~nabijaczleweli/febug

ref: 8bab4a8dfa99590e4cc577551a2d9fa36fe5578b febug/Debian/febug-abi.5.html -rw-r--r-- 13.4 KiB
8bab4a8d — наб autouploader Debian manpage update by job 412471 8 months ago
                                                                                
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  <title>FEBUG-ABI(5)</title>
</head>
<body>
<table class="head">
  <tr>
    <td class="head-ltitle">FEBUG-ABI(5)</td>
    <td class="head-vol">File Formats Manual</td>
    <td class="head-rtitle">FEBUG-ABI(5)</td>
  </tr>
</table>
<div class="manual-text">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<code class="Nm">struct febug_message</code>,
  <code class="Nm">struct stop_febug_message</code>,
  <code class="Nm">struct attn_febug_message</code> &#x2014;
<div class="Nd">User-space debugfs ABI</div>
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<code class="In">#include
  &lt;<a class="In" href="https://git.sr.ht/~nabijaczleweli/febug/tree/trunk/item/include/febug-abi.h">febug-abi.h</a>&gt;</code>
<div class="Pp"></div>
<b class="Sy">struct febug_message;</b>
<div class="Pp"></div>
<b class="Sy">struct stop_febug_message;</b>
<div class="Pp"></div>
<b class="Sy">struct attn_febug_message;</b>
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
The febug ABI consists of two messages sent from the program wishing to be
  debugged to <a class="Xr" href="febug.8.html">febug(8)</a>, and one sent from
  <a class="Xr" href="febug.8.html">febug(8)</a> to the program.
<div class="Pp"></div>
To be debugged, the program must create a socket with
  <code class="Li">socket(AF_UNIX, SOCK_SEQPACKET, 0)</code> and
  <a class="Xr">connect(2)</a> to the appropriate end-point
  (<span class="Pa">/run/febug.sock</span>, conventionally). Sending
  the first message will pass along client credentials; sending the null message
  is a valid way to trigger this. After <a class="Xr" href="febug.8.html">febug(8)</a>
  receives credentials, a directory corresponding to the debugged process' PID
  will be created in the filesystem.
<div class="Pp"></div>
<i class="Em">All</i> messages must be sent in a single
  <a class="Xr">send(2)</a> or
  <a class="Xr">sendmsg(2)</a> call, specifying the exact size of the
  message, as that's what's used to differentiate between different messages.
  <a class="Xr" href="febug.8.html">febug(8)</a> will ignore messages (whose sizes) it
  does not recognise.
<div class="Pp"></div>
Afterward, for each variable of interest, the process should send a 4096-byte
  <b class="Sy">febug_message</b>, defined as follows:
<div class="Pp"></div>
<div class="Bd Bd-indent">
<pre class="Li">
struct [[packed]] febug_message { 
    uint64_t variable_id; 
    uint64_t variable_type; 
    uint8_t signal; 
    char name[/* Enough to bring the overall size to 4096. */]; 
};
</pre>
</div>
<div class="Pp"></div>
Wherein:
<dl class="Bl-tag">
  <dt></dt>
  <dd><i class="Em">variable_id</i> is the locally unique identifier
      of the variable (e.g. a pointer to that variable).</dd>
  <dt></dt>
  <dd><i class="Em">variable_type</i> is the moral equivalent of
      <var class="Vt">void *</var>
      <var class="Va">userdata</var> &#x2014; it is simply passed
      back to the program, unchanged (e.g. a function pointer to a
    formatter).</dd>
  <dt></dt>
  <dd><i class="Em">signal</i> is the signal to send to the program
      when a variable is to be read (see below).
