[PATCH v6 00/21] Add gdb python scripts as kernel debugging helpers

[PATCH v6 00/21] Add gdb python scripts as kernel debugging helpers

[Jan Kiszka]

It's been a while since my last update of these patches. This one is
mostly about cleaning up and making some details more convenient:
 - proper registration of module data segments to access module
   variables - this obsoletes lx_modvar again
 - stable breakpoint target on do_init_module in order to track module
   loading more reliably from the debugger
 - internal refactoring with the aim to "pythonize" the scripts (credits
   for all valuable suggestions belong to Tatiana, many thanks, for
   improper implementations to me)

See http://lkml.indiana.edu/hypermail/linux/kernel/1210.0/01598.html for
the original description and

    git://git.kiszka.org/linux.git queues/gdb-scripts

for the latest version.

Jan

CC: "David S. Miller" <davem@davemloft.net>
CC: Fenghua Yu <fenghua.yu@intel.com>
CC: Kay Sievers <kay@vrfy.org>
CC: linux-doc@vger.kernel.org
CC: linux-ia64@vger.kernel.org
CC: linux-kbuild@vger.kernel.org
CC: Michal Marek <mmarek@suse.cz>
CC: Rob Landley <rob@landley.net>
CC: sparclinux@vger.kernel.org
CC: Tony Luck <tony.luck@intel.com>

Jan Kiszka (21):
  scripts/gdb: Add infrastructure
  scripts/gdb: Add cache for type objects
  scripts/gdb: Add container_of helper and convenience function
  scripts/gdb: Add module iteration class
  scripts/gdb: Add lx-symbols command
  module: Do not inline do_init_module
  scripts/gdb: Add automatic symbol reloading on module insertion
  scripts/gdb: Add internal helper and convenience function to look up a
    module
  scripts/gdb: Add get_target_endianness helper
  scripts/gdb: Add read_u16/32/64 helpers
  scripts/gdb: Add lx-dmesg command
  scripts/gdb: Add task iteration class
  scripts/gdb: Add helper and convenience function to look up tasks
  scripts/gdb: Add is_target_arch helper
  scripts/gdb: Add internal helper and convenience function to retrieve
    thread_info
  scripts/gdb: Add get_gdbserver_type helper
  scripts/gdb: Add internal helper and convenience function for per-cpu
    lookup
  scripts/gdb: Add lx_current convenience function
  scripts/gdb: Add class to iterate over CPU masks
  scripts/gdb: Add lx-lsmod command
  scripts/gdb: Add basic documentation

 Documentation/gdb-kernel-debugging.txt | 159 +++++++++++++++++++++++++++++++
 Makefile                               |   5 +-
 kernel/module.c                        |   9 +-
 scripts/Makefile                       |   3 +-
 scripts/gdb/Makefile                   |  11 +++
 scripts/gdb/linux/Makefile             |   9 ++
 scripts/gdb/linux/__init__.py          |   0
 scripts/gdb/linux/cpus.py              | 139 +++++++++++++++++++++++++++
 scripts/gdb/linux/dmesg.py             |  64 +++++++++++++
 scripts/gdb/linux/modules.py           | 111 ++++++++++++++++++++++
 scripts/gdb/linux/symbols.py           | 166 +++++++++++++++++++++++++++++++++
 scripts/gdb/linux/tasks.py             | 108 +++++++++++++++++++++
 scripts/gdb/linux/utils.py             | 156 +++++++++++++++++++++++++++++++
 scripts/gdb/vmlinux-gdb.py             |  30 ++++++
 14 files changed, 966 insertions(+), 4 deletions(-)
 create mode 100644 Documentation/gdb-kernel-debugging.txt
 create mode 100644 scripts/gdb/Makefile
 create mode 100644 scripts/gdb/linux/Makefile
 create mode 100644 scripts/gdb/linux/__init__.py
 create mode 100644 scripts/gdb/linux/cpus.py
 create mode 100644 scripts/gdb/linux/dmesg.py
 create mode 100644 scripts/gdb/linux/modules.py
 create mode 100644 scripts/gdb/linux/symbols.py
 create mode 100644 scripts/gdb/linux/tasks.py
 create mode 100644 scripts/gdb/linux/utils.py
 create mode 100644 scripts/gdb/vmlinux-gdb.py

-- 
1.8.1.1.298.ge7eed54

[PATCH v6 00/21] Add gdb python scripts as kernel debugging helpers

[Jan Kiszka]

It's been a while since my last update of these patches. This one is
mostly about cleaning up and making some details more convenient:
 - proper registration of module data segments to access module
   variables - this obsoletes lx_modvar again
 - stable breakpoint target on do_init_module in order to track module
   loading more reliably from the debugger
 - internal refactoring with the aim to "pythonize" the scripts (credits
   for all valuable suggestions belong to Tatiana, many thanks, for
   improper implementations to me)

See http://lkml.indiana.edu/hypermail/linux/kernel/1210.0/01598.html for
the original description and

    git://git.kiszka.org/linux.git queues/gdb-scripts

for the latest version.

Jan

CC: "David S. Miller" <davem@davemloft.net>
CC: Fenghua Yu <fenghua.yu@intel.com>
CC: Kay Sievers <kay@vrfy.org>
CC: linux-doc@vger.kernel.org
CC: linux-ia64@vger.kernel.org
CC: linux-kbuild@vger.kernel.org
CC: Michal Marek <mmarek@suse.cz>
CC: Rob Landley <rob@landley.net>
CC: sparclinux@vger.kernel.org
CC: Tony Luck <tony.luck@intel.com>

Jan Kiszka (21):
  scripts/gdb: Add infrastructure
  scripts/gdb: Add cache for type objects
  scripts/gdb: Add container_of helper and convenience function
  scripts/gdb: Add module iteration class
  scripts/gdb: Add lx-symbols command
  module: Do not inline do_init_module
  scripts/gdb: Add automatic symbol reloading on module insertion
  scripts/gdb: Add internal helper and convenience function to look up a
    module
  scripts/gdb: Add get_target_endianness helper
  scripts/gdb: Add read_u16/32/64 helpers
  scripts/gdb: Add lx-dmesg command
  scripts/gdb: Add task iteration class
  scripts/gdb: Add helper and convenience function to look up tasks
  scripts/gdb: Add is_target_arch helper
  scripts/gdb: Add internal helper and convenience function to retrieve
    thread_info
  scripts/gdb: Add get_gdbserver_type helper
  scripts/gdb: Add internal helper and convenience function for per-cpu
    lookup
  scripts/gdb: Add lx_current convenience function
  scripts/gdb: Add class to iterate over CPU masks
  scripts/gdb: Add lx-lsmod command
  scripts/gdb: Add basic documentation

 Documentation/gdb-kernel-debugging.txt | 159 +++++++++++++++++++++++++++++++
 Makefile                               |   5 +-
 kernel/module.c                        |   9 +-
 scripts/Makefile                       |   3 +-
 scripts/gdb/Makefile                   |  11 +++
 scripts/gdb/linux/Makefile             |   9 ++
 scripts/gdb/linux/__init__.py          |   0
 scripts/gdb/linux/cpus.py              | 139 +++++++++++++++++++++++++++
 scripts/gdb/linux/dmesg.py             |  64 +++++++++++++
 scripts/gdb/linux/modules.py           | 111 ++++++++++++++++++++++
 scripts/gdb/linux/symbols.py           | 166 +++++++++++++++++++++++++++++++++
 scripts/gdb/linux/tasks.py             | 108 +++++++++++++++++++++
 scripts/gdb/linux/utils.py             | 156 +++++++++++++++++++++++++++++++
 scripts/gdb/vmlinux-gdb.py             |  30 ++++++
 14 files changed, 966 insertions(+), 4 deletions(-)
 create mode 100644 Documentation/gdb-kernel-debugging.txt
 create mode 100644 scripts/gdb/Makefile
 create mode 100644 scripts/gdb/linux/Makefile
 create mode 100644 scripts/gdb/linux/__init__.py
 create mode 100644 scripts/gdb/linux/cpus.py
 create mode 100644 scripts/gdb/linux/dmesg.py
 create mode 100644 scripts/gdb/linux/modules.py
 create mode 100644 scripts/gdb/linux/symbols.py
 create mode 100644 scripts/gdb/linux/tasks.py
 create mode 100644 scripts/gdb/linux/utils.py
 create mode 100644 scripts/gdb/vmlinux-gdb.py

-- 
1.8.1.1.298.ge7eed54

[PATCH v6 01/21] scripts/gdb: Add infrastructure

[Jan Kiszka]

This provides the basic infrastructure to load kernel-specific python
helper scripts when debugging the kernel in gdb.

The loading mechanism is based on gdb loading for <objfile>-gdb.py when
opening <objfile>. Therefore, this places a corresponding link to the
main helper script into the output directory that contains vmlinux.

