EI_MAG1] = ELFMAG1;
283 hdr->kh_ehdr.e_ident[EI_MAG2] = ELFMAG2;
284 hdr->kh_ehdr.e_ident[EI_MAG3] = ELFMAG3;
285 hdr->kh_ehdr.e_ident[EI_DATA] = ELF_DATA;
286 hdr->kh_ehdr.e_ident[EI_OSABI] = ELFOSABI_FREEBSD;
287 hdr->kh_ehdr.e_ident[EI_CLASS] = ELF_CLASS;
288 hdr->kh_ehdr.e_ident[EI_VERSION] = EV_CURRENT;
289 hdr->kh_ehdr.e_ident[EI_ABIVERSION] = 0;
290 hdr->kh_ehdr.e_type = ET_EXEC;
291 hdr->kh_ehdr.e_machine = ELF_ARCH;
292 hdr->kh_ehdr.e_version = EV_CURRENT;
293 hdr->kh_ehdr.e_entry = 0;
294 hdr->kh_ehdr.e_phoff = offsetof(struct ksyms_hdr, kh_txtphdr);
295 hdr->kh_ehdr.e_shoff = offsetof(struct ksyms_hdr, kh_shdr);
296 hdr->kh_ehdr.e_flags = 0;
297 hdr->kh_ehdr.e_ehsize = sizeof(Elf_Ehdr);
298 hdr->kh_ehdr.e_phentsize = sizeof(Elf_Phdr);
299 hdr->kh_ehdr.e_phnum = 2; /* Text and Data */
300 hdr->kh_ehdr.e_shentsize = sizeof(Elf_Shdr);
301 hdr->kh_ehdr.e_shnum = SHDR_NUM;
302 hdr->kh_ehdr.e_shstrndx = SHDR_SHSTRTAB;
303
304 /*
305 * Add both the text and data program headers.
306 */
307 hdr->kh_txtphdr.p_type = PT_LOAD;
308 /* XXX - is there a way to put the actual .text addr/size here? */
309 hdr->kh_txtphdr.p_vaddr = 0;
310 hdr->kh_txtphdr.p_memsz = 0;
311 hdr->kh_txtphdr.p_flags = PF_R | PF_X;
312
313 hdr->kh_datphdr.p_type = PT_LOAD;
314 /* XXX - is there a way to put the actual .data addr/size here? */
315 hdr->kh_datphdr.p_vaddr = 0;
316 hdr->kh_datphdr.p_memsz = 0;
317 hdr->kh_datphdr.p_flags = PF_R | PF_W | PF_X;
318
319 /*
320 * Add the section headers: null, symtab, strtab, shstrtab.
321 */
322
323 /* First section header - null */
324
325 /* Second section header - symtab */
326 hdr->kh_shdr[SHDR_SYMTAB].sh_name = 1; /* String offset (skip null) */
327 hdr->kh_shdr[SHDR_SYMTAB].sh_type = SHT_SYMTAB;
328 hdr->kh_shdr[SHDR_SYMTAB].sh_flags = 0;
329 hdr->kh_shdr[SHDR_SYMTAB].sh_addr = 0;
330 hdr->kh_shdr[SHDR_SYMTAB].sh_offset = sizeof(*hdr);
331 hdr->kh_shdr[SHDR_SYMTAB].sh_size = ts->ts_symsz;
332 hdr->kh_shdr[SHDR_SYMTAB].sh_link = SHDR_STRTAB;
333 hdr->kh_shdr[SHDR_SYMTAB].sh_info = ts->ts_symsz / sizeof(Elf_Sym);
334 hdr->kh_shdr[SHDR_SYMTAB].sh_addralign = sizeof(long);
335 hdr->kh_shdr[SHDR_SYMTAB].sh_entsize = sizeof(Elf_Sym);
336
337 /* Third section header - strtab */
338 hdr->kh_shdr[SHDR_STRTAB].sh_name = 1 + sizeof(STR_SYMTAB);
339 hdr->kh_shdr[SHDR_STRTAB].sh_type = SHT_STRTAB;
340 hdr->kh_shdr[SHDR_STRTAB].sh_flags = 0;
341 hdr->kh_shdr[SHDR_STRTAB].sh_addr = 0;
342 hdr->kh_shdr[SHDR_STRTAB].sh_offset =
343 hdr->kh_shdr[SHDR_SYMTAB].sh_offset + ts->ts_symsz;
344 hdr->kh_shdr[SHDR_STRTAB].sh_size = ts->ts_strsz;
345 hdr->kh_shdr[SHDR_STRTAB].sh_link = 0;
346 hdr->kh_shdr[SHDR_STRTAB].sh_info = 0;
347 hdr->kh_shdr[SHDR_STRTAB].sh_addralign = sizeof(char);
348 hdr->kh_shdr[SHDR_STRTAB].sh_entsize = 0;
349
350 /* Fourth section - shstrtab */
351 hdr->kh_shdr[SHDR_SHSTRTAB].sh_name = 1 + sizeof(STR_SYMTAB) +
352 sizeof(STR_STRTAB);
353 hdr->kh_shdr[SHDR_SHSTRTAB].sh_type = SHT_STRTAB;
354 hdr->kh_shdr[SHDR_SHSTRTAB].sh_flags = 0;
355 hdr->kh_shdr[SHDR_SHSTRTAB].sh_addr = 0;
356 hdr->kh_shdr[SHDR_SHSTRTAB].sh_offset =
357 offsetof(struct ksyms_hdr, kh_shstrtab);
358 hdr->kh_shdr[SHDR_SHSTRTAB].sh_size = sizeof(ksyms_shstrtab);
359 hdr->kh_shdr[SHDR_SHSTRTAB].sh_link = 0;
360 hdr->kh_shdr[SHDR_SHSTRTAB].sh_info = 0;
361 hdr->kh_shdr[SHDR_SHSTRTAB].sh_addralign = 0 /* sizeof(char) */;
362 hdr->kh_shdr[SHDR_SHSTRTAB].sh_entsize = 0;
363
364 /* Copy shstrtab into the header. */
365 bcopy(ksyms_shstrtab, hdr->kh_shstrtab, sizeof(ksyms_shstrtab));
366
367 to.to_sc = sc;
368 to.to_symoff = hdr->kh_shdr[SHDR_SYMTAB].sh_offset;
369 to.to_stroff = hdr->kh_shdr[SHDR_STRTAB].sh_offset;
370 to.to_stridx = 0;
371 to.to_resid = sc->sc_objsz - sizeof(struct ksyms_hdr);
372
373 /* emit header */
374 error = ksyms_emit(sc, hdr, 0, sizeof(*hdr));
375 free(hdr, M_KSYMS);
376 if (error != 0)
377 return (error);
378
379 /* Add symbol and string tables for each kernel module. */
380 error = linker_file_foreach(ksyms_add, &to);
381 if (error != 0)
382 return (error);
383 if (to.to_resid != 0)
384 return (ENXIO);
385 return (0);
386 }
387
388 static void
389 ksyms_cdevpriv_dtr(void *data)
390 {
391 struct ksyms_softc *sc;
392 vm_object_t obj;
393
394 sc = (struct ksyms_softc *)data;
395
396 sx_xlock(&ksyms_mtx);
397 LIST_REMOVE(sc, sc_list);
398 sx_xunlock(&ksyms_mtx);
399 obj = sc->sc_obj;
400 if (obj != NULL)
401 vm_object_deallocate(obj);
402 free(sc, M_KSYMS);
403 }
404
405 static int
406 ksyms_open(struct cdev *dev, int flags, int fmt __unused, struct thread *td)
407 {
408 struct tsizes ts;
409 struct ksyms_softc *sc;
410 vm_object_t object;
411 vm_size_t elfsz;
412 int error, try;
413
414 /*
415 * Limit one open() per process. The process must close()
416 * before open()'ing again.
