2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 2008-2009, Stacey Son <sson@freebsd.org>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
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.
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
31 #include <sys/param.h>
32 #include <sys/systm.h>
33 #include <sys/kernel.h>
37 #include <sys/linker.h>
38 #include <sys/malloc.h>
40 #include <sys/module.h>
42 #include <sys/queue.h>
43 #include <sys/resourcevar.h>
48 #include <machine/elf.h>
52 #include <vm/vm_extern.h>
53 #include <vm/vm_object.h>
55 #include "linker_if.h"
60 #define SHDR_SHSTRTAB 3
64 #define STR_SYMTAB ".symtab"
65 #define STR_STRTAB ".strtab"
66 #define STR_SHSTRTAB ".shstrtab"
68 #define KSYMS_DNAME "ksyms"
70 static d_open_t ksyms_open;
71 static d_read_t ksyms_read;
72 static d_mmap_single_t ksyms_mmap_single;
74 static struct cdevsw ksyms_cdevsw = {
75 .d_version = D_VERSION,
79 .d_mmap_single = ksyms_mmap_single,
84 LIST_ENTRY(ksyms_softc) sc_list;
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);
96 static const char ksyms_shstrtab[] =
97 "\0" STR_SYMTAB "\0" STR_STRTAB "\0" STR_SHSTRTAB "\0";
103 Elf_Shdr kh_shdr[SHDR_NUM];
104 char kh_shstrtab[sizeof(ksyms_shstrtab)];
113 struct ksyms_softc *to_sc;
114 vm_offset_t to_symoff;
115 vm_offset_t to_stroff;
120 static MALLOC_DEFINE(M_KSYMS, "KSYMS", "Kernel Symbol Table");
123 * Get the symbol and string table sizes for a kernel module. Add it to the
127 ksyms_size_permod(linker_file_t lf, void *arg)
130 const Elf_Sym *symtab;
136 syms = LINKER_SYMTAB_GET(lf, &symtab);
137 ts->ts_symsz += syms * sizeof(Elf_Sym);
138 ts->ts_strsz += LINKER_STRTAB_GET(lf, &strtab);
144 * For kernel module get the symbol and string table sizes, returning the
148 ksyms_size_calc(struct tsizes *ts)
154 (void)linker_file_foreach(ksyms_size_permod, ts);
158 ksyms_emit(struct ksyms_softc *sc, void *buf, off_t off, size_t sz)
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;
173 return (uiomove_object(sc->sc_obj, sc->sc_objsz, &uio));
176 #define SYMBLKSZ (256 * sizeof(Elf_Sym))
179 * For a kernel module, add the symbol and string tables into the
180 * snapshot buffer. Fix up the offsets in the tables.
183 ksyms_add(linker_file_t lf, void *arg)
186 struct ksyms_softc *sc;
188 const Elf_Sym *symtab;
191 size_t len, numsyms, strsz, symsz;
192 linker_symval_t symval;
195 buf = malloc(SYMBLKSZ, M_KSYMS, M_WAITOK);
200 numsyms = LINKER_SYMTAB_GET(lf, &symtab);
201 strsz = LINKER_STRTAB_GET(lf, &strtab);
202 symsz = numsyms * sizeof(Elf_Sym);
205 len = min(SYMBLKSZ, symsz);
206 bcopy(symtab, buf, len);
209 * Fix up symbol table for kernel modules:
210 * string offsets need adjusted
211 * symbol values made absolute
213 symp = (Elf_Sym *) buf;
214 nsyms = len / sizeof(Elf_Sym);
215 for (i = 0; i < nsyms; i++) {
216 symp[i].st_name += to->to_stridx;
217 if (lf->id > 1 && LINKER_SYMBOL_VALUES(lf,
218 (c_linker_sym_t)&symtab[i], &symval) == 0) {
219 symp[i].st_value = (uintptr_t)symval.value;
223 if (len > to->to_resid) {
229 error = ksyms_emit(sc, buf, to->to_symoff, len);
230 to->to_symoff += len;
243 if (strsz > to->to_resid)
245 to->to_resid -= strsz;
246 error = ksyms_emit(sc, strtab, to->to_stroff, strsz);
247 to->to_stroff += strsz;
248 to->to_stridx += strsz;
254 * Create a single ELF symbol table for the kernel and kernel modules loaded
255 * at this time. Write this snapshot out in the process address space. Return
256 * 0 on success, otherwise error.
259 ksyms_snapshot(struct ksyms_softc *sc, struct tsizes *ts)
262 struct ksyms_hdr *hdr;
265 hdr = malloc(sizeof(*hdr), M_KSYMS, M_WAITOK | M_ZERO);
268 * Create the ELF header.
