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  62. <body lang="en">

  63. <a name="Tracepoint-Packets"></a>

  64. <div class="header">

  65. <p>

  66. Next: <a href="Host-I_002fO-Packets.html#Host-I_002fO-Packets" accesskey="n" rel="next">Host I/O Packets</a>, Previous: <a href="Architecture_002dSpecific-Protocol-Details.html#Architecture_002dSpecific-Protocol-Details" accesskey="p" rel="prev">Architecture-Specific Protocol Details</a>, Up: <a href="Remote-Protocol.html#Remote-Protocol" accesskey="u" rel="up">Remote Protocol</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>

  67. </div>

  68. <hr>

  69. <a name="Tracepoint-Packets-1"></a>

  70. <h3 class="section">E.6 Tracepoint Packets</h3>

  71. <a name="index-tracepoint-packets"></a>

  72. <a name="index-packets_002c-tracepoint"></a>

  73. 

  74. <p>Here we describe the packets <small>GDB</small> uses to implement

  75. tracepoints (see <a href="Tracepoints.html#Tracepoints">Tracepoints</a>).

  76. </p>

  77. <dl compact="compact">

  78. <dt>&lsquo;<samp>QTDP:<var>n</var>:<var>addr</var>:<var>ena</var>:<var>step</var>:<var>pass</var>[:F<var>flen</var>][:X<var>len</var>,<var>bytes</var>]<span class="roman">[</span>-<span class="roman">]</span></samp>&rsquo;</dt>

  79. <dd><a name="index-QTDP-packet"></a>

  80. <p>Create a new tracepoint, number <var>n</var>, at <var>addr</var>.  If <var>ena</var>

  81. is &lsquo;<samp>E</samp>&rsquo;, then the tracepoint is enabled; if it is &lsquo;<samp>D</samp>&rsquo;, then

  82. the tracepoint is disabled.  The <var>step</var> gives the tracepoint&rsquo;s step

  83. count, and <var>pass</var> gives its pass count.  If an &lsquo;<samp>F</samp>&rsquo; is present,

  84. then the tracepoint is to be a fast tracepoint, and the <var>flen</var> is

  85. the number of bytes that the target should copy elsewhere to make room

  86. for the tracepoint.  If an &lsquo;<samp>X</samp>&rsquo; is present, it introduces a

  87. tracepoint condition, which consists of a hexadecimal length, followed

  88. by a comma and hex-encoded bytes, in a manner similar to action

  89. encodings as described below.  If the trailing &lsquo;<samp>-</samp>&rsquo; is present,

  90. further &lsquo;<samp>QTDP</samp>&rsquo; packets will follow to specify this tracepoint&rsquo;s

  91. actions.

  92. </p>

  93. <p>Replies:

  94. </p><dl compact="compact">

  95. <dt>&lsquo;<samp>OK</samp>&rsquo;</dt>

  96. <dd><p>The packet was understood and carried out.

  97. </p></dd>

  98. <dt>&lsquo;<samp>qRelocInsn</samp>&rsquo;</dt>

  99. <dd><p>See <a href="#Tracepoint-Packets">Relocate instruction reply packet</a>.

  100. </p></dd>

  101. <dt>&lsquo;<samp><!-- /@w --></samp>&rsquo;</dt>

  102. <dd><p>The packet was not recognized.

  103. </p></dd>

  104. </dl>

  105. 

  106. </dd>

  107. <dt>&lsquo;<samp>QTDP:-<var>n</var>:<var>addr</var>:<span class="roman">[</span>S<span class="roman">]</span><var>action</var>&hellip;<span class="roman">[</span>-<span class="roman">]</span></samp>&rsquo;</dt>

  108. <dd><p>Define actions to be taken when a tracepoint is hit.  The <var>n</var> and

  109. <var>addr</var> must be the same as in the initial &lsquo;<samp>QTDP</samp>&rsquo; packet for

  110. this tracepoint.  This packet may only be sent immediately after

  111. another &lsquo;<samp>QTDP</samp>&rsquo; packet that ended with a &lsquo;<samp>-</samp>&rsquo;.  If the

  112. trailing &lsquo;<samp>-</samp>&rsquo; is present, further &lsquo;<samp>QTDP</samp>&rsquo; packets will follow,

  113. specifying more actions for this tracepoint.

  114. </p>

  115. <p>In the series of action packets for a given tracepoint, at most one

  116. can have an &lsquo;<samp>S</samp>&rsquo; before its first <var>action</var>.  If such a packet

  117. is sent, it and the following packets define &ldquo;while-stepping&rdquo;

  118. actions.  Any prior packets define ordinary actions &mdash; that is, those

  119. taken when the tracepoint is first hit.  If no action packet has an

  120. &lsquo;<samp>S</samp>&rsquo;, then all the packets in the series specify ordinary

  121. tracepoint actions.

  122. </p>

  123. <p>The &lsquo;<samp><var>action</var>&hellip;</samp>&rsquo; portion of the packet is a series of

  124. actions, concatenated without separators.  Each action has one of the

  125. following forms:

  126. </p>

  127. <dl compact="compact">

  128. <dt>&lsquo;<samp>R <var>mask</var></samp>&rsquo;</dt>

  129. <dd><p>Collect the registers whose bits are set in <var>mask</var>,

  130. a hexadecimal number whose <var>i</var>&rsquo;th bit is set if register number

  131. <var>i</var> should be collected.  (The least significant bit is numbered

  132. zero.)  Note that <var>mask</var> may be any number of digits long; it may

  133. not fit in a 32-bit word.

  134. </p>

  135. </dd>

  136. <dt>&lsquo;<samp>M <var>basereg</var>,<var>offset</var>,<var>len</var></samp>&rsquo;</dt>

  137. <dd><p>Collect <var>len</var> bytes of memory starting at the address in register

  138. number <var>basereg</var>, plus <var>offset</var>.  If <var>basereg</var> is

  139. &lsquo;<samp>-1</samp>&rsquo;, then the range has a fixed address: <var>offset</var> is the

  140. address of the lowest byte to collect.  The <var>basereg</var>,

  141. <var>offset</var>, and <var>len</var> parameters are all unsigned hexadecimal

  142. values (the &lsquo;<samp>-1</samp>&rsquo; value for <var>basereg</var> is a special case).

  143. </p>

  144. </dd>

  145. <dt>&lsquo;<samp>X <var>len</var>,<var>expr</var></samp>&rsquo;</dt>

  146. <dd><p>Evaluate <var>expr</var>, whose length is <var>len</var>, and collect memory as

  147. it directs.  The agent expression <var>expr</var> is as described in

  148. <a href="Agent-Expressions.html#Agent-Expressions">Agent Expressions</a>.  Each byte of the expression is encoded as a

  149. two-digit hex number in the packet; <var>len</var> is the number of bytes

  150. in the expression (and thus one-half the number of hex digits in the

  151. packet).

  152. </p>

  153. </dd>

  154. </dl>

  155. 

  156. <p>Any number of actions may be packed together in a single &lsquo;<samp>QTDP</samp>&rsquo;

  157. packet, as long as the packet does not exceed the maximum packet

  158. length (400 bytes, for many stubs).  There may be only one &lsquo;<samp>R</samp>&rsquo;

  159. action per tracepoint, and it must precede any &lsquo;<samp>M</samp>&rsquo; or &lsquo;<samp>X</samp>&rsquo;

  160. actions.  Any registers referred to by &lsquo;<samp>M</samp>&rsquo; and &lsquo;<samp>X</samp>&rsquo; actions

  161. must be collected by a preceding &lsquo;<samp>R</samp>&rsquo; action.  (The

  162. &ldquo;while-stepping&rdquo; actions are treated as if they were attached to a

  163. separate tracepoint, as far as these restrictions are concerned.)

  164. </p>

  165. <p>Replies:

  166. </p><dl compact="compact">

  167. <dt>&lsquo;<samp>OK</samp>&rsquo;</dt>

  168. <dd><p>The packet was understood and carried out.

  169. </p></dd>

  170. <dt>&lsquo;<samp>qRelocInsn</samp>&rsquo;</dt>

  171. <dd><p>See <a href="#Tracepoint-Packets">Relocate instruction reply packet</a>.

  172. </p></dd>

  173. <dt>&lsquo;<samp><!-- /@w --></samp>&rsquo;</dt>

  174. <dd><p>The packet was not recognized.

  175. </p></dd>

  176. </dl>

  177. 

  178. </dd>

  179. <dt>&lsquo;<samp>QTDPsrc:<var>n</var>:<var>addr</var>:<var>type</var>:<var>start</var>:<var>slen</var>:<var>bytes</var></samp>&rsquo;</dt>

  180. <dd><a name="index-QTDPsrc-packet"></a>

  181. <p>Specify a source string of tracepoint <var>n</var> at address <var>addr</var>.

  182. This is useful to get accurate reproduction of the tracepoints

  183. originally downloaded at the beginning of the trace run.  The <var>type</var>

  184. is the name of the tracepoint part, such as &lsquo;<samp>cond</samp>&rsquo; for the

  185. tracepoint&rsquo;s conditional expression (see below for a list of types), while

  186. <var>bytes</var> is the string, encoded in hexadecimal.