The main scripts will pull in submodules containing Linux specific gdb
commands and functions. To avoid polluting the source directory with
compiled python modules, we link to them from the object directory.

Due to gdb.parse_and_eval and string redirection for gdb.execute, we
depend on gdb >= 7.2.

This feature depends on CONFIG_DEBUG_INFO.

CC: Michal Marek <mmarek@suse.cz>
CC: linux-kbuild@vger.kernel.org
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 Makefile                      |  5 ++++-
 scripts/Makefile              |  3 ++-
 scripts/gdb/Makefile          | 11 +++++++++++
 scripts/gdb/linux/Makefile    |  9 +++++++++
 scripts/gdb/linux/__init__.py |  0
 scripts/gdb/vmlinux-gdb.py    | 23 +++++++++++++++++++++++
 6 files changed, 49 insertions(+), 2 deletions(-)
 create mode 100644 scripts/gdb/Makefile
 create mode 100644 scripts/gdb/linux/Makefile
 create mode 100644 scripts/gdb/linux/__init__.py
 create mode 100644 scripts/gdb/vmlinux-gdb.py

diff --git a/Makefile b/Makefile
index 868c0eb..0e222d7 100644
--- a/Makefile
+++ b/Makefile
@@ -778,6 +778,9 @@ endif
 ifdef CONFIG_BUILD_DOCSRC
 	$(Q)$(MAKE) $(build)=Documentation
 endif
+ifdef CONFIG_DEBUG_INFO
+	$(Q)ln -fsn $(srctree)/scripts/gdb/vmlinux-gdb.py
+endif
 	+$(call if_changed,link-vmlinux)
 
 # The actual objects are generated when descending, 
@@ -1026,7 +1029,7 @@ MRPROPER_FILES += .config .config.old .version .old_version $(version_h) \
 		  Module.symvers tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS \
 		  signing_key.priv signing_key.x509 x509.genkey		\
 		  extra_certificates signing_key.x509.keyid		\
-		  signing_key.x509.signer
+		  signing_key.x509.signer vmlinux-gdb.py
 
 # clean - Delete most, but leave enough to build external modules
 #
diff --git a/scripts/Makefile b/scripts/Makefile
index 01e7adb..3204b91 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -37,6 +37,7 @@ subdir-$(CONFIG_MODVERSIONS) += genksyms
 subdir-y                     += mod
 subdir-$(CONFIG_SECURITY_SELINUX) += selinux
 subdir-$(CONFIG_DTC)         += dtc
+subdir-$(CONFIG_DEBUG_INFO)  += gdb
 
 # Let clean descend into subdirs
-subdir-	+= basic kconfig package selinux
+subdir-	+= basic kconfig package selinux gdb
diff --git a/scripts/gdb/Makefile b/scripts/gdb/Makefile
new file mode 100644
index 0000000..c0e2fd3
--- /dev/null
+++ b/scripts/gdb/Makefile
@@ -0,0 +1,11 @@
+subdir-y := linux
+
+always := gdb-scripts
+
+$(obj)/gdb-scripts:
+ifneq ($(KBUILD_SRC),)
+	$(Q)ln -fsn $(srctree)/$(obj)/*.py $(objtree)/$(obj)
+endif
+	@:
+
+clean-files := *.pyc $(if $(KBUILD_SRC),*.py)
diff --git a/scripts/gdb/linux/Makefile b/scripts/gdb/linux/Makefile
new file mode 100644
index 0000000..34ccd06
--- /dev/null
+++ b/scripts/gdb/linux/Makefile
@@ -0,0 +1,9 @@
+always := gdb-scripts
+
+$(obj)/gdb-scripts:
+ifneq ($(KBUILD_SRC),)
+	$(Q)ln -fsn $(srctree)/$(obj)/*.py $(objtree)/$(obj)
+endif
+	@:
+
+clean-files := *.pyc $(if $(KBUILD_SRC),*.py)
diff --git a/scripts/gdb/linux/__init__.py b/scripts/gdb/linux/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
new file mode 100644
index 0000000..c1d90ce
--- /dev/null
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -0,0 +1,23 @@
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  loader module
+#
+# Copyright (c) Siemens AG, 2012, 2013
+#
+# Authors:
+#  Jan Kiszka <jan.kiszka@siemens.com>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+import os
+
+sys.path.insert(0, os.path.dirname(__file__) + "/scripts/gdb")
+
+try:
+    gdb.parse_and_eval("0")
+    gdb.execute("", to_string=True)
+except:
+    gdb.write("NOTE: gdb 7.2 or later required for Linux helper scripts to "
+              "work.\n")
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 02/21] scripts/gdb: Add cache for type objects

[Jan Kiszka]

Type lookups are very slow in gdb-python which is often noticeable when
iterating over a number of objects. Introduce the helper class
CachedType that keeps a reference to a gdb.Type object but also
refreshes it after an object file has been loaded.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/utils.py | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 scripts/gdb/linux/utils.py

diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py
new file mode 100644
index 0000000..f883611
--- /dev/null
+++ b/scripts/gdb/linux/utils.py
@@ -0,0 +1,34 @@
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  common utilities
+#
+# Copyright (c) Siemens AG, 2011-2013
+#
+# Authors:
+#  Jan Kiszka <jan.kiszka@siemens.com>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+import gdb
+
+
+class CachedType:
+    def __init__(self, name):
+        self._type = None
+        self._name = name
+
+    def _new_objfile_handler(self, event):
+        self._type = None
+        gdb.events.new_objfile.disconnect(self._new_objfile_handler)
+
+    def get_type(self):
+        if self._type is None:
+            self._type = gdb.lookup_type(self._name)
+            if self._type is None:
+                raise gdb.GdbError(
+                    "cannot resolve type '{0}'".format(self._name))
+            if hasattr(gdb, 'events') and hasattr(gdb.events, 'new_objfile'):
+                gdb.events.new_objfile.connect(self._new_objfile_handler)
+        return self._type
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 03/21] scripts/gdb: Add container_of helper and convenience function

[Jan Kiszka]

Provide an internal helper with container_of semantics. As type lookups
are very slow in gdb-python and we need a type "long" for this, cache
the reference to this type object. Then export the helper also as a
convenience function form use at the gdb command line.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/utils.py | 35 +++++++++++++++++++++++++++++++++++
 scripts/gdb/vmlinux-gdb.py |  2 ++
 2 files changed, 37 insertions(+)

diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py
index f883611..c9d705b 100644
--- a/scripts/gdb/linux/utils.py
+++ b/scripts/gdb/linux/utils.py
@@ -32,3 +32,38 @@ class CachedType:
             if hasattr(gdb, 'events') and hasattr(gdb.events, 'new_objfile'):
                 gdb.events.new_objfile.connect(self._new_objfile_handler)
         return self._type
+
+
+long_type = CachedType("long")
+
+
+def get_long_type():
+    global long_type
+    return long_type.get_type()
+
+
+def offset_of(typeobj, field):
+    element = gdb.Value(0).cast(typeobj)
+    return int(str(element[field].address).split()[0], 16)
+
+
+def container_of(ptr, typeobj, member):
+    return (ptr.cast(get_long_type()) -
+            offset_of(typeobj, member)).cast(typeobj)
+
+
+class ContainerOf(gdb.Function):
+    """Return pointer to containing data structure.
+
+$container_of(PTR, "TYPE", "ELEMENT"): Given PTR, return a pointer to the
+data structure of the type TYPE in which PTR is the address of ELEMENT.
+Note that TYPE and ELEMENT have to be quoted as strings."""
+
+    def __init__(self):
+        super(ContainerOf, self).__init__("container_of")
+
+    def invoke(self, ptr, typename, elementname):
+        return container_of(ptr, gdb.lookup_type(typename.string()).pointer(),
+                            elementname.string())
+
+ContainerOf()
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
index c1d90ce..6495841 100644
--- a/scripts/gdb/vmlinux-gdb.py
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -21,3 +21,5 @@ try:
 except:
     gdb.write("NOTE: gdb 7.2 or later required for Linux helper scripts to "
               "work.\n")
+else:
+    import linux.utils
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 04/21] scripts/gdb: Add module iteration class

[Jan Kiszka]

