From 63877f9e86e2b79218b3f08c1ec4613cfe354744 Mon Sep 17 00:00:00 2001
From: Florian Larysch <fl@n621.de>
Date: Sat, 31 May 2025 02:05:41 +0200
Subject: [PATCH] support/misc/relocate-sdk.sh: pre-calculate files in need of
 relocation

Currently, the relocate-sdk.sh script scans the whole extracted SDK tree
to find instances of paths it needs to replace, which can take a
significant amount of time when the SDK is large, particularly relative
to the number of files that actually need to change.

However, the resulting list only depends on the SDK tarball itself, so
we can calculate it at build time and ship it with the tarball so
relocate-sdk.sh can use it directly.

Testing this on my machine with somewhat IOPS-limited rotating media,
the time goes down from:

$ time ./relocate-sdk.sh
Relocating the buildroot SDK from [...] to [...] ...
./relocate-sdk.sh  5.19s user 26.21s system 9% cpu 5:34.40 total

To:

$ time ./relocate-sdk.sh
Relocating the buildroot SDK from [...] to [...] ...
./relocate-sdk.sh  0.49s user 0.29s system 103% cpu 0.749 total

Signed-off-by: Florian Larysch <fl@n621.de>
Signed-off-by: Arnout Vandecappelle <arnout@rnout.be>
---
 Makefile                     | 10 ++++++++++
 support/misc/relocate-sdk.sh | 11 +++--------
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/Makefile b/Makefile
index 004039d847..4cf8750bfb 100644
--- a/Makefile
+++ b/Makefile
@@ -602,6 +602,16 @@ prepare-sdk: world
 	@$(call MESSAGE,"Preparing the SDK")
 	$(INSTALL) -m 755 $(TOPDIR)/support/misc/relocate-sdk.sh $(HOST_DIR)/relocate-sdk.sh
 	mkdir -p $(HOST_DIR)/share/buildroot
+	(\
+		export LC_ALL=C; \
+		grep -lr '$(HOST_DIR)' '$(HOST_DIR)' | while read -r FILE; do \
+			if file -b --mime-type "$$FILE" | grep -q '^text/' && \
+			   [ "$$FILE" != '$(HOST_DIR)/share/buildroot/sdk-location' ] && \
+			   [ "$$FILE" != '$(HOST_DIR)/share/buildroot/sdk-relocs' ]; then \
+				echo "$$FILE"; \
+			fi; \
+		done \
+	) | sed -e 's|^$(HOST_DIR)|.|g' > $(HOST_DIR)/share/buildroot/sdk-relocs
 	echo $(HOST_DIR) > $(HOST_DIR)/share/buildroot/sdk-location
 
 BR2_SDK_PREFIX ?= $(GNU_TARGET_NAME)_sdk-buildroot
diff --git a/support/misc/relocate-sdk.sh b/support/misc/relocate-sdk.sh
index 981d272425..d25bc55279 100755
--- a/support/misc/relocate-sdk.sh
+++ b/support/misc/relocate-sdk.sh
@@ -37,15 +37,10 @@ fi
 
 echo "Relocating the buildroot SDK from ${OLDPATH} to ${NEWPATH} ..."
 
-# Make sure file uses the right language
-export LC_ALL=C
 # Replace the old path with the new one in all text files
-grep -lr "${OLDPATH}" . | while read -r FILE ; do
-    if file -b --mime-type "${FILE}" | grep -q '^text/' && [ "${FILE}" != "${LOCFILE}" ]
-    then
-        sed -i "s|${OLDPATH}|${NEWPATH}|g" "${FILE}"
-    fi
-done
+while read -r FILE ; do
+    sed -i "s|${OLDPATH}|${NEWPATH}|g" "${FILE}"
+done < share/buildroot/sdk-relocs
 
 # At the very end, we update the location file to not break the
 # SDK if this script gets interruted.