Experimental Clang support

Allows building with Clang with "make COMPILER=clang [other flags...]".
The clang command has to be in the $PATH, as well as the associated
tools (clang-cpp, ld.lld, llvm-ar, llvm-nm, llvm-objcopy and
llvm-readelf).

Tested with Clang built from the master branch of [1] (development
version for 9.0):

 mkdir build; cd build
 cmake -G Ninja -DCMAKE_BUILD_TYPE=Release \
       -DCMAKE_INSTALL_PREFIX=~/llvm-install \
       -DLLVM_ENABLE_PROJECTS="clang;lld" \
       -DLLVM_TARGETS_TO_BUILD="AArch64;ARM" \
       ~/llvm-project/llvm
 ninja && ninja install

Limitations:

 - CFG_CORE_SANITIZE_KADDRESS=y is not supported.
 - CFG_WITH_PAGER is supported, but requires that the TEE core be
   linked with the GNU linker. The reason is documented in
   mk/clang.mk.

Bug:

 - ldelf assertion failure in xtest 1019 when CFG_ULIBS_SHARED=y (QEMU)
   E/LD:  assertion 'maps[map_idx].sz == sz' failed at ldelf/ta_elf.c:1114 in ta_elf_print_mappings()
   Prevents ldelf from displaying the TA mappings on abort or panic, but
   does not seem to cause any other problem.

Link: [1] https://github.com/llvm/llvm-project/commits/8351c327647
Signed-off-by: Jerome Forissier <jerome@forissier.org>
Tested-by: Jerome Forissier <jerome@forissier.org> (QEMU pager/no pager)
Tested-by: Jerome Forissier <jerome@forissier.org> (QEMUv8, pager/no pager)
Tested-by: Jerome Forissier <jerome@forissier.org> (HiKey960, 32/64, GP)
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>

1 files changed, 88 insertions, 0 deletions

diff --git a/scripts/llvm-objcopy-wrapper b/scripts/llvm-objcopy-wrapper
new file mode 100755
index 00000000..fb67a987
--- /dev/null
+++ b/scripts/llvm-objcopy-wrapper
@@ -0,0 +1,88 @@
+#!/bin/bash
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (c) 2019, Linaro Limited
+#
+# This is a wrapper script to llvm-objcopy to add support for:
+#  - The --pad-to argument
+#  - Regular expressions in --only-section= and --remove-section
+#  - Creating empty output files when no section match
+#  - Allowing removal of sections that are referenced by some other sections
+#    by default (--allow-broken-links).
+#
+# Depends on llvm-readelf.
+
+args=("--allow-broken-links") # llvm-objcopy >= 9.0
+only_section_re=()
+remove_section_re=()
+for arg in "$@"; do
+	if [ "$pad_found" ]; then
+		pad_addr="$arg"
+		pad_found=
+		continue
+	fi
+	case "$arg" in
+		--pad-to)
+			pad_found=1
+			continue
+			;;
+		--only-section=*)
+			re=$(echo "$arg" | sed s/--only-section=//)
+			only_section_re+=("$re")
+			continue
+			;;
+		--remove-section=*)
+			re=$(echo "$arg" | sed s/--remove-section=//)
+			remove_section_re+=("$re")
+			continue
+			;;
+	esac
+	args+=("$arg")
+done
+
+in="${@: -2:1}"
+out="${@: -1:1}"
+if [ ! -e "$in" ]; then
+	in=$out # That is good enough for our use cases
+fi
+
+if [ '${only_section_re[@]}''${remove_section_re[@]}' ]; then
+	sections=$(llvm-readelf -sections $in | grep ' *\[ *[0-9]*] [^ ]' | sed 's/ *\[ *[0-9]*] \(.[^ ]*\).*/\1/')
+	for s in $sections; do
+		for re in "${only_section_re[@]}"; do
+			if [ "$(echo $s | grep -- $re)" != "" ]; then
+				args+=("--only-section=$s")
+				break
+			fi
+		done
+		for re in "${remove_section_re[@]}"; do
+			if [ "$(echo $s | grep -- $re)" != "" ]; then
+				args+=("--remove-section=$s")
+				break
+			fi
+		done
+	done
+fi
+
+pad_sz=0
+if [ "$pad_addr" ]; then
+
+	# Find address and size of last PROGBITS section in input file
+	addr_sz=$(llvm-readelf -sections $in | grep PROGBITS | sed 's/.*PROGBITS *\([^ ]*\) [^ ]* \([^ ]*\).*/\1 \2/' | sort -n | tail -1)
+	read addr sz <<< "$addr_sz"
+
+	# Now figure out the size of the padding. Can be 0.
+	pad_sz=$(($pad_addr - 0x$addr - 0x$sz))
+fi
+
+# Run llvm-objcopy without "--pad-to <addr>" and with expanded
+# --only-section/--remove-section
+if [ "$VV" = 1 ]; then
+	echo Running: llvm-objcopy "${args[@]}"
+fi
+llvm-objcopy "${args[@]}" || exit $?
+
+# Pad with zeroes if necessary
+if [ $pad_sz -gt 0 ]; then
+	truncate -s +$pad_sz $out
+fi