  187. </p>

  188. <p><var>start</var> is the offset of the <var>bytes</var> within the overall source

  189. string, while <var>slen</var> is the total length of the source string.

  190. This is intended for handling source strings that are longer than will

  191. fit in a single packet.

  192. </p>

  193. <p>The available string types are &lsquo;<samp>at</samp>&rsquo; for the location,

  194. &lsquo;<samp>cond</samp>&rsquo; for the conditional, and &lsquo;<samp>cmd</samp>&rsquo; for an action command.

  195. <small>GDB</small> sends a separate packet for each command in the action

  196. list, in the same order in which the commands are stored in the list.

  197. </p>

  198. <p>The target does not need to do anything with source strings except

  199. report them back as part of the replies to the &lsquo;<samp>qTfP</samp>&rsquo;/&lsquo;<samp>qTsP</samp>&rsquo;

  200. query packets.

  201. </p>

  202. <p>Although this packet is optional, and <small>GDB</small> will only send it

  203. if the target replies with &lsquo;<samp>TracepointSource</samp>&rsquo; See <a href="General-Query-Packets.html#General-Query-Packets">General Query Packets</a>, it makes both disconnected tracing and trace files

  204. much easier to use.  Otherwise the user must be careful that the

  205. tracepoints in effect while looking at trace frames are identical to

  206. the ones in effect during the trace run; even a small discrepancy

  207. could cause &lsquo;<samp>tdump</samp>&rsquo; not to work, or a particular trace frame not

  208. be found.

  209. </p>

  210. </dd>

  211. <dt>&lsquo;<samp>QTDV:<var>n</var>:<var>value</var>:<var>builtin</var>:<var>name</var></samp>&rsquo;</dt>

  212. <dd><a name="index-define-trace-state-variable_002c-remote-request"></a>

  213. <a name="index-QTDV-packet"></a>

  214. <p>Create a new trace state variable, number <var>n</var>, with an initial

  215. value of <var>value</var>, which is a 64-bit signed integer.  Both <var>n</var>

  216. and <var>value</var> are encoded as hexadecimal values. <small>GDB</small> has

  217. the option of not using this packet for initial values of zero; the

  218. target should simply create the trace state variables as they are

  219. mentioned in expressions.  The value <var>builtin</var> should be 1 (one)

  220. if the trace state variable is builtin and 0 (zero) if it is not builtin.

  221. <small>GDB</small> only sets <var>builtin</var> to 1 if a previous &lsquo;<samp>qTfV</samp>&rsquo; or

  222. &lsquo;<samp>qTsV</samp>&rsquo; packet had it set.  The contents of <var>name</var> is the

  223. hex-encoded name (without the leading &lsquo;<samp>$</samp>&rsquo;) of the trace state

  224. variable.

  225. </p>

  226. </dd>

  227. <dt>&lsquo;<samp>QTFrame:<var>n</var></samp>&rsquo;</dt>

  228. <dd><a name="index-QTFrame-packet"></a>

  229. <p>Select the <var>n</var>&rsquo;th tracepoint frame from the buffer, and use the

  230. register and memory contents recorded there to answer subsequent

  231. request packets from <small>GDB</small>.

  232. </p>

  233. <p>A successful reply from the stub indicates that the stub has found the

  234. requested frame.  The response is a series of parts, concatenated

  235. without separators, describing the frame we selected.  Each part has

  236. one of the following forms:

  237. </p>

  238. <dl compact="compact">

  239. <dt>&lsquo;<samp>F <var>f</var></samp>&rsquo;</dt>

  240. <dd><p>The selected frame is number <var>n</var> in the trace frame buffer;

  241. <var>f</var> is a hexadecimal number.  If <var>f</var> is &lsquo;<samp>-1</samp>&rsquo;, then there

  242. was no frame matching the criteria in the request packet.

  243. </p>

  244. </dd>

  245. <dt>&lsquo;<samp>T <var>t</var></samp>&rsquo;</dt>

  246. <dd><p>The selected trace frame records a hit of tracepoint number <var>t</var>;

  247. <var>t</var> is a hexadecimal number.

  248. </p>

  249. </dd>

  250. </dl>

  251. 

  252. </dd>

  253. <dt>&lsquo;<samp>QTFrame:pc:<var>addr</var></samp>&rsquo;</dt>

  254. <dd><p>Like &lsquo;<samp>QTFrame:<var>n</var></samp>&rsquo;, but select the first tracepoint frame after the

  255. currently selected frame whose PC is <var>addr</var>;

  256. <var>addr</var> is a hexadecimal number.

