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--- warnerlosh:a_brief_guide_to_cross_compiling_freebsd [2006/07/20 22:29] – WarnerLosh
+++ warnerlosh:a_brief_guide_to_cross_compiling_freebsd [2021/04/26 04:26] (current) – Add CategoryStale KubilayKocak
@@ Line 1: / Line 1: @@
 ====== Cross Compiling FreeBSD for Fun and Profit ======
-===== Summary off steps =====
+===== Summary =====
-  * Obtain %%FreeBSD%% sources
+  * Introduction
-  * setup build environment
+  * Obtaining %%FreeBSD%%
-  * Build
+  * Setting up Build Environment
+  * Building World
+  * What's Next
+  * Cheatsheet
-===== Obtaining FreeBSD sources =====
+===== Introduction =====
-See http://www.freebsd.org for details.  This article will assume that you've obtained the sources, placed them in /home/bob/src and wish to build into /home/bob/obj.  We'll assume the user is familiar with csh commands, and will be able to translate them into whatever shell that they use.
+==== Notes ====
-===== Setup Build Environment =====
+For the sake of illustration, the document assumes that:
-For architectures that are supported by %%FreeBSD%%, cross building is relatively easy.  For those that %%FreeBSD%% doesn't support, there's a lot more work.
+  * All files will be placed under ///home/bob// .
+  * The architecture being built will be (big-endian) ARM, aka //armeb//.
+  * The installed world will be placed under ///home/bob/my-armeb//.
-The %%FreeBSD%% build system uses three environment variables to control which platform to build for, and where to put the results.  By default, %%FreeBSD%% will build natively for the current architecture and place the results in /usr/obj.
+==== Notation Used ====
-Most people will want to change the location of the build.  /usr/obj is far too generic a place for developers to build into.  The environment variable MAKEOBJDIRPREFIX controls where the files are placed.
+  * Any line preceded by a //%// is to be executed in a system shell.
+  * The reader can specify make variables in one of three ways:
+    * In a custom //make.conf// file and call make with \_\_MAKE_CONF=/full/path/to/make.conf .
+    * Set the variables in the environment, e.g. with env, export, or setenv.
+    * Explicitly on the command line. **NOTE**: this is how the writeup specifies the values.
-setenv MAKEOBJDIRPREFIX /home/bob/obj
+===== Obtaining FreeBSD =====
-To control which architecture to build for, set TARGET and TARGET_ARCH
+The reader can obtain the sources as noted in the Handbook chapter titled [[http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/mirrors.html|Obtaining FreeBSD]]. The reader should place the sources in ///home/bob/src//.
-setenv TARGET arm
+===== Setting up Build Environment =====
-setenv TARGET_ARCH
-TARGET matches MACHINE while TARGET_ARCH matches MACHINE_ARCH.
+For architectures that are supported by %%FreeBSD%%, cross-building is relatively easy. For architectures that %%FreeBSD%% doesn't support, more work is required.
+The %%FreeBSD%% build system uses three environment variables to control which platform to build (TARGET), which target architecture to build (TARGET_ARCH), and where to put the results (MAKEOBJDIRPREFX). By default, %%FreeBSD%% builds the current architecture and places the results in ///usr/obj//, or in this example ///home/bob/obj//.
+When cross-compiling however, %%FreeBSD%% places binaries in //$MAKEOBJDIRPREFIX/$TARGET// (for cases where //$TARGET// == //$TARGET_ARCH//, e.g. amd64) or //$MAKEOBJDIRPREFIX/$TARGET.$TARGET_ARCH// (for cases where //$TARGET// != //$TARGET_ARCH//). In this example, the directory used will be ///home/bob/obj/arm.armeb//.
+Note that a non-default value of MAKEOBJDIRPREFIX must be passed to make as an environment variable.  It cannot be set as an argument to make directly.
+==== make.conf / src.conf ====
+A standard make.conf and src.conf file can contain variables or make snippets which tune build behavior. /usr/share/examples/etc/make.conf has more details on some recommended make.conf tunable items, and src.conf(5) lists some of the variables that one could put in src.conf . The following notes some potential pitfalls in using these files for cross-compiling, make universe, make tinderbox, etc:
+  * Explicitly setting CPUTYPE. The following incorrect example would explicitly attempt to build binaries optimizing for the core2 Intel architecture:
+<code>
+CPUTYPE= core2
+</code>
+The reader should instead set the CPUTYPE as follows:
+<code>
+CPUTYPE?= core2
+</code>
+  * Explicitly setting KERNCONF. The following incorrect example would explicitly build the XEN KERNCONF (which only exists for i386 and amd64):
+<code>
+KERNCONF= XEN
+</code>
+The reader should instead set KERNCONF as follows:
+<code>
+KERNCONF?= XEN
+</code>
+===== Building and Installing World =====
+The following subsections show the reader how they could build and install world for the big-endian ARM architecture from scratch.
+==== Go to the Source Directory ====
+<code>
+% cd /home/bob/src
+</code>
+==== Build World ====
+<code>
+% env MAKEOBJDIRPREFIX=/home/bob/obj make buildworld TARGET=arm TARGET_ARCH=armeb
+</code>
+==== Install World ====
+  * First and foremost, one must create the install directory:
+<code>
+% mkdir /home/bob/my-armeb
+</code>
+  * Then one must run make installworld to install the binaries produced in buildworld:
+<code>
+% env MAKEOBJDIRPREFIX=/home/bob/obj make installworld DESTDIR=/home/bob/my-armeb TARGET=arm TARGET_ARCH=armeb
+</code>
+  * And last but not least, one must run make distribution to populate the world with important files from ///etc//:
+<code>
+% env MAKEOBJDIRPREFIX=/home/bob/obj make distribution DESTDIR=/home/bob/my-armeb TARGET=arm TARGET_ARCH=armeb
+</code>
+**NOTE**: You could invoke mergemaster instead of running make distribution; mergemaster does a few things that make distribution does not do; see [[http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html|The Canonical Way to Update Your System]] for more details, and please consult mergemaster(8).
+===== What's Next =====
+The above example demonstrated how one could build world and install world with armeb. This should provide you with the building blocks required to build the %%FreeBSD%% base system for any cross-compilation environment.
 ===== Cheat sheet =====
 http://lists.freebsd.org/pipermail/freebsd-current/2006-July/064384.html
+----
+{{tag>Stale}}