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| author | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
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| committer | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
| commit | abdaadbcae30fe0c9a66c7516798279fdfd97750 (patch) | |
| tree | 00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/stabs/ELF-Linker-Relocation.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
Change-Id: I7303388733328cd98ab9aa3c30236db67f2e9e9c
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diff --git a/share/doc/stabs/ELF-Linker-Relocation.html b/share/doc/stabs/ELF-Linker-Relocation.html new file mode 100644 index 0000000..7eb4cc7 --- /dev/null +++ b/share/doc/stabs/ELF-Linker-Relocation.html @@ -0,0 +1,133 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1992-2023 Free Software Foundation, Inc. +Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon, +and David MacKenzie. + +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 no +Invariant Sections, with no Front-Cover Texts, and with no Back-Cover +Texts. A copy of the license is included in the section entitled "GNU +Free Documentation License". --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>STABS: ELF Linker Relocation</title> + +<meta name="description" content="STABS: ELF Linker Relocation"> +<meta name="keywords" content="STABS: ELF Linker Relocation"> +<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="Symbol-Types-Index.html#Symbol-Types-Index" rel="index" title="Symbol Types Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Stab-Sections.html#Stab-Sections" rel="up" title="Stab Sections"> +<link href="GNU-Free-Documentation-License.html#GNU-Free-Documentation-License" rel="next" title="GNU Free Documentation License"> +<link href="Stab-Section-Basics.html#Stab-Section-Basics" rel="previous" title="Stab Section Basics"> +<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="ELF-Linker-Relocation"></a> +<div class="header"> +<p> +Previous: <a href="Stab-Section-Basics.html#Stab-Section-Basics" accesskey="p" rel="previous">Stab Section Basics</a>, Up: <a href="Stab-Sections.html#Stab-Sections" accesskey="u" rel="up">Stab Sections</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Types-Index.html#Symbol-Types-Index" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Having-the-Linker-Relocate-Stabs-in-ELF"></a> +<h3 class="appendixsec">F.2 Having the Linker Relocate Stabs in ELF</h3> + +<p>This section describes some Sun hacks for Stabs in ELF; it does not +apply to COFF or SOM. While <small>GDB</small> no longer supports this hack +for Sun Stabs in ELF, this section is kept to document the issue. +</p> +<p>To keep linking fast, you don’t want the linker to have to relocate very +many stabs. Making sure this is done for <code>N_SLINE</code>, +<code>N_RBRAC</code>, and <code>N_LBRAC</code> stabs is the most important thing +(see the descriptions of those stabs for more information). But Sun’s +stabs in ELF has taken this further, to make all addresses in the +<code>n_value</code> field (functions and static variables) relative to the +source file. For the <code>N_SO</code> symbol itself, Sun simply omits the +address. To find the address of each section corresponding to a given +source file, the compiler puts out symbols giving the address of each +section for a given source file. Since these are ELF (not stab) +symbols, the linker relocates them correctly without having to touch the +stabs section. They are named <code>Bbss.bss</code> for the bss section, +<code>Ddata.data</code> for the data section, and <code>Drodata.rodata</code> for +the rodata section. For the text section, there is no such symbol (but +there should be, see below). For an example of how these symbols work, +See <a href="Stab-Section-Transformations.html#Stab-Section-Transformations">Stab Section Transformations</a>. GCC does not provide these symbols; +it instead relies on the stabs getting relocated. Thus addresses which +would normally be relative to <code>Bbss.bss</code>, etc., are already +relocated. The Sun linker provided with Solaris 2.2 and earlier +relocates stabs using normal ELF relocation information, as it would do +for any section. Sun has been threatening to kludge their linker to not +do this (to speed up linking), even though the correct way to avoid +having the linker do these relocations is to have the compiler no longer +output relocatable values. Last I heard they had been talked out of the +linker kludge. See Sun point patch 101052-01 and Sun bug 1142109. With +the Sun compiler this affects ‘<samp>S</samp>’ symbol descriptor stabs +(see <a href="Statics.html#Statics">Statics</a>) and functions (see <a href="Procedures.html#Procedures">Procedures</a>). In the latter +case, to adopt the clean solution (making the value of the stab relative +to the start of the compilation unit), it would be necessary to invent a +<code>Ttext.text</code> symbol, analogous to the <code>Bbss.bss</code>, etc., +symbols. I recommend this rather than using a zero value and getting +the address from the ELF symbols. +</p> +<p>Finding the correct <code>Bbss.bss</code>, etc., symbol is difficult, because +the linker simply concatenates the <code>.stab</code> sections from each +<samp>.o</samp> file without including any information about which part of a +<code>.stab</code> section comes from which <samp>.o</samp> file. The way GDB use to +do this is to look for an ELF <code>STT_FILE</code> symbol which has the same +name as the last component of the file name from the <code>N_SO</code> symbol +in the stabs (for example, if the file name is <samp>../../gdb/main.c</samp>, +it looks for an ELF <code>STT_FILE</code> symbol named <code>main.c</code>). This +loses if different files have the same name (they could be in different +directories, a library could have been copied from one system to +another, etc.). It would be much cleaner to have the <code>Bbss.bss</code> +symbols in the stabs themselves. Having the linker relocate them there +is no more work than having the linker relocate ELF symbols, and it +solves the problem of having to associate the ELF and stab symbols. +However, no one has yet designed or implemented such a scheme. +</p> +<hr> +<div class="header"> +<p> +Previous: <a href="Stab-Section-Basics.html#Stab-Section-Basics" accesskey="p" rel="previous">Stab Section Basics</a>, Up: <a href="Stab-Sections.html#Stab-Sections" accesskey="u" rel="up">Stab Sections</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Types-Index.html#Symbol-Types-Index" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |