+++ /dev/null
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
-
-<book id="debug-objects-guide">
- <bookinfo>
- <title>Debug objects life time</title>
-
- <authorgroup>
- <author>
- <firstname>Thomas</firstname>
- <surname>Gleixner</surname>
- <affiliation>
- <address>
- <email>tglx@linutronix.de</email>
- </address>
- </affiliation>
- </author>
- </authorgroup>
-
- <copyright>
- <year>2008</year>
- <holder>Thomas Gleixner</holder>
- </copyright>
-
- <legalnotice>
- <para>
- This documentation is free software; you can redistribute
- it and/or modify it under the terms of the GNU General Public
- License version 2 as published by the Free Software Foundation.
- </para>
-
- <para>
- This program is distributed in the hope that it will be
- useful, but WITHOUT ANY WARRANTY; without even the implied
- warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
- See the GNU General Public License for more details.
- </para>
-
- <para>
- You should have received a copy of the GNU General Public
- License along with this program; if not, write to the Free
- Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
- MA 02111-1307 USA
- </para>
-
- <para>
- For more details see the file COPYING in the source
- distribution of Linux.
- </para>
- </legalnotice>
- </bookinfo>
-
-<toc></toc>
-
- <chapter id="intro">
- <title>Introduction</title>
- <para>
- debugobjects is a generic infrastructure to track the life time
- of kernel objects and validate the operations on those.
- </para>
- <para>
- debugobjects is useful to check for the following error patterns:
- <itemizedlist>
- <listitem><para>Activation of uninitialized objects</para></listitem>
- <listitem><para>Initialization of active objects</para></listitem>
- <listitem><para>Usage of freed/destroyed objects</para></listitem>
- </itemizedlist>
- </para>
- <para>
- debugobjects is not changing the data structure of the real
- object so it can be compiled in with a minimal runtime impact
- and enabled on demand with a kernel command line option.
- </para>
- </chapter>
-
- <chapter id="howto">
- <title>Howto use debugobjects</title>
- <para>
- A kernel subsystem needs to provide a data structure which
- describes the object type and add calls into the debug code at
- appropriate places. The data structure to describe the object
- type needs at minimum the name of the object type. Optional
- functions can and should be provided to fixup detected problems
- so the kernel can continue to work and the debug information can
- be retrieved from a live system instead of hard core debugging
- with serial consoles and stack trace transcripts from the
- monitor.
- </para>
- <para>
- The debug calls provided by debugobjects are:
- <itemizedlist>
- <listitem><para>debug_object_init</para></listitem>
- <listitem><para>debug_object_init_on_stack</para></listitem>
- <listitem><para>debug_object_activate</para></listitem>
- <listitem><para>debug_object_deactivate</para></listitem>
- <listitem><para>debug_object_destroy</para></listitem>
- <listitem><para>debug_object_free</para></listitem>
- <listitem><para>debug_object_assert_init</para></listitem>
- </itemizedlist>
- Each of these functions takes the address of the real object and
- a pointer to the object type specific debug description
- structure.
- </para>
- <para>
- Each detected error is reported in the statistics and a limited
- number of errors are printk'ed including a full stack trace.
- </para>
- <para>
- The statistics are available via /sys/kernel/debug/debug_objects/stats.
- They provide information about the number of warnings and the
- number of successful fixups along with information about the
- usage of the internal tracking objects and the state of the
- internal tracking objects pool.
- </para>
- </chapter>
- <chapter id="debugfunctions">
- <title>Debug functions</title>
- <sect1 id="prototypes">
- <title>Debug object function reference</title>
-!Elib/debugobjects.c
- </sect1>
- <sect1 id="debug_object_init">
- <title>debug_object_init</title>
- <para>
- This function is called whenever the initialization function
- of a real object is called.