Will soon be used for loading symbols, printing global variables or
listing modules.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/modules.py | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 scripts/gdb/linux/modules.py

diff --git a/scripts/gdb/linux/modules.py b/scripts/gdb/linux/modules.py
new file mode 100644
index 0000000..8a65c3d
--- /dev/null
+++ b/scripts/gdb/linux/modules.py
@@ -0,0 +1,39 @@
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  module tools
+#
+# Copyright (c) Siemens AG, 2013
+#
+# Authors:
+#  Jan Kiszka <jan.kiszka@siemens.com>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+import gdb
+
+from linux import utils
+
+
+module_type = utils.CachedType("struct module")
+
+
+class ModuleList:
+    def __init__(self):
+        global module_type
+        self.module_ptr_type = module_type.get_type().pointer()
+        modules = gdb.parse_and_eval("modules")
+        self.curr_entry = modules['next']
+        self.end_of_list = modules.address
+
+    def __iter__(self):
+        return self
+
+    def next(self):
+        entry = self.curr_entry
+        if entry != self.end_of_list:
+            self.curr_entry = entry['next']
+            return utils.container_of(entry, self.module_ptr_type, "list")
+        else:
+            raise StopIteration
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 05/21] scripts/gdb: Add lx-symbols command

[Jan Kiszka]

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 <jan.kiszka@siemens.com>
---
 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 0000000..bd21a96
--- /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 <jan.kiszka@siemens.com>
+#
+# 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 6495841..0b0faa4 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
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 06/21] module: Do not inline do_init_module

[Jan Kiszka]

This provides a reliable breakpoint target, required for automatic
symbol loading via the gdb helper command 'lx-symbols'.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 kernel/module.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index dc58274..a40d48a 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3035,8 +3035,13 @@ static void do_mod_ctors(struct module *mod)
 #endif
 }
 
-/* This is where the real work happens */
-static int do_init_module(struct module *mod)
+/*
+ * This is where the real work happens.
+ *
+ * Keep it uninlined to provide a reliable breakpoint target, e.g. for the gdb
+ * helper command 'lx-symbols'.
+ */
+static noinline int do_init_module(struct module *mod)
 {
 	int ret = 0;
 
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 07/21] scripts/gdb: Add automatic symbol reloading on module insertion

[Jan Kiszka]

This installs a silent breakpoint on the do_init_module function. The
breakpoint handler will try to load symbols from the module files found
during lx-symbols execution. This way, breakpoints can be set to module
initialization functions, and there is no need to explicitly call
lx-symbols after (re-)loading a module.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/symbols.py | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/scripts/gdb/linux/symbols.py b/scripts/gdb/linux/symbols.py
index bd21a96..139841f 100644
--- a/scripts/gdb/linux/symbols.py
+++ b/scripts/gdb/linux/symbols.py
@@ -19,6 +19,30 @@ import string
 from linux import modules, utils
 
 
+if hasattr(gdb, 'Breakpoint'):
+    class LoadModuleBreakpoint(gdb.Breakpoint):
+        def __init__(self, spec, gdb_command):
+            super(LoadModuleBreakpoint, self).__init__(spec, internal=True)
+            self.silent = True
+            self.gdb_command = gdb_command
+
+        def stop(self):
+            module = gdb.parse_and_eval("mod")
+            module_name = module['name'].string()
+            cmd = self.gdb_command
+
+            # enforce update if object file is not found
+            cmd.module_files_updated = False
+
+            if module_name in cmd.loaded_modules:
+                gdb.write("refreshing all symbols to reload module "
+                          "'{0}'\n".format(module_name))
+                cmd.load_all_symbols()
+            else:
+                cmd.load_module_symbols(module)
+            return False
+
+
 class LxSymbols(gdb.Command):
     """(Re-)load symbols of Linux kernel and currently loaded modules.
 
@@ -30,6 +54,8 @@ lx-symbols command."""
     module_paths = []
     module_files = []
     module_files_updated = False
+    loaded_modules = []
+    breakpoint = None
 
     def __init__(self):
         super(LxSymbols, self).__init__("lx-symbols", gdb.COMMAND_FILES,
@@ -87,6 +113,8 @@ lx-symbols command."""
                 addr=module_addr,
                 sections=self._section_arguments(module))
             gdb.execute(cmdline, to_string=True)
+            if not module_name in self.loaded_modules:
+                self.loaded_modules.append(module_name)
         else:
             gdb.write("no module object found for '{0}'\n".format(module_name))
 
@@ -104,6 +132,7 @@ lx-symbols command."""
         gdb.execute("symbol-file", to_string=True)
         gdb.execute("symbol-file vmlinux")
 
+        self.loaded_modules = []
         module_list = modules.ModuleList()
         if not module_list:
             gdb.write("no modules found\n")
@@ -123,5 +152,15 @@ lx-symbols command."""
 
         self.load_all_symbols()
 
+        if hasattr(gdb, 'Breakpoint'):
+            if not self.breakpoint is None:
+                self.breakpoint.delete()
+                self.breakpoint = None
+            self.breakpoint = LoadModuleBreakpoint(
+                "kernel/module.c:do_init_module", self)
+        else:
+            gdb.write("Note: symbol update on module loading not supported "
+                      "with this gdb version\n")
+
 
 LxSymbols()
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 08/21] scripts/gdb: Add internal helper and convenience function to look up a module

[Jan Kiszka]

Add the internal helper get_module_by_name to obtain the module
structure corresponding to the given name. Also export this service as a
convenience function.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/modules.py | 28 ++++++++++++++++++++++++++++
 scripts/gdb/vmlinux-gdb.py   |  1 +
 2 files changed, 29 insertions(+)

diff --git a/scripts/gdb/linux/modules.py b/scripts/gdb/linux/modules.py
index 8a65c3d..531f763 100644
--- a/scripts/gdb/linux/modules.py
+++ b/scripts/gdb/linux/modules.py
@@ -37,3 +37,31 @@ class ModuleList:
             return utils.container_of(entry, self.module_ptr_type, "list")
         else:
             raise StopIteration
+
+
+def find_module_by_name(name):
+    for module in ModuleList():
+        if module['name'].string() == name:
+            return module
+    return None
+
+
+class LxModule(gdb.Function):
+    """Find module by name and return the module variable.
+
+$lx_module("MODULE"): Given the name MODULE, iterate over all loaded modules
+of the target and return that module variable which MODULE matches."""
+
+    def __init__(self):
+        super(LxModule, self).__init__("lx_module")
+
+    def invoke(self, mod_name):
+        mod_name = mod_name.string()
+        module = find_module_by_name(mod_name)
+        if module:
+            return module.dereference()
+        else:
+            raise gdb.GdbError("Unable to find MODULE " + mod_name)
+
+
+LxModule()
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
index 0b0faa4..cf2e716 100644
--- a/scripts/gdb/vmlinux-gdb.py
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -24,3 +24,4 @@ except:
 else:
     import linux.utils
     import linux.symbols
+    import linux.modules
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 09/21] scripts/gdb: Add get_target_endianness helper

[Jan Kiszka]

Parse the target endianness from the output of "show endian" and cache
the result to return it via the new helper get_target_endiannes. We will
need it for reading integers from buffers that contain target memory.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/utils.py | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py
index c9d705b..10a227b 100644
--- a/scripts/gdb/linux/utils.py
+++ b/scripts/gdb/linux/utils.py
@@ -67,3 +67,21 @@ Note that TYPE and ELEMENT have to be quoted as strings."""
                             elementname.string())
 
 ContainerOf()
+
+
+BIG_ENDIAN = 0
+LITTLE_ENDIAN = 1
+target_endianness = None
+
+
+def get_target_endianness():
+    global target_endianness
+    if target_endianness is None:
+        endian = gdb.execute("show endian", to_string=True)
+        if "little endian" in endian:
+            target_endianness = LITTLE_ENDIAN
+        elif "big endian" in endian:
+            target_endianness = BIG_ENDIAN
+        else:
+            raise gdb.GdgError("unknown endianness '{0}'".format(endian))
+    return target_endianness
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 10/21] scripts/gdb: Add read_u16/32/64 helpers

[Jan Kiszka]

Add helpers for reading integers from target memory buffers. Required
when caching the memory access is more efficient than reading individual
values via gdb.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/utils.py | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py
index 10a227b..808a265 100644
--- a/scripts/gdb/linux/utils.py
+++ b/scripts/gdb/linux/utils.py
@@ -85,3 +85,24 @@ def get_target_endianness():
         else:
             raise gdb.GdgError("unknown endianness '{0}'".format(endian))
     return target_endianness
+
+
+def read_u16(buffer):
+    if get_target_endianness() == LITTLE_ENDIAN:
+        return ord(buffer[0]) + (ord(buffer[1]) << 8)
+    else:
+        return ord(buffer[1]) + (ord(buffer[0]) << 8)
+
+
+def read_u32(buffer):
+    if get_target_endianness() == LITTLE_ENDIAN:
+        return read_u16(buffer[0:2]) + (read_u16(buffer[2:4]) << 16)
+    else:
+        return read_u16(buffer[2:4]) + (read_u16(buffer[0:2]) << 16)
+
+
+def read_u64(buffer):
+    if get_target_endianness() == LITTLE_ENDIAN:
+        return read_u32(buffer[0:4]) + (read_u32(buffer[4:8]) << 32)
+    else:
+        return read_u32(buffer[4:8]) + (read_u32(buffer[0:4]) << 32)
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 11/21] scripts/gdb: Add lx-dmesg command

[Jan Kiszka]

This pokes into the log buffer of the debugged kernel, dumping it to the
gdb console. Helping in case the target should or can no longer execute
dmesg itself.

