Make:Remove calls to shell from makefiles.

As an initial stage of making Trusted Firmware build environment more
portable, we remove most uses of the $(shell ) function and replace them
with more portable make function based solutions.

Note that the setting of BUILD_STRING still uses $(shell ) since it's
not possible to reimplement this as a make function. Avoiding invocation
of this on incompatible host platforms will be implemented separately.

Change-Id: I768e2f9a265c78814a4adf2edee4cc46cda0f5b8

2 files changed, 74 insertions, 1 deletions

diff --git a/make_helpers/build_macros.mk b/make_helpers/build_macros.mk
index b22eaf90..274f365a 100644
--- a/make_helpers/build_macros.mk
+++ b/make_helpers/build_macros.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2015, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2015-2016, ARM Limited and Contributors. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are met:
@@ -28,6 +28,17 @@
 # POSSIBILITY OF SUCH DAMAGE.
 #
 
+# Some utility macros for manipulating awkward (whitespace) characters.
+blank			:=
+space			:=${blank} ${blank}
+
+# A user defined function to recursively search for a filename below a directory
+#    $1 is the directory root of the recursive search (blank for current directory).
+#    $2 is the file name to search for.
+define rwildcard
+$(strip $(foreach d,$(wildcard ${1}*),$(call rwildcard,${d}/,${2}) $(filter $(subst *,%,%${2}),${d})))
+endef
+
 # This table is used in converting lower case to upper case.
 uppercase_table:=a,A b,B c,C d,D e,E f,F g,G h,H i,I j,J k,K l,L m,M n,N o,O p,P q,Q r,R s,S t,T u,U v,V w,W x,X y,Y z,Z
 
diff --git a/make_helpers/plat_helpers.mk b/make_helpers/plat_helpers.mk
new file mode 100644
index 00000000..85ba84fe
--- /dev/null
+++ b/make_helpers/plat_helpers.mk
@@ -0,0 +1,62 @@
+#
+# Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# Redistributions of source code must retain the above copyright notice, this
+# list of conditions and the following disclaimer.
+#
+# Redistributions in binary form must reproduce the above copyright notice,
+# this list of conditions and the following disclaimer in the documentation
+# and/or other materials provided with the distribution.
+#
+# Neither the name of ARM nor the names of its contributors may be used
+# to endorse or promote products derived from this software without specific
+# prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+
+################################################################################
+# Helpers for finding and referencing platform directories
+################################################################################
+
+ifndef PLAT_HELPERS_MK
+    PLAT_HELPERS_MK := $(lastword $(MAKEFILE_LIST))
+
+    ifeq (${PLAT},)
+        $(error "Error: Unknown platform. Please use PLAT=<platform name> to specify the platform")
+    endif
+
+    # PLATFORM_ROOT can be overridden for when building tools directly
+    PLATFORM_ROOT               ?= plat/
+    PLAT_MAKEFILE               := platform.mk
+
+    # Generate the platforms list by recursively searching for all directories
+    # under /plat containing a PLAT_MAKEFILE. Append each platform with a `|`
+    # char and strip out the final '|'.
+    ALL_PLATFORM_MK_FILES       := $(call rwildcard,${PLATFORM_ROOT},${PLAT_MAKEFILE})
+    ALL_PLATFORM_DIRS           := $(patsubst %/,%,$(dir ${ALL_PLATFORM_MK_FILES}))
+    ALL_PLATFORMS               := $(sort $(notdir ${ALL_PLATFORM_DIRS}))
+
+    PLAT_MAKEFILE_FULL          := $(filter %/${PLAT}/${PLAT_MAKEFILE},${ALL_PLATFORM_MK_FILES})
+    PLATFORM_LIST               := $(subst ${space},|,${ALL_PLATFORMS})
+    ifeq ($(PLAT_MAKEFILE_FULL),)
+        $(error "Error: Invalid platform. The following platforms are available: ${PLATFORM_LIST}")
+    endif
+
+    # Record the directory where the platform make file was found.
+    PLAT_DIR                    := $(dir ${PLAT_MAKEFILE_FULL})
+
+endif