- </para>
- <para>
- When the real object is already tracked by debugobjects it is
- checked, whether the object can be initialized. Initializing
- is not allowed for active and destroyed objects. When
- debugobjects detects an error, then it calls the fixup_init
- function of the object type description structure if provided
- by the caller. The fixup function can correct the problem
- before the real initialization of the object happens. E.g. it
- can deactivate an active object in order to prevent damage to
- the subsystem.
- </para>
- <para>
- When the real object is not yet tracked by debugobjects,
- debugobjects allocates a tracker object for the real object
- and sets the tracker object state to ODEBUG_STATE_INIT. It
- verifies that the object is not on the callers stack. If it is
- on the callers stack then a limited number of warnings
- including a full stack trace is printk'ed. The calling code
- must use debug_object_init_on_stack() and remove the object
- before leaving the function which allocated it. See next
- section.
- </para>
- </sect1>
-
- <sect1 id="debug_object_init_on_stack">
- <title>debug_object_init_on_stack</title>
- <para>
- This function is called whenever the initialization function
- of a real object which resides on the stack is called.
- </para>
- <para>
- When the real object is already tracked by debugobjects it is
- checked, whether the object can be initialized. Initializing
- is not allowed for active and destroyed objects. When
- debugobjects detects an error, then it calls the fixup_init
- function of the object type description structure if provided
- by the caller. The fixup function can correct the problem
- before the real initialization of the object happens. E.g. it
- can deactivate an active object in order to prevent damage to
- the subsystem.
- </para>
- <para>
- When the real object is not yet tracked by debugobjects
- debugobjects allocates a tracker object for the real object
- and sets the tracker object state to ODEBUG_STATE_INIT. It
- verifies that the object is on the callers stack.
- </para>
- <para>
- An object which is on the stack must be removed from the
- tracker by calling debug_object_free() before the function
- which allocates the object returns. Otherwise we keep track of
- stale objects.
- </para>
- </sect1>
-
- <sect1 id="debug_object_activate">
- <title>debug_object_activate</title>
- <para>
- This function is called whenever the activation function of a
- real object is called.
- </para>
- <para>
- When the real object is already tracked by debugobjects it is
- checked, whether the object can be activated. Activating is
- not allowed for active and destroyed objects. When
- debugobjects detects an error, then it calls the
- fixup_activate function of the object type description
- structure if provided by the caller. The fixup function can
- correct the problem before the real activation of the object
- happens. E.g. it can deactivate an active object in order to
- prevent damage to the subsystem.
- </para>
- <para>
- When the real object is not yet tracked by debugobjects then
- the fixup_activate function is called if available. This is
- necessary to allow the legitimate activation of statically
- allocated and initialized objects. The fixup function checks
- whether the object is valid and calls the debug_objects_init()
- function to initialize the tracking of this object.
- </para>
- <para>
- When the activation is legitimate, then the state of the
- associated tracker object is set to ODEBUG_STATE_ACTIVE.
- </para>
- </sect1>
-
- <sect1 id="debug_object_deactivate">
- <title>debug_object_deactivate</title>
- <para>
- This function is called whenever the deactivation function of
- a real object is called.
- </para>
- <para>
- When the real object is tracked by debugobjects it is checked,
- whether the object can be deactivated. Deactivating is not
- allowed for untracked or destroyed objects.
- </para>
- <para>
- When the deactivation is legitimate, then the state of the
- associated tracker object is set to ODEBUG_STATE_INACTIVE.
- </para>
- </sect1>
-
- <sect1 id="debug_object_destroy">
- <title>debug_object_destroy</title>
- <para>
- This function is called to mark an object destroyed. This is
- useful to prevent the usage of invalid objects, which are
- still available in memory: either statically allocated objects
- or objects which are freed later.
- </para>
- <para>
- When the real object is tracked by debugobjects it is checked,
- whether the object can be destroyed. Destruction is not
- allowed for active and destroyed objects. When debugobjects
- detects an error, then it calls the fixup_destroy function of
- the object type description structure if provided by the
- caller. The fixup function can correct the problem before the
- real destruction of the object happens. E.g. it can deactivate
- an active object in order to prevent damage to the subsystem.
