docs-rst: create an user's manual book

Place README, REPORTING-BUGS, SecurityBugs and kernel-parameters
on an user's manual book.

As we'll be numbering the user's manual, remove the manual
numbering from SecurityBugs.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

1 files changed, 353 insertions, 0 deletions

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+Dynamic debug
++++++++++++++
+
+
+Introduction
+============
+
+This document describes how to use the dynamic debug (dyndbg) feature.
+
+Dynamic debug is designed to allow you to dynamically enable/disable
+kernel code to obtain additional kernel information.  Currently, if
+``CONFIG_DYNAMIC_DEBUG`` is set, then all ``pr_debug()``/``dev_dbg()`` and
+``print_hex_dump_debug()``/``print_hex_dump_bytes()`` calls can be dynamically
+enabled per-callsite.
+
+If ``CONFIG_DYNAMIC_DEBUG`` is not set, ``print_hex_dump_debug()`` is just
+shortcut for ``print_hex_dump(KERN_DEBUG)``.
+
+For ``print_hex_dump_debug()``/``print_hex_dump_bytes()``, format string is
+its ``prefix_str`` argument, if it is constant string; or ``hexdump``
+in case ``prefix_str`` is build dynamically.
+
+Dynamic debug has even more useful features:
+
+ * Simple query language allows turning on and off debugging
+   statements by matching any combination of 0 or 1 of:
+
+   - source filename
+   - function name
+   - line number (including ranges of line numbers)
+   - module name
+   - format string
+
+ * Provides a debugfs control file: ``<debugfs>/dynamic_debug/control``
+   which can be read to display the complete list of known debug
+   statements, to help guide you
+
+Controlling dynamic debug Behaviour
+===================================
+
+The behaviour of ``pr_debug()``/``dev_dbg()`` are controlled via writing to a
+control file in the 'debugfs' filesystem. Thus, you must first mount
+the debugfs filesystem, in order to make use of this feature.
+Subsequently, we refer to the control file as:
+``<debugfs>/dynamic_debug/control``. For example, if you want to enable
+printing from source file ``svcsock.c``, line 1603 you simply do::
+
+  nullarbor:~ # echo 'file svcsock.c line 1603 +p' >
+				<debugfs>/dynamic_debug/control
+
+If you make a mistake with the syntax, the write will fail thus::
+
+  nullarbor:~ # echo 'file svcsock.c wtf 1 +p' >
+				<debugfs>/dynamic_debug/control
+  -bash: echo: write error: Invalid argument
+
+Viewing Dynamic Debug Behaviour
+===============================
+
+You can view the currently configured behaviour of all the debug
+statements via::
+
+  nullarbor:~ # cat <debugfs>/dynamic_debug/control
+  # filename:lineno [module]function flags format
+  /usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:323 [svcxprt_rdma]svc_rdma_cleanup =_ "SVCRDMA Module Removed, deregister RPC RDMA transport\012"
+  /usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:341 [svcxprt_rdma]svc_rdma_init =_ "\011max_inline       : %d\012"
+  /usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:340 [svcxprt_rdma]svc_rdma_init =_ "\011sq_depth         : %d\012"
+  /usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:338 [svcxprt_rdma]svc_rdma_init =_ "\011max_requests     : %d\012"
+  ...
+
+
+You can also apply standard Unix text manipulation filters to this
+data, e.g.::
+
+  nullarbor:~ # grep -i rdma <debugfs>/dynamic_debug/control  | wc -l
+  62
+
+  nullarbor:~ # grep -i tcp <debugfs>/dynamic_debug/control | wc -l
+  42
+
+The third column shows the currently enabled flags for each debug
+statement callsite (see below for definitions of the flags).  The
+default value, with no flags enabled, is ``=_``.  So you can view all
+the debug statement callsites with any non-default flags::
+
+  nullarbor:~ # awk '$3 != "=_"' <debugfs>/dynamic_debug/control
+  # filename:lineno [module]function flags format
+  /usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svcsock.c:1603 [sunrpc]svc_send p "svc_process: st_sendto returned %d\012"
+
+Command Language Reference
+==========================
+
+At the lexical level, a command comprises a sequence of words separated
+by spaces or tabs.  So these are all equivalent::
+
+  nullarbor:~ # echo -c 'file svcsock.c line 1603 +p' >
+				<debugfs>/dynamic_debug/control
+  nullarbor:~ # echo -c '  file   svcsock.c     line  1603 +p  ' >
+				<debugfs>/dynamic_debug/control
+  nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
+				<debugfs>/dynamic_debug/control
+
+Command submissions are bounded by a write() system call.
+Multiple commands can be written together, separated by ``;`` or ``\n``::
+
+  ~# echo "func pnpacpi_get_resources +p; func pnp_assign_mem +p" \
+     > <debugfs>/dynamic_debug/control
+
+If your query set is big, you can batch them too::
+
+  ~# cat query-batch-file > <debugfs>/dynamic_debug/control
+
+A another way is to use wildcard. The match rule support ``*`` (matches
+zero or more characters) and ``?`` (matches exactly one character).For
+example, you can match all usb drivers::
+
+  ~# echo "file drivers/usb/* +p" > <debugfs>/dynamic_debug/control
+
+At the syntactical level, a command comprises a sequence of match
+specifications, followed by a flags change specification::
+
+  command ::= match-spec* flags-spec
+
+The match-spec's are used to choose a subset of the known pr_debug()
+callsites to which to apply the flags-spec.  Think of them as a query
+with implicit ANDs between each pair.  Note that an empty list of
+match-specs will select all debug statement callsites.
+
+A match specification comprises a keyword, which controls the
+attribute of the callsite to be compared, and a value to compare
+against.  Possible keywords are:::
+
+  match-spec ::= 'func' string |
+		 'file' string |
+		 'module' string |
+		 'format' string |
+		 'line' line-range
+
+  line-range ::= lineno |
+		 '-'lineno |
+		 lineno'-' |
+		 lineno'-'lineno
+
+  lineno ::= unsigned-int
+
+.. note::
+
+  ``line-range`` cannot contain space, e.g.
+  "1-30" is valid range but "1 - 30" is not.
+
+
+The meanings of each keyword are:
+
+func
+    The given string is compared against the function name
+    of each callsite.  Example::
+
+	func svc_tcp_accept
+
+file
+    The given string is compared against either the full pathname, the
+    src-root relative pathname, or the basename of the source file of
+    each callsite.  Examples::
+
+	file svcsock.c
+	file kernel/freezer.c
+	file /usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svcsock.c
+
+module
+    The given string is compared against the module name
+    of each callsite.  The module name is the string as
+    seen in ``lsmod``, i.e. without the directory or the ``.ko``
+    suffix and with ``-`` changed to ``_``.  Examples::
+
+	module sunrpc
+	module nfsd
+
+format
+    The given string is searched for in the dynamic debug format
+    string.  Note that the string does not need to match the
+    entire format, only some part.  Whitespace and other
+    special characters can be escaped using C octal character
+    escape ``\ooo`` notation, e.g. the space character is ``\040``.
+    Alternatively, the string can be enclosed in double quote
+    characters (``"``) or single quote characters (``'``).
+    Examples::
+
+	format svcrdma:         // many of the NFS/RDMA server pr_debugs
+	format readahead        // some pr_debugs in the readahead cache
+	format nfsd:\040SETATTR // one way to match a format with whitespace
+	format "nfsd: SETATTR"  // a neater way to match a format with whitespace
+	format 'nfsd: SETATTR'  // yet another way to match a format with whitespace
+
+line
+    The given line number or range of line numbers is compared
+    against the line number of each ``pr_debug()`` callsite.  A single
+    line number matches the callsite line number exactly.  A
+    range of line numbers matches any callsite between the first
+    and last line number inclusive.  An empty first number means
+    the first line in the file, an empty line number means the
+    last number in the file.  Examples::
+
+	line 1603           // exactly line 1603
+	line 1600-1605      // the six lines from line 1600 to line 1605
+	line -1605          // the 1605 lines from line 1 to line 1605
+	line 1600-          // all lines from line 1600 to the end of the file
+
+The flags specification comprises a change operation followed
+by one or more flag characters.  The change operation is one
+of the characters::
+
+  -    remove the given flags
+  +    add the given flags
+  =    set the flags to the given flags
+
+The flags are::
+
+  p    enables the pr_debug() callsite.
+  f    Include the function name in the printed message
+  l    Include line number in the printed message
+  m    Include module name in the printed message
+  t    Include thread ID in messages not generated from interrupt context
+  _    No flags are set. (Or'd with others on input)
+
+For ``print_hex_dump_debug()`` and ``print_hex_dump_bytes()``, only ``p`` flag
+have meaning, other flags ignored.
+
+For display, the flags are preceded by ``=``
+(mnemonic: what the flags are currently equal to).
+
+Note the regexp ``^[-+=][flmpt_]+$`` matches a flags specification.
+To clear all flags at once, use ``=_`` or ``-flmpt``.
+
+
+Debug messages during Boot Process
+==================================
+
+To activate debug messages for core code and built-in modules during
+the boot process, even before userspace and debugfs exists, use
+``dyndbg="QUERY"``, ``module.dyndbg="QUERY"``, or ``ddebug_query="QUERY"``
+(``ddebug_query`` is obsoleted by ``dyndbg``, and deprecated).  QUERY follows
+the syntax described above, but must not exceed 1023 characters.  Your
+bootloader may impose lower limits.
