1// SPDX-License-Identifier: GPL-2.0
2#include <ctype.h>
3#include <stdio.h>
4#include <stdlib.h>
5#include <string.h>
6#include <assert.h>
7#include <errno.h>
8#include <fcntl.h>
9#include <poll.h>
10#include <pthread.h>
11#include <unistd.h>
12#include <linux/perf_event.h>
13#include <sys/mman.h>
14#include "trace_helpers.h"
15#include <linux/limits.h>
16#include <libelf.h>
17#include <gelf.h>
18#include "bpf/libbpf_internal.h"
19
20#define TRACEFS_PIPE "/sys/kernel/tracing/trace_pipe"
21#define DEBUGFS_PIPE "/sys/kernel/debug/tracing/trace_pipe"
22
23struct ksyms {
24 struct ksym *syms;
25 size_t sym_cap;
26 size_t sym_cnt;
27};
28
29static struct ksyms *ksyms;
30static pthread_mutex_t ksyms_mutex = PTHREAD_MUTEX_INITIALIZER;
31
32static int ksyms__add_symbol(struct ksyms *ksyms, const char *name,
33 unsigned long addr)
34{
35 void *tmp;
36
37 tmp = strdup(name);
38 if (!tmp)
39 return -ENOMEM;
40 ksyms->syms[ksyms->sym_cnt].addr = addr;
41 ksyms->syms[ksyms->sym_cnt].name = tmp;
42 ksyms->sym_cnt++;
43 return 0;
44}
45
46void free_kallsyms_local(struct ksyms *ksyms)
47{
48 unsigned int i;
49
50 if (!ksyms)
51 return;
52
53 if (!ksyms->syms) {
54 free(ksyms);
55 return;
56 }
57
58 for (i = 0; i < ksyms->sym_cnt; i++)
59 free(ksyms->syms[i].name);
60 free(ksyms->syms);
61 free(ksyms);
62}
63
64static int ksym_cmp(const void *p1, const void *p2)
65{
66 return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr;
67}
68
69struct ksyms *load_kallsyms_local(void)
70{
71 FILE *f;
72 char func[256], buf[256];
73 char symbol;
74 void *addr;
75 int ret;
76 struct ksyms *ksyms;
77
78 f = fopen("/proc/kallsyms", "r");
79 if (!f)
80 return NULL;
81
82 ksyms = calloc(1, sizeof(struct ksyms));
83 if (!ksyms) {
84 fclose(f);
85 return NULL;
86 }
87
88 while (fgets(buf, sizeof(buf), f)) {
89 if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3)
90 break;
91 if (!addr)
92 continue;
93
94 ret = libbpf_ensure_mem((void **) &ksyms->syms, &ksyms->sym_cap,
95 sizeof(struct ksym), ksyms->sym_cnt + 1);
96 if (ret)
97 goto error;
98 ret = ksyms__add_symbol(ksyms, name: func, addr: (unsigned long)addr);
99 if (ret)
100 goto error;
101 }
102 fclose(f);
103 qsort(ksyms->syms, ksyms->sym_cnt, sizeof(struct ksym), ksym_cmp);
104 return ksyms;
105
106error:
107 fclose(f);
108 free_kallsyms_local(ksyms);
109 return NULL;
110}
111
112int load_kallsyms(void)
113{
114 pthread_mutex_lock(&ksyms_mutex);
115 if (!ksyms)
116 ksyms = load_kallsyms_local();
117 pthread_mutex_unlock(&ksyms_mutex);
118 return ksyms ? 0 : 1;
119}
120
121struct ksym *ksym_search_local(struct ksyms *ksyms, long key)
122{
123 int start = 0, end = ksyms->sym_cnt;
124 int result;
125
126 /* kallsyms not loaded. return NULL */
127 if (ksyms->sym_cnt <= 0)
128 return NULL;
129
130 while (start < end) {
131 size_t mid = start + (end - start) / 2;