- </para>
- <para>
- When the destruction is legitimate, then the state of the
- associated tracker object is set to ODEBUG_STATE_DESTROYED.
- </para>
- </sect1>
-
- <sect1 id="debug_object_free">
- <title>debug_object_free</title>
- <para>
- This function is called before an object is freed.
- </para>
- <para>
- When the real object is tracked by debugobjects it is checked,
- whether the object can be freed. Free is not allowed for
- active objects. When debugobjects detects an error, then it
- calls the fixup_free function of the object type description
- structure if provided by the caller. The fixup function can
- correct the problem before the real free of the object
- happens. E.g. it can deactivate an active object in order to
- prevent damage to the subsystem.
- </para>
- <para>
- Note that debug_object_free removes the object from the
- tracker. Later usage of the object is detected by the other
- debug checks.
- </para>
- </sect1>
-
- <sect1 id="debug_object_assert_init">
- <title>debug_object_assert_init</title>
- <para>
- This function is called to assert that an object has been
- initialized.
- </para>
- <para>
- When the real object is not tracked by debugobjects, it calls
- fixup_assert_init of the object type description structure
- provided by the caller, with the hardcoded object state
- ODEBUG_NOT_AVAILABLE. The fixup function can correct the problem
- by calling debug_object_init and other specific initializing
- functions.
- </para>
- <para>
- When the real object is already tracked by debugobjects it is
- ignored.
- </para>
- </sect1>
- </chapter>
- <chapter id="fixupfunctions">
- <title>Fixup functions</title>
- <sect1 id="debug_obj_descr">
- <title>Debug object type description structure</title>
-!Iinclude/linux/debugobjects.h
- </sect1>
- <sect1 id="fixup_init">
- <title>fixup_init</title>
- <para>
- This function is called from the debug code whenever a problem
- in debug_object_init is detected. The function takes the
- address of the object and the state which is currently
- recorded in the tracker.
- </para>
- <para>
- Called from debug_object_init when the object state is:
- <itemizedlist>
- <listitem><para>ODEBUG_STATE_ACTIVE</para></listitem>
- </itemizedlist>
- </para>
- <para>
- The function returns true when the fixup was successful,
- otherwise false. The return value is used to update the
- statistics.
- </para>
- <para>
- Note, that the function needs to call the debug_object_init()
- function again, after the damage has been repaired in order to
- keep the state consistent.
- </para>
- </sect1>
-
- <sect1 id="fixup_activate">
- <title>fixup_activate</title>
- <para>
- This function is called from the debug code whenever a problem
- in debug_object_activate is detected.
- </para>
- <para>
- Called from debug_object_activate when the object state is:
- <itemizedlist>
- <listitem><para>ODEBUG_STATE_NOTAVAILABLE</para></listitem>
- <listitem><para>ODEBUG_STATE_ACTIVE</para></listitem>
- </itemizedlist>
- </para>
- <para>
- The function returns true when the fixup was successful,
- otherwise false. The return value is used to update the
- statistics.
- </para>
- <para>
- Note that the function needs to call the debug_object_activate()
- function again after the damage has been repaired in order to
- keep the state consistent.
- </para>
- <para>
- The activation of statically initialized objects is a special
- case. When debug_object_activate() has no tracked object for
- this object address then fixup_activate() is called with
- object state ODEBUG_STATE_NOTAVAILABLE. The fixup function
- needs to check whether this is a legitimate case of a
- statically initialized object or not. In case it is it calls
- debug_object_init() and debug_object_activate() to make the
- object known to the tracker and marked active. In this case
- the function should return false because this is not a real
- fixup.
- </para>
- </sect1>
-
- <sect1 id="fixup_destroy">
- <title>fixup_destroy</title>
- <para>
- This function is called from the debug code whenever a problem
- in debug_object_destroy is detected.