CC: Kay Sievers <kay@vrfy.org>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/dmesg.py | 64 ++++++++++++++++++++++++++++++++++++++++++++++
 scripts/gdb/vmlinux-gdb.py |  1 +
 2 files changed, 65 insertions(+)
 create mode 100644 scripts/gdb/linux/dmesg.py

diff --git a/scripts/gdb/linux/dmesg.py b/scripts/gdb/linux/dmesg.py
new file mode 100644
index 0000000..7650f24
--- /dev/null
+++ b/scripts/gdb/linux/dmesg.py
@@ -0,0 +1,64 @@
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  kernel log buffer dump
+#
+# Copyright (c) Siemens AG, 2011, 2012
+#
+# Authors:
+#  Jan Kiszka <jan.kiszka@siemens.com>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+import gdb
+import string
+
+from linux import utils
+
+
+class LxDmesg(gdb.Command):
+    """Print Linux kernel log buffer."""
+
+    def __init__(self):
+        super(LxDmesg, self).__init__("lx-dmesg", gdb.COMMAND_DATA)
+
+    def invoke(self, arg, from_tty):
+        log_buf_addr = int(str(gdb.parse_and_eval("log_buf")).split()[0], 16)
+        log_first_idx = int(gdb.parse_and_eval("log_first_idx"))
+        log_next_idx = int(gdb.parse_and_eval("log_next_idx"))
+        log_buf_len = int(gdb.parse_and_eval("log_buf_len"))
+
+        inf = gdb.inferiors()[0]
+        start = log_buf_addr + log_first_idx
+        if log_first_idx < log_next_idx:
+            log_buf_2nd_half = -1
+            length = log_next_idx - log_first_idx
+            log_buf = inf.read_memory(start, length)
+        else:
+            log_buf_2nd_half = log_buf_len - log_first_idx
+            log_buf = inf.read_memory(start, log_buf_2nd_half) + \
+                inf.read_memory(log_buf_addr, log_next_idx)
+
+        pos = 0
+        while pos < log_buf.__len__():
+            length = utils.read_u16(log_buf[pos + 8:pos + 10])
+            if length == 0:
+                if log_buf_2nd_half == -1:
+                    gdb.write("Corrupted log buffer!\n")
+                    break
+                pos = log_buf_2nd_half
+                continue
+
+            text_len = utils.read_u16(log_buf[pos + 10:pos + 12])
+            time_stamp = utils.read_u64(log_buf[pos:pos + 8])
+
+            for line in log_buf[pos + 16:pos + 16 + text_len].splitlines():
+                gdb.write("[{time:12.6f}] {line}\n".format(
+                    time=time_stamp / 1000000000.0,
+                    line=line))
+
+            pos += length
+
+
+LxDmesg()
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
index cf2e716..fa66d23 100644
--- a/scripts/gdb/vmlinux-gdb.py
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -25,3 +25,4 @@ else:
     import linux.utils
     import linux.symbols
     import linux.modules
+    import linux.dmesg
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 12/21] scripts/gdb: Add task iteration class

[Jan Kiszka]

This class allows to iterate over all tasks of the target.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/tasks.py | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 scripts/gdb/linux/tasks.py

diff --git a/scripts/gdb/linux/tasks.py b/scripts/gdb/linux/tasks.py
new file mode 100644
index 0000000..cd25984
--- /dev/null
+++ b/scripts/gdb/linux/tasks.py
@@ -0,0 +1,46 @@
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  task & thread tools
+#
+# Copyright (c) Siemens AG, 2011-2013
+#
+# Authors:
+#  Jan Kiszka <jan.kiszka@siemens.com>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+import gdb
+
+from linux import utils
+
+
+task_type = utils.CachedType("struct task_struct")
+
+
+class TaskList:
+    def __init__(self):
+        global task_type
+        self.task_ptr_type = task_type.get_type().pointer()
+        self.init_task = gdb.parse_and_eval("init_task")
+        self.curr_group = self.init_task.address
+        self.curr_task = None
+
+    def __iter__(self):
+        return self
+
+    def next(self):
+        t = self.curr_task
+        if not t or t == self.curr_group:
+            self.curr_group = \
+                utils.container_of(self.curr_group['tasks']['next'],
+                                   self.task_ptr_type, "tasks")
+            if self.curr_group == self.init_task.address:
+                raise StopIteration
+            t = self.curr_task = self.curr_group
+        else:
+            self.curr_task = \
+                utils.container_of(t['thread_group']['next'],
+                                   self.task_ptr_type, "thread_group")
+        return t
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 13/21] scripts/gdb: Add helper and convenience function to look up tasks

[Jan Kiszka]

Add the helper task_by_pid that can look up a task by its PID. Also
export it as a convenience function.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/tasks.py | 27 +++++++++++++++++++++++++++
 scripts/gdb/vmlinux-gdb.py |  1 +
 2 files changed, 28 insertions(+)

diff --git a/scripts/gdb/linux/tasks.py b/scripts/gdb/linux/tasks.py
index cd25984..13bb97c 100644
--- a/scripts/gdb/linux/tasks.py
+++ b/scripts/gdb/linux/tasks.py
@@ -44,3 +44,30 @@ class TaskList:
                 utils.container_of(t['thread_group']['next'],
                                    self.task_ptr_type, "thread_group")
         return t
+
+
+def get_task_by_pid(pid):
+    for task in TaskList():
+        if int(task['pid']) == pid:
+            return task
+    return None
+
+
+class LxTaskByPidFunc(gdb.Function):
+    """Find Linux task by PID and return the task_struct variable.
+
+$lx_task_by_pid(PID): Given PID, iterate over all tasks of the target and
+return that task_struct variable which PID matches."""
+
+    def __init__(self):
+        super(LxTaskByPidFunc, self).__init__("lx_task_by_pid")
+
+    def invoke(self, pid):
+        task = get_task_by_pid(pid)
+        if task:
+            return task.dereference()
+        else:
+            raise gdb.GdbError("No task of PID " + str(pid))
+
+
+LxTaskByPidFunc()
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
index fa66d23..4d7eb2c 100644
--- a/scripts/gdb/vmlinux-gdb.py
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -26,3 +26,4 @@ else:
     import linux.symbols
     import linux.modules
     import linux.dmesg
+    import linux.tasks
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 14/21] scripts/gdb: Add is_target_arch helper

[Jan Kiszka]

This helper caches to result of "show architecture" and matches the
provided arch (sub-)string against that output.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/utils.py | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py
index 808a265..71ee48c 100644
--- a/scripts/gdb/linux/utils.py
+++ b/scripts/gdb/linux/utils.py
@@ -106,3 +106,16 @@ def read_u64(buffer):
         return read_u32(buffer[0:4]) + (read_u32(buffer[4:8]) << 32)
     else:
         return read_u32(buffer[4:8]) + (read_u32(buffer[0:4]) << 32)
+
+
+target_arch = None
+
+
+def is_target_arch(arch):
+    if hasattr(gdb.Frame, 'architecture'):
+        return arch in gdb.newest_frame().architecture().name()
+    else:
+        global target_arch
+        if target_arch is None:
+            target_arch = gdb.execute("show architecture", to_string=True)
+        return arch in target_arch
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 15/21] scripts/gdb: Add internal helper and convenience function to retrieve thread_info

[Jan Kiszka]

Add the internal helper get_thread_info that calculates the thread_info
from a given task variable. Also export this service as a convenience
function.

Note: ia64 version is untested.

CC: Tony Luck <tony.luck@intel.com>
CC: Fenghua Yu <fenghua.yu@intel.com>
CC: linux-ia64@vger.kernel.org
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/tasks.py | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/scripts/gdb/linux/tasks.py b/scripts/gdb/linux/tasks.py
index 13bb97c..63cd6c5 100644
--- a/scripts/gdb/linux/tasks.py
+++ b/scripts/gdb/linux/tasks.py
@@ -71,3 +71,38 @@ return that task_struct variable which PID matches."""
 
