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
diff --git a/Makefile b/Makefile
index 6d17cfd..26cfd5e 100644
--- a/Makefile
+++ b/Makefile
@@ -37,7 +37,8 @@
 # Default goal is build all images
 .DEFAULT_GOAL			:= all
 
-include make_helpers/build_macros.mk
+MAKE_HELPERS_DIRECTORY := make_helpers/
+include ${MAKE_HELPERS_DIRECTORY}build_macros.mk
 
 ################################################################################
 # Default values for build configurations
@@ -111,9 +112,10 @@
 CHECKPATCH_ARGS		:=	--no-tree --no-signoff ${CHECK_IGNORE}
 CHECKCODE_ARGS		:=	--no-patch --no-tree --no-signoff ${CHECK_IGNORE}
 # Do not check the coding style on C library files
-CHECK_PATHS		:=	$(shell ls -I include -I lib) \
-				$(addprefix include/,$(shell ls -I stdlib include)) \
-				$(addprefix lib/,$(shell ls -I stdlib lib))
+INCLUDE_DIRS_TO_CHECK	:=	$(sort $(filter-out include/stdlib, $(wildcard include/*)))
+LIB_DIRS_TO_CHECK	:=	$(sort $(filter-out lib/stdlib, $(wildcard lib/*)))
+ROOT_DIRS_TO_CHECK	:=	$(sort $(filter-out lib include, $(wildcard *))))
+CHECK_PATHS		:=	${ROOT_DIRS_TO_CHECK} ${INCLUDE_DIRS_TO_CHECK} ${LIB_DIRS_TO_CHECK}
 
 
 ################################################################################
@@ -235,17 +237,12 @@
 # Generic definitions
 ################################################################################
 
+include ${MAKE_HELPERS_DIRECTORY}plat_helpers.mk
+
 BUILD_BASE		:=	./build
 BUILD_PLAT		:=	${BUILD_BASE}/${PLAT}/${BUILD_TYPE}
 
-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 '|'.
-PLATFORMS		:=	$(shell find plat/ -name '${PLAT_MAKEFILE}' -print0 |			\
-					sed -r 's%[^\x00]*\/([^/]*)\/${PLAT_MAKEFILE}\x00%\1|%g' |	\
-					sed -r 's/\|$$//')
-SPDS			:=	$(shell ls -I none services/spd)
+SPDS			:=	$(sort $(filter-out none, $(patsubst services/spd/%,%,$(wildcard services/spd/*))))
 
 # Platforms providing their own TBB makefile may override this value
 INCLUDE_TBBR_MK		:=	1
@@ -261,7 +258,7 @@
         $(warning "The SPD and its BL32 companion will be present but ignored.")
 endif
         # We expect to locate an spd.mk under the specified SPD directory
-        SPD_MAKE	:=	$(shell m="services/spd/${SPD}/${SPD}.mk"; [ -f "$$m" ] && echo "$$m")
+        SPD_MAKE	:=	$(wildcard services/spd/${SPD}/${SPD}.mk)
 
         ifeq (${SPD_MAKE},)
                 $(error Error: No services/spd/${SPD}/${SPD}.mk located)
@@ -286,14 +283,6 @@
 # makefile may use all previous definitions in this file)
 ################################################################################
 
-ifeq (${PLAT},)
-        $(error "Error: Unknown platform. Please use PLAT=<platform name> to specify the platform")
-endif
-PLAT_MAKEFILE_FULL	:=	$(shell find plat/ -wholename '*/${PLAT}/${PLAT_MAKEFILE}')
-ifeq ($(PLAT_MAKEFILE_FULL),)
-        $(error "Error: Invalid platform. The following platforms are available: ${PLATFORMS}")
-endif
-
 include ${PLAT_MAKEFILE_FULL}
 
 # If the platform has not defined ENABLE_PLAT_COMPAT, then enable it by default
@@ -622,7 +611,7 @@
 	${Q}cscope -b -q -k
 
 help:
-	@echo "usage: ${MAKE} PLAT=<${PLATFORMS}> [OPTIONS] [TARGET]"
+	@echo "usage: ${MAKE} PLAT=<${PLATFORM_LIST}> [OPTIONS] [TARGET]"
 	@echo ""
 	@echo "PLAT is used to specify which platform you wish to build."
 	@echo "If no platform is specified, PLAT defaults to: ${DEFAULT_PLAT}"
diff --git a/bl32/tsp/tsp.mk b/bl32/tsp/tsp.mk
index 9919fe4..a502428 100644
--- a/bl32/tsp/tsp.mk
+++ b/bl32/tsp/tsp.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2013-2014, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2013-2016, 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:
@@ -52,8 +52,8 @@
 # Include the platform-specific TSP Makefile
 # If no platform-specific TSP Makefile exists, it means TSP is not supported
 # on this platform.
-TSP_PLAT_MAKEFILE := $(shell find plat/ -wholename '*/${PLAT}/tsp/tsp-${PLAT}.mk')
-ifeq (,$(wildcard ${TSP_PLAT_MAKEFILE}))
+TSP_PLAT_MAKEFILE := $(wildcard ${PLAT_DIR}/tsp/tsp-${PLAT}.mk)
+ifeq (,${TSP_PLAT_MAKEFILE})
   $(error TSP is not supported on platform ${PLAT})
 else
   include ${TSP_PLAT_MAKEFILE}
diff --git a/make_helpers/build_macros.mk b/make_helpers/build_macros.mk
index b22eaf9..274f365 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 0000000..85ba84f
--- /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
diff --git a/tools/cert_create/Makefile b/tools/cert_create/Makefile
index 8d7b8a5..4a6dd6b 100644
--- a/tools/cert_create/Makefile
+++ b/tools/cert_create/Makefile
@@ -47,15 +47,16 @@
 
 CFLAGS := -Wall -std=c99
 
-# Check the platform
-ifeq (${PLAT},none)
-  $(error "Error: Unknown platform. Please use PLAT=<platform name> to specify the platform")
-endif
-PLAT_MAKEFILE		:=	platform.mk
-PLAT_INCLUDE	:=	$(shell find ../../plat/ -wholename '*/${PLAT}/${PLAT_MAKEFILE}' |	\
-				sed 's/${PLAT_MAKEFILE}/include/')
+MAKE_HELPERS_DIRECTORY := ../../make_helpers/
+include ${MAKE_HELPERS_DIRECTORY}build_macros.mk
+
+PLATFORM_ROOT		:=	../../plat/
+include ${MAKE_HELPERS_DIRECTORY}plat_helpers.mk
+
+PLAT_INCLUDE		:=	$(wildcard ${PLAT_DIR}include)
+
 ifeq ($(PLAT_INCLUDE),)
-  $(error "Error: Invalid platform '${PLAT}'")
+  $(error "Error: Invalid platform '${PLAT}' has no include directory.")
 endif
 
 ifeq (${DEBUG},1)