diff --git a/Documentation/kbuild/kbuild.txt b/Documentation