Fix debuginfo search on Ubuntu

bcc on Ubuntu picks up the glibc binary instead of the debuginfo file
because find_debug_via_debuglink() doesn't handle symbolic or hard
links when checking if two paths point to the same file.

Add a helper, same_file() which uses the device and inode to check if
the two paths do point to the same file.

Signed-off-by: Anton Blanchard <[email protected]>

src/cc/bcc_elf.c

@@ -453,6 +453,21 @@ static int verify_checksum(const char *file, unsigned int crc) {
  return actual == crc;
 }
 
+// Check if two filenames point to the same file, including hard or soft links.
+static bool same_file(char *a, const char *b)
+{
+ struct stat stat_a, stat_b;
+
+ if (stat(a, &stat_a) || stat(b, &stat_b))
+ return false;
+
+ if ((stat_a.st_dev == stat_b.st_dev) &&
+ (stat_a.st_ino == stat_b.st_ino))
+ return true;
+ else
+ return false;
+}
+
 static char *find_debug_via_debuglink(Elf *e, const char *binpath,
  int check_crc) {
  char fullpath[PATH_MAX];
@@ -473,7 +488,7 @@ static char *find_debug_via_debuglink(Elf *e, const char *binpath,
  // and it might contain poorer symbols (e.g. stripped or partial symbols)
  // than the external debuginfo that might be available elsewhere.
  snprintf(fullpath, sizeof(fullpath),"%s/%s", bindir, name);
- if (strcmp(fullpath, binpath) != 0 && access(fullpath, F_OK) != -1) {
+ if (same_file(fullpath, binpath) != true && access(fullpath, F_OK) != -1) {
  res = strdup(fullpath);
  goto DONE;
  }