Commit 66051720 authored by Jan Kiszka's avatar Jan Kiszka Committed by Linus Torvalds
Browse files

scripts/gdb: add lx-symbols command

This is probably the most useful helper when debugging kernel modules:
lx-symbols first reloads vmlinux.  Then it searches recursively for *.ko
files in the specified paths and the current directory.  Finally it walks
the kernel's module list, issuing the necessary add-symbol-file command
for each loaded module so that gdb knows which module symbol corresponds
to which address.  It also looks up variable sections (bss, data, rodata)
and appends their address to the add-symbole-file command line.  This
allows to access global module variables just like any other variable.
Signed-off-by: Jan Kiszka's avatarJan Kiszka <>
Cc: Thomas Gleixner <>
Cc: Jason Wessel <>
Cc: Andi Kleen <>
Cc: Ben Widawsky <>
Cc: Borislav Petkov <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 850202e1
# gdb helper commands and functions for Linux kernel debugging
# load kernel and module symbols
# Copyright (c) Siemens AG, 2011-2013
# Authors:
# Jan Kiszka <>
# This work is licensed under the terms of the GNU GPL version 2.
import gdb
import os
import re
import string
from linux import modules, utils
class LxSymbols(gdb.Command):
"""(Re-)load symbols of Linux kernel and currently loaded modules.
The kernel (vmlinux) is taken from the current working directly. Modules (.ko)
are scanned recursively, starting in the same directory. Optionally, the module
search path can be extended by a space separated list of paths passed to the
lx-symbols command."""
module_paths = []
module_files = []
module_files_updated = False
def __init__(self):
super(LxSymbols, self).__init__("lx-symbols", gdb.COMMAND_FILES,
def _update_module_files(self):
self.module_files = []
for path in self.module_paths:
gdb.write("scanning for modules in {0}\n".format(path))
for root, dirs, files in os.walk(path):
for name in files:
if name.endswith(".ko"):
self.module_files.append(root + "/" + name)
self.module_files_updated = True
def _get_module_file(self, module_name):
module_pattern = ".*/{0}\.ko$".format(
string.replace(module_name, "_", r"[_\-]"))
for name in self.module_files:
if re.match(module_pattern, name) and os.path.exists(name):
return name
return None
def _section_arguments(self, module):
sect_attrs = module['sect_attrs'].dereference()
except gdb.error:
return ""
attrs = sect_attrs['attrs']
section_name_to_address = {
attrs[n]['name'].string() : attrs[n]['address']
for n in range(sect_attrs['nsections'])}
args = []
for section_name in [".data", ".data..read_mostly", ".rodata", ".bss"]:
address = section_name_to_address.get(section_name)
if address:
args.append(" -s {name} {addr}".format(
name=section_name, addr=str(address)))
return "".join(args)
def load_module_symbols(self, module):
module_name = module['name'].string()
module_addr = str(module['module_core']).split()[0]
module_file = self._get_module_file(module_name)
if not module_file and not self.module_files_updated:
module_file = self._get_module_file(module_name)
if module_file:
gdb.write("loading @{addr}: {filename}\n".format(
addr=module_addr, filename=module_file))
cmdline = "add-symbol-file {filename} {addr}{sections}".format(
gdb.execute(cmdline, to_string=True)
gdb.write("no module object found for '{0}'\n".format(module_name))
def load_all_symbols(self):
gdb.write("loading vmlinux\n")
# Dropping symbols will disable all breakpoints. So save their states
# and restore them afterward.
saved_states = []
if hasattr(gdb, 'breakpoints') and not gdb.breakpoints() is None:
for bp in gdb.breakpoints():
saved_states.append({'breakpoint': bp, 'enabled': bp.enabled})
# drop all current symbols and reload vmlinux
gdb.execute("symbol-file", to_string=True)
gdb.execute("symbol-file vmlinux")
module_list = modules.ModuleList()
if not module_list:
gdb.write("no modules found\n")
[self.load_module_symbols(module) for module in module_list]
for saved_state in saved_states:
saved_state['breakpoint'].enabled = saved_state['enabled']
def invoke(self, arg, from_tty):
self.module_paths = arg.split()
# enforce update
self.module_files = []
self.module_files_updated = False
......@@ -23,3 +23,4 @@ except:
import linux.utils
import linux.symbols
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