132
133 result = key - ksyms->syms[mid].addr;
134 if (result < 0)
135 end = mid;
136 else if (result > 0)
137 start = mid + 1;
138 else
139 return &ksyms->syms[mid];
140 }
141
142 if (start >= 1 && ksyms->syms[start - 1].addr < key &&
143 key < ksyms->syms[start].addr)
144 /* valid ksym */
145 return &ksyms->syms[start - 1];
146
147 /* out of range. return _stext */
148 return &ksyms->syms[0];
149}
150
151struct ksym *ksym_search(long key)
152{
153 if (!ksyms)
154 return NULL;
155 return ksym_search_local(ksyms, key);
156}
157
158long ksym_get_addr_local(struct ksyms *ksyms, const char *name)
159{
160 int i;
161
162 for (i = 0; i < ksyms->sym_cnt; i++) {
163 if (strcmp(ksyms->syms[i].name, name) == 0)
164 return ksyms->syms[i].addr;
165 }
166
167 return 0;
168}
169
170long ksym_get_addr(const char *name)
171{
172 if (!ksyms)
173 return 0;
174 return ksym_get_addr_local(ksyms, name);
175}
176
177/* open kallsyms and read symbol addresses on the fly. Without caching all symbols,
178 * this is faster than load + find.
179 */
180int kallsyms_find(const char *sym, unsigned long long *addr)
181{
182 char type, name[500];
183 unsigned long long value;
184 int err = 0;
185 FILE *f;
186
187 f = fopen("/proc/kallsyms", "r");
188 if (!f)
189 return -EINVAL;
190
191 while (fscanf(f, "%llx %c %499s%*[^\n]\n", &value, &type, name) > 0) {
192 if (strcmp(name, sym) == 0) {
193 *addr = value;
194 goto out;
195 }
196 }
197 err = -ENOENT;
198
199out:
200 fclose(f);
201 return err;
202}
203
204void read_trace_pipe(void)
205{
206 int trace_fd;
207
208 if (access(TRACEFS_PIPE, F_OK) == 0)
209 trace_fd = open(TRACEFS_PIPE, O_RDONLY, 0);
210 else
211 trace_fd = open(DEBUGFS_PIPE, O_RDONLY, 0);
212 if (trace_fd < 0)
213 return;
214
215 while (1) {
216 static char buf[4096];
217 ssize_t sz;
218
219 sz = read(trace_fd, buf, sizeof(buf) - 1);
220 if (sz > 0) {
221 buf[sz] = 0;
222 puts(buf);
223 }
224 }
225}
226
227ssize_t get_uprobe_offset(const void *addr)
228{
229 size_t start, end, base;
230 char buf[256];
231 bool found = false;
232 FILE *f;
233
234 f = fopen("/proc/self/maps", "r");
235 if (!f)
236 return -errno;
237
238 while (fscanf(f, "%zx-%zx %s %zx %*[^\n]\n", &start, &end, buf, &base) == 4) {
239 if (buf[2] == 'x' && (uintptr_t)addr >= start && (uintptr_t)addr < end) {
240 found = true;
241 break;
242 }
243 }
244
245 fclose(f);
246
247 if (!found)
248 return -ESRCH;
249
250#if defined(__powerpc64__) && defined(_CALL_ELF) && _CALL_ELF == 2
251
252#define OP_RT_RA_MASK 0xffff0000UL
253#define LIS_R2 0x3c400000UL
254#define ADDIS_R2_R12 0x3c4c0000UL
255#define ADDI_R2_R2 0x38420000UL
256
257 /*
258 * A PPC64 ABIv2 function may have a local and a global entry
259 * point. We need to use the local entry point when patching
260 * functions, so identify and step over the global entry point
261 * sequence.
