From 66051720b84127cac32f34a30c91390c0ebf898f Mon Sep 17 00:00:00 2001 From: Jan Kiszka Date: Tue, 17 Feb 2015 13:46:47 -0800 Subject: [PATCH] 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 Cc: Thomas Gleixner Cc: Jason Wessel Cc: Andi Kleen Cc: Ben Widawsky Cc: Borislav Petkov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- scripts/gdb/linux/symbols.py | 127 +++++++++++++++++++++++++++++++++++ scripts/gdb/vmlinux-gdb.py | 1 + 2 files changed, 128 insertions(+) create mode 100644 scripts/gdb/linux/symbols.py diff --git a/scripts/gdb/linux/symbols.py b/scripts/gdb/linux/symbols.py new file mode 100644 index 000000000000..bd21a9624428 --- /dev/null +++ b/scripts/gdb/linux/symbols.py @@ -0,0 +1,127 @@ +# +# 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, + gdb.COMPLETE_FILENAME) + + 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): + try: + 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: + self._update_module_files() + 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( + filename=module_file, + addr=module_addr, + sections=self._section_arguments(module)) + gdb.execute(cmdline, to_string=True) + else: + 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") + else: + [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() + self.module_paths.append(os.getcwd()) + + # enforce update + self.module_files = [] + self.module_files_updated = False + + self.load_all_symbols() + + +LxSymbols() diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py index 649584105a72..0b0faa4cb5a0 100644 --- a/scripts/gdb/vmlinux-gdb.py +++ b/scripts/gdb/vmlinux-gdb.py @@ -23,3 +23,4 @@ except: "work.\n") else: import linux.utils + import linux.symbols -- 2.20.1