- </para>
- <para>
- Called from debug_object_destroy when the object state is:
- <itemizedlist>
- <listitem><para>ODEBUG_STATE_ACTIVE</para></listitem>
- </itemizedlist>
- </para>
- <para>
- The function returns true when the fixup was successful,
- otherwise false. The return value is used to update the
- statistics.
- </para>
- </sect1>
- <sect1 id="fixup_free">
- <title>fixup_free</title>
- <para>
- This function is called from the debug code whenever a problem
- in debug_object_free is detected. Further it can be called
- from the debug checks in kfree/vfree, when an active object is
- detected from the debug_check_no_obj_freed() sanity checks.
- </para>
- <para>
- Called from debug_object_free() or debug_check_no_obj_freed()
- when the object state is:
- <itemizedlist>
- <listitem><para>ODEBUG_STATE_ACTIVE</para></listitem>
- </itemizedlist>
- </para>
- <para>
- The function returns true when the fixup was successful,
- otherwise false. The return value is used to update the
- statistics.
- </para>
- </sect1>
- <sect1 id="fixup_assert_init">
- <title>fixup_assert_init</title>
- <para>
- This function is called from the debug code whenever a problem
- in debug_object_assert_init is detected.
- </para>
- <para>
- Called from debug_object_assert_init() with a hardcoded state
- ODEBUG_STATE_NOTAVAILABLE when the object is not found in the
- debug bucket.
- </para>
- <para>
- The function returns true when the fixup was successful,
- otherwise false. The return value is used to update the
- statistics.
- </para>
- <para>
- Note, this function should make sure debug_object_init() is
- called before returning.
- </para>
- <para>
- The handling of statically initialized objects is a special
- case. The fixup function should check if this is a legitimate
- case of a statically initialized object or not. In this case only
- debug_object_init() should be called to make the object known to
- the tracker. Then the function should return false because this
- is not
- a real fixup.
- </para>
- </sect1>
- </chapter>
- <chapter id="bugs">
- <title>Known Bugs And Assumptions</title>
- <para>
- None (knock on wood).
- </para>
- </chapter>
-</book>
--- /dev/null
+============================================
+The object-lifetime debugging infrastructure
+============================================
+
+:Author: Thomas Gleixner
+
+Introduction
+============
+
+debugobjects is a generic infrastructure to track the life time of
+kernel objects and validate the operations on those.
+
+debugobjects is useful to check for the following error patterns:
+
+- Activation of uninitialized objects
+
+- Initialization of active objects
+
+- Usage of freed/destroyed objects
+
+debugobjects is not changing the data structure of the real object so it
+can be compiled in with a minimal runtime impact and enabled on demand
+with a kernel command line option.
+
+Howto use debugobjects
+======================
+
+A kernel subsystem needs to provide a data structure which describes the
+object type and add calls into the debug code at appropriate places. The
+data structure to describe the object type needs at minimum the name of
+the object type. Optional functions can and should be provided to fixup
+detected problems so the kernel can continue to work and the debug
+information can be retrieved from a live system instead of hard core
+debugging with serial consoles and stack trace transcripts from the
+monitor.
+
+The debug calls provided by debugobjects are:
+
+- debug_object_init
+
+- debug_object_init_on_stack
+
+- debug_object_activate
+
+- debug_object_deactivate
+
+- debug_object_destroy
+
+- debug_object_free
+
+- debug_object_assert_init
+
+Each of these functions takes the address of the real object and a
+pointer to the object type specific debug description structure.
+
+Each detected error is reported in the statistics and a limited number
+of errors are printk'ed including a full stack trace.
+
+The statistics are available via /sys/kernel/debug/debug_objects/stats.
+They provide information about the number of warnings and the number of
+successful fixups along with information about the usage of the internal
+tracking objects and the state of the internal tracking objects pool.
+
+Debug functions
+===============
+
+Debug object function reference
+-------------------------------
+
+.. kernel-doc:: lib/debugobjects.c
+ :export:
+
+debug_object_init
+-------------------
+
+This function is called whenever the initialization function of a real
+object is called.