270 hdr->kh_ehdr.e_ident[EI_PAD] = 0;
271 hdr->kh_ehdr.e_ident[EI_MAG0] = ELFMAG0;
272 hdr->kh_ehdr.e_ident[EI_MAG1] = ELFMAG1;
273 hdr->kh_ehdr.e_ident[EI_MAG2] = ELFMAG2;
274 hdr->kh_ehdr.e_ident[EI_MAG3] = ELFMAG3;
275 hdr->kh_ehdr.e_ident[EI_DATA] = ELF_DATA;
276 hdr->kh_ehdr.e_ident[EI_OSABI] = ELFOSABI_FREEBSD;
277 hdr->kh_ehdr.e_ident[EI_CLASS] = ELF_CLASS;
278 hdr->kh_ehdr.e_ident[EI_VERSION] = EV_CURRENT;
279 hdr->kh_ehdr.e_ident[EI_ABIVERSION] = 0;
280 hdr->kh_ehdr.e_type = ET_EXEC;
281 hdr->kh_ehdr.e_machine = ELF_ARCH;
282 hdr->kh_ehdr.e_version = EV_CURRENT;
283 hdr->kh_ehdr.e_entry = 0;
284 hdr->kh_ehdr.e_phoff = offsetof(struct ksyms_hdr, kh_txtphdr);
285 hdr->kh_ehdr.e_shoff = offsetof(struct ksyms_hdr, kh_shdr);
286 hdr->kh_ehdr.e_flags = 0;
287 hdr->kh_ehdr.e_ehsize = sizeof(Elf_Ehdr);
288 hdr->kh_ehdr.e_phentsize = sizeof(Elf_Phdr);
289 hdr->kh_ehdr.e_phnum = 2; /* Text and Data */
290 hdr->kh_ehdr.e_shentsize = sizeof(Elf_Shdr);
291 hdr->kh_ehdr.e_shnum = SHDR_NUM;
292 hdr->kh_ehdr.e_shstrndx = SHDR_SHSTRTAB;
295 * Add both the text and data program headers.
297 hdr->kh_txtphdr.p_type = PT_LOAD;
298 /* XXX - is there a way to put the actual .text addr/size here? */
299 hdr->kh_txtphdr.p_vaddr = 0;
300 hdr->kh_txtphdr.p_memsz = 0;
301 hdr->kh_txtphdr.p_flags = PF_R | PF_X;
303 hdr->kh_datphdr.p_type = PT_LOAD;
304 /* XXX - is there a way to put the actual .data addr/size here? */
305 hdr->kh_datphdr.p_vaddr = 0;
306 hdr->kh_datphdr.p_memsz = 0;
307 hdr->kh_datphdr.p_flags = PF_R | PF_W | PF_X;
310 * Add the section headers: null, symtab, strtab, shstrtab.
313 /* First section header - null */
315 /* Second section header - symtab */
316 hdr->kh_shdr[SHDR_SYMTAB].sh_name = 1; /* String offset (skip null) */
317 hdr->kh_shdr[SHDR_SYMTAB].sh_type = SHT_SYMTAB;
318 hdr->kh_shdr[SHDR_SYMTAB].sh_flags = 0;
319 hdr->kh_shdr[SHDR_SYMTAB].sh_addr = 0;
320 hdr->kh_shdr[SHDR_SYMTAB].sh_offset = sizeof(*hdr);
321 hdr->kh_shdr[SHDR_SYMTAB].sh_size = ts->ts_symsz;
322 hdr->kh_shdr[SHDR_SYMTAB].sh_link = SHDR_STRTAB;
323 hdr->kh_shdr[SHDR_SYMTAB].sh_info = ts->ts_symsz / sizeof(Elf_Sym);
324 hdr->kh_shdr[SHDR_SYMTAB].sh_addralign = sizeof(long);
325 hdr->kh_shdr[SHDR_SYMTAB].sh_entsize = sizeof(Elf_Sym);
327 /* Third section header - strtab */
328 hdr->kh_shdr[SHDR_STRTAB].sh_name = 1 + sizeof(STR_SYMTAB);
329 hdr->kh_shdr[SHDR_STRTAB].sh_type = SHT_STRTAB;
330 hdr->kh_shdr[SHDR_STRTAB].sh_flags = 0;
331 hdr->kh_shdr[SHDR_STRTAB].sh_addr = 0;
332 hdr->kh_shdr[SHDR_STRTAB].sh_offset =
333 hdr->kh_shdr[SHDR_SYMTAB].sh_offset + ts->ts_symsz;
334 hdr->kh_shdr[SHDR_STRTAB].sh_size = ts->ts_strsz;
335 hdr->kh_shdr[SHDR_STRTAB].sh_link = 0;
336 hdr->kh_shdr[SHDR_STRTAB].sh_info = 0;
337 hdr->kh_shdr[SHDR_STRTAB].sh_addralign = sizeof(char);
338 hdr->kh_shdr[SHDR_STRTAB].sh_entsize = 0;
340 /* Fourth section - shstrtab */
341 hdr->kh_shdr[SHDR_SHSTRTAB].sh_name = 1 + sizeof(STR_SYMTAB) +
343 hdr->kh_shdr[SHDR_SHSTRTAB].sh_type = SHT_STRTAB;
344 hdr->kh_shdr[SHDR_SHSTRTAB].sh_flags = 0;
345 hdr->kh_shdr[SHDR_SHSTRTAB].sh_addr = 0;
346 hdr->kh_shdr[SHDR_SHSTRTAB].sh_offset =