      <i class="Em">name</i> is the globally unique name of this
      variable &#x2014; a NUL terminator is respected, if it occurs before the
      end of the array, but is not required if the name truly spans to the final
      byte. If the name is the same as one of an already-present variable, it
      will be overridden.</dd>
</dl>
<div class="Pp"></div>
When <a class="Xr" href="febug.8.html">febug(8)</a> receives
  <b class="Sy">febug_message</b>, it creates a file under the
  process' directory. When that file is opened,
  <a class="Xr" href="febug.8.html">febug(8)</a> will:
<ol class="Bl-enum">
  <li>send the process an <b class="Sy">attn_febug_message</b> with a
      single file descriptor via <code class="Dv">SCM_RIGHTS</code>
      auxilliary data (confer <a class="Xr">cmsg(3)</a>) representing
      the write end of a pipe &#x2014; subsequent reads are serviced directly by
      the opposing end.</li>
  <li><a class="Xr">kill(2)</a> the process with the signal from the
      <var class="Va">signal</var> field if it wasn't
      <code class="Dv">SIGKILL</code>.</li>
</ol>
<div class="Pp"></div>
Note, that the sent file descriptor <i class="Em">must</i> be closed
  by the program when it's done serialising the variable, and therefore, if the
  process opts not to receive a signal, it <i class="Em">must</i>
  handle the message through some other mechanism.
<div class="Pp"></div>
<b class="Sy">attn_febug_message</b> is 16 bytes, and defined as
  follows:
<div class="Pp"></div>
<div class="Bd Bd-indent">
<pre class="Li">
struct [[packed]] attn_febug_message { 
    uint64_t variable_id; 
    uint64_t variable_type; 
};
</pre>
</div>
<div class="Pp"></div>
Both fields correspond to the ones sent in the
  <b class="Sy">febug_message</b> that installed the variable.
<div class="Pp"></div>
The process may receive any amount of
  <b class="Sy">attn_febug_message</b> until it sends an 8-byte
  <b class="Sy">stop_febug_message</b>, defined as follows:
<div class="Pp"></div>
<div class="Bd Bd-indent">
<pre class="Li">
struct [[packed]] stop_febug_message { 
    uint64_t variable_id; 
};
</pre>
</div>
<div class="Pp"></div>
Upon receipt, the corresponding variable, if any, is removed from the
  filesystem.
<div class="Pp"></div>
When the process' end of the socket is closed, all extant variables are freed,
  and the process' directory is removed.
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
  ALSO</a></h1>
<a class="Xr" href="libfebug.3.html">libfebug(3)</a> and
  <a class="Xr" href="libfebug++.3.html">libfebug++(3)</a> &#x2014; libraries that wrap this
  ABI.
<h1 class="Sh" id="AUTHORS"><a class="permalink" href="#AUTHORS">AUTHORS</a></h1>
Written by <span class="An">&#x043D;&#x0430;&#x0431;</span>
  &lt;<a class="Mt" href="mailto:nabijaczleweli@nabijaczleweli.xyz">nabijaczleweli@nabijaczleweli.xyz</a>&gt;
<h1 class="Sh" id="SPECIAL_THANKS"><a class="permalink" href="#SPECIAL_THANKS">SPECIAL
  THANKS</a></h1>
To all who support further development, in particular:
<ul class="Bl-bullet Bl-compact">
  <li>ThePhD</li>
  <li>Embark Studios</li>
</ul>
<h1 class="Sh" id="REPORTING_BUGS"><a class="permalink" href="#REPORTING_BUGS">REPORTING
  BUGS</a></h1>
<a class="Lk" href="https://todo.sr.ht/~nabijaczleweli/febug">febug
  tracker</a>
<div class="Pp"></div>
febug mailing list:
  &lt;<a class="Mt" href="mailto:~nabijaczleweli/febug@lists.sr.ht">~nabijaczleweli/febug@lists.sr.ht</a>&gt;
  archived at
  <a class="Lk" href="https://lists.sr.ht/~nabijaczleweli/febug">https://lists.sr.ht/~nabijaczleweli/febug</a></div>
<table class="foot">
  <tr>
    <td class="foot-date">January 31, 2021</td>
    <td class="foot-os">Debian</td>
  </tr>
</table>
</body>
</html>