 
 LxTaskByPidFunc()
+
+
+thread_info_type = utils.CachedType("struct thread_info")
+
+ia64_task_size = None
+
+
+def get_thread_info(task):
+    global thread_info_type
+    thread_info_ptr_type = thread_info_type.get_type().pointer()
+    if utils.is_target_arch("ia64"):
+        global ia64_task_size
+        if ia64_task_size is None:
+            ia64_task_size = gdb.parse_and_eval("sizeof(struct task_struct)")
+        thread_info_addr = task.address + ia64_task_size
+        thread_info = thread_info_addr.cast(thread_info_ptr_type)
+    else:
+        thread_info = task['stack'].cast(thread_info_ptr_type)
+    return thread_info.dereference()
+
+
+class LxThreadInfoFunc (gdb.Function):
+    """Calculate Linux thread_info from task variable.
+
+$lx_thread_info(TASK): Given TASK, return the corresponding thread_info
+variable."""
+
+    def __init__(self):
+        super(LxThreadInfoFunc, self).__init__("lx_thread_info")
+
+    def invoke(self, task):
+        return get_thread_info(task)
+
+
+LxThreadInfoFunc()
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 15/21] scripts/gdb: Add internal helper and convenience function to retrieve thread_info

[Jan Kiszka]

Add the internal helper get_thread_info that calculates the thread_info
from a given task variable. Also export this service as a convenience
function.

Note: ia64 version is untested.

CC: Tony Luck <tony.luck@intel.com>
CC: Fenghua Yu <fenghua.yu@intel.com>
CC: linux-ia64@vger.kernel.org
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/tasks.py | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/scripts/gdb/linux/tasks.py b/scripts/gdb/linux/tasks.py
index 13bb97c..63cd6c5 100644
--- a/scripts/gdb/linux/tasks.py
+++ b/scripts/gdb/linux/tasks.py
@@ -71,3 +71,38 @@ return that task_struct variable which PID matches."""
 
 
 LxTaskByPidFunc()
+
+
+thread_info_type = utils.CachedType("struct thread_info")
+
+ia64_task_size = None
+
+
+def get_thread_info(task):
+    global thread_info_type
+    thread_info_ptr_type = thread_info_type.get_type().pointer()
+    if utils.is_target_arch("ia64"):
+        global ia64_task_size
+        if ia64_task_size is None:
+            ia64_task_size = gdb.parse_and_eval("sizeof(struct task_struct)")
+        thread_info_addr = task.address + ia64_task_size
+        thread_info = thread_info_addr.cast(thread_info_ptr_type)
+    else:
+        thread_info = task['stack'].cast(thread_info_ptr_type)
+    return thread_info.dereference()
+
+
+class LxThreadInfoFunc (gdb.Function):
+    """Calculate Linux thread_info from task variable.
+
+$lx_thread_info(TASK): Given TASK, return the corresponding thread_info
+variable."""
+
+    def __init__(self):
+        super(LxThreadInfoFunc, self).__init__("lx_thread_info")
+
+    def invoke(self, task):
+        return get_thread_info(task)
+
+
+LxThreadInfoFunc()
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 16/21] scripts/gdb: Add get_gdbserver_type helper

[Jan Kiszka]

This helper probes the type of the gdb server. Supported are QEMU and
KGDB so far. Knowledge about the gdb server is required e.g. to retrieve
the current CPU or current task.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/utils.py | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py
index 71ee48c..a4a1640 100644
--- a/scripts/gdb/linux/utils.py
+++ b/scripts/gdb/linux/utils.py
@@ -119,3 +119,38 @@ def is_target_arch(arch):
         if target_arch is None:
             target_arch = gdb.execute("show architecture", to_string=True)
         return arch in target_arch
+
+
+GDBSERVER_QEMU = 0
+GDBSERVER_KGDB = 1
+gdbserver_type = None
+
+
+def get_gdbserver_type():
+    def exit_handler(event):
+        global gdbserver_type
+        gdbserver_type = None
+        gdb.events.exited.disconnect(exit_handler)
+
+    def probe_qemu():
+        try:
+            return gdb.execute("monitor info version", to_string=True) != ""
+        except:
+            return False
+
+    def probe_kgdb():
+        try:
+            thread_info = gdb.execute("info thread 2", to_string=True)
+            return "shadowCPU0" in thread_info
+        except:
+            return False
+
+    global gdbserver_type
+    if gdbserver_type is None:
+        if probe_qemu():
+            gdbserver_type = GDBSERVER_QEMU
+        elif probe_kgdb():
+            gdbserver_type = GDBSERVER_KGDB
+        if not gdbserver_type is None and hasattr(gdb, 'events'):
+            gdb.events.exited.connect(exit_handler)
+    return gdbserver_type
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 17/21] scripts/gdb: Add internal helper and convenience function for per-cpu lookup

[Jan Kiszka]

This function allows to obtain a per-cpu variable, either of the current
or an explicitly specified CPU.

Note: sparc64 version is untested.

CC: "David S. Miller" <davem@davemloft.net>
CC: sparclinux@vger.kernel.org
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/cpus.py  | 68 ++++++++++++++++++++++++++++++++++++++++++++++
 scripts/gdb/vmlinux-gdb.py |  1 +
 2 files changed, 69 insertions(+)
 create mode 100644 scripts/gdb/linux/cpus.py

diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py
new file mode 100644
index 0000000..18337e0
--- /dev/null
+++ b/scripts/gdb/linux/cpus.py
@@ -0,0 +1,68 @@
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  per-cpu tools
+#
+# Copyright (c) Siemens AG, 2011-2013
+#
+# Authors:
+#  Jan Kiszka <jan.kiszka@siemens.com>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+import gdb
+
+from linux import tasks, utils
+
+
+MAX_CPUS = 4096
+
+
+def get_current_cpu():
+    if utils.get_gdbserver_type() == utils.GDBSERVER_QEMU:
+        return gdb.selected_thread().num - 1
+    elif utils.get_gdbserver_type() == utils.GDBSERVER_KGDB:
+        tid = gdb.selected_thread().ptid[2]
+        if tid > (0x100000000 - MAX_CPUS - 2):
+            return 0x100000000 - tid - 2
+        else:
+            return tasks.get_thread_info(tasks.get_task_by_pid(tid))['cpu']
+    else:
+        raise gdb.GdbError("Sorry, obtaining the current CPU is not yet "
+                           "supported with this gdb server.")
+
+
+def per_cpu(var_ptr, cpu):
+    if cpu == -1:
+        cpu = get_current_cpu()
+    if utils.is_target_arch("sparc:v9"):
+        offset = gdb.parse_and_eval(
+            "trap_block[{0}].__per_cpu_base".format(str(cpu)))
+    else:
+        try:
+            offset = gdb.parse_and_eval(
+                "__per_cpu_offset[{0}]".format(str(cpu)))
+        except gdb.error:
+            # !CONFIG_SMP case
+            offset = 0
+    pointer = var_ptr.cast(utils.get_long_type()) + offset
+    return pointer.cast(var_ptr.type).dereference()
+
+
+class PerCpu(gdb.Function):
+    """Return per-cpu variable.
+
+$lx_per_cpu("VAR"[, CPU]): Return the per-cpu variable called VAR for the
+given CPU number. If CPU is omitted, the CPU of the current context is used.
+Note that VAR has to be quoted as string."""
+
+    def __init__(self):
+        super(PerCpu, self).__init__("lx_per_cpu")
+
+    def invoke(self, var_name, cpu=-1):
+        var_ptr = gdb.parse_and_eval("&" + var_name.string())
+        return per_cpu(var_ptr, cpu)
+
+
+PerCpu()
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
index 4d7eb2c..4848928 100644
--- a/scripts/gdb/vmlinux-gdb.py
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -27,3 +27,4 @@ else:
     import linux.modules
     import linux.dmesg
     import linux.tasks
+    import linux.cpus
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 17/21] scripts/gdb: Add internal helper and convenience function for per-cpu lookup

[Jan Kiszka]

This function allows to obtain a per-cpu variable, either of the current
or an explicitly specified CPU.

Note: sparc64 version is untested.