347 offsetof(struct ksyms_hdr, kh_shstrtab);
348 hdr->kh_shdr[SHDR_SHSTRTAB].sh_size = sizeof(ksyms_shstrtab);
349 hdr->kh_shdr[SHDR_SHSTRTAB].sh_link = 0;
350 hdr->kh_shdr[SHDR_SHSTRTAB].sh_info = 0;
351 hdr->kh_shdr[SHDR_SHSTRTAB].sh_addralign = 0 /* sizeof(char) */;
352 hdr->kh_shdr[SHDR_SHSTRTAB].sh_entsize = 0;
354 /* Copy shstrtab into the header. */
355 bcopy(ksyms_shstrtab, hdr->kh_shstrtab, sizeof(ksyms_shstrtab));
358 to.to_symoff = hdr->kh_shdr[SHDR_SYMTAB].sh_offset;
359 to.to_stroff = hdr->kh_shdr[SHDR_STRTAB].sh_offset;
361 to.to_resid = sc->sc_objsz - sizeof(struct ksyms_hdr);
364 error = ksyms_emit(sc, hdr, 0, sizeof(*hdr));
369 /* Add symbol and string tables for each kernel module. */
370 error = linker_file_foreach(ksyms_add, &to);
373 if (to.to_resid != 0)
379 ksyms_cdevpriv_dtr(void *data)
381 struct ksyms_softc *sc;
384 sc = (struct ksyms_softc *)data;
386 sx_xlock(&ksyms_mtx);
387 LIST_REMOVE(sc, sc_list);
388 sx_xunlock(&ksyms_mtx);
391 vm_object_deallocate(obj);
396 ksyms_open(struct cdev *dev, int flags, int fmt __unused, struct thread *td)
399 struct ksyms_softc *sc;
404 * Limit one open() per process. The process must close()
405 * before open()'ing again.
407 sx_xlock(&ksyms_mtx);
408 LIST_FOREACH(sc, &ksyms_list, sc_list) {
409 if (sc->sc_proc == td->td_proc) {
410 sx_xunlock(&ksyms_mtx);
415 sc = malloc(sizeof(*sc), M_KSYMS, M_WAITOK | M_ZERO);
416 sc->sc_proc = td->td_proc;
417 LIST_INSERT_HEAD(&ksyms_list, sc, sc_list);
418 sx_xunlock(&ksyms_mtx);
420 error = devfs_set_cdevpriv(sc, ksyms_cdevpriv_dtr);
422 ksyms_cdevpriv_dtr(sc);
427 * MOD_SLOCK doesn't work here (because of a lock reversal with
428 * KLD_SLOCK). Therefore, simply try up to 3 times to get a "clean"
429 * snapshot of the kernel symbol table. This should work fine in the
430 * rare case of a kernel module being loaded/unloaded at the same
433 for (try = 0; try < 3; try++) {
434 ksyms_size_calc(&ts);
435 elfsz = sizeof(struct ksyms_hdr) + ts.ts_symsz + ts.ts_strsz;
437 sc->sc_obj = vm_object_allocate(OBJT_DEFAULT,
438 OFF_TO_IDX(round_page(elfsz)));
439 sc->sc_objsz = elfsz;
441 error = ksyms_snapshot(sc, &ts);
445 vm_object_deallocate(sc->sc_obj);
452 ksyms_read(struct cdev *dev, struct uio *uio, int flags __unused)
454 struct ksyms_softc *sc;
457 error = devfs_get_cdevpriv((void **)&sc);
460 return (uiomove_object(sc->sc_obj, sc->sc_objsz, uio));
464 ksyms_mmap_single(struct cdev *dev, vm_ooffset_t *offset, vm_size_t size,
465 vm_object_t *objp, int nprot)
467 struct ksyms_softc *sc;
471 error = devfs_get_cdevpriv((void **)&sc);
475 if (*offset < 0 || *offset >= round_page(sc->sc_objsz) ||
476 size > round_page(sc->sc_objsz) - *offset ||
477 (nprot & ~PROT_READ) != 0)
481 vm_object_reference(obj);
487 ksyms_modevent(module_t mod __unused, int type, void *data __unused)
494 sx_init(&ksyms_mtx, "KSyms mtx");
495 ksyms_dev = make_dev(&ksyms_cdevsw, 0, UID_ROOT, GID_WHEEL,
499 if (!LIST_EMPTY(&ksyms_list))
501 destroy_dev(ksyms_dev);
502 sx_destroy(&ksyms_mtx);
513 DEV_MODULE(ksyms, ksyms_modevent, NULL);
514 MODULE_VERSION(ksyms, 1);