  257. </p>

  258. </dd>

  259. <dt>&lsquo;<samp>QTFrame:tdp:<var>t</var></samp>&rsquo;</dt>

  260. <dd><p>Like &lsquo;<samp>QTFrame:<var>n</var></samp>&rsquo;, but select the first tracepoint frame after the

  261. currently selected frame that is a hit of tracepoint <var>t</var>; <var>t</var>

  262. is a hexadecimal number.

  263. </p>

  264. </dd>

  265. <dt>&lsquo;<samp>QTFrame:range:<var>start</var>:<var>end</var></samp>&rsquo;</dt>

  266. <dd><p>Like &lsquo;<samp>QTFrame:<var>n</var></samp>&rsquo;, but select the first tracepoint frame after the

  267. currently selected frame whose PC is between <var>start</var> (inclusive)

  268. and <var>end</var> (inclusive); <var>start</var> and <var>end</var> are hexadecimal

  269. numbers.

  270. </p>

  271. </dd>

  272. <dt>&lsquo;<samp>QTFrame:outside:<var>start</var>:<var>end</var></samp>&rsquo;</dt>

  273. <dd><p>Like &lsquo;<samp>QTFrame:range:<var>start</var>:<var>end</var></samp>&rsquo;, but select the first

  274. frame <em>outside</em> the given range of addresses (exclusive).

  275. </p>

  276. </dd>

  277. <dt>&lsquo;<samp>qTMinFTPILen</samp>&rsquo;</dt>

  278. <dd><a name="index-qTMinFTPILen-packet"></a>

  279. <p>This packet requests the minimum length of instruction at which a fast

  280. tracepoint (see <a href="Set-Tracepoints.html#Set-Tracepoints">Set Tracepoints</a>) may be placed.  For instance, on

  281. the 32-bit x86 architecture, it is possible to use a 4-byte jump, but

  282. it depends on the target system being able to create trampolines in

  283. the first 64K of memory, which might or might not be possible for that

  284. system.  So the reply to this packet will be 4 if it is able to

  285. arrange for that.

  286. </p>

  287. <p>Replies:

  288. </p>

  289. <dl compact="compact">

  290. <dt>&lsquo;<samp>0</samp>&rsquo;</dt>

  291. <dd><p>The minimum instruction length is currently unknown.

  292. </p></dd>

  293. <dt>&lsquo;<samp><var>length</var></samp>&rsquo;</dt>

  294. <dd><p>The minimum instruction length is <var>length</var>, where <var>length</var>

  295. is a hexadecimal number greater or equal to 1.  A reply

  296. of 1 means that a fast tracepoint may be placed on any instruction

  297. regardless of size.

  298. </p></dd>

  299. <dt>&lsquo;<samp>E</samp>&rsquo;</dt>

  300. <dd><p>An error has occurred.

  301. </p></dd>

  302. <dt>&lsquo;<samp><!-- /@w --></samp>&rsquo;</dt>

  303. <dd><p>An empty reply indicates that the request is not supported by the stub.

  304. </p></dd>

  305. </dl>

  306. 

  307. </dd>

  308. <dt>&lsquo;<samp>QTStart</samp>&rsquo;</dt>

  309. <dd><a name="index-QTStart-packet"></a>

  310. <p>Begin the tracepoint experiment.  Begin collecting data from

  311. tracepoint hits in the trace frame buffer.  This packet supports the

  312. &lsquo;<samp>qRelocInsn</samp>&rsquo; reply (see <a href="#Tracepoint-Packets">Relocate

  313. instruction reply packet</a>).

  314. </p>

  315. </dd>

  316. <dt>&lsquo;<samp>QTStop</samp>&rsquo;</dt>

  317. <dd><a name="index-QTStop-packet"></a>

  318. <p>End the tracepoint experiment.  Stop collecting trace frames.

  319. </p>

  320. </dd>

  321. <dt>&lsquo;<samp>QTEnable:<var>n</var>:<var>addr</var></samp>&rsquo;</dt>

  322. <dd><a name="QTEnable"></a><a name="index-QTEnable-packet"></a>

  323. <p>Enable tracepoint <var>n</var> at address <var>addr</var> in a started tracepoint

  324. experiment.  If the tracepoint was previously disabled, then collection

  325. of data from it will resume.

  326. </p>

  327. </dd>

  328. <dt>&lsquo;<samp>QTDisable:<var>n</var>:<var>addr</var></samp>&rsquo;</dt>

  329. <dd><a name="QTDisable"></a><a name="index-QTDisable-packet"></a>

  330. <p>Disable tracepoint <var>n</var> at address <var>addr</var> in a started tracepoint

  331. experiment.  No more data will be collected from the tracepoint unless

  332. &lsquo;<samp>QTEnable:<var>n</var>:<var>addr</var></samp>&rsquo; is subsequently issued.