CC: "David S. Miller" <davem@davemloft.net>
CC: sparclinux@vger.kernel.org
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/cpus.py  | 68 ++++++++++++++++++++++++++++++++++++++++++++++
 scripts/gdb/vmlinux-gdb.py |  1 +
 2 files changed, 69 insertions(+)
 create mode 100644 scripts/gdb/linux/cpus.py

diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py
new file mode 100644
index 0000000..18337e0
--- /dev/null
+++ b/scripts/gdb/linux/cpus.py
@@ -0,0 +1,68 @@
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  per-cpu tools
+#
+# Copyright (c) Siemens AG, 2011-2013
+#
+# Authors:
+#  Jan Kiszka <jan.kiszka@siemens.com>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+import gdb
+
+from linux import tasks, utils
+
+
+MAX_CPUS = 4096
+
+
+def get_current_cpu():
+    if utils.get_gdbserver_type() = utils.GDBSERVER_QEMU:
+        return gdb.selected_thread().num - 1
+    elif utils.get_gdbserver_type() = utils.GDBSERVER_KGDB:
+        tid = gdb.selected_thread().ptid[2]
+        if tid > (0x100000000 - MAX_CPUS - 2):
+            return 0x100000000 - tid - 2
+        else:
+            return tasks.get_thread_info(tasks.get_task_by_pid(tid))['cpu']
+    else:
+        raise gdb.GdbError("Sorry, obtaining the current CPU is not yet "
+                           "supported with this gdb server.")
+
+
+def per_cpu(var_ptr, cpu):
+    if cpu = -1:
+        cpu = get_current_cpu()
+    if utils.is_target_arch("sparc:v9"):
+        offset = gdb.parse_and_eval(
+            "trap_block[{0}].__per_cpu_base".format(str(cpu)))
+    else:
+        try:
+            offset = gdb.parse_and_eval(
+                "__per_cpu_offset[{0}]".format(str(cpu)))
+        except gdb.error:
+            # !CONFIG_SMP case
+            offset = 0
+    pointer = var_ptr.cast(utils.get_long_type()) + offset
+    return pointer.cast(var_ptr.type).dereference()
+
+
+class PerCpu(gdb.Function):
+    """Return per-cpu variable.
+
+$lx_per_cpu("VAR"[, CPU]): Return the per-cpu variable called VAR for the
+given CPU number. If CPU is omitted, the CPU of the current context is used.
+Note that VAR has to be quoted as string."""
+
+    def __init__(self):
+        super(PerCpu, self).__init__("lx_per_cpu")
+
+    def invoke(self, var_name, cpu=-1):
+        var_ptr = gdb.parse_and_eval("&" + var_name.string())
+        return per_cpu(var_ptr, cpu)
+
+
+PerCpu()
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
index 4d7eb2c..4848928 100644
--- a/scripts/gdb/vmlinux-gdb.py
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -27,3 +27,4 @@ else:
     import linux.modules
     import linux.dmesg
     import linux.tasks
+    import linux.cpus
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 18/21] scripts/gdb: Add lx_current convenience function

[Jan Kiszka]

This is a shorthand for *$lx_per_cpu("current_task"), i.e. a convenience
function to retrieve the currently running task of the active context.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/cpus.py | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py
index 18337e0..b683da9 100644
--- a/scripts/gdb/linux/cpus.py
+++ b/scripts/gdb/linux/cpus.py
@@ -66,3 +66,20 @@ Note that VAR has to be quoted as string."""
 
 
 PerCpu()
+
+
+class LxCurrentFunc(gdb.Function):
+    """Return current task.
+
+$lx_current([CPU]): Return the per-cpu task variable for the given CPU
+number. If CPU is omitted, the CPU of the current context is used."""
+
+    def __init__(self):
+        super(LxCurrentFunc, self).__init__("lx_current")
+
+    def invoke(self, cpu=-1):
+        var_ptr = gdb.parse_and_eval("&current_task")
+        return per_cpu(var_ptr, cpu).dereference()
+
+
+LxCurrentFunc()
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 19/21] scripts/gdb: Add class to iterate over CPU masks

[Jan Kiszka]

Will be used first to count module references. It is optimized to read
the mask only once per stop.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/cpus.py | 54 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py
index b683da9..c1441f2 100644
--- a/scripts/gdb/linux/cpus.py
+++ b/scripts/gdb/linux/cpus.py
@@ -50,6 +50,60 @@ def per_cpu(var_ptr, cpu):
     return pointer.cast(var_ptr.type).dereference()
 
 
+cpu_mask = {}
+
+
+def cpu_mask_invalidate(event):
+    global cpu_mask
+    cpu_mask = {}
+    gdb.events.stop.disconnect(cpu_mask_invalidate)
+    if hasattr(gdb.events, 'new_objfile'):
+        gdb.events.new_objfile.disconnect(cpu_mask_invalidate)
+
+
+class CpuList():
+    def __init__(self, mask_name):
+        global cpu_mask
+        self.mask = None
+        if mask_name in cpu_mask:
+            self.mask = cpu_mask[mask_name]
+        if self.mask is None:
+            self.mask = gdb.parse_and_eval(mask_name + ".bits")
+            if hasattr(gdb, 'events'):
+                cpu_mask[mask_name] = self.mask
+                gdb.events.stop.connect(cpu_mask_invalidate)
+                if hasattr(gdb.events, 'new_objfile'):
+                    gdb.events.new_objfile.connect(cpu_mask_invalidate)
+        self.bits_per_entry = self.mask[0].type.sizeof * 8
+        self.num_entries = self.mask.type.sizeof * 8 / self.bits_per_entry
+        self.entry = -1
+        self.bits = 0
+
+    def __iter__(self):
+        return self
+
+    def next(self):
+        while self.bits == 0:
+            self.entry += 1
+            if self.entry == self.num_entries:
+                raise StopIteration
+            self.bits = self.mask[self.entry]
+            if self.bits != 0:
+                self.bit = 0
+                break
+
+        while self.bits & 1 == 0:
+            self.bits >>= 1
+            self.bit += 1
+
+        cpu = self.entry * self.bits_per_entry + self.bit
+
+        self.bits >>= 1
+        self.bit += 1
+
+        return cpu
+
+
 class PerCpu(gdb.Function):
     """Return per-cpu variable.
 
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 20/21] scripts/gdb: Add lx-lsmod command

[Jan Kiszka]

This adds a lsmod-like command to list all currently loaded modules of
the target.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/modules.py | 46 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 45 insertions(+), 1 deletion(-)

diff --git a/scripts/gdb/linux/modules.py b/scripts/gdb/linux/modules.py
index 531f763..e7c99e9 100644
--- a/scripts/gdb/linux/modules.py
+++ b/scripts/gdb/linux/modules.py
@@ -13,7 +13,7 @@
 
 import gdb
 
-from linux import utils
+from linux import cpus, utils
 
 
 module_type = utils.CachedType("struct module")
@@ -65,3 +65,47 @@ of the target and return that module variable which MODULE matches."""
 
 
 LxModule()
+
+
+class LxLsmod(gdb.Command):
+    """List currently loaded modules."""
+
+    _module_use_type = utils.CachedType("struct module_use")
+
+    def __init__(self):
+        super(LxLsmod, self).__init__("lx-lsmod", gdb.COMMAND_DATA)
+
+    def invoke(self, arg, from_tty):
+        gdb.write(
+            "Address{0}    Module                  Size  Used by\n".format(
+                "        " if utils.get_long_type().sizeof == 8 else ""))
+
+        for module in ModuleList():
+            ref = 0
+            module_refptr = module['refptr']
+            for cpu in cpus.CpuList("cpu_possible_mask"):
+                refptr = cpus.per_cpu(module_refptr, cpu)
+                ref += refptr['incs']
+                ref -= refptr['decs']
+
+            gdb.write("{address} {name:<19} {size:>8}  {ref}".format(
+                address=str(module['module_core']).split()[0],
+                name=module['name'].string(),
+                size=module['core_size'],
+                ref=ref))
+
+            source_list = module['source_list']
+            t = self._module_use_type.get_type().pointer()
+            entry = source_list['next']
+            first = True
+            while entry != source_list.address:
+                use = utils.container_of(entry, t, "source_list")
+                gdb.write("{separator}{name}".format(
+                    separator=" " if first else ",",
+                    name=use['source']['name'].string()))
+                first = False
+                entry = entry['next']
+            gdb.write("\n")
+
+
+LxLsmod()
-- 
1.8.1.1.298.ge7eed54

[PATCH v6 21/21] scripts/gdb: Add basic documentation

[Jan Kiszka]

CC: Rob Landley <rob@landley.net>
CC: linux-doc@vger.kernel.org
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 Documentation/gdb-kernel-debugging.txt | 159 +++++++++++++++++++++++++++++++++
 1 file changed, 159 insertions(+)
 create mode 100644 Documentation/gdb-kernel-debugging.txt

diff --git a/Documentation/gdb-kernel-debugging.txt b/Documentation/gdb-kernel-debugging.txt
new file mode 100644
index 0000000..944f2d2
--- /dev/null
+++ b/Documentation/gdb-kernel-debugging.txt
@@ -0,0 +1,159 @@
+Debugging kernel and modules via gdb
+====================================
+
+The kernel debugger kgdb, hypervisors like QEMU or JTAG-based hardware
+interfaces allow to debug the Linux kernel and its modules during runtime
+using gdb. Gdb comes with a powerful scripting interface for python. The
+kernel provides a collection of helper scripts that can simplify typical
+kernel debugging steps. This is a short tutorial about how to enable and use
+them. It focuses on QEMU/KVM virtual machines as target, but the examples can
+be transferred to the other gdb stubs as well.
+
+
+Requirements
+------------
+
+ o gdb 7.2+ (recommended: 7.4+) with python support enabled (typically true
+   for distributions)
+
+
+Setup
+-----
+
+ o Create a virtual Linux machine for QEMU/KVM (see www.linux-kvm.org and
+   www.qemu.org for more details). For cross-development,
+   http://landley.net/aboriginal/bin keeps a pool of machine images and
+   toolchains that can be helpful to start from.
+
+ o Build the kernel with CONFIG_DEBUG_INFO and CONFIG_KALLSYMS enabled, but
+   leave CONFIG_DEBUG_INFO_REDUCED off.
+
+ o Install that kernel on the guest.
+
+   Alternatively, QEMU allows to boot the kernel directly using -kernel,
+   -append, -initrd command line switches. This is generally only useful if
+   you do not depend on modules. See QEMU documentation for more details on
+   this mode.
+
+ o Enable the gdb stub of QEMU/KVM, either
+    - at VM startup time by appending "-s" to the QEMU command line
+   or
+    - during runtime by issuing "gdbserver" from the QEMU monitor
+      console
+
+ o cd /path/to/linux-build
+
+ o Start gdb: gdb vmlinux
+
+   Note: Some distros may restrict auto-loading of gdb scripts to known safe
+   directories. In case gdb reports to refuse loading vmlinux-gdb.py, add
+
+    add-add-auto-load-safe-path /path/to/linux-build
+
+   to ~/.gdbinit. See gdb help for more details.
+
+ o Attach to the booted guest:
+    (gdb) target remote :1234
+
+
+Examples of using the Linux-provided gdb helpers
+------------------------------------------------
+
+ o Load module (and main kernel) symbols:
+    (gdb) lx-symbols
+    loading vmlinux
+    scanning for modules in /home/user/linux/build
+    loading @0xffffffffa0020000: /home/user/linux/build/net/netfilter/xt_tcpudp.ko
+    loading @0xffffffffa0016000: /home/user/linux/build/net/netfilter/xt_pkttype.ko
+    loading @0xffffffffa0002000: /home/user/linux/build/net/netfilter/xt_limit.ko
+    loading @0xffffffffa00ca000: /home/user/linux/build/net/packet/af_packet.ko
+    loading @0xffffffffa003c000: /home/user/linux/build/fs/fuse/fuse.ko
+    ...
+    loading @0xffffffffa0000000: /home/user/linux/build/drivers/ata/ata_generic.ko
+
+ o Set a breakpoint on some not yet loaded module function, e.g.:
+    (gdb) b btrfs_init_sysfs
+    Function "btrfs_init_sysfs" not defined.
+    Make breakpoint pending on future shared library load? (y or [n]) y
+    Breakpoint 1 (btrfs_init_sysfs) pending.
+
+ o Continue the target
+    (gdb) c
+
+ o Load the module on the target and watch the symbols being loaded as well as
+   the breakpoint hit:
+    loading @0xffffffffa0034000: /home/user/linux/build/lib/libcrc32c.ko
+    loading @0xffffffffa0050000: /home/user/linux/build/lib/lzo/lzo_compress.ko
+    loading @0xffffffffa006e000: /home/user/linux/build/lib/zlib_deflate/zlib_deflate.ko
+    loading @0xffffffffa01b1000: /home/user/linux/build/fs/btrfs/btrfs.ko
+
+    Breakpoint 1, btrfs_init_sysfs () at /home/user/linux/fs/btrfs/sysfs.c:36
+    36              btrfs_kset = kset_create_and_add("btrfs", NULL, fs_kobj);
+
+ o Dump the log buffer of the target kernel:
+    (gdb) lx-dmesg
+    [     0.000000] Initializing cgroup subsys cpuset
+    [     0.000000] Initializing cgroup subsys cpu
+    [     0.000000] Linux version 3.8.0-rc4-dbg+ (...
+    [     0.000000] Command line: root=/dev/sda2 resume=/dev/sda1 vga=0x314
+    [     0.000000] e820: BIOS-provided physical RAM map:
+    [     0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
+    [     0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
+    ....
+
+ o Examine fields of the current task struct:
+    (gdb) p $lx_current().pid
+    $1 = 4998
+    (gdb) p $lx_current().comm
+    $2 = "modprobe\000\000\000\000\000\000\000"
+
+ o Make use of the per-cpu function for the current or a specified CPU:
+    (gdb) p $lx_per_cpu("runqueues").nr_running
+    $3 = 1
+    (gdb) p $lx_per_cpu("runqueues", 2).nr_running
+    $4 = 0
+
+ o Dig into hrtimers using the container_of helper:
+    (gdb) set $next = $lx_per_cpu("hrtimer_bases").clock_base[0].active.next
+    (gdb) p *$container_of($next, "struct hrtimer", "node")
+    $5 = {
+      node = {
+        node = {
+          __rb_parent_color = 18446612133355256072,
+          rb_right = 0x0 <irq_stack_union>,
+          rb_left = 0x0 <irq_stack_union>
+        },
+        expires = {
+          tv64 = 1835268000000
+        }
+      },
+      _softexpires = {
+        tv64 = 1835268000000
+      },
+      function = 0xffffffff81078232 <tick_sched_timer>,
+      base = 0xffff88003fd0d6f0,
+      state = 1,
+      start_pid = 0,
+      start_site = 0xffffffff81055c1f <hrtimer_start_range_ns+20>,
+      start_comm = "swapper/2\000\000\000\000\000\000"
+    }
+
+
+List of commands and functions
+------------------------------
+
+The number of commands and convenience functions may evolve over the time,
+this is just a snapshot of the initial version:
+
+ (gdb) apropos lx
+ function lx_current -- Return current task
+ function lx_module -- Find module by name and return the module variable
+ function lx_per_cpu -- Return per-cpu variable
+ function lx_task_by_pid -- Find Linux task by PID and return the task_struct variable
+ function lx_thread_info -- Calculate Linux thread_info from task variable
+ lx-dmesg -- Print Linux kernel log buffer
+ lx-lsmod -- List currently loaded modules
+ lx-symbols -- (Re-)load symbols of Linux kernel and currently loaded modules
+
+Detailed help can be obtained via "help <command-name>" for commands and "help
+function <function-name>" for convenience functions.
-- 
1.8.1.1.298.ge7eed54

Re: [PATCH v6 01/21] scripts/gdb: Add infrastructure

[Andi Kleen]

> The loading mechanism is based on gdb loading for <objfile>-gdb.py when
> opening <objfile>. Therefore, this places a corresponding link to the
> main helper script into the output directory that contains vmlinux.

> This feature depends on CONFIG_DEBUG_INFO.

Could you make this a separate config option? Having the links for
people who don't use gdb would be ugly.

-Andi

Re: [PATCH v6 01/21] scripts/gdb: Add infrastructure

[Jan Kiszka]

On 2013-10-30 06:35, Andi Kleen wrote:
>> The loading mechanism is based on gdb loading for <objfile>-gdb.py when
>> opening <objfile>. Therefore, this places a corresponding link to the
>> main helper script into the output directory that contains vmlinux.
> 
>> This feature depends on CONFIG_DEBUG_INFO.
> 
> Could you make this a separate config option? Having the links for
> people who don't use gdb would be ugly.
> 

Like this?

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 06344d9..d66a8f8 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -143,6 +143,17 @@ config DEBUG_INFO_REDUCED
 	  DEBUG_INFO build and compile times are reduced too.
 	  Only works with newer gcc versions.
 
+config GDB_SCRIPTS
+	bool "Provide GDB scripts for kernel debugging"
+	select DEBUG_INFO
+	help
+	  This creates the required links to GDB helper scripts in the
+	  build directory. If you load vmlinux into gdb, the helper
+	  scripts will be automatically imported by gdb as well, and
+	  additional functions are available to analyze a Linux kernel
+	  instance. See Documentation/gdb-kernel-debugging.txt for further
+	  details.
+
 config ENABLE_WARN_DEPRECATED
 	bool "Enable __deprecated logic"
 	default y

Will send an updated series soon, also adjusting the docs, just waiting
for potential further comments.

