commit 4ee196b1308105e974333a0db8191fdc7451220b
parent 4a549347c833366566dfb2bb396ace26afe8d5b8
Author: Roberto Vargas <roberto.vargas@arm.com>
Date: Wed, 24 Apr 2019 11:30:14 +0100
[doc] Add documentation about the build system.
Change-Id: I1c04162d8c0631c9cbbc3769ebaf62d99a08b49b
Diffstat:
| M | doc/DESIGN | | | 44 | +++++++++++++++++++++++++++++++++++++++++++- |
1 file changed, 43 insertions(+), 1 deletion(-)
diff --git a/doc/DESIGN b/doc/DESIGN
@@ -175,6 +175,48 @@ TBD
4) Build system
---------------
-TBD
+The rcode build system is based in fully portable POSIX Makefiles. They
+are structured in a recursive fashion, having a Makefile per directory
+that in case of being needed recurse in the appropiate subdirectories.
+Every Makefile begins with lines similar to:
+
+.POSIX:
+PROJECTDIR=../..
+include $(PROJECTDIR)/scripts/rules.mk
+
+The first line specifies to the make program that this is a POSIX
+Makefile, switching on the POSIX mode of the tool in case of accepting
+different modes. The second line specifies where is the root of the
+project related to the current directory and the third line includes the
+file rules.mk. The file rules.mk uses the definition of PROJECTDIR to
+define a set of macros and rules that will be used by all the Makefiles
+of the project.
+
+The build process depends of three variables:
+
+ - CONF: This variable specifies the system configuration of
+ the target. By default it has the value "arm64-rcode".
+
+ - TOOL: This variable specifies the toolchain used to build
+ the target. By default it has the value "gnu".
+
+ - CROSS_COMPILE: This variable specifies a prefix used
+ for the binaries of the toolchain. By default it
+ has an empty value.
+
+There are several make variables that must be exported to the shell
+because there are shell scripts that use them, and for this reason the
+top Makefile generates the file scripts/env.sh which is sourced before
+recursing. For this reason, some Makefiles may not work when make is
+executed in one subdirectory (unless the user sources them in his shell).
+Anyway, the build system only guarantees a correct build when make
+is executed from the root directory of the project, otherwise some
+dependencies may be not correctly tracked.
+
+There are several Makefiles (drivers, src/romfw, src/ramfw) that produce
+a filed called builtin.o as target. This file is the composition of
+all the object files compiled in that directory. This avoid having
+dependencies between the top Makefile and the lower Makefiles as
+the top Makefile doesn't need to know what object files must be linked.
[0] http://www.simple-cc.org