+
+When the real object is already tracked by debugobjects it is checked,
+whether the object can be initialized. Initializing is not allowed for
+active and destroyed objects. When debugobjects detects an error, then
+it calls the fixup_init function of the object type description
+structure if provided by the caller. The fixup function can correct the
+problem before the real initialization of the object happens. E.g. it
+can deactivate an active object in order to prevent damage to the
+subsystem.
+
+When the real object is not yet tracked by debugobjects, debugobjects
+allocates a tracker object for the real object and sets the tracker
+object state to ODEBUG_STATE_INIT. It verifies that the object is not
+on the callers stack. If it is on the callers stack then a limited
+number of warnings including a full stack trace is printk'ed. The
+calling code must use debug_object_init_on_stack() and remove the
+object before leaving the function which allocated it. See next section.
+
+debug_object_init_on_stack
+------------------------------
+
+This function is called whenever the initialization function of a real
+object which resides on the stack is called.
+
+When the real object is already tracked by debugobjects it is checked,
+whether the object can be initialized. Initializing is not allowed for
+active and destroyed objects. When debugobjects detects an error, then
+it calls the fixup_init function of the object type description
+structure if provided by the caller. The fixup function can correct the
+problem before the real initialization of the object happens. E.g. it
+can deactivate an active object in order to prevent damage to the
+subsystem.
+
+When the real object is not yet tracked by debugobjects debugobjects
+allocates a tracker object for the real object and sets the tracker
+object state to ODEBUG_STATE_INIT. It verifies that the object is on
+the callers stack.
+
+An object which is on the stack must be removed from the tracker by
+calling debug_object_free() before the function which allocates the
+object returns. Otherwise we keep track of stale objects.
+
+debug_object_activate
+-----------------------
+
+This function is called whenever the activation function of a real
+object is called.
+
+When the real object is already tracked by debugobjects it is checked,
+whether the object can be activated. Activating is not allowed for
+active and destroyed objects. When debugobjects detects an error, then
+it calls the fixup_activate function of the object type description
+structure if provided by the caller. The fixup function can correct the
+problem before the real activation of the object happens. E.g. it can
+deactivate an active object in order to prevent damage to the subsystem.
+
+When the real object is not yet tracked by debugobjects then the
+fixup_activate function is called if available. This is necessary to
+allow the legitimate activation of statically allocated and initialized
+objects. The fixup function checks whether the object is valid and calls
+the debug_objects_init() function to initialize the tracking of this
+object.
+
+When the activation is legitimate, then the state of the associated
+tracker object is set to ODEBUG_STATE_ACTIVE.
+
+debug_object_deactivate
+-------------------------
+
+This function is called whenever the deactivation function of a real
+object is called.
+
+When the real object is tracked by debugobjects it is checked, whether
+the object can be deactivated. Deactivating is not allowed for untracked
+or destroyed objects.
+
+When the deactivation is legitimate, then the state of the associated
+tracker object is set to ODEBUG_STATE_INACTIVE.
+
+debug_object_destroy
+----------------------
+
+This function is called to mark an object destroyed. This is useful to
+prevent the usage of invalid objects, which are still available in
+memory: either statically allocated objects or objects which are freed
+later.
+
+When the real object is tracked by debugobjects it is checked, whether
+the object can be destroyed. Destruction is not allowed for active and
+destroyed objects. When debugobjects detects an error, then it calls the
+fixup_destroy function of the object type description structure if
+provided by the caller. The fixup function can correct the problem
+before the real destruction of the object happens. E.g. it can
+deactivate an active object in order to prevent damage to the subsystem.
+
+When the destruction is legitimate, then the state of the associated
+tracker object is set to ODEBUG_STATE_DESTROYED.
+
+debug_object_free
+-------------------
+
+This function is called before an object is freed.
+
+When the real object is tracked by debugobjects it is checked, whether
+the object can be freed. Free is not allowed for active objects. When
+debugobjects detects an error, then it calls the fixup_free function of
+the object type description structure if provided by the caller. The
+fixup function can correct the problem before the real free of the
+object happens. E.g. it can deactivate an active object in order to
+prevent damage to the subsystem.
