coredump: fix section name parsing in python utility

elf.py assumed every section header name had its own string in
shstrtab, but multiple sections may reuse the same substring with
different offsets.

components/espcoredump/corefile/elf.py

@@ -121,7 +121,6 @@ class ElfFile(object):
 
         self._struct = None  # type: Optional[Struct]
         self._model = None  # type: Optional[Container]
-        self._section_names = {}  # type: dict[int, str]
 
         self.sections = []  # type: list[ElfSection]
         self.load_segments = []  # type: list[ElfSegment]
@@ -146,36 +145,28 @@ class ElfFile(object):
         self._struct = self._generate_struct_from_headers(header_tables)
         self._model = self._struct.parse(elf_bytes)
 
-        if 'string_table' in self._model:
-            self._section_names = self._parse_string_table(self._model.string_table)
-
         self.load_segments = [ElfSegment(seg.ph.p_vaddr,
                                          seg.data,
                                          seg.ph.p_flags) for seg in self._model.load_segments]
         self.note_segments = [ElfNoteSegment(seg.ph.p_vaddr,
                                              seg.data,
                                              seg.ph.p_flags) for seg in self._model.note_segments]
-        self.sections = [ElfSection(self._section_names[sec.sh.sh_name],
+        self.sections = [ElfSection(self._parse_string_table(self._model.string_table, sec.sh.sh_name),
                                     sec.sh.sh_addr,
                                     sec.data,
                                     sec.sh.sh_flags) for sec in self._model.sections]
 
     @staticmethod
-    def _parse_string_table(byte_str):  # type: (bytes) -> dict
+    def _parse_string_table(byte_str, offset):  # type: (bytes, int) -> str
-        name = ''
+        section_name_str = byte_str[offset:]
-        index = 0
+        string_end = section_name_str.find(0x00)
-        res = {}
+
-        for i, c in enumerate(byte_str):
+        if (string_end == -1):
-            if c in [0x00, '\x00']:  # a workaround for python 2 bytes is actually string
+            raise ValueError('Unable to get section name from section header string table')
-                res[index] = name
+
-                name = ''
+        name = section_name_str[:string_end].decode('utf-8')
-                index = i + 1
+
-                continue
+        return name
-            if isinstance(c, int):
-                name += chr(c)
-            else:
-                name += c
-        return res
 
     def _generate_struct_from_headers(self, header_tables):  # type: (Container) -> Struct
         """

tools/ci/mypy_ignore_list.txt

@@ -3,7 +3,6 @@ components/efuse/efuse_table_gen.py
 components/efuse/test_efuse_host/efuse_tests.py
 components/esp_local_ctrl/python/esp_local_ctrl_pb2.py
 components/esp_netif/test_apps/component_ut_test.py
-components/espcoredump/corefile/elf.py
 components/espcoredump/corefile/gdb.py
 components/espcoredump/test/test_espcoredump.py
 components/lwip/weekend_test/net_suite_test.py