417 */
418 sx_xlock(&ksyms_mtx);
419 LIST_FOREACH(sc, &ksyms_list, sc_list) {
420 if (sc->sc_proc == td->td_proc) {
421 sx_xunlock(&ksyms_mtx);
422 return (EBUSY);
423 }
424 }
425
426 sc = malloc(sizeof(*sc), M_KSYMS, M_WAITOK | M_ZERO);
427 sc->sc_proc = td->td_proc;
428 LIST_INSERT_HEAD(&ksyms_list, sc, sc_list);
429 sx_xunlock(&ksyms_mtx);
430
431 error = devfs_set_cdevpriv(sc, ksyms_cdevpriv_dtr);
432 if (error != 0) {
433 ksyms_cdevpriv_dtr(sc);
434 return (error);
435 }
436
437 /*
438 * MOD_SLOCK doesn't work here (because of a lock reversal with
439 * KLD_SLOCK). Therefore, simply try up to 3 times to get a "clean"
440 * snapshot of the kernel symbol table. This should work fine in the
441 * rare case of a kernel module being loaded/unloaded at the same
442 * time.
443 */
444 for (try = 0; try < 3; try++) {
445 ksyms_size_calc(&ts);
446 elfsz = sizeof(struct ksyms_hdr) + ts.ts_symsz + ts.ts_strsz;
447
448 object = vm_pager_allocate(OBJT_PHYS, NULL, round_page(elfsz),
449 VM_PROT_ALL, 0, td->td_ucred);
450 sc->sc_obj = object;
451 sc->sc_objsz = elfsz;
452
453 error = ksyms_snapshot(sc, &ts);
454 if (error == 0)
455 break;
456
457 vm_object_deallocate(sc->sc_obj);
458 sc->sc_obj = NULL;
459 }
460 return (error);
461 }
462
463 static int
464 ksyms_read(struct cdev *dev, struct uio *uio, int flags __unused)
465 {
466 struct ksyms_softc *sc;
467 int error;
468
469 error = devfs_get_cdevpriv((void **)&sc);
470 if (error != 0)
471 return (error);
472 return (uiomove_object(sc->sc_obj, sc->sc_objsz, uio));
473 }
474
475 static int
476 ksyms_mmap_single(struct cdev *dev, vm_ooffset_t *offset, vm_size_t size,
477 vm_object_t *objp, int nprot)
478 {
479 struct ksyms_softc *sc;
480 vm_object_t obj;
481 int error;
482
483 error = devfs_get_cdevpriv((void **)&sc);
484 if (error != 0)
485 return (error);
486
487 if (*offset >= round_page(sc->sc_objsz) ||
488 size > round_page(sc->sc_objsz) - *offset ||
489 (nprot & ~PROT_READ) != 0)
490 return (EINVAL);
491
492 obj = sc->sc_obj;
493 vm_object_reference(obj);
494 *objp = obj;
495 return (0);
496 }
497
498 static int
499 ksyms_modevent(module_t mod __unused, int type, void *data __unused)
500 {
501 int error;
502
503 error = 0;
504 switch (type) {
505 case MOD_LOAD:
506 sx_init(&ksyms_mtx, "KSyms mtx");
507 ksyms_dev = make_dev(&ksyms_cdevsw, 0, UID_ROOT, GID_WHEEL,
508 0400, KSYMS_DNAME);
509 break;
510 case MOD_UNLOAD:
511 if (!LIST_EMPTY(&ksyms_list))
512 return (EBUSY);
513 destroy_dev(ksyms_dev);
514 sx_destroy(&ksyms_mtx);
515 break;
516 case MOD_SHUTDOWN:
517 break;
518 default:
519 error = EOPNOTSUPP;
520 break;
521 }
522 return (error);
523 }
524
525 DEV_MODULE(ksyms, ksyms_modevent, NULL);
526 MODULE_VERSION(ksyms, 1);
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