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux

Re: [PATCH v6 21/21] scripts/gdb: Add basic documentation

[Borislav Petkov]

On Mon, Oct 28, 2013 at 09:58:58AM +0100, Jan Kiszka wrote:
> CC: Rob Landley <rob@landley.net>
> CC: linux-doc@vger.kernel.org
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>  Documentation/gdb-kernel-debugging.txt | 159 +++++++++++++++++++++++++++++++++
>  1 file changed, 159 insertions(+)
>  create mode 100644 Documentation/gdb-kernel-debugging.txt
> 
> diff --git a/Documentation/gdb-kernel-debugging.txt b/Documentation/gdb-kernel-debugging.txt
> new file mode 100644
> index 0000000..944f2d2
> --- /dev/null
> +++ b/Documentation/gdb-kernel-debugging.txt
> @@ -0,0 +1,159 @@
> +Debugging kernel and modules via gdb
> +====================================
> +
> +The kernel debugger kgdb, hypervisors like QEMU or JTAG-based hardware
> +interfaces allow to debug the Linux kernel and its modules during runtime
> +using gdb. Gdb comes with a powerful scripting interface for python. The
> +kernel provides a collection of helper scripts that can simplify typical
> +kernel debugging steps. This is a short tutorial about how to enable and use
> +them. It focuses on QEMU/KVM virtual machines as target, but the examples can
> +be transferred to the other gdb stubs as well.
> +
> +
> +Requirements
> +------------
> +
> + o gdb 7.2+ (recommended: 7.4+) with python support enabled (typically true
> +   for distributions)
> +
> +
> +Setup
> +-----
> +
> + o Create a virtual Linux machine for QEMU/KVM (see www.linux-kvm.org and
> +   www.qemu.org for more details). For cross-development,
> +   http://landley.net/aboriginal/bin keeps a pool of machine images and
> +   toolchains that can be helpful to start from.
> +
> + o Build the kernel with CONFIG_DEBUG_INFO and CONFIG_KALLSYMS enabled, but
> +   leave CONFIG_DEBUG_INFO_REDUCED off.
> +
> + o Install that kernel on the guest.
> +
> +   Alternatively, QEMU allows to boot the kernel directly using -kernel,
> +   -append, -initrd command line switches. This is generally only useful if
> +   you do not depend on modules. See QEMU documentation for more details on
> +   this mode.
> +
> + o Enable the gdb stub of QEMU/KVM, either
> +    - at VM startup time by appending "-s" to the QEMU command line
> +   or
> +    - during runtime by issuing "gdbserver" from the QEMU monitor
> +      console
> +
> + o cd /path/to/linux-build
> +
> + o Start gdb: gdb vmlinux
> +
> +   Note: Some distros may restrict auto-loading of gdb scripts to known safe
> +   directories. In case gdb reports to refuse loading vmlinux-gdb.py, add
> +
> +    add-add-auto-load-safe-path /path/to/linux-build

Only one "add-" should be enough :)

Btw, gdb is nice enough to tell me:

$ gdb vmlinux
Reading symbols from /w/kernel/linux-2.6/vmlinux...done.
warning: File "/w/kernel/linux-2.6/scripts/gdb/vmlinux-gdb.py" auto-loading has been declined by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load".
To enable execution of this file add
        add-auto-load-safe-path /w/kernel/linux-2.6/scripts/gdb/vmlinux-gdb.py
line to your configuration file "/home/boris/.gdbinit".
To completely disable this security protection add
        set auto-load safe-path /
line to your configuration file "/home/boris/.gdbinit".
For more information about this security protection see the
"Auto-loading safe path" section in the GDB manual.  E.g., run from the shell:
        info "(gdb)Auto-loading safe path"

Other than that, that's a very cool stuff and I'll make sure to be using
it the next time.

Acked-by: Borislav Petkov <bp@suse.de>

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
--

Re: [PATCH v6 21/21] scripts/gdb: Add basic documentation

[Jan Kiszka]

On 2013-10-30 12:17, Borislav Petkov wrote:
> On Mon, Oct 28, 2013 at 09:58:58AM +0100, Jan Kiszka wrote:
>> CC: Rob Landley <rob@landley.net>
>> CC: linux-doc@vger.kernel.org
>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>> ---
>>  Documentation/gdb-kernel-debugging.txt | 159 +++++++++++++++++++++++++++++++++
>>  1 file changed, 159 insertions(+)
>>  create mode 100644 Documentation/gdb-kernel-debugging.txt
>>
>> diff --git a/Documentation/gdb-kernel-debugging.txt b/Documentation/gdb-kernel-debugging.txt
>> new file mode 100644
>> index 0000000..944f2d2
>> --- /dev/null
>> +++ b/Documentation/gdb-kernel-debugging.txt
>> @@ -0,0 +1,159 @@
>> +Debugging kernel and modules via gdb
>> +====================================
>> +
>> +The kernel debugger kgdb, hypervisors like QEMU or JTAG-based hardware
>> +interfaces allow to debug the Linux kernel and its modules during runtime
>> +using gdb. Gdb comes with a powerful scripting interface for python. The
>> +kernel provides a collection of helper scripts that can simplify typical
>> +kernel debugging steps. This is a short tutorial about how to enable and use
>> +them. It focuses on QEMU/KVM virtual machines as target, but the examples can
>> +be transferred to the other gdb stubs as well.
>> +
>> +
>> +Requirements
>> +------------
>> +
>> + o gdb 7.2+ (recommended: 7.4+) with python support enabled (typically true
>> +   for distributions)
>> +
>> +
>> +Setup
>> +-----
>> +
>> + o Create a virtual Linux machine for QEMU/KVM (see www.linux-kvm.org and
>> +   www.qemu.org for more details). For cross-development,
>> +   http://landley.net/aboriginal/bin keeps a pool of machine images and
>> +   toolchains that can be helpful to start from.
>> +
>> + o Build the kernel with CONFIG_DEBUG_INFO and CONFIG_KALLSYMS enabled, but
>> +   leave CONFIG_DEBUG_INFO_REDUCED off.
>> +
>> + o Install that kernel on the guest.
>> +
>> +   Alternatively, QEMU allows to boot the kernel directly using -kernel,
>> +   -append, -initrd command line switches. This is generally only useful if
>> +   you do not depend on modules. See QEMU documentation for more details on
>> +   this mode.
>> +
>> + o Enable the gdb stub of QEMU/KVM, either
>> +    - at VM startup time by appending "-s" to the QEMU command line
>> +   or
>> +    - during runtime by issuing "gdbserver" from the QEMU monitor
>> +      console
>> +
>> + o cd /path/to/linux-build
>> +
>> + o Start gdb: gdb vmlinux
>> +
>> +   Note: Some distros may restrict auto-loading of gdb scripts to known safe
>> +   directories. In case gdb reports to refuse loading vmlinux-gdb.py, add
>> +
>> +    add-add-auto-load-safe-path /path/to/linux-build
> 
> Only one "add-" should be enough :)

Thanks, fixed. Need to update this file anyway.

> 
> Btw, gdb is nice enough to tell me:
> 
> $ gdb vmlinux
> Reading symbols from /w/kernel/linux-2.6/vmlinux...done.
> warning: File "/w/kernel/linux-2.6/scripts/gdb/vmlinux-gdb.py" auto-loading has been declined by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load".
> To enable execution of this file add
>         add-auto-load-safe-path /w/kernel/linux-2.6/scripts/gdb/vmlinux-gdb.py

Is that sufficient to be able to import all the sub-scripts as well?

> line to your configuration file "/home/boris/.gdbinit".
> To completely disable this security protection add
>         set auto-load safe-path /
> line to your configuration file "/home/boris/.gdbinit".
> For more information about this security protection see the
> "Auto-loading safe path" section in the GDB manual.  E.g., run from the shell:
>         info "(gdb)Auto-loading safe path"
> 
> Other than that, that's a very cool stuff and I'll make sure to be using
> it the next time.
> 
> Acked-by: Borislav Petkov <bp@suse.de>
> 

Thanks!

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux

Re: [PATCH v6 21/21] scripts/gdb: Add basic documentation

[Borislav Petkov]

On Wed, Oct 30, 2013 at 12:22:15PM +0100, Jan Kiszka wrote:
> > $ gdb vmlinux
> > Reading symbols from /w/kernel/linux-2.6/vmlinux...done.
> > warning: File "/w/kernel/linux-2.6/scripts/gdb/vmlinux-gdb.py" auto-loading has been declined by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load".
> > To enable execution of this file add
> >         add-auto-load-safe-path /w/kernel/linux-2.6/scripts/gdb/vmlinux-gdb.py
> 
> Is that sufficient to be able to import all the sub-scripts as well?

If by that you mean whether I was able to use all commands in the
'apropos lx' list, then yes, it seems to work. Here's an arbitrary example:

(gdb) set $p = $lx_task_by_pid(12)
(gdb) p $lx_thread_info($p)
$8 = {task = 0xffff88007bcedb40, exec_domain = 0xffffffff8186c8a0 <default_exec_domain>, flags = 0, status = 0, cpu = 1, 
  saved_preempt_count = -2147483646, addr_limit = {seg = 18446744073709551615}, restart_block = {
    fn = 0xffffffff8105c3c0 <do_no_restart_syscall>, {futex = {uaddr = 0x0 <irq_stack_union>, val = 0, flags = 0, bitset = 0, time = 0, 
        uaddr2 = 0x0 <irq_stack_union>}, nanosleep = {clockid = 0, rmtp = 0x0 <irq_stack_union>, compat_rmtp = 0x0 <irq_stack_union>, 
        expires = 0}, poll = {ufds = 0x0 <irq_stack_union>, nfds = 0, has_timeout = 0, tv_sec = 0, tv_nsec = 0}}}, 
  sysenter_return = 0x0 <irq_stack_union>, sig_on_uaccess_error = 0, uaccess_err = 0}

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
--