====== Embedded Handbook ======
This Handbook is dedicated for all kernel developer beginners. It provides useful snippets of code and use-cases for begginers. This will not cover the theory of %%FreeBSD%%'s kernel architecture. Please, read the handbooks, given in links section.

====== Compiling ======
Environment variables for building kernel/world:

<code>
ARCH=arm
TARGET_ARCH=arm
MAKEOBJDIRPREFIX=/home/aleek/obj
</code>

===== Kernel =====

<code>
export MAKEOBJDIRPREFIX=/home/aleek/obj
export ARCH=arm
export TARGET_ARCH=arm
make kernel-toolchain (not necessary, when building world before kernel)
make buildkernel KERNCONF=BEAGLEBOARD-XM
make buildworld
</code>

All object files will be written to MAKEOBJDIRPREFIX directory. Kernel config files are stored in ''%%sys/$ARCH/conf%%''

Compiler kernel is stored in ''%%$MAKEOBJDIRPREFIX/$TARGET_ARCH.$ARCH/usr/$MAKEOBJDIRPREFIX/sys/$KERNCONF/%%'' i.e. ''%%/home/aleek/obj/arm.arm/usr/home/aleek/armv6/sys/BEAGLEBOARD-XM%%''. You are interested in 3 of them:

<code>
$ file kernel
kernel: ELF 32-bit LSB executable, ARM, version 1 (FreeBSD), dynamically linked (uses shared libs), not stripped
$ file kernel.bin     // raw kernel
kernel.bin: data
$ file kernel.debug   // kernel with debugging symbols, useful for gdb 
kernel.debug: ELF 32-bit LSB executable, ARM, version 1 (FreeBSD), dynamically linked (uses shared libs), not stripped
</code>

You can make developer's toolchain, instead of regular:

<code>
make xdev XDEV=arm XDEV_ARCH=arm
</code>

RTEMS provides set of GNU debuggers for a couple of architectures:

<code>
# cd /usr/ports; make search name=rtems-gdb                                                                                                                                                                                                                                                                                                    
Port:   arm-rtems-gdb-7.2
Path:   /usr/ports/devel/arm-rtems-gdb
Info:   GNU gdb port for cross-target development
Maint:  ports@FreeBSD.org

Port:   i386-rtems-gdb-7.2
Path:   /usr/ports/devel/i386-rtems-gdb
Info:   GNU gdb port for cross-target development
Maint:  ports@FreeBSD.org

Port:   m68k-rtems-gdb-7.2
Path:   /usr/ports/devel/m68k-rtems-gdb
Info:   GNU gdb port for cross-target development
Maint:  ports@FreeBSD.org

Port:   mips-rtems-gdb-7.2
Path:   /usr/ports/devel/mips-rtems-gdb
Info:   GNU gdb port for cross-target development
Maint:  ports@FreeBSD.org

Port:   powerpc-rtems-gdb-7.2
Path:   /usr/ports/devel/powerpc-rtems-gdb
Info:   GNU gdb port for cross-target development
Maint:  ports@FreeBSD.org

Port:   sh-rtems-gdb-7.2
Path:   /usr/ports/devel/sh-rtems-gdb
Info:   GNU gdb port for cross-target development
Maint:  ports@FreeBSD.org

Port:   sparc-rtems-gdb-7.2
Path:   /usr/ports/devel/sparc-rtems-gdb
Info:   GNU gdb port for cross-target development
Maint:  ports@FreeBSD.org
</code>

===== world =====

<code>
make TARGET_ARCH=arm TARGET_CPUTYPE=armv6 buildworld
make TARGET_ARCH=arm TARGET_CPUTYPE=armv6 DESTDIR=/home/alek/beagle_rootfs SHAREOWN=alek SHAREGRP=wheel INSTALL=/home/alek/beagle-armv6/tools/install.sh installworld -DWITHOUT_SHAREDOCS -DWITHOUT_EXAMPLES -DWITHOUT_GAMES -DWITHOUT_HTML -DWITHOUT_INFO -DWITHOUT_MAN
make distrib-dirs DESTDIR=/home/alek/beagle_rootfs
make distribution DESTDIR=/home/alek/beagle_rootfs
</code>

''%%distrib-dirs%%'' makes dirs for rootfs (var, etc, usr ), and ''%%distribution%%'' "populates DESTDIR with various configuration files and scripts, obviously mostly etc, but it will add some files to rootdir, var and probably somewhere else as well"

====== Running ======
===== u-boot with tftp =====
===== rootfs via nfs =====
===== debugging =====
==== kdb ====
==== j-tag and gdb ====

====== Porting FreeBSD to new boards ======
Let's see, how to port %%FreeBSD%% by example: %%BeagleBoard%%-xM. The port is using [[FlattenedDeviceTree|Flattened Device Tree]] for describing the software.

===== Config file =====
Useful options during development:

<code>
makeoptions     DEBUG=-g                #Build kernel with gdb(1) debug symbols
options         BREAK_TO_DEBUGGER       #also ALT_BREAK_TO_DEBUGGER
options         VERBOSE_SYSINIT         #Enable verbose sysinit messages
options         KDB
options         DDB                     #Enable the kernel debugger
options         INVARIANTS              #Enable calls of extra sanity checking
options         INVARIANT_SUPPORT       #Extra sanity checks of internal structures, required by INVARIANTS
options         WITNESS                 #Enable checks to detect deadlocks and cycles
options         WITNESS_SKIPSPIN        #Don't run witness on spinlocks for speed
options         DIAGNOSTIC
options         DEBUG
</code>

===== initarm() =====

====== Useful Links ======

  * [[http://www.freebsd.org/doc/en/books/arch-handbook/|FreeBSD Architecture Handbook]]

  * [[http://www.freebsd.org/doc/en/books/developers-handbook/|FreeBSD Developers' Handbook]]

  * [[irc://irc.efnet.pl/#bsdmips]] - The IRC channel for %%FreeBSD%% on ARM, AVR32 and %%PowerPC%%!

----

{{tag>HowTo}}