  333. </p>

  334. </dd>

  335. <dt>&lsquo;<samp>QTinit</samp>&rsquo;</dt>

  336. <dd><a name="index-QTinit-packet"></a>

  337. <p>Clear the table of tracepoints, and empty the trace frame buffer.

  338. </p>

  339. </dd>

  340. <dt>&lsquo;<samp>QTro:<var>start1</var>,<var>end1</var>:<var>start2</var>,<var>end2</var>:&hellip;</samp>&rsquo;</dt>

  341. <dd><a name="index-QTro-packet"></a>

  342. <p>Establish the given ranges of memory as &ldquo;transparent&rdquo;.  The stub

  343. will answer requests for these ranges from memory&rsquo;s current contents,

  344. if they were not collected as part of the tracepoint hit.

  345. </p>

  346. <p><small>GDB</small> uses this to mark read-only regions of memory, like those

  347. containing program code.  Since these areas never change, they should

  348. still have the same contents they did when the tracepoint was hit, so

  349. there&rsquo;s no reason for the stub to refuse to provide their contents.

  350. </p>

  351. </dd>

  352. <dt>&lsquo;<samp>QTDisconnected:<var>value</var></samp>&rsquo;</dt>

  353. <dd><a name="index-QTDisconnected-packet"></a>

  354. <p>Set the choice to what to do with the tracing run when <small>GDB</small>

  355. disconnects from the target.  A <var>value</var> of 1 directs the target to

  356. continue the tracing run, while 0 tells the target to stop tracing if

  357. <small>GDB</small> is no longer in the picture.

  358. </p>

  359. </dd>

  360. <dt>&lsquo;<samp>qTStatus</samp>&rsquo;</dt>

  361. <dd><a name="index-qTStatus-packet"></a>

  362. <p>Ask the stub if there is a trace experiment running right now.

  363. </p>

  364. <p>The reply has the form:

  365. </p>

  366. <dl compact="compact">

  367. <dt>&lsquo;<samp>T<var>running</var><span class="roman">[</span>;<var>field</var><span class="roman">]</span>&hellip;</samp>&rsquo;</dt>

  368. <dd><p><var>running</var> is a single digit <code>1</code> if the trace is presently

  369. running, or <code>0</code> if not.  It is followed by semicolon-separated

  370. optional fields that an agent may use to report additional status.

  371. </p>

  372. </dd>

  373. </dl>

  374. 

  375. <p>If the trace is not running, the agent may report any of several

  376. explanations as one of the optional fields:

  377. </p>

  378. <dl compact="compact">

  379. <dt>&lsquo;<samp>tnotrun:0</samp>&rsquo;</dt>

  380. <dd><p>No trace has been run yet.

  381. </p>

  382. </dd>

  383. <dt>&lsquo;<samp>tstop[:<var>text</var>]:0</samp>&rsquo;</dt>

  384. <dd><p>The trace was stopped by a user-originated stop command.  The optional

  385. <var>text</var> field is a user-supplied string supplied as part of the

  386. stop command (for instance, an explanation of why the trace was

  387. stopped manually).  It is hex-encoded.

  388. </p>

  389. </dd>

  390. <dt>&lsquo;<samp>tfull:0</samp>&rsquo;</dt>

  391. <dd><p>The trace stopped because the trace buffer filled up.

  392. </p>

  393. </dd>

  394. <dt>&lsquo;<samp>tdisconnected:0</samp>&rsquo;</dt>

  395. <dd><p>The trace stopped because <small>GDB</small> disconnected from the target.

  396. </p>

  397. </dd>

  398. <dt>&lsquo;<samp>tpasscount:<var>tpnum</var></samp>&rsquo;</dt>

  399. <dd><p>The trace stopped because tracepoint <var>tpnum</var> exceeded its pass count.

  400. </p>

  401. </dd>

  402. <dt>&lsquo;<samp>terror:<var>text</var>:<var>tpnum</var></samp>&rsquo;</dt>

  403. <dd><p>The trace stopped because tracepoint <var>tpnum</var> had an error.  The

  404. string <var>text</var> is available to describe the nature of the error

  405. (for instance, a divide by zero in the condition expression); it

  406. is hex encoded.

  407. </p>

  408. </dd>

  409. <dt>&lsquo;<samp>tunknown:0</samp>&rsquo;</dt>

  410. <dd><p>The trace stopped for some other reason.

  411. </p>

  412. </dd>

  413. </dl>

  414. 

  415. <p>Additional optional fields supply statistical and other information.

