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-<h1>README</h1><div class="fragment"><pre class="fragment">00001 <span class="comment">/** @mainpage SystemTap Runtime</span>
-00002 <span class="comment"></span>
-00003 <span class="comment">@section intro_sec Introduction</span>
-00004 <span class="comment"></span>
-00005 <span class="comment">This document describes the implementation of the SystemTap Runtime. It is intended for developers</span>
-00006 <span class="comment">of the SystemTap Language translator or, possibly TapSet authors. These functions are not directly</span>
-00007 <span class="comment">available from the SystemTap Language.</span>
-00008 <span class="comment"></span>
-00009 <span class="comment">The SystemTap Runtime Library consists of all functions</span>
-00010 <span class="comment">and code fragments needed by the compiler/translator to</span>
-00011 <span class="comment">include in building a kernel module using kprobes. It</span>
-00012 <span class="comment">also include I/O code to transmit its output from the kernel to userspace.</span>
-00013 <span class="comment"> </span>
-00014 <span class="comment">In addition to the library, the runtime includes a SystemTap user-space daemon</span>
-00015 <span class="comment">(stpd). Stpd grabs data sent from the I/O code in the runtime and displays it</span>
-00016 <span class="comment">and/or saves it to files. Stpd (or a script invoking it) will handle other issues like</span>
-00017 <span class="comment">inserting and removing modules.</span>
-00018 <span class="comment"></span>
-00019 <span class="comment">Stpd and the I/O code make use of both relayfs and netlink for communication. For</span>
-00020 <span class="comment">kernels without relayfs builtin, it is provided as a standalone module under the runtime directory.</span>
-00021 <span class="comment"></span>
-00022 <span class="comment">@section design_sec Design</span>
-00023 <span class="comment">@subsection impl_sec Implementation</span>
-00024 <span class="comment">The library is written in C and is really not a library but a collection of code</span>
-00025 <span class="comment">That can be conditionally included in a modules. It may become a library later, but for now</span>
-00026 <span class="comment">there are some advantages to being able to change the sizes of static items with simple #defines.</span>
-00027 <span class="comment"></span>
-00028 <span class="comment">@subsection map_sec Maps (Associative Arrays)</span>
-00029 <span class="comment">Maps are implemented as hash lists. It is not expected that users will</span>
-00030 <span class="comment">attempt to collect so much data in kernel space that performance problems will require</span>
-00031 <span class="comment">more complex solutions such as AVL trees.</span>
-00032 <span class="comment"></span>
-00033 <span class="comment">Maps are created with _stp_map_new(). Each map can hold only one type of </span>
-00034 <span class="comment">data; int64, string, or statistics. Each element belonging to a map can have up to 2 keys</span>
-00035 <span class="comment">and a value. Implemented key types are strings and longs.</span>
-00036 <span class="comment"> </span>
-00037 <span class="comment">To simplify the implementation, the functions to set the key and the functions to set the data are separated.</span>
-00038 <span class="comment">That means we need only 4 functions to set the key and 3 functions to set the value. </span>
-00039 <span class="comment"></span>
-00040 <span class="comment">For example:</span>
-00041 <span class="comment">\code</span>
-00042 <span class="comment">/* create a map with a max of 100 elements */</span>
-00043 <a class="code" href="group__maps.html#ga1">MAP</a> mymap = map_new(100, INT64);
-00044
-00045 <span class="comment">/* mymap[birth year] = 2000 */</span>
-00046 map_key_str (mymap, <span class="stringliteral">"birth year"</span>);
-00047 map_set_int64 (mymap, 2000);
-00048 \endcode
-00049
-00050 All elements have a <span class="keywordflow">default</span> value of 0 (or NULL). Elements are only saved to the map when their value is set
-00051 to something nonzero. This means that querying <span class="keywordflow">for</span> the existance of a key is inexpensive because
-00052 no element is created, just a hash table lookup.
-00053
-00054 @subsection list_sec Lists
-00055 A list is a special map which has internally ascending <span class="keywordtype">long</span> integer keys. Adding a value to
-00056 a list does not require setting a key first. Create a list with <a class="code" href="group__lists.html#ga0">_stp_list_new</a>(). Add to it
-00057 with <a class="code" href="group__lists.html#ga2">_stp_list_add_str</a>() and _stp_list_add_int64(). Clear it with _stp_list_clear().
-00058
-00059 @subsection string_sec Strings
-00060 One of the biggest restrictions the library has is that it cannot allocate things like strings off the stack.
-00061 It is also not a good idea to dynamically allocate space for strings with kmalloc(). That leaves us with
-00062 statically allocated space for strings. This is what is implemented in the String module. Strings use
-00063 preallocated per-cpu buffers and are safe to use (unlike C strings).
-00064
-00065 @subsection io_sec I/O
-00066 Generally things are written to a "print buffer" using the internal
-00067 functions _stp_print_xxx().
-00068 \code
-00069 _stp_print ("Output is: ");
-00070 _stp_printf ("pid is %d ", current-&gt;pid);
-00071 _stp_printf ("name is %s", current-&gt;comm);
-00072 \endcode
-00073 before the probe returns it must call _stp_print_flush(). This
-00074 timestamps the accumulated print buffer and sends it to relayfs.
-00075 When relayfs fills an internal buffer, the user-space daemon is notified
-00076 data is ready and reads a bug per-cpu chunk, which contains a line like:
-00077 \verbatim
-00078 [123456.000002] Output is: pid is 1234 name is bash
-00079 \endverbatim
-00080
-00081 The user-daemon (stpd) saves this data to a file named something like
-00082 "stpd_cpu2". When the user hits ^c, a timer expires, or the probe
-00083 module notifies stpd (through a netlink command channel) that it wants
-00084 to terminate, stpd does "system(rmmod)" then collects the last output
-00085 before exiting.
-00086 As an option, if we don't need bulk per-cpu data, we can put
-00087 \code
-00088 #define STP_NETLINK_ONLY
-00089 \endcode
-00090 at the top of the module and all output will go over a netlink channel.
-00091 In the SystemTap language, we will provide some simple functions to control the buffering policy, which
-00092 will control the use of netlink and parameters to relayfs and stpd.
-00093
-00094 @section status_sec Status
-00095 @li Maps are implemented and tested. Histograms are not yet finished.
-00096 @li Copy_From_User functions are done.
-00097 @li If maps overflow or memory runs out for some reason, globals are set but nothing is done yet.
-00098 I expect to implement a function to tell the system to either ignore it or unload the module and quit.
-00099 @li Stack functions need much improvement.
-00100
-00101 @section probe_sec Example Probes
-00102
-00103 Working sample probe code using the runtime is in runtime/probes.
-00104 &lt;a href="dir_000000.html"&gt; Browse probes.&lt;/a&gt;
-00105
-00106 @section todo_sec ToDo
-00107 \link todo Click Here for Complete List \endlink
-00108
-00109 @section links Links
-00110 &lt;a href="http:<span class="comment">//sources.redhat.com/systemtap/"&gt;SystemTap Project Page&lt;/a&gt;</span>
-00111 */
-</pre></div></body></html>