diff options
Diffstat (limited to 'share/doc/gdb/Protocol-Basics.html')
| -rw-r--r-- | share/doc/gdb/Protocol-Basics.html | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/share/doc/gdb/Protocol-Basics.html b/share/doc/gdb/Protocol-Basics.html new file mode 100644 index 0000000..fa5b60a --- /dev/null +++ b/share/doc/gdb/Protocol-Basics.html @@ -0,0 +1,140 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1988-2023 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 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>Debugging with GDB: Protocol Basics</title> + +<meta name="description" content="Debugging with GDB: Protocol Basics"> +<meta name="keywords" content="Debugging with GDB: Protocol Basics"> +<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="previous" title="File-I/O Overview"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +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.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<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="previous">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="previous">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> |