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127 lines
6.6 KiB
HTML
127 lines
6.6 KiB
HTML
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<title>Interrupts (Debugging with GDB)</title>
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<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Remote-Protocol.html#Remote-Protocol" rel="up" title="Remote Protocol">
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<link href="Notification-Packets.html#Notification-Packets" rel="next" title="Notification Packets">
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<a name="Interrupts"></a>
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<div class="header">
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<p>
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Next: <a href="Notification-Packets.html#Notification-Packets" accesskey="n" rel="next">Notification Packets</a>, Previous: <a href="Host-I_002fO-Packets.html#Host-I_002fO-Packets" accesskey="p" rel="prev">Host I/O Packets</a>, Up: <a href="Remote-Protocol.html#Remote-Protocol" accesskey="u" rel="up">Remote Protocol</a> [<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>
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</div>
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<hr>
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<a name="Interrupts-1"></a>
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<h3 class="section">E.8 Interrupts</h3>
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<a name="index-interrupts-_0028remote-protocol_0029"></a>
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<a name="interrupting-remote-targets"></a>
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<p>In all-stop mode, when a program on the remote target is running,
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<small>GDB</small> may attempt to interrupt it by sending a ‘<samp>Ctrl-C</samp>’,
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<code>BREAK</code> or a <code>BREAK</code> followed by <code>g</code>, control of which
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is specified via <small>GDB</small>’s ‘<samp>interrupt-sequence</samp>’.
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</p>
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<p>The precise meaning of <code>BREAK</code> is defined by the transport
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mechanism and may, in fact, be undefined. <small>GDB</small> does not
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currently define a <code>BREAK</code> mechanism for any of the network
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interfaces except for TCP, in which case <small>GDB</small> sends the
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<code>telnet</code> BREAK sequence.
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</p>
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<p>‘<samp>Ctrl-C</samp>’, on the other hand, is defined and implemented for all
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transport mechanisms. It is represented by sending the single byte
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<code>0x03</code> without any of the usual packet overhead described in
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the Overview section (see <a href="Overview.html#Overview">Overview</a>). When a <code>0x03</code> byte is
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transmitted as part of a packet, it is considered to be packet data
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and does <em>not</em> represent an interrupt. E.g., an ‘<samp>X</samp>’ packet
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(see <a href="Packets.html#X-packet">X packet</a>), used for binary downloads, may include an unescaped
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<code>0x03</code> as part of its packet.
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</p>
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<p><code>BREAK</code> followed by <code>g</code> is also known as Magic SysRq g.
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When Linux kernel receives this sequence from serial port,
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it stops execution and connects to gdb.
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</p>
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<p>In non-stop mode, because packet resumptions are asynchronous
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(see <a href="Packets.html#vCont-packet">vCont packet</a>), <small>GDB</small> is always free to send a remote
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command to the remote stub, even when the target is running. For that
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reason, <small>GDB</small> instead sends a regular packet (see <a href="Packets.html#vCtrlC-packet">vCtrlC packet</a>) with the usual packet framing instead of the single byte
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<code>0x03</code>.
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</p>
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<p>Stubs are not required to recognize these interrupt mechanisms and the
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precise meaning associated with receipt of the interrupt is
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implementation defined. If the target supports debugging of multiple
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threads and/or processes, it should attempt to interrupt all
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currently-executing threads and processes.
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If the stub is successful at interrupting the
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running program, it should send one of the stop
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reply packets (see <a href="Stop-Reply-Packets.html#Stop-Reply-Packets">Stop Reply Packets</a>) to <small>GDB</small> as a result
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of successfully stopping the program in all-stop mode, and a stop reply
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for each stopped thread in non-stop mode.
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Interrupts received while the
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program is stopped are queued and the program will be interrupted when
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it is resumed next time.
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Notification-Packets.html#Notification-Packets" accesskey="n" rel="next">Notification Packets</a>, Previous: <a href="Host-I_002fO-Packets.html#Host-I_002fO-Packets" accesskey="p" rel="prev">Host I/O Packets</a>, Up: <a href="Remote-Protocol.html#Remote-Protocol" accesskey="u" rel="up">Remote Protocol</a> [<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>
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