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<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 15. 32-Bit and 64-Bit Applications in a 64-Bit System Environment</title><link rel="stylesheet" href="susebooks.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.75.2"><link rel="home" href="index.html" title="Documentation"><link rel="up" href="part.reference.system.html" title="Part IV. System"><link rel="prev" href="part.reference.system.html" title="Part IV. System"><link rel="next" href="cha.boot.html" title="Chapter 16. Booting and Configuring a Linux System"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header" border="0" class="bctable"><tr><td width="80%"><div class="breadcrumbs"><p><a href="index.html"> Documentation</a><span class="breadcrumbs-sep"> > </span><a href="book.opensuse.reference.html">Reference</a><span class="breadcrumbs-sep"> > </span><a href="part.reference.system.html">System</a><span class="breadcrumbs-sep"> > </span><strong><a accesskey="p" title="Part IV. System" href="part.reference.system.html"><span>◀</span></a> <a accesskey="n" title="Chapter 16. Booting and Configuring a Linux System" href="cha.boot.html"><span>▶</span></a></strong></p></div></td></tr></table></div><div class="chapter" title="Chapter 15. 32-Bit and 64-Bit Applications in a 64-Bit System Environment"><div class="titlepage"><div><div><h2 class="title"><a name="cha.64bit"></a>Chapter 15. 32-Bit and 64-Bit Applications in a 64-Bit System Environment<span class="permalink"><a alt="Permalink" title="Copy Permalink" href="#cha.64bit">¶</a></span></h2></div></div></div><div class="toc"><p><b>Contents</b></p><dl><dt><span class="sect1"><a href="cha.64bit.html#sec.64bit.runt">15.1. Runtime Support</a></span></dt><dt><span class="sect1"><a href="cha.64bit.html#sec.64bit.devel">15.2. Software Development</a></span></dt><dt><span class="sect1"><a href="cha.64bit.html#sec.64bit.biarch">15.3. Software Compilation on Biarch Platforms</a></span></dt><dt><span class="sect1"><a href="cha.64bit.html#sec.64bit.kernel">15.4. Kernel Specifications</a></span></dt></dl></div><a class="indexterm" name="id459460"></a><p>
openSUSE® is available for
64-bit platforms. This does not necessarily mean that all the applications
included have already been ported to 64-bit platforms. openSUSE
supports the use of 32-bit applications in a 64-bit system environment.
This chapter offers a brief overview of how this support is implemented on
64-bit openSUSE platforms. It explains how 32-bit applications are
executed (runtime support) and how 32-bit applications should be compiled
to enable them to run both in 32-bit and 64-bit system environments.
Additionally, find information about the kernel API and an explanation of
how 32-bit applications can run under a 64-bit kernel.
</p><p>
<span>openSUSE for the
64-bit platforms amd64 and Intel 64</span> is designed so that existing
32-bit applications run in the 64-bit environment
<span class="quote">“<span class="quote">out-of-the-box.</span>”</span>
This support means that you can continue to use your preferred 32-bit
applications without waiting for a corresponding 64-bit port to become
available.
</p><div class="sect1" title="15.1. Runtime Support"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="sec.64bit.runt"></a>15.1. Runtime Support<span class="permalink"><a alt="Permalink" title="Copy Permalink" href="#sec.64bit.runt">¶</a></span></h2></div></div></div><a class="indexterm" name="id459507"></a><div class="important"><table border="0" cellpadding="3" cellspacing="0" width="100%" summary="Important: Conflicts between Application Versions"><tr class="head"><td width="32"><img alt="[Important]" src="admon/important.png"></td><th align="left">Conflicts between Application Versions</th></tr><tr><td colspan="2" align="left" valign="top"><p>
If an application is available both for 32-bit and 64-bit environments,
parallel installation of both versions is bound to lead to problems. In
such cases, decide on one of the two versions and install and use this.
</p><p>
An exception to this rule is PAM (pluggable authentication modules).
openSUSE uses PAM in the authentication process as a layer that
mediates between user and application. On a 64-bit operating system that
also runs 32-bit applications it is necessary to always install both
versions of a PAM module.
</p></td></tr></table></div><p>
To be executed correctly, every application requires a range of
libraries. Unfortunately, the names for the 32-bit and 64-bit versions of
these libraries are identical. They must be differentiated from each
other in another way.
</p><p>
To retain compatibility with the 32-bit version, the libraries are stored
at the same place in the system as in the 32-bit environment. The 32-bit
version of <code class="filename">libc.so.6</code> is located under
<code class="filename">/lib/libc.so.6</code> in both the 32-bit and 64-bit
environments.
</p><p>
All 64-bit libraries and object files are located in directories called
<code class="filename">lib64</code>. The 64-bit object files that you would
normally expect to find under <code class="filename">/lib</code> and
<code class="filename">/usr/lib</code> are now found under
<code class="filename">/lib64</code> and <code class="filename">/usr/lib64</code>. This
means that there is space for the 32-bit libraries under
<code class="filename">/lib</code> and <code class="filename">/usr/lib</code>, so the
filename for both versions can remain unchanged.
</p><p>
Subdirectories of 32-bit <code class="filename">/lib</code> directories which
contain data content that does not depend on the word size are not moved.
This scheme conforms to LSB (Linux Standards Base) and FHS (File System
Hierarchy Standard).
</p></div><div class="sect1" title="15.2. Software Development"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="sec.64bit.devel"></a>15.2. Software Development<span class="permalink"><a alt="Permalink" title="Copy Permalink" href="#sec.64bit.devel">¶</a></span></h2></div></div></div><a class="indexterm" name="id459608"></a><p>
A biarch development tool chain allows generation of 32-bit and 64-bit
objects. The default is to compile 64-bit objects. It is possible to
generate 32-bit objects by using special flags. For GCC, this special
flag is <code class="option">-m32</code>.
</p><p>
All header files must be written in an architecture-independent form. The
installed 32-bit and 64-bit libraries must have an API (application
programming interface) that matches the installed header files. The
normal openSUSE environment is designed according to this principle.
In the case of manually updated libraries, resolve these issues yourself.
</p></div><div class="sect1" title="15.3. Software Compilation on Biarch Platforms"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="sec.64bit.biarch"></a>15.3. Software Compilation on Biarch Platforms<span class="permalink"><a alt="Permalink" title="Copy Permalink" href="#sec.64bit.biarch">¶</a></span></h2></div></div></div><p>
To develop binaries for the other architecture on a biarch architecture,
the respective libraries for the second architecture must additionally be
installed. These packages are called
<code class="systemitem">rpmname-32bit</code>. You also need the
respective headers and libraries from the
<code class="systemitem">rpmname-devel</code> packages and the
development libraries for the second architecture from
<code class="systemitem">rpmname-devel-32bit</code>.
</p><p>
Most open source programs use an <span class="command"><strong>autoconf</strong></span>-based
program configuration. To use <span class="command"><strong>autoconf</strong></span> for configuring
a program for the second architecture, overwrite the normal compiler and
linker settings of <span class="command"><strong>autoconf</strong></span> by running the
<span class="command"><strong>configure</strong></span> script with additional environment
variables.
</p><p>
The following example refers to an x86_64 system with x86 as the second
architecture.
</p><div class="procedure"><ol class="procedure" type="1"><li><p>
Use the 32-bit compiler:
</p><pre class="screen">CC="gcc -m32"</pre></li><li><p>
Instruct the linker to process 32-bit objects (always use <span class="command"><strong>gcc</strong></span> as the
linker front-end):
</p><pre class="screen">LD="gcc -m32"</pre></li><li><p>
Set the assembler to generate 32-bit objects:
</p><pre class="screen">AS="gcc -c -m32"</pre></li><li><p>
Specify linker flags, such as the location of 32-bit libraries, for
example:
</p><pre class="screen">LDFLAGS="-L/usr/lib"</pre></li><li><p>
Specify the location for the 32-bit object code libraries:
</p><pre class="screen">--libdir=/usr/lib</pre></li><li><p>
Specify the location for the 32-bit X libraries:
</p><pre class="screen">--x-libraries=/usr/lib</pre></li></ol></div><p>
Not all of these variables are needed for every program. Adapt them to
the respective program.
</p><pre class="screen">CC="gcc -m32"
LDFLAGS="-L/usr/lib;"
./configure --prefix=/usr --libdir=/usr/lib --x-libraries=/usr/lib
make
make install</pre></div><div class="sect1" title="15.4. Kernel Specifications"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="sec.64bit.kernel"></a>15.4. Kernel Specifications<span class="permalink"><a alt="Permalink" title="Copy Permalink" href="#sec.64bit.kernel">¶</a></span></h2></div></div></div><a class="indexterm" name="id459808"></a><p>
The 64-bit kernels for x86_64 offer both a 64-bit and a 32-bit kernel ABI
(application binary interface). The latter is identical with the ABI for
the corresponding 32-bit kernel. This means that the 32-bit application
can communicate with the 64-bit kernel in the same way as with the 32-bit
kernel.
</p><p>
The 32-bit emulation of system calls for a 64-bit kernel does not support
all the APIs used by system programs. This depends on the platform. For
this reason, a small number of applications, like
<span class="command"><strong>lspci</strong></span>, must be compiled.
</p><p>
A 64-bit kernel can only load 64-bit kernel modules that have been
specially compiled for this kernel. It is not possible to use 32-bit
kernel modules.
</p><div class="tip"><table border="0" cellpadding="3" cellspacing="0" width="100%" summary="Tip: Kernel-loadable Modules"><tr class="head"><td width="32"><img alt="[Tip]" src="admon/tip.png"></td><th align="left">Kernel-loadable Modules</th></tr><tr><td colspan="2" align="left" valign="top"><p>
Some applications require separate kernel-loadable modules. If you
intend to use such a 32-bit application in a 64-bit system environment,
contact the provider of this application and Novell to make sure that
the 64-bit version of the kernel-loadable module and the 32-bit compiled
version of the kernel API are available for this module.
</p></td></tr></table></div></div></div><div class="navfooter"><table width="100%" summary="Navigation footer" border="0" class="bctable"><tr><td width="80%"><div class="breadcrumbs"><p><a href="index.html"> Documentation</a><span class="breadcrumbs-sep"> > </span><a href="book.opensuse.reference.html">Reference</a><span class="breadcrumbs-sep"> > </span><a href="part.reference.system.html">System</a><span class="breadcrumbs-sep"> > </span><strong><a accesskey="p" title="Part IV. System" href="part.reference.system.html"><span>◀</span></a> <a accesskey="n" title="Chapter 16. Booting and Configuring a Linux System" href="cha.boot.html"><span>▶</span></a></strong></p></div></td></tr></table></div></body></html>
ACC SHELL 2018