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