262 *
263 * The global entry point sequence is always of the form:
264 *
265 * addis r2,r12,XXXX
266 * addi r2,r2,XXXX
267 *
268 * A linker optimisation may convert the addis to lis:
269 *
270 * lis r2,XXXX
271 * addi r2,r2,XXXX
272 */
273 {
274 const __u32 *insn = (const __u32 *)(uintptr_t)addr;
275
276 if ((((*insn & OP_RT_RA_MASK) == ADDIS_R2_R12) ||
277 ((*insn & OP_RT_RA_MASK) == LIS_R2)) &&
278 ((*(insn + 1) & OP_RT_RA_MASK) == ADDI_R2_R2))
279 return (uintptr_t)(insn + 2) - start + base;
280 }
281#endif
282 return (uintptr_t)addr - start + base;
283}
284
285ssize_t get_rel_offset(uintptr_t addr)
286{
287 size_t start, end, offset;
288 char buf[256];
289 FILE *f;
290
291 f = fopen("/proc/self/maps", "r");
292 if (!f)
293 return -errno;
294
295 while (fscanf(f, "%zx-%zx %s %zx %*[^\n]\n", &start, &end, buf, &offset) == 4) {
296 if (addr >= start && addr < end) {
297 fclose(f);
298 return (size_t)addr - start + offset;
299 }
300 }
301
302 fclose(f);
303 return -EINVAL;
304}
305
306static int
307parse_build_id_buf(const void *note_start, Elf32_Word note_size, char *build_id)
308{
309 Elf32_Word note_offs = 0;
310
311 while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
312 Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
313
314 if (nhdr->n_type == 3 && nhdr->n_namesz == sizeof("GNU") &&
315 !strcmp((char *)(nhdr + 1), "GNU") && nhdr->n_descsz > 0 &&
316 nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
317 memcpy(build_id, note_start + note_offs +
318 ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr), nhdr->n_descsz);
319 memset(build_id + nhdr->n_descsz, 0, BPF_BUILD_ID_SIZE - nhdr->n_descsz);
320 return (int) nhdr->n_descsz;
321 }
322
323 note_offs = note_offs + sizeof(Elf32_Nhdr) +
324 ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
325 }
326
327 return -ENOENT;
328}
329
330/* Reads binary from *path* file and returns it in the *build_id* buffer
331 * with *size* which is expected to be at least BPF_BUILD_ID_SIZE bytes.
332 * Returns size of build id on success. On error the error value is
333 * returned.
334 */
335int read_build_id(const char *path, char *build_id, size_t size)
336{
337 int fd, err = -EINVAL;
338 Elf *elf = NULL;
339 GElf_Ehdr ehdr;
340 size_t max, i;
341
342 if (size < BPF_BUILD_ID_SIZE)
343 return -EINVAL;
344
345 fd = open(path, O_RDONLY | O_CLOEXEC);
346 if (fd < 0)
347 return -errno;
348
349 (void)elf_version(EV_CURRENT);
350
351 elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
352 if (!elf)
353 goto out;
354 if (elf_kind(elf) != ELF_K_ELF)
355 goto out;
356 if (!gelf_getehdr(elf, &ehdr))
357 goto out;
358
359 for (i = 0; i < ehdr.e_phnum; i++) {
360 GElf_Phdr mem, *phdr;
361 char *data;
362
363 phdr = gelf_getphdr(elf, i, &mem);
364 if (!phdr)
365 goto out;
366 if (phdr->p_type != PT_NOTE)
367 continue;
368 data = elf_rawfile(elf, &max);
369 if (!data)
370 goto out;
371 if (phdr->p_offset + phdr->p_memsz > max)
372 goto out;
373 err = parse_build_id_buf(data + phdr->p_offset, phdr->p_memsz, build_id);
374 if (err > 0)
375 break;
376 }
377
378out:
379 if (elf)
380 elf_end(elf);
381 close(fd);
382 return err;
383}
384

source code of linux/tools/testing/selftests/bpf/trace_helpers.c