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;
196 buf = malloc(SYMBLKSZ, M_KSYMS, M_WAITOK);
201 numsyms = LINKER_SYMTAB_GET(lf, &symtab);
202 strsz = LINKER_STRTAB_GET(lf, &strtab);
203 symsz = numsyms * sizeof(Elf_Sym);
212 len = min(SYMBLKSZ, symsz);
213 bcopy(symtab, buf, len);
216 * Fix up symbol table for kernel modules:
217 * string offsets need adjusted
218 * symbol values made absolute
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;
230 if (len > to->to_resid) {
236 error = ksyms_emit(sc, buf, to->to_symoff, len);
237 to->to_symoff += len;
250 if (strsz > to->to_resid)
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;
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.
266 ksyms_snapshot(struct ksyms_softc *sc, struct tsizes *ts)
269 struct ksyms_hdr *hdr;
272 hdr = malloc(sizeof(*hdr), M_KSYMS, M_WAITOK | M_ZERO);
275 * Create the ELF header.
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;
302 * Add both the text and data program headers.
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;
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;
317 * Add the section headers: null, symtab, strtab, shstrtab.
320 /* First section header - null */
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);
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;
347 /* Fourth section - shstrtab */
348 hdr->kh_shdr[SHDR_SHSTRTAB].sh_name = 1 + sizeof(STR_SYMTAB) +
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;
361 /* Copy shstrtab into the header. */
362 bcopy(ksyms_shstrtab, hdr->kh_shstrtab, sizeof(ksyms_shstrtab));
365 to.to_symoff = hdr->kh_shdr[SHDR_SYMTAB].sh_offset;
366 to.to_stroff = hdr->kh_shdr[SHDR_STRTAB].sh_offset;
368 to.to_resid = sc->sc_objsz - sizeof(struct ksyms_hdr);
371 error = ksyms_emit(sc, hdr, 0, sizeof(*hdr));
376 /* Add symbol and string tables for each kernel module. */
377 error = linker_file_foreach(ksyms_add, &to);
380 if (to.to_resid != 0)
386 ksyms_cdevpriv_dtr(void *data)
388 struct ksyms_softc *sc;
391 sc = (struct ksyms_softc *)data;
393 sx_xlock(&ksyms_mtx);
394 LIST_REMOVE(sc, sc_list);
395 sx_xunlock(&ksyms_mtx);
398 vm_object_deallocate(obj);
403 ksyms_open(struct cdev *dev, int flags, int fmt __unused, struct thread *td)
406 struct ksyms_softc *sc;
412 * Limit one open() per process. The process must close()
413 * before open()'ing again.
415 sx_xlock(&ksyms_mtx);
416 LIST_FOREACH(sc, &ksyms_list, sc_list) {
417 if (sc->sc_proc == td->td_proc) {
418 sx_xunlock(&ksyms_mtx);
423 sc = malloc(sizeof(*sc), M_KSYMS, M_WAITOK | M_ZERO);
424 sc->sc_proc = td->td_proc;
425 LIST_INSERT_HEAD(&ksyms_list, sc, sc_list);
426 sx_xunlock(&ksyms_mtx);
428 error = devfs_set_cdevpriv(sc, ksyms_cdevpriv_dtr);
430 ksyms_cdevpriv_dtr(sc);
435 * MOD_SLOCK doesn't work here (because of a lock reversal with
436 * KLD_SLOCK). Therefore, simply try up to 3 times to get a "clean"
437 * snapshot of the kernel symbol table. This should work fine in the
438 * rare case of a kernel module being loaded/unloaded at the same
441 for (try = 0; try < 3; try++) {
442 ksyms_size_calc(&ts);
443 elfsz = sizeof(struct ksyms_hdr) + ts.ts_symsz + ts.ts_strsz;
445 object = vm_object_allocate(OBJT_PHYS,
446 OFF_TO_IDX(round_page(elfsz)));
448 sc->sc_objsz = elfsz;
450 error = ksyms_snapshot(sc, &ts);
454 vm_object_deallocate(sc->sc_obj);
461 ksyms_read(struct cdev *dev, struct uio *uio, int flags __unused)
463 struct ksyms_softc *sc;
466 error = devfs_get_cdevpriv((void **)&sc);
469 return (uiomove_object(sc->sc_obj, sc->sc_objsz, uio));
473 ksyms_mmap_single(struct cdev *dev, vm_ooffset_t *offset, vm_size_t size,
474 vm_object_t *objp, int nprot)
476 struct ksyms_softc *sc;
480 error = devfs_get_cdevpriv((void **)&sc);
484 if (*offset < 0 || *offset >= round_page(sc->sc_objsz) ||
485 size > round_page(sc->sc_objsz) - *offset ||
486 (nprot & ~PROT_READ) != 0)
490 vm_object_reference(obj);
496 ksyms_modevent(module_t mod __unused, int type, void *data __unused)
503 sx_init(&ksyms_mtx, "KSyms mtx");
504 ksyms_dev = make_dev(&ksyms_cdevsw, 0, UID_ROOT, GID_WHEEL,
508 if (!LIST_EMPTY(&ksyms_list))
510 destroy_dev(ksyms_dev);
511 sx_destroy(&ksyms_mtx);
522 DEV_MODULE(ksyms, ksyms_modevent, NULL);
523 MODULE_VERSION(ksyms, 1);