You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
86 lines
3.8 KiB
HTML
86 lines
3.8 KiB
HTML
4 years ago
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<html>
|
||
|
|
<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
|
||
|
|
<head>
|
||
|
|
<title>Exception handler (Embed with GNU)</title>
|
||
|
|
|
||
|
|
<meta name="description" content="Exception handler (Embed with GNU)">
|
||
|
|
<meta name="keywords" content="Exception handler (Embed with GNU)">
|
||
|
|
<meta name="resource-type" content="document">
|
||
|
|
<meta name="distribution" content="global">
|
||
|
|
<meta name="Generator" content="makeinfo">
|
||
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
||
|
|
<link href="index.html#Top" rel="start" title="Top">
|
||
|
|
<link href="leds_002ec.html#SEC_Contents" rel="contents" title="Table of Contents">
|
||
|
|
<link href="GDB.html#GDB" rel="up" title="GDB">
|
||
|
|
<link href="ROM-monitors.html#ROM-monitors" rel="next" title="ROM monitors">
|
||
|
|
<link href="GNU-remote-protocol.html#GNU-remote-protocol" rel="prev" title="GNU remote protocol">
|
||
|
|
<style type="text/css">
|
||
|
|
<!--
|
||
|
|
a.summary-letter {text-decoration: none}
|
||
|
|
blockquote.indentedblock {margin-right: 0em}
|
||
|
|
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
|
||
|
|
blockquote.smallquotation {font-size: smaller}
|
||
|
|
div.display {margin-left: 3.2em}
|
||
|
|
div.example {margin-left: 3.2em}
|
||
|
|
div.lisp {margin-left: 3.2em}
|
||
|
|
div.smalldisplay {margin-left: 3.2em}
|
||
|
|
div.smallexample {margin-left: 3.2em}
|
||
|
|
div.smalllisp {margin-left: 3.2em}
|
||
|
|
kbd {font-style: oblique}
|
||
|
|
pre.display {font-family: inherit}
|
||
|
|
pre.format {font-family: inherit}
|
||
|
|
pre.menu-comment {font-family: serif}
|
||
|
|
pre.menu-preformatted {font-family: serif}
|
||
|
|
pre.smalldisplay {font-family: inherit; font-size: smaller}
|
||
|
|
pre.smallexample {font-size: smaller}
|
||
|
|
pre.smallformat {font-family: inherit; font-size: smaller}
|
||
|
|
pre.smalllisp {font-size: smaller}
|
||
|
|
span.nolinebreak {white-space: nowrap}
|
||
|
|
span.roman {font-family: initial; font-weight: normal}
|
||
|
|
span.sansserif {font-family: sans-serif; font-weight: normal}
|
||
|
|
ul.no-bullet {list-style: none}
|
||
|
|
-->
|
||
|
|
</style>
|
||
|
|
|
||
|
|
|
||
|
|
</head>
|
||
|
|
|
||
|
|
<body lang="en">
|
||
|
|
<a name="Exception-handler"></a>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="ROM-monitors.html#ROM-monitors" accesskey="n" rel="next">ROM monitors</a>, Previous: <a href="GNU-remote-protocol.html#GNU-remote-protocol" accesskey="p" rel="prev">GNU remote protocol</a>, Up: <a href="GDB.html#GDB" accesskey="u" rel="up">GDB</a> [<a href="leds_002ec.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p>
|
||
|
|
</div>
|
||
|
|
<hr>
|
||
|
|
<a name="A-linked-in-exception-handler"></a>
|
||
|
|
<h3 class="section">4.2 A linked in exception handler</h3>
|
||
|
|
|
||
|
|
<p>A <em>GDB stub</em> consists of two parts, support for the exception
|
||
|
|
handler, and the exception handler itself. The exception handler needs
|
||
|
|
to communicate to GDB on the host whenever there is a breakpoint
|
||
|
|
exception. When GDB starts a program running on the target, it’s polling
|
||
|
|
the serial port during execution looking for any debug packets. So when
|
||
|
|
a breakpoint occurs, the exception handler needs to save state, and send
|
||
|
|
a GDB remote protocol packet to GDB on the host. GDB takes any output
|
||
|
|
that isn’t a debug command packet and displays it in the command window.
|
||
|
|
</p>
|
||
|
|
<p>Support for the exception handler varies between processors, but the
|
||
|
|
minimum supported functions are those needed by GDB. These are functions
|
||
|
|
to support the reading and writing of registers, the reading and writing
|
||
|
|
of memory, start execution at an address, single step, and last signal.
|
||
|
|
Sometimes other functions for adjusting the baud rate, or resetting the
|
||
|
|
hardware are implemented.
|
||
|
|
</p>
|
||
|
|
<p>Once GDB gets the command packet from the breakpoint, it will read a few
|
||
|
|
registers and memory locations an then wait for the user. When the user
|
||
|
|
types <code>run</code> or <code>continue</code> a <code>continue</code> command is issued
|
||
|
|
to the backend, and control returns from the breakpoint routine to the
|
||
|
|
application.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|