  416. Although not required, they are extremely useful for users monitoring

  417. the progress of a trace run.  If a trace has stopped, and these

  418. numbers are reported, they must reflect the state of the just-stopped

  419. trace.

  420. </p>

  421. <dl compact="compact">

  422. <dt>&lsquo;<samp>tframes:<var>n</var></samp>&rsquo;</dt>

  423. <dd><p>The number of trace frames in the buffer.

  424. </p>

  425. </dd>

  426. <dt>&lsquo;<samp>tcreated:<var>n</var></samp>&rsquo;</dt>

  427. <dd><p>The total number of trace frames created during the run. This may

  428. be larger than the trace frame count, if the buffer is circular.

  429. </p>

  430. </dd>

  431. <dt>&lsquo;<samp>tsize:<var>n</var></samp>&rsquo;</dt>

  432. <dd><p>The total size of the trace buffer, in bytes.

  433. </p>

  434. </dd>

  435. <dt>&lsquo;<samp>tfree:<var>n</var></samp>&rsquo;</dt>

  436. <dd><p>The number of bytes still unused in the buffer.

  437. </p>

  438. </dd>

  439. <dt>&lsquo;<samp>circular:<var>n</var></samp>&rsquo;</dt>

  440. <dd><p>The value of the circular trace buffer flag.  <code>1</code> means that the

  441. trace buffer is circular and old trace frames will be discarded if

  442. necessary to make room, <code>0</code> means that the trace buffer is linear

  443. and may fill up.

  444. </p>

  445. </dd>

  446. <dt>&lsquo;<samp>disconn:<var>n</var></samp>&rsquo;</dt>

  447. <dd><p>The value of the disconnected tracing flag.  <code>1</code> means that

  448. tracing will continue after <small>GDB</small> disconnects, <code>0</code> means

  449. that the trace run will stop.

  450. </p>

  451. </dd>

  452. </dl>

  453. 

  454. </dd>

  455. <dt>&lsquo;<samp>qTP:<var>tp</var>:<var>addr</var></samp>&rsquo;</dt>

  456. <dd><a name="index-tracepoint-status_002c-remote-request"></a>

  457. <a name="index-qTP-packet"></a>

  458. <p>Ask the stub for the current state of tracepoint number <var>tp</var> at

  459. address <var>addr</var>.

  460. </p>

  461. <p>Replies:

  462. </p><dl compact="compact">

  463. <dt>&lsquo;<samp>V<var>hits</var>:<var>usage</var></samp>&rsquo;</dt>

  464. <dd><p>The tracepoint has been hit <var>hits</var> times so far during the trace

  465. run, and accounts for <var>usage</var> in the trace buffer.  Note that

  466. <code>while-stepping</code> steps are not counted as separate hits, but the

  467. steps&rsquo; space consumption is added into the usage number.

  468. </p>

  469. </dd>

  470. </dl>

  471. 

  472. </dd>

  473. <dt>&lsquo;<samp>qTV:<var>var</var></samp>&rsquo;</dt>

  474. <dd><a name="index-trace-state-variable-value_002c-remote-request"></a>

  475. <a name="index-qTV-packet"></a>

  476. <p>Ask the stub for the value of the trace state variable number <var>var</var>.

  477. </p>

  478. <p>Replies:

  479. </p><dl compact="compact">

  480. <dt>&lsquo;<samp>V<var>value</var></samp>&rsquo;</dt>

  481. <dd><p>The value of the variable is <var>value</var>.  This will be the current

  482. value of the variable if the user is examining a running target, or a

  483. saved value if the variable was collected in the trace frame that the

  484. user is looking at.  Note that multiple requests may result in

  485. different reply values, such as when requesting values while the

  486. program is running.

  487. </p>

  488. </dd>

  489. <dt>&lsquo;<samp>U</samp>&rsquo;</dt>

  490. <dd><p>The value of the variable is unknown.  This would occur, for example,

  491. if the user is examining a trace frame in which the requested variable

  492. was not collected.

  493. </p></dd>

  494. </dl>

  495. 

  496. </dd>

  497. <dt>&lsquo;<samp>qTfP</samp>&rsquo;</dt>

  498. <dd><a name="index-qTfP-packet"></a>

  499. </dd>

  500. <dt>&lsquo;<samp>qTsP</samp>&rsquo;</dt>

  501. <dd><a name="index-qTsP-packet"></a>

  502. <p>These packets request data about tracepoints that are being used by

  503. the target.  <small>GDB</small> sends <code>qTfP</code> to get the first piece

  504. of data, and multiple <code>qTsP</code> to get additional pieces.  Replies

  505. to these packets generally take the form of the <code>QTDP</code> packets

  506. that define tracepoints. (FIXME add detailed syntax)

  507. </p>

  508. </dd>

  509. <dt>&lsquo;<samp>qTfV</samp>&rsquo;</dt>

  510. <dd><a name="index-qTfV-packet"></a>

  511. </dd>

  512. <dt>&lsquo;<samp>qTsV</samp>&rsquo;</dt>

  513. <dd><a name="index-qTsV-packet"></a>

  514. <p>These packets request data about trace state variables that are on the

  515. target.  <small>GDB</small> sends <code>qTfV</code> to get the first vari of data,

  516. and multiple <code>qTsV</code> to get additional variables.  Replies to

  517. these packets follow the syntax of the <code>QTDV</code> packets that define

  518. trace state variables.

