*/
#include <sys/types.h>
#include <sys/stat.h>
+#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
+#include <libgen.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
#include <gelf.h>
#include "bcc_elf.h"
return 0;
}
-int bcc_elf_foreach_sym(const char *path, bcc_elf_symcb callback,
- void *payload) {
+static Elf_Data * get_section_elf_data(Elf *e, const char *section_name) {
+ Elf_Scn *section = NULL;
+ GElf_Shdr header;
+ char *name;
+
+ size_t stridx;
+ if (elf_getshdrstrndx(e, &stridx) != 0)
+ return NULL;
+
+ while ((section = elf_nextscn(e, section)) != 0) {
+ if (!gelf_getshdr(section, &header))
+ continue;
+
+ name = elf_strptr(e, stridx, header.sh_name);
+ if (name && !strcmp(name, section_name)) {
+ return elf_getdata(section, NULL);
+ }
+ }
+
+ return NULL;
+}
+
+static int find_debuglink(Elf *e, char **debug_file, unsigned int *crc) {
+ Elf_Data *data = NULL;
+
+ *debug_file = NULL;
+ *crc = 0;
+
+ data = get_section_elf_data(e, ".gnu_debuglink");
+ if (!data || data->d_size <= 5)
+ return 0;
+
+ *debug_file = (char *)data->d_buf;
+ *crc = *(unsigned int*)((char *)data->d_buf + data->d_size - 4);
+
+ return *debug_file ? 1 : 0;
+}
+
+static int find_buildid(Elf *e, char *buildid) {
+ Elf_Data *data = get_section_elf_data(e, ".note.gnu.build-id");
+ if (data->d_size <= 16 || strcmp((char *)data->d_buf + 12, "GNU"))
+ return 0;
+
+ char *buf = (char *)data->d_buf + 16;
+ size_t length = data->d_size - 16;
+ for (size_t i = 0; i < length; ++i) {
+ sprintf(buildid + (i * 2), "%02hhx", buf[i]);
+ }
+
+ return 1;
+}
+
+// The CRC algorithm used by GNU debuglink. Taken from:
+// https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html
+static unsigned int gnu_debuglink_crc32(unsigned int crc,
+ char *buf, size_t len) {
+ static const unsigned int crc32_table[256] =
+ {
+ 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
+ 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
+ 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
+ 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
+ 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
+ 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
+ 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
+ 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
+ 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
+ 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
+ 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
+ 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
+ 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
+ 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
+ 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
+ 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
+ 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
+ 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
+ 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
+ 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
+ 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
+ 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
+ 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
+ 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
+ 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
+ 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
+ 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
+ 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
+ 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
+ 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
+ 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
+ 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
+ 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
+ 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
+ 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
+ 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
+ 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
+ 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
+ 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
+ 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
+ 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
+ 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
+ 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
+ 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
+ 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
+ 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
+ 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
+ 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
+ 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
+ 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
+ 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
+ 0x2d02ef8d
+ };
+ char *end;
+
+ crc = ~crc & 0xffffffff;
+ for (end = buf + len; buf < end; ++buf)
+ crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
+ return ~crc & 0xffffffff;
+}
+
+static int verify_checksum(const char *file, unsigned int crc) {
+ struct stat st;
+ int fd;
+ void *buf;
+ unsigned int actual;
+
+ fd = open(file, O_RDONLY);
+ if (fd < 0)
+ return 0;
+
+ if (fstat(fd, &st) < 0)
+ return 0;
+
+ buf = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+ if (!buf) {
+ close(fd);
+ return 0;
+ }
+
+ actual = gnu_debuglink_crc32(0, buf, st.st_size);
+
+ munmap(buf, st.st_size);
+ close(fd);
+ return actual == crc;
+}
+
+static char *find_debug_via_debuglink(Elf *e, const char *binpath) {
+ char fullpath[PATH_MAX];
+ char *bindir = NULL;
+ char *res = NULL;
+ unsigned int crc;
+ char *name; // the name of the debuginfo file
+
+ if (!find_debuglink(e, &name, &crc))
+ return NULL;
+
+ bindir = strdup(binpath);
+ bindir = dirname(bindir);
+
+ // Search for the file in 'binpath'
+ sprintf(fullpath, "%s/%s", bindir, name);
+ if (access(fullpath, F_OK) != -1) {
+ res = strdup(fullpath);
+ goto DONE;
+ }
+
+ // Search for the file in 'binpath'/.debug
+ sprintf(fullpath, "%s/.debug/%s", bindir, name);
+ if (access(fullpath, F_OK) != -1) {
+ res = strdup(fullpath);
+ goto DONE;
+ }
+
+ // Search for the file in the global debug directory /usr/lib/debug/'binpath'
+ sprintf(fullpath, "/usr/lib/debug%s/%s", bindir, name);
+ if (access(fullpath, F_OK) != -1) {
+ res = strdup(fullpath);
+ goto DONE;
+ }
+
+DONE:
+ free(bindir);
+ if (verify_checksum(res, crc))
+ return res;
+ return NULL;
+}
+
+static char *find_debug_via_buildid(Elf *e) {
+ char fullpath[PATH_MAX];
+ char buildid[128]; // currently 40 seems to be default, let's be safe
+
+ if (!find_buildid(e, buildid))
+ return NULL;
+
+ // Search for the file in the global debug directory with a sub-path:
+ // mm/nnnnnn...nnnn.debug
+ // Where mm are the first two characters of the buildid, and nnnn are the
+ // rest of the build id, followed by .debug.
+ sprintf(fullpath, "/usr/lib/debug/.build-id/%c%c/%s.debug",
+ buildid[0], buildid[1], buildid + 2);
+ if (access(fullpath, F_OK) != -1) {
+ return strdup(fullpath);
+ }
+
+ return NULL;
+}
+
+static int foreach_sym_core(const char *path, bcc_elf_symcb callback,
+ void *payload, int is_debug_file) {
Elf *e;
int fd, res;
+ char *debug_file;
if (openelf(path, &e, &fd) < 0)
return -1;
+ // If there is a separate debuginfo file, try to locate and read it, first
+ // using the build-id section, then using the debuglink section. These are
+ // also the rules that GDB folows.
+ // See: https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html
+ if (!is_debug_file) {
+ // The is_debug_file argument helps avoid infinitely resolving debuginfo
+ // files for debuginfo files and so on.
+ debug_file = find_debug_via_buildid(e);
+ if (!debug_file)
+ debug_file = find_debug_via_debuglink(e, path);
+ if (debug_file) {
+ foreach_sym_core(debug_file, callback, payload, 1);
+ free(debug_file);
+ }
+ }
+
res = listsymbols(e, callback, payload);
elf_end(e);
close(fd);
return res;
}
+int bcc_elf_foreach_sym(const char *path, bcc_elf_symcb callback,
+ void *payload) {
+ return foreach_sym_core(path, callback, payload, 0);
+}
+
static int loadaddr(Elf *e, uint64_t *addr) {
size_t phnum, i;
int main(int argc, char *argv[])
{
- uint64_t addr;
- if (bcc_elf_findsym(argv[1], argv[2], -1, STT_FUNC, &addr) < 0)
- return -1;
+ uint64_t addr;
+ if (bcc_elf_findsym(argv[1], argv[2], -1, STT_FUNC, &addr) < 0)
+ return -1;
- printf("%s: %p\n", argv[2], (void *)addr);
- return 0;
+ printf("%s: %p\n", argv[2], (void *)addr);
+ return 0;
}
#endif