+
+These ``dyndbg`` params are processed just after the ddebug tables are
+processed, as part of the arch_initcall.  Thus you can enable debug
+messages in all code run after this arch_initcall via this boot
+parameter.
+
+On an x86 system for example ACPI enablement is a subsys_initcall and::
+
+   dyndbg="file ec.c +p"
+
+will show early Embedded Controller transactions during ACPI setup if
+your machine (typically a laptop) has an Embedded Controller.
+PCI (or other devices) initialization also is a hot candidate for using
+this boot parameter for debugging purposes.
+
+If ``foo`` module is not built-in, ``foo.dyndbg`` will still be processed at
+boot time, without effect, but will be reprocessed when module is
+loaded later. ``dyndbg_query=`` and bare ``dyndbg=`` are only processed at
+boot.
+
+
+Debug Messages at Module Initialization Time
+============================================
+
+When ``modprobe foo`` is called, modprobe scans ``/proc/cmdline`` for
+``foo.params``, strips ``foo.``, and passes them to the kernel along with
+params given in modprobe args or ``/etc/modprob.d/*.conf`` files,
+in the following order:
+
+1. parameters given via ``/etc/modprobe.d/*.conf``::
+
+	options foo dyndbg=+pt
+	options foo dyndbg # defaults to +p
+
+2. ``foo.dyndbg`` as given in boot args, ``foo.`` is stripped and passed::
+
+	foo.dyndbg=" func bar +p; func buz +mp"
+
+3. args to modprobe::
+
+	modprobe foo dyndbg==pmf # override previous settings
+
+These ``dyndbg`` queries are applied in order, with last having final say.
+This allows boot args to override or modify those from ``/etc/modprobe.d``
+(sensible, since 1 is system wide, 2 is kernel or boot specific), and
+modprobe args to override both.
+
+In the ``foo.dyndbg="QUERY"`` form, the query must exclude ``module foo``.
+``foo`` is extracted from the param-name, and applied to each query in
+``QUERY``, and only 1 match-spec of each type is allowed.
+
+The ``dyndbg`` option is a "fake" module parameter, which means:
+
+- modules do not need to define it explicitly
+- every module gets it tacitly, whether they use pr_debug or not
+- it doesn't appear in ``/sys/module/$module/parameters/``
+  To see it, grep the control file, or inspect ``/proc/cmdline.``
+
+For ``CONFIG_DYNAMIC_DEBUG`` kernels, any settings given at boot-time (or
+enabled by ``-DDEBUG`` flag during compilation) can be disabled later via
+the sysfs interface if the debug messages are no longer needed::
+
+   echo "module module_name -p" > <debugfs>/dynamic_debug/control
+
+Examples
+========
+
+::
+
+  // enable the message at line 1603 of file svcsock.c
+  nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
+				<debugfs>/dynamic_debug/control
+
+  // enable all the messages in file svcsock.c
+  nullarbor:~ # echo -n 'file svcsock.c +p' >
+				<debugfs>/dynamic_debug/control
+
+  // enable all the messages in the NFS server module
+  nullarbor:~ # echo -n 'module nfsd +p' >
+				<debugfs>/dynamic_debug/control
+
+  // enable all 12 messages in the function svc_process()
+  nullarbor:~ # echo -n 'func svc_process +p' >
+				<debugfs>/dynamic_debug/control
+
+  // disable all 12 messages in the function svc_process()
+  nullarbor:~ # echo -n 'func svc_process -p' >
+				<debugfs>/dynamic_debug/control
+
+  // enable messages for NFS calls READ, READLINK, READDIR and READDIR+.
+  nullarbor:~ # echo -n 'format "nfsd: READ" +p' >
+				<debugfs>/dynamic_debug/control
+
+  // enable messages in files of which the paths include string "usb"
+  nullarbor:~ # echo -n '*usb* +p' > <debugfs>/dynamic_debug/control
+
+  // enable all messages
+  nullarbor:~ # echo -n '+p' > <debugfs>/dynamic_debug/control
+
+  // add module, function to all enabled messages
+  nullarbor:~ # echo -n '+mf' > <debugfs>/dynamic_debug/control
+
+  // boot-args example, with newlines and comments for readability
+  Kernel command line: ...
+    // see whats going on in dyndbg=value processing
+    dynamic_debug.verbose=1
+    // enable pr_debugs in 2 builtins, #cmt is stripped
+    dyndbg="module params +p #cmt ; module sys +p"
+    // enable pr_debugs in 2 functions in a module loaded later
+    pc87360.dyndbg="func pc87360_init_device +p; func pc87360_find +p"