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![Douglas Anderson](/assets/img/avatar_default.png)
Some systems (like Chrome OS) may use "split debug" for kernel modules. That means that the debug symbols are in a different file than the main elf file. Let's handle that by also searching for debug symbols that end in ".ko.debug". This is a packaging topic. You can take a normal elf file and split the debug out of it using objcopy. Try "man objcopy" and then take a look at the "--only-keep-debug" option. It'll give you a whole recipe for doing splitdebug. The suffix used for the debug symbols is arbitrary. If people have other another suffix besides ".ko.debug" then we could presumably support that too... For portage (which is the packaging system used by Chrome OS) split debug is supported by default (and the suffix is .ko.debug). ...and so in Chrome OS we always get the installed elf files stripped and then the symbols stashed away. At the moment we don't actually use the normal portage magic to do this for the kernel though since it affects our ability to get good stack dumps in the kernel. We instead pass a script as "strip" [1]. [1] https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/refs/heads/master/eclass/cros-kernel/strip_splitdebug Link: http://lkml.kernel.org/r/20190730234052.148744-1-dianders@chromium.org Signed-off-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Stephen Boyd <swboyd@chromium.org> Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com> Cc: Kieran Bingham <kbingham@kernel.org> Cc: Jason Wessel <jason.wessel@windriver.com> Cc: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
180 lines
6.4 KiB
Python
180 lines
6.4 KiB
Python
#
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# gdb helper commands and functions for Linux kernel debugging
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#
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# load kernel and module symbols
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#
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# Copyright (c) Siemens AG, 2011-2013
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#
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# Authors:
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# Jan Kiszka <jan.kiszka@siemens.com>
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#
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# This work is licensed under the terms of the GNU GPL version 2.
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#
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import gdb
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import os
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import re
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from linux import modules
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if hasattr(gdb, 'Breakpoint'):
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class LoadModuleBreakpoint(gdb.Breakpoint):
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def __init__(self, spec, gdb_command):
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super(LoadModuleBreakpoint, self).__init__(spec, internal=True)
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self.silent = True
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self.gdb_command = gdb_command
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def stop(self):
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module = gdb.parse_and_eval("mod")
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module_name = module['name'].string()
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cmd = self.gdb_command
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# enforce update if object file is not found
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cmd.module_files_updated = False
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# Disable pagination while reporting symbol (re-)loading.
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# The console input is blocked in this context so that we would
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# get stuck waiting for the user to acknowledge paged output.
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show_pagination = gdb.execute("show pagination", to_string=True)
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pagination = show_pagination.endswith("on.\n")
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gdb.execute("set pagination off")
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if module_name in cmd.loaded_modules:
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gdb.write("refreshing all symbols to reload module "
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"'{0}'\n".format(module_name))
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cmd.load_all_symbols()
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else:
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cmd.load_module_symbols(module)
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# restore pagination state
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gdb.execute("set pagination %s" % ("on" if pagination else "off"))
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return False
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class LxSymbols(gdb.Command):
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"""(Re-)load symbols of Linux kernel and currently loaded modules.
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The kernel (vmlinux) is taken from the current working directly. Modules (.ko)
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are scanned recursively, starting in the same directory. Optionally, the module
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search path can be extended by a space separated list of paths passed to the
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lx-symbols command."""
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module_paths = []
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module_files = []
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module_files_updated = False
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loaded_modules = []
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breakpoint = None
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def __init__(self):
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super(LxSymbols, self).__init__("lx-symbols", gdb.COMMAND_FILES,
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gdb.COMPLETE_FILENAME)
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def _update_module_files(self):
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self.module_files = []
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for path in self.module_paths:
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gdb.write("scanning for modules in {0}\n".format(path))
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for root, dirs, files in os.walk(path):
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for name in files:
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if name.endswith(".ko") or name.endswith(".ko.debug"):
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self.module_files.append(root + "/" + name)
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self.module_files_updated = True
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def _get_module_file(self, module_name):
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module_pattern = ".*/{0}\.ko(?:.debug)?$".format(
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module_name.replace("_", r"[_\-]"))
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for name in self.module_files:
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if re.match(module_pattern, name) and os.path.exists(name):
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return name
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return None
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def _section_arguments(self, module):
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try:
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sect_attrs = module['sect_attrs'].dereference()
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except gdb.error:
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return ""
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attrs = sect_attrs['attrs']
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section_name_to_address = {
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attrs[n]['name'].string(): attrs[n]['address']
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for n in range(int(sect_attrs['nsections']))}
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args = []
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for section_name in [".data", ".data..read_mostly", ".rodata", ".bss"]:
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address = section_name_to_address.get(section_name)
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if address:
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args.append(" -s {name} {addr}".format(
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name=section_name, addr=str(address)))
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return "".join(args)
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def load_module_symbols(self, module):
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module_name = module['name'].string()
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module_addr = str(module['core_layout']['base']).split()[0]
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module_file = self._get_module_file(module_name)
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if not module_file and not self.module_files_updated:
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self._update_module_files()
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module_file = self._get_module_file(module_name)
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if module_file:
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gdb.write("loading @{addr}: {filename}\n".format(
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addr=module_addr, filename=module_file))
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cmdline = "add-symbol-file {filename} {addr}{sections}".format(
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filename=module_file,
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addr=module_addr,
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sections=self._section_arguments(module))
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gdb.execute(cmdline, to_string=True)
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if module_name not in self.loaded_modules:
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self.loaded_modules.append(module_name)
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else:
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gdb.write("no module object found for '{0}'\n".format(module_name))
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def load_all_symbols(self):
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gdb.write("loading vmlinux\n")
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# Dropping symbols will disable all breakpoints. So save their states
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# and restore them afterward.
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saved_states = []
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if hasattr(gdb, 'breakpoints') and not gdb.breakpoints() is None:
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for bp in gdb.breakpoints():
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saved_states.append({'breakpoint': bp, 'enabled': bp.enabled})
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# drop all current symbols and reload vmlinux
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orig_vmlinux = 'vmlinux'
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for obj in gdb.objfiles():
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if obj.filename.endswith('vmlinux'):
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orig_vmlinux = obj.filename
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gdb.execute("symbol-file", to_string=True)
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gdb.execute("symbol-file {0}".format(orig_vmlinux))
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self.loaded_modules = []
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module_list = modules.module_list()
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if not module_list:
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gdb.write("no modules found\n")
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else:
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[self.load_module_symbols(module) for module in module_list]
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for saved_state in saved_states:
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saved_state['breakpoint'].enabled = saved_state['enabled']
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def invoke(self, arg, from_tty):
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self.module_paths = [os.path.expanduser(p) for p in arg.split()]
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self.module_paths.append(os.getcwd())
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# enforce update
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self.module_files = []
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self.module_files_updated = False
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self.load_all_symbols()
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if hasattr(gdb, 'Breakpoint'):
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if self.breakpoint is not None:
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self.breakpoint.delete()
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self.breakpoint = None
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self.breakpoint = LoadModuleBreakpoint(
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"kernel/module.c:do_init_module", self)
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else:
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gdb.write("Note: symbol update on module loading not supported "
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"with this gdb version\n")
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LxSymbols()
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