stack decode: handle address offsets

tools/stack_decode.py

@@ -21,7 +21,7 @@
 # contain backtrace output extract the address and call add2line to get the file
 # and line information. Output appended to end of original backtrace line. Output
 # any nonmatching lines unmodified. End when EOF received.
-def decode_stacktrace_log(object_file, input_source):
+def decode_stacktrace_log(object_file, input_source, address_offset=0):
   traces = {}
   # Match something like:
   #     [backtrace] [bazel-out/local-dbg/bin/source/server/_virtual_includes/backtrace_lib/server/backtrace.h:84]
@@ -45,9 +45,14 @@ def decode_stacktrace_log(object_file, input_source):
         stackaddr_match = asan_re.search(line)
       if stackaddr_match:
         address = stackaddr_match.groups()[0]
+        if address_offset != 0:
+          address = hex(int(address, 16) - address_offset)
         file_and_line_number = run_addr2line(object_file, address)
         file_and_line_number = trim_proc_cwd(file_and_line_number)
-        sys.stdout.write("%s %s" % (line.strip(), file_and_line_number))
+        if address_offset != 0:
+          sys.stdout.write("%s->[%s] %s" % (line.strip(), address, file_and_line_number))
+        else:
+          sys.stdout.write("%s %s" % (line.strip(), file_and_line_number))
         continue
       else:
         # Pass through print all other log lines:
@@ -72,6 +77,27 @@ def trim_proc_cwd(file_and_line_number):
   return re.sub(trim_regex, '', file_and_line_number)
 
 
+# Execute pmap with a pid to calculate the addr offset
+#
+# Returns list of extended process memory information.
+def run_pmap(pid):
+  return subprocess.check_output(['pmap', '-qX', str(pid)]).decode('utf-8')[1:]
+
+
+# Find the virtual address offset of the process. This may be needed due ASLR.
+#
+# Returns the virtual address offset as an integer, or 0 if unable to determine.
+def find_address_offset(pid):
+  try:
+    proc_memory = run_pmap(pid)
+    match = re.search(r'([a-f0-9]+)\s+r-xp', proc_memory)
+    if match is None:
+      return 0
+    return int(match.group(1), 16)
+  except (subprocess.CalledProcessError, PermissionError):
+    return 0
+
+
 if __name__ == "__main__":
   if len(sys.argv) > 2 and sys.argv[1] == '-s':
     decode_stacktrace_log(sys.argv[2], sys.stdin)
@@ -81,7 +107,8 @@ def trim_proc_cwd(file_and_line_number):
                                 stdout=subprocess.PIPE,
                                 stderr=subprocess.STDOUT,
                                 universal_newlines=True)
-    decode_stacktrace_log(sys.argv[1], rununder.stdout)
+    offset = find_address_offset(rununder.pid)
+    decode_stacktrace_log(sys.argv[1], rununder.stdout, offset)
     rununder.wait()
     sys.exit(rununder.returncode)  # Pass back test pass/fail result
   else: