support/scripts/fix-rpath: parallelize patching files

Using "xargs" instead of "while read" loop allows for the patching of
files to be parallelized. This significantly reduces the amount of
time it takes to fix all the paths.  On a larger RFS(~300MB) this
script was taking 5 minutes, it now only takes about 30s on a 12 core
machine.

Signed-off-by: Victor Dumas <dumasv.dev@gmail.com>
[Thomas: take into account the suggestion of Quentin Schulz to pass
PARALLEL_JOBS through the environment down to the fix-rpath script]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

Makefile

@@ -594,8 +594,12 @@ world: target-post-image
 .PHONY: prepare-sdk
 prepare-sdk: world
 	@$(call MESSAGE,"Rendering the SDK relocatable")
-	PER_PACKAGE_DIR=$(PER_PACKAGE_DIR) $(TOPDIR)/support/scripts/fix-rpath host
-	PER_PACKAGE_DIR=$(PER_PACKAGE_DIR) $(TOPDIR)/support/scripts/fix-rpath staging
+	PARALLEL_JOBS=$(PARALLEL_JOBS) \
+		PER_PACKAGE_DIR=$(PER_PACKAGE_DIR) \
+		$(TOPDIR)/support/scripts/fix-rpath host
+	PARALLEL_JOBS=$(PARALLEL_JOBS) \
+		PER_PACKAGE_DIR=$(PER_PACKAGE_DIR) \
+		$(TOPDIR)/support/scripts/fix-rpath staging
 	$(INSTALL) -m 755 $(TOPDIR)/support/misc/relocate-sdk.sh $(HOST_DIR)/relocate-sdk.sh
 	mkdir -p $(HOST_DIR)/share/buildroot
 	echo $(HOST_DIR) > $(HOST_DIR)/share/buildroot/sdk-location
@@ -765,7 +769,9 @@ endif
 	ln -sf ../usr/lib/os-release $(TARGET_DIR)/etc
 
 	@$(call MESSAGE,"Sanitizing RPATH in target tree")
-	PER_PACKAGE_DIR=$(PER_PACKAGE_DIR) $(TOPDIR)/support/scripts/fix-rpath target
+	PARALLEL_JOBS=$(PARALLEL_JOBS) \
+		PER_PACKAGE_DIR=$(PER_PACKAGE_DIR) \
+		$(TOPDIR)/support/scripts/fix-rpath target
 
 # For a merged /usr, ensure that /lib, /bin and /sbin and their /usr
 # counterparts are appropriately setup as symlinks ones to the others.

support/scripts/fix-rpath

@@ -46,6 +46,8 @@ Environment:
     TOOLCHAIN_EXTERNAL_DOWNLOAD_INSTALL_DIR
                  (default HOST_DIR/opt/ext-toolchain)
 
+    PARALLEL_JOBS number of parallel jobs to run
+
 Returns:         0 if success or 1 in case of error
 
 EOF
@@ -58,6 +60,38 @@ HOST_EXCLUDEPATHS="/share/terminfo"
 STAGING_EXCLUDEPATHS="/usr/include /usr/share/terminfo"
 TARGET_EXCLUDEPATHS="/lib/firmware"
 
+patch_file() {
+    PATCHELF="${1}"
+    rootdir="${2}"
+    sanitize_extra_args="${3}"
+    file="${4}"
+
+    # check if it's an ELF file
+    rpath=$(${PATCHELF} --print-rpath "${file}" 2>&1)
+    if test $? -ne 0 ; then
+        return 0
+    fi
+
+    # make files writable if necessary
+    changed=$(chmod -c u+w "${file}")
+
+    # With per-package directory support, most RPATH of host
+    # binaries will point to per-package directories. This won't
+    # work with the --make-rpath-relative ${rootdir} invocation as
+    # the per-package host directory is not within ${rootdir}. So,
+    # we rewrite all RPATHs pointing to per-package directories so
+    # that they point to the global host directry.
+    changed_rpath=$(echo ${rpath} | sed "s@${PER_PACKAGE_DIR}/[^/]\+/host@${HOST_DIR}@")
+    if test "${rpath}" != "${changed_rpath}" ; then
+        ${PATCHELF} --set-rpath ${changed_rpath} "${file}"
+    fi
+
+    # call patchelf to sanitize the rpath
+    ${PATCHELF} --make-rpath-relative "${rootdir}" ${sanitize_extra_args[@]} "${file}"
+    # restore the original permission
+    test "${changed}" != "" && chmod u-w "${file}"
+}
+
 main() {
     local rootdir
     local tree="${1}"
@@ -123,34 +157,11 @@ main() {
             ;;
     esac
 
-    find_args+=( "-type" "f" "-print" )
-
-    while read file ; do
-        # check if it's an ELF file
-        rpath=$(${PATCHELF} --print-rpath "${file}" 2>&1)
-        if test $? -ne 0 ; then
-            continue
-        fi
-
-        # make files writable if necessary
-        changed=$(chmod -c u+w "${file}")
-
-        # With per-package directory support, most RPATH of host
-        # binaries will point to per-package directories. This won't
-        # work with the --make-rpath-relative ${rootdir} invocation as
-        # the per-package host directory is not within ${rootdir}. So,
-        # we rewrite all RPATHs pointing to per-package directories so
-        # that they point to the global host directry.
-        changed_rpath=$(echo ${rpath} | sed "s@${PER_PACKAGE_DIR}/[^/]\+/host@${HOST_DIR}@")
-        if test "${rpath}" != "${changed_rpath}" ; then
-            ${PATCHELF} --set-rpath ${changed_rpath} "${file}"
-        fi
-
-        # call patchelf to sanitize the rpath
-        ${PATCHELF} --make-rpath-relative "${rootdir}" ${sanitize_extra_args[@]} "${file}"
-        # restore the original permission
-        test "${changed}" != "" && chmod u-w "${file}"
-    done < <(find "${rootdir}" ${find_args[@]})
+    find_args+=( "-type" "f" "-print0" )
+
+    export -f patch_file
+    # Limit the number of cores used
+    find "${rootdir}" ${find_args[@]} | xargs -0 -r -P ${PARALLEL_JOBS} -I {} bash -c "patch_file '${PATCHELF}' '${rootdir}' '${sanitize_extra_args}' $@" _ {}
 
     # Restore patched patchelf utility
     test "${tree}" = "host" && mv "${PATCHELF}.__to_be_patched" "${PATCHELF}"