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
14import gdb
15import os
16import re
17
18from linux import modules, utils
19
20
21if 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
56class LxSymbols(gdb.Command):
57    """(Re-)load symbols of Linux kernel and currently loaded modules.
58
59The kernel (vmlinux) is taken from the current working directly. Modules (.ko)
60are scanned recursively, starting in the same directory. Optionally, the module
61search path can be extended by a space separated list of paths passed to the
62lx-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") or name.endswith(".ko.debug"):
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(?:.debug)?$".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                             ".text", ".text.hot", ".text.unlikely"]:
104            address = section_name_to_address.get(section_name)
105            if address:
106                args.append(" -s {name} {addr}".format(
107                    name=section_name, addr=str(address)))
108        return "".join(args)
109
110    def load_module_symbols(self, module):
111        module_name = module['name'].string()
112        module_addr = str(module['core_layout']['base']).split()[0]
113
114        module_file = self._get_module_file(module_name)
115        if not module_file and not self.module_files_updated:
116            self._update_module_files()
117            module_file = self._get_module_file(module_name)
118
119        if module_file:
120            if utils.is_target_arch('s390'):
121                # Module text is preceded by PLT stubs on s390.
122                module_arch = module['arch']
123                plt_offset = int(module_arch['plt_offset'])
124                plt_size = int(module_arch['plt_size'])
125                module_addr = hex(int(module_addr, 0) + plt_offset + plt_size)
126            gdb.write("loading @{addr}: {filename}\n".format(
127                addr=module_addr, filename=module_file))
128            cmdline = "add-symbol-file {filename} {addr}{sections}".format(
129                filename=module_file,
130                addr=module_addr,
131                sections=self._section_arguments(module))
132            gdb.execute(cmdline, to_string=True)
133            if module_name not in self.loaded_modules:
134                self.loaded_modules.append(module_name)
135        else:
136            gdb.write("no module object found for '{0}'\n".format(module_name))
137
138    def load_all_symbols(self):
139        gdb.write("loading vmlinux\n")
140
141        # Dropping symbols will disable all breakpoints. So save their states
142        # and restore them afterward.
143        saved_states = []
144        if hasattr(gdb, 'breakpoints') and not gdb.breakpoints() is None:
145            for bp in gdb.breakpoints():
146                saved_states.append({'breakpoint': bp, 'enabled': bp.enabled})
147
148        # drop all current symbols and reload vmlinux
149        orig_vmlinux = 'vmlinux'
150        for obj in gdb.objfiles():
151            if obj.filename.endswith('vmlinux'):
152                orig_vmlinux = obj.filename
153        gdb.execute("symbol-file", to_string=True)
154        gdb.execute("symbol-file {0}".format(orig_vmlinux))
155
156        self.loaded_modules = []
157        module_list = modules.module_list()
158        if not module_list:
159            gdb.write("no modules found\n")
160        else:
161            [self.load_module_symbols(module) for module in module_list]
162
163        for saved_state in saved_states:
164            saved_state['breakpoint'].enabled = saved_state['enabled']
165
166    def invoke(self, arg, from_tty):
167        self.module_paths = [os.path.expanduser(p) for p in arg.split()]
168        self.module_paths.append(os.getcwd())
169
170        # enforce update
171        self.module_files = []
172        self.module_files_updated = False
173
174        self.load_all_symbols()
175
176        if hasattr(gdb, 'Breakpoint'):
177            if self.breakpoint is not None:
178                self.breakpoint.delete()
179                self.breakpoint = None
180            self.breakpoint = LoadModuleBreakpoint(
181                "kernel/module.c:do_init_module", self)
182        else:
183            gdb.write("Note: symbol update on module loading not supported "
184                      "with this gdb version\n")
185
186
187LxSymbols()
188