1 /* $NetBSD: ksyms.c,v 1.3 2024/04/01 18:33:24 riastradh Exp $ */ 2 3 /* 4 * Copyright (c) 2010,2011,2012 YAMAMOTO Takashi, 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 29 #include <sys/cdefs.h> 30 #ifndef lint 31 __RCSID("$NetBSD: ksyms.c,v 1.3 2024/04/01 18:33:24 riastradh Exp $"); 32 #endif /* not lint */ 33 34 #include <assert.h> 35 #include <err.h> 36 #include <fcntl.h> 37 #include <gelf.h> 38 #include <libelf.h> 39 #include <paths.h> 40 #include <stdlib.h> 41 #include <string.h> 42 #include <unistd.h> 43 #include <util.h> 44 #include "ksyms.h" 45 46 static struct sym **syms = NULL; 47 static size_t nsyms = 0; 48 49 static int 50 compare_value(const void *p1, const void *p2) 51 { 52 const struct sym *s1 = *(const struct sym * const *)p1; 53 const struct sym *s2 = *(const struct sym * const *)p2; 54 55 if (s1->value > s2->value) { 56 return -1; 57 } else if (s1->value < s2->value) { 58 return 1; 59 } 60 /* 61 * to produce a stable result, it's better not to return 0 62 * even for __strong_alias. 63 */ 64 if (s1->size > s2->size) { 65 return -1; 66 } else if (s1->size < s2->size) { 67 return 1; 68 } 69 return strcmp(s1->name, s2->name); 70 } 71 72 struct sym ** 73 ksymload(size_t *nsymp) 74 { 75 Elf *e; 76 Elf_Scn *s; 77 GElf_Shdr sh_store; 78 GElf_Shdr *sh; 79 Elf_Data *d; 80 int fd; 81 size_t size, i; 82 83 fd = open(_PATH_KSYMS, O_RDONLY); 84 if (fd == -1) { 85 err(EXIT_FAILURE, "open " _PATH_KSYMS); 86 } 87 if (elf_version(EV_CURRENT) == EV_NONE) { 88 goto elffail; 89 } 90 e = elf_begin(fd, ELF_C_READ, NULL); 91 if (e == NULL) { 92 goto elffail; 93 } 94 for (s = elf_nextscn(e, NULL); s != NULL; s = elf_nextscn(e, s)) { 95 sh = gelf_getshdr(s, &sh_store); 96 if (sh == NULL) { 97 goto elffail; 98 } 99 if (sh->sh_type == SHT_SYMTAB) { 100 break; 101 } 102 } 103 if (s == NULL) { 104 errx(EXIT_FAILURE, "no symtab"); 105 } 106 d = elf_getdata(s, NULL); 107 if (d == NULL) { 108 goto elffail; 109 } 110 assert(sh->sh_size == d->d_size); 111 size = sh->sh_size / sh->sh_entsize; 112 for (i = 1; i < size; i++) { 113 GElf_Sym st_store; 114 GElf_Sym *st; 115 struct sym *sym; 116 117 st = gelf_getsym(d, (int)i, &st_store); 118 if (st == NULL) { 119 goto elffail; 120 } 121 if (GELF_ST_TYPE(st->st_info) != STT_FUNC) { 122 continue; 123 } 124 sym = emalloc(sizeof(*sym)); 125 sym->name = estrdup(elf_strptr(e, sh->sh_link, st->st_name)); 126 sym->value = (uint64_t)st->st_value; 127 sym->size = st->st_size; 128 nsyms++; 129 syms = erealloc(syms, sizeof(*syms) * nsyms); 130 syms[nsyms - 1] = sym; 131 } 132 elf_end(e); 133 close(fd); 134 qsort(syms, nsyms, sizeof(*syms), compare_value); 135 if (nsymp != NULL) 136 *nsymp = nsyms; 137 return syms; 138 elffail: 139 errx(EXIT_FAILURE, "libelf: %s", elf_errmsg(elf_errno())); 140 } 141 142 const char * 143 ksymlookup(uint64_t value, uint64_t *offset, size_t *n) 144 { 145 size_t hi; 146 size_t lo; 147 size_t i; 148 149 /* 150 * try to find the smallest i for which syms[i]->value <= value. 151 * syms[] is ordered by syms[]->value in the descending order. 152 */ 153 154 hi = nsyms - 1; 155 lo = 0; 156 while (lo < hi) { 157 const size_t mid = (lo + hi) / 2; 158 const struct sym *sym = syms[mid]; 159 160 assert(syms[lo]->value >= sym->value); 161 assert(sym->value >= syms[hi]->value); 162 if (sym->value <= value) { 163 hi = mid; 164 continue; 165 } 166 lo = mid + 1; 167 } 168 assert(lo == nsyms - 1 || syms[lo]->value <= value); 169 assert(lo == 0 || syms[lo - 1]->value > value); 170 for (i = lo; i < nsyms; i++) { 171 const struct sym *sym = syms[i]; 172 173 if (sym->value <= value && 174 (sym->size == 0 || value - sym->value <= sym->size )) { 175 *offset = value - sym->value; 176 if (n != NULL) 177 *n = i; 178 return sym->name; 179 } 180 if (sym->size != 0 && sym->value + sym->size < value) { 181 break; 182 } 183 } 184 return NULL; 185 } 186