70 lines
2.6 KiB
Plaintext
70 lines
2.6 KiB
Plaintext
// -*- mode:doc; -*-
|
|
// vim: set syntax=asciidoc:
|
|
|
|
== How Buildroot works
|
|
|
|
As mentioned above, Buildroot is basically a set of Makefiles that
|
|
download, configure, and compile software with the correct options. It
|
|
also includes patches for various software packages - mainly the ones
|
|
involved in the cross-compilation toolchain (+gcc+, +binutils+ and
|
|
+uClibc+).
|
|
|
|
There is basically one Makefile per software package, and they are
|
|
named with the +.mk+ extension. Makefiles are split into many different
|
|
parts.
|
|
|
|
* The +toolchain/+ directory contains the Makefiles
|
|
and associated files for all software related to the
|
|
cross-compilation toolchain: +binutils+, +gcc+, +gdb+,
|
|
+kernel-headers+ and +uClibc+.
|
|
|
|
* The +arch/+ directory contains the definitions for all the processor
|
|
architectures that are supported by Buildroot.
|
|
|
|
* The +package/+ directory contains the Makefiles and
|
|
associated files for all user-space tools and libraries that Buildroot
|
|
can compile and add to the target root filesystem. There is one
|
|
sub-directory per package.
|
|
|
|
* The +linux/+ directory contains the Makefiles and associated files for
|
|
the Linux kernel.
|
|
|
|
* The +boot/+ directory contains the Makefiles and associated files for
|
|
the bootloaders supported by Buildroot.
|
|
|
|
* The +system/+ directory contains support for system integration, e.g.
|
|
the target filesystem skeleton and the selection of an init system.
|
|
|
|
* The +fs/+ directory contains the Makefiles and
|
|
associated files for software related to the generation of the
|
|
target root filesystem image.
|
|
|
|
Each directory contains at least 2 files:
|
|
|
|
* +something.mk+ is the Makefile that downloads, configures,
|
|
compiles and installs the package +something+.
|
|
|
|
* +Config.in+ is a part of the configuration tool
|
|
description file. It describes the options related to the
|
|
package.
|
|
|
|
The main Makefile performs the following steps (once the
|
|
configuration is done):
|
|
|
|
* Create all the output directories: +staging+, +target+, +build+,
|
|
etc. in the output directory (+output/+ by default,
|
|
another value can be specified using +O=+)
|
|
|
|
* Generate the toolchain target. When an internal toolchain is used, this
|
|
means generating the cross-compilation toolchain. When an external
|
|
toolchain is used, this means checking the features of the external
|
|
toolchain and importing it into the Buildroot environment.
|
|
|
|
* Generate all the targets listed in the +TARGETS+ variable. This
|
|
variable is filled by all the individual components'
|
|
Makefiles. Generating these targets will trigger the compilation of
|
|
the userspace packages (libraries, programs), the kernel, the
|
|
bootloader and the generation of the root filesystem images,
|
|
depending on the configuration.
|
|
|