[PATCH v3 20/21] klp-build: Support cross-compilation

[Josh Poimboeuf <jpoimboe@kernel.org>]

Add support for cross-compilation.  The user must export ARCH, and
either CROSS_COMPILE or LLVM as needed.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 scripts/livepatch/klp-build | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build
index 911ada05673c2..e83973567c878 100755
--- a/scripts/livepatch/klp-build
+++ b/scripts/livepatch/klp-build
@@ -432,6 +432,25 @@ validate_patches() {
 	revert_patches
 }
 
+cross_compile_init() {
+	if [[ -v LLVM && -n "$LLVM" ]]; then
+		local prefix=""
+		local suffix=""
+
+		if [[ "$LLVM" == */ ]]; then
+			# LLVM=/path/to/bin/
+			prefix="$LLVM"
+		elif [[ "$LLVM" == -* ]]; then
+			# LLVM=-14
+			suffix="$LLVM"
+		fi
+
+		OBJCOPY="${prefix}llvm-objcopy${suffix}"
+	else
+		OBJCOPY="${CROSS_COMPILE:-}objcopy"
+	fi
+}
+
 do_init() {
 	# We're not yet smart enough to handle anything other than in-tree
 	# builds in pwd.
@@ -462,6 +481,7 @@ do_init() {
 	validate_config
 	set_module_name
 	set_kernelversion
+	cross_compile_init
 }
 
 # Refresh the patch hunk headers, specifically the line numbers and counts.
@@ -871,7 +891,7 @@ build_patch_module() {
 	cp -f "$kmod_file" "$kmod_file.orig"
 
 	# Work around issue where slight .config change makes corrupt BTF
-	objcopy --remove-section=.BTF "$kmod_file"
+	"$OBJCOPY" --remove-section=.BTF "$kmod_file"
 
 	# Fix (and work around) linker wreckage for klp syms / relocs
 	"$OBJTOOL" klp post-link "$kmod_file" || die "objtool klp post-link failed"
-- 
2.53.0