scripts/gdb/linux/symbols.py

   1 #
   2 # gdb helper commands and functions for Linux kernel debugging
   3 #
   4 #  load kernel and module symbols
   5 #
   6 # Copyright (c) Siemens AG, 2011-2013
   7 #
   8 # Authors:
   9 #  Jan Kiszka <jan.kiszka@siemens.com>
  10 #
  11 # This work is licensed under the terms of the GNU GPL version 2.
  12 #
  13
  14 import gdb
  15 import os
  16 import re
  17
  18 from linux import modules
  19
  20
  21 if hasattr(gdb, 'Breakpoint'):
  22     class LoadModuleBreakpoint(gdb.Breakpoint):
  23         def __init__(self, spec, gdb_command):
  24             super(LoadModuleBreakpoint, self).__init__(spec, internal=True)
  25             self.silent = True
  26             self.gdb_command = gdb_command
  27
  28         def stop(self):
  29             module = gdb.parse_and_eval("mod")
  30             module_name = module['name'].string()
  31             cmd = self.gdb_command
  32
  33             # enforce update if object file is not found
  34             cmd.module_files_updated = False
  35
  36             # Disable pagination while reporting symbol (re-)loading.
  37             # The console input is blocked in this context so that we would
  38             # get stuck waiting for the user to acknowledge paged output.
  39             show_pagination = gdb.execute("show pagination", to_string=True)
  40             pagination = show_pagination.endswith("on.\n")
  41             gdb.execute("set pagination off")
  42
  43             if module_name in cmd.loaded_modules:
  44                 gdb.write("refreshing all symbols to reload module "
  45                           "'{0}'\n".format(module_name))
  46                 cmd.load_all_symbols()
  47             else:
  48                 cmd.load_module_symbols(module)
  49
  50             # restore pagination state
  51             gdb.execute("set pagination %s" % ("on" if pagination else "off"))
  52
  53             return False
  54
  55
  56 class LxSymbols(gdb.Command):
  57     """(Re-)load symbols of Linux kernel and currently loaded modules.
  58
  59 The kernel (vmlinux) is taken from the current working directly. Modules (.ko)
  60 are scanned recursively, starting in the same directory. Optionally, the module
  61 search path can be extended by a space separated list of paths passed to the
  62 lx-symbols command."""
  63
  64     module_paths = []
  65     module_files = []
  66     module_files_updated = False
  67     loaded_modules = []
  68     breakpoint = None
  69
  70     def __init__(self):
  71         super(LxSymbols, self).__init__("lx-symbols", gdb.COMMAND_FILES,
  72                                         gdb.COMPLETE_FILENAME)
  73
  74     def _update_module_files(self):
  75         self.module_files = []
  76         for path in self.module_paths:
  77             gdb.write("scanning for modules in {0}\n".format(path))
  78             for root, dirs, files in os.walk(path):
  79                 for name in files:
  80                     if name.endswith(".ko"):
  81                         self.module_files.append(root + "/" + name)
  82         self.module_files_updated = True
  83
  84     def _get_module_file(self, module_name):
  85         module_pattern = ".*/{0}\.ko$".format(
  86             module_name.replace("_", r"[_\-]"))
  87         for name in self.module_files:
  88             if re.match(module_pattern, name) and os.path.exists(name):
  89                 return name
  90         return None
  91
  92     def _section_arguments(self, module):
  93         try:
  94             sect_attrs = module['sect_attrs'].dereference()
  95         except gdb.error:
  96             return ""
  97         attrs = sect_attrs['attrs']
  98         section_name_to_address = {
  99             attrs[n]['name'].string(): attrs[n]['address']
 100             for n in range(int(sect_attrs['nsections']))}
 101         args = []
 102         for section_name in [".data", ".data..read_mostly", ".rodata", ".bss"]:
 103             address = section_name_to_address.get(section_name)
 104             if address:
 105                 args.append(" -s {name} {addr}".format(
 106                     name=section_name, addr=str(address)))
 107         return "".join(args)
 108
 109     def load_module_symbols(self, module):
 110         module_name = module['name'].string()
 111         module_addr = str(module['core_layout']['base']).split()[0]
 112
 113         module_file = self._get_module_file(module_name)
 114         if not module_file and not self.module_files_updated:
 115             self._update_module_files()
 116             module_file = self._get_module_file(module_name)
 117
 118         if module_file:
 119             gdb.write("loading @{addr}: {filename}\n".format(
 120                 addr=module_addr, filename=module_file))
 121             cmdline = "add-symbol-file {filename} {addr}{sections}".format(
 122                 filename=module_file,
 123                 addr=module_addr,
 124                 sections=self._section_arguments(module))
 125             gdb.execute(cmdline, to_string=True)
 126             if module_name not in self.loaded_modules:
 127                 self.loaded_modules.append(module_name)
 128         else:
 129             gdb.write("no module object found for '{0}'\n".format(module_name))
 130
 131     def load_all_symbols(self):
 132         gdb.write("loading vmlinux\n")
 133
 134         # Dropping symbols will disable all breakpoints. So save their states
 135         # and restore them afterward.
 136         saved_states = []
 137         if hasattr(gdb, 'breakpoints') and not gdb.breakpoints() is None:
 138             for bp in gdb.breakpoints():
 139                 saved_states.append({'breakpoint': bp, 'enabled': bp.enabled})
 140
 141         # drop all current symbols and reload vmlinux
 142         gdb.execute("symbol-file", to_string=True)
 143         gdb.execute("symbol-file vmlinux")
 144
 145         self.loaded_modules = []
 146         module_list = modules.module_list()
 147         if not module_list:
 148             gdb.write("no modules found\n")
 149         else:
 150             [self.load_module_symbols(module) for module in module_list]
 151
 152         for saved_state in saved_states:
 153             saved_state['breakpoint'].enabled = saved_state['enabled']
 154
 155     def invoke(self, arg, from_tty):
 156         self.module_paths = [os.path.expanduser(p) for p in arg.split()]
 157         self.module_paths.append(os.getcwd())
 158
 159         # enforce update
 160         self.module_files = []
 161         self.module_files_updated = False
 162
 163         self.load_all_symbols()
 164
 165         if hasattr(gdb, 'Breakpoint'):
 166             if self.breakpoint is not None:
 167                 self.breakpoint.delete()
 168                 self.breakpoint = None
 169             self.breakpoint = LoadModuleBreakpoint(
 170                 "kernel/module.c:do_init_module", self)
 171         else:
 172             gdb.write("Note: symbol update on module loading not supported "
 173                       "with this gdb version\n")
 174
 175
 176 LxSymbols()