1 /* $NetBSD: ksyms.c,v 1.2 2022/12/01 00:43:27 ryo 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 1.2 2022/12/01 00:43:27 ryo 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
compare_value(const void * p1,const void * p2)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 **
ksymload(size_t * nsymp)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 (ELF_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 *
ksymlookup(uint64_t value,uint64_t * offset,size_t * n)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