  519. </p>

  520. </dd>

  521. <dt>&lsquo;<samp>qTfSTM</samp>&rsquo;</dt>

  522. <dt>&lsquo;<samp>qTsSTM</samp>&rsquo;</dt>

  523. <dd><a name="qTfSTM"></a><a name="qTsSTM"></a><a name="index-qTfSTM-packet"></a>

  524. <a name="index-qTsSTM-packet"></a>

  525. <p>These packets request data about static tracepoint markers that exist

  526. in the target program.  <small>GDB</small> sends <code>qTfSTM</code> to get the

  527. first piece of data, and multiple <code>qTsSTM</code> to get additional

  528. pieces.  Replies to these packets take the following form:

  529. </p>

  530. <p>Reply:

  531. </p><dl compact="compact">

  532. <dt>&lsquo;<samp>m <var>address</var>:<var>id</var>:<var>extra</var></samp>&rsquo;</dt>

  533. <dd><p>A single marker

  534. </p></dd>

  535. <dt>&lsquo;<samp>m <var>address</var>:<var>id</var>:<var>extra</var>,<var>address</var>:<var>id</var>:<var>extra</var>&hellip;</samp>&rsquo;</dt>

  536. <dd><p>a comma-separated list of markers

  537. </p></dd>

  538. <dt>&lsquo;<samp>l</samp>&rsquo;</dt>

  539. <dd><p>(lower case letter &lsquo;<samp>L</samp>&rsquo;) denotes end of list.

  540. </p></dd>

  541. <dt>&lsquo;<samp>E <var>nn</var></samp>&rsquo;</dt>

  542. <dd><p>An error occurred.  The error number <var>nn</var> is given as hex digits.

  543. </p></dd>

  544. <dt>&lsquo;<samp><!-- /@w --></samp>&rsquo;</dt>

  545. <dd><p>An empty reply indicates that the request is not supported by the

  546. stub.

  547. </p></dd>

  548. </dl>

  549. 

  550. <p>The <var>address</var> is encoded in hex;

  551. <var>id</var> and <var>extra</var> are strings encoded in hex.

  552. </p>

  553. <p>In response to each query, the target will reply with a list of one or

  554. more markers, separated by commas.  <small>GDB</small> will respond to each

  555. reply with a request for more markers (using the &lsquo;<samp>qs</samp>&rsquo; form of the

  556. query), until the target responds with &lsquo;<samp>l</samp>&rsquo; (lower-case ell, for

  557. <em>last</em>).

  558. </p>

  559. </dd>

  560. <dt>&lsquo;<samp>qTSTMat:<var>address</var></samp>&rsquo;</dt>

  561. <dd><a name="qTSTMat"></a><a name="index-qTSTMat-packet"></a>

  562. <p>This packets requests data about static tracepoint markers in the

  563. target program at <var>address</var>.  Replies to this packet follow the

  564. syntax of the &lsquo;<samp>qTfSTM</samp>&rsquo; and <code>qTsSTM</code> packets that list static

  565. tracepoint markers.

  566. </p>

  567. </dd>

  568. <dt>&lsquo;<samp>QTSave:<var>filename</var></samp>&rsquo;</dt>

  569. <dd><a name="index-QTSave-packet"></a>

  570. <p>This packet directs the target to save trace data to the file name

  571. <var>filename</var> in the target&rsquo;s filesystem.  The <var>filename</var> is encoded

  572. as a hex string; the interpretation of the file name (relative vs

  573. absolute, wild cards, etc) is up to the target.

  574. </p>

  575. </dd>

  576. <dt>&lsquo;<samp>qTBuffer:<var>offset</var>,<var>len</var></samp>&rsquo;</dt>

  577. <dd><a name="index-qTBuffer-packet"></a>

  578. <p>Return up to <var>len</var> bytes of the current contents of trace buffer,

  579. starting at <var>offset</var>.  The trace buffer is treated as if it were

  580. a contiguous collection of traceframes, as per the trace file format.

  581. The reply consists as many hex-encoded bytes as the target can deliver

  582. in a packet; it is not an error to return fewer than were asked for.

  583. A reply consisting of just <code>l</code> indicates that no bytes are

  584. available.

  585. </p>

  586. </dd>

  587. <dt>&lsquo;<samp>QTBuffer:circular:<var>value</var></samp>&rsquo;</dt>

  588. <dd><p>This packet directs the target to use a circular trace buffer if

  589. <var>value</var> is 1, or a linear buffer if the value is 0.

  590. </p>

  591. </dd>

  592. <dt>&lsquo;<samp>QTBuffer:size:<var>size</var></samp>&rsquo;</dt>

  593. <dd><a name="QTBuffer_002dsize"></a><a name="index-QTBuffer-size-packet"></a>

  594. <p>This packet directs the target to make the trace buffer be of size

  595. <var>size</var> if possible.  A value of <code>-1</code> tells the target to

  596. use whatever size it prefers.

  597. </p>

  598. </dd>

  599. <dt>&lsquo;<samp>QTNotes:<span class="roman">[</span><var>type</var>:<var>text</var><span class="roman">]</span><span class="roman">[</span>;<var>type</var>:<var>text</var><span class="roman">]</span>&hellip;</samp>&rsquo;</dt>

  600. <dd><a name="index-QTNotes-packet"></a>

  601. <p>This packet adds optional textual notes to the trace run.  Allowable

  602. types include <code>user</code>, <code>notes</code>, and <code>tstop</code>, the

  603. <var>text</var> fields are arbitrary strings, hex-encoded.

  604. </p>

  605. </dd>

  606. </dl>

  607. 

  608. <a name="Relocate-instruction-reply-packet"></a>

  609. <h4 class="subsection">E.6.1 Relocate instruction reply packet</h4>

  610. <p>When installing fast tracepoints in memory, the target may need to

  611. relocate the instruction currently at the tracepoint address to a

  612. different address in memory.  For most instructions, a simple copy is

  613. enough, but, for example, call instructions that implicitly push the

  614. return address on the stack, and relative branches or other

  615. PC-relative instructions require offset adjustment, so that the effect

  616. of executing the instruction at a different address is the same as if

  617. it had executed in the original location.

  618. </p>

  619. <p>In response to several of the tracepoint packets, the target may also

  620. respond with a number of intermediate &lsquo;<samp>qRelocInsn</samp>&rsquo; request

  621. packets before the final result packet, to have <small>GDB</small> handle

  622. this relocation operation.  If a packet supports this mechanism, its

  623. documentation will explicitly say so.  See for example the above

  624. descriptions for the &lsquo;<samp>QTStart</samp>&rsquo; and &lsquo;<samp>QTDP</samp>&rsquo; packets.  The

  625. format of the request is:

  626. </p>

  627. <dl compact="compact">

  628. <dt>&lsquo;<samp>qRelocInsn:<var>from</var>;<var>to</var></samp>&rsquo;</dt>

  629. <dd>

  630. <p>This requests <small>GDB</small> to copy instruction at address <var>from</var>

  631. to address <var>to</var>, possibly adjusted so that executing the

  632. instruction at <var>to</var> has the same effect as executing it at

  633. <var>from</var>.  <small>GDB</small> writes the adjusted instruction to target

  634. memory starting at <var>to</var>.

  635. </p></dd>

  636. </dl>

  637. 

  638. <p>Replies:

  639. </p><dl compact="compact">

  640. <dt>&lsquo;<samp>qRelocInsn:<var>adjusted_size</var></samp>&rsquo;</dt>

  641. <dd><p>Informs the stub the relocation is complete.  The <var>adjusted_size</var> is

  642. the length in bytes of resulting relocated instruction sequence.

  643. </p></dd>

  644. <dt>&lsquo;<samp>E <var>NN</var></samp>&rsquo;</dt>

  645. <dd><p>A badly formed request was detected, or an error was encountered while

  646. relocating the instruction.

  647. </p></dd>

  648. </dl>

  649. 

  650. <hr>

  651. <div class="header">

  652. <p>

  653. Next: <a href="Host-I_002fO-Packets.html#Host-I_002fO-Packets" accesskey="n" rel="next">Host I/O Packets</a>, Previous: <a href="Architecture_002dSpecific-Protocol-Details.html#Architecture_002dSpecific-Protocol-Details" accesskey="p" rel="prev">Architecture-Specific Protocol Details</a>, Up: <a href="Remote-Protocol.html#Remote-Protocol" accesskey="u" rel="up">Remote Protocol</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>

  654. </div>

  655. 

  656. 

  657. 

  658. </body>

  659. </html>