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.
140 lines
6.6 KiB
HTML
140 lines
6.6 KiB
HTML
4 years ago
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<html>
|
||
|
|
<!-- Copyright (C) 1988-2019 Free Software Foundation, Inc.
|
||
|
|
|
||
|
|
Permission is granted to copy, distribute and/or modify this document
|
||
|
|
under the terms of the GNU Free Documentation License, Version 1.3 or
|
||
|
|
any later version published by the Free Software Foundation; with the
|
||
|
|
Invariant Sections being "Free Software" and "Free Software Needs
|
||
|
|
Free Documentation", with the Front-Cover Texts being "A GNU Manual,"
|
||
|
|
and with the Back-Cover Texts as in (a) below.
|
||
|
|
|
||
|
|
(a) The FSF's Back-Cover Text is: "You are free to copy and modify
|
||
|
|
this GNU Manual. Buying copies from GNU Press supports the FSF in
|
||
|
|
developing GNU and promoting software freedom." -->
|
||
|
|
<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
|
||
|
|
<head>
|
||
|
|
<title>Protocol Basics (Debugging with GDB)</title>
|
||
|
|
|
||
|
|
<meta name="description" content="Protocol Basics (Debugging with GDB)">
|
||
|
|
<meta name="keywords" content="Protocol Basics (Debugging with GDB)">
|
||
|
|
<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="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
|
||
|
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
||
|
|
<link href="File_002dI_002fO-Remote-Protocol-Extension.html#File_002dI_002fO-Remote-Protocol-Extension" rel="up" title="File-I/O Remote Protocol Extension">
|
||
|
|
<link href="The-F-Request-Packet.html#The-F-Request-Packet" rel="next" title="The F Request Packet">
|
||
|
|
<link href="File_002dI_002fO-Overview.html#File_002dI_002fO-Overview" rel="prev" title="File-I/O Overview">
|
||
|
|
<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="Protocol-Basics"></a>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="The-F-Request-Packet.html#The-F-Request-Packet" accesskey="n" rel="next">The F Request Packet</a>, Previous: <a href="File_002dI_002fO-Overview.html#File_002dI_002fO-Overview" accesskey="p" rel="prev">File-I/O Overview</a>, Up: <a href="File_002dI_002fO-Remote-Protocol-Extension.html#File_002dI_002fO-Remote-Protocol-Extension" accesskey="u" rel="up">File-I/O Remote Protocol Extension</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>
|
||
|
|
</div>
|
||
|
|
<hr>
|
||
|
|
<a name="Protocol-Basics-1"></a>
|
||
|
|
<h4 class="subsection">E.13.2 Protocol Basics</h4>
|
||
|
|
<a name="index-protocol-basics_002c-file_002di_002fo"></a>
|
||
|
|
|
||
|
|
<p>The File-I/O protocol uses the <code>F</code> packet as the request as well
|
||
|
|
as reply packet. Since a File-I/O system call can only occur when
|
||
|
|
<small>GDB</small> is waiting for a response from the continuing or stepping target,
|
||
|
|
the File-I/O request is a reply that <small>GDB</small> has to expect as a result
|
||
|
|
of a previous ‘<samp>C</samp>’, ‘<samp>c</samp>’, ‘<samp>S</samp>’ or ‘<samp>s</samp>’ packet.
|
||
|
|
This <code>F</code> packet contains all information needed to allow <small>GDB</small>
|
||
|
|
to call the appropriate host system call:
|
||
|
|
</p>
|
||
|
|
<ul>
|
||
|
|
<li> A unique identifier for the requested system call.
|
||
|
|
|
||
|
|
</li><li> All parameters to the system call. Pointers are given as addresses
|
||
|
|
in the target memory address space. Pointers to strings are given as
|
||
|
|
pointer/length pair. Numerical values are given as they are.
|
||
|
|
Numerical control flags are given in a protocol-specific representation.
|
||
|
|
|
||
|
|
</li></ul>
|
||
|
|
|
||
|
|
<p>At this point, <small>GDB</small> has to perform the following actions.
|
||
|
|
</p>
|
||
|
|
<ul>
|
||
|
|
<li> If the parameters include pointer values to data needed as input to a
|
||
|
|
system call, <small>GDB</small> requests this data from the target with a
|
||
|
|
standard <code>m</code> packet request. This additional communication has to be
|
||
|
|
expected by the target implementation and is handled as any other <code>m</code>
|
||
|
|
packet.
|
||
|
|
|
||
|
|
</li><li> <small>GDB</small> translates all value from protocol representation to host
|
||
|
|
representation as needed. Datatypes are coerced into the host types.
|
||
|
|
|
||
|
|
</li><li> <small>GDB</small> calls the system call.
|
||
|
|
|
||
|
|
</li><li> It then coerces datatypes back to protocol representation.
|
||
|
|
|
||
|
|
</li><li> If the system call is expected to return data in buffer space specified
|
||
|
|
by pointer parameters to the call, the data is transmitted to the
|
||
|
|
target using a <code>M</code> or <code>X</code> packet. This packet has to be expected
|
||
|
|
by the target implementation and is handled as any other <code>M</code> or <code>X</code>
|
||
|
|
packet.
|
||
|
|
|
||
|
|
</li></ul>
|
||
|
|
|
||
|
|
<p>Eventually <small>GDB</small> replies with another <code>F</code> packet which contains all
|
||
|
|
necessary information for the target to continue. This at least contains
|
||
|
|
</p>
|
||
|
|
<ul>
|
||
|
|
<li> Return value.
|
||
|
|
|
||
|
|
</li><li> <code>errno</code>, if has been changed by the system call.
|
||
|
|
|
||
|
|
</li><li> “Ctrl-C” flag.
|
||
|
|
|
||
|
|
</li></ul>
|
||
|
|
|
||
|
|
<p>After having done the needed type and value coercion, the target continues
|
||
|
|
the latest continue or step action.
|
||
|
|
</p>
|
||
|
|
<hr>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="The-F-Request-Packet.html#The-F-Request-Packet" accesskey="n" rel="next">The F Request Packet</a>, Previous: <a href="File_002dI_002fO-Overview.html#File_002dI_002fO-Overview" accesskey="p" rel="prev">File-I/O Overview</a>, Up: <a href="File_002dI_002fO-Remote-Protocol-Extension.html#File_002dI_002fO-Remote-Protocol-Extension" accesskey="u" rel="up">File-I/O Remote Protocol Extension</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>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|