+
+Note that debug_object_free removes the object from the tracker. Later
+usage of the object is detected by the other debug checks.
+
+debug_object_assert_init
+---------------------------
+
+This function is called to assert that an object has been initialized.
+
+When the real object is not tracked by debugobjects, it calls
+fixup_assert_init of the object type description structure provided by
+the caller, with the hardcoded object state ODEBUG_NOT_AVAILABLE. The
+fixup function can correct the problem by calling debug_object_init
+and other specific initializing functions.
+
+When the real object is already tracked by debugobjects it is ignored.
+
+Fixup functions
+===============
+
+Debug object type description structure
+---------------------------------------
+
+.. kernel-doc:: include/linux/debugobjects.h
+ :internal:
+
+fixup_init
+-----------
+
+This function is called from the debug code whenever a problem in
+debug_object_init is detected. The function takes the address of the
+object and the state which is currently recorded in the tracker.
+
+Called from debug_object_init when the object state is:
+
+- ODEBUG_STATE_ACTIVE
+
+The function returns true when the fixup was successful, otherwise
+false. The return value is used to update the statistics.
+
+Note, that the function needs to call the debug_object_init() function
+again, after the damage has been repaired in order to keep the state
+consistent.
+
+fixup_activate
+---------------
+
+This function is called from the debug code whenever a problem in
+debug_object_activate is detected.
+
+Called from debug_object_activate when the object state is:
+
+- ODEBUG_STATE_NOTAVAILABLE
+
+- ODEBUG_STATE_ACTIVE
+
+The function returns true when the fixup was successful, otherwise
+false. The return value is used to update the statistics.
+
+Note that the function needs to call the debug_object_activate()
+function again after the damage has been repaired in order to keep the
+state consistent.
+
+The activation of statically initialized objects is a special case. When
+debug_object_activate() has no tracked object for this object address
+then fixup_activate() is called with object state
+ODEBUG_STATE_NOTAVAILABLE. The fixup function needs to check whether
+this is a legitimate case of a statically initialized object or not. In
+case it is it calls debug_object_init() and debug_object_activate()
+to make the object known to the tracker and marked active. In this case
+the function should return false because this is not a real fixup.
+
+fixup_destroy
+--------------
+
+This function is called from the debug code whenever a problem in
+debug_object_destroy is detected.
+
+Called from debug_object_destroy when the object state is:
+
+- ODEBUG_STATE_ACTIVE
+
+The function returns true when the fixup was successful, otherwise
+false. The return value is used to update the statistics.
+
+fixup_free
+-----------
+
+This function is called from the debug code whenever a problem in
+debug_object_free is detected. Further it can be called from the debug
+checks in kfree/vfree, when an active object is detected from the
+debug_check_no_obj_freed() sanity checks.
+
+Called from debug_object_free() or debug_check_no_obj_freed() when
+the object state is:
+
+- ODEBUG_STATE_ACTIVE
+
+The function returns true when the fixup was successful, otherwise
+false. The return value is used to update the statistics.
+
+fixup_assert_init
+-------------------
+
+This function is called from the debug code whenever a problem in
+debug_object_assert_init is detected.
+
+Called from debug_object_assert_init() with a hardcoded state
+ODEBUG_STATE_NOTAVAILABLE when the object is not found in the debug
+bucket.
+
+The function returns true when the fixup was successful, otherwise
+false. The return value is used to update the statistics.
+
+Note, this function should make sure debug_object_init() is called
+before returning.
+
+The handling of statically initialized objects is a special case. The
+fixup function should check if this is a legitimate case of a statically
+initialized object or not. In this case only debug_object_init()
+should be called to make the object known to the tracker. Then the
+function should return false because this is not a real fixup.
+
+Known Bugs And Assumptions
+==========================
+
+None (knock on wood).
projects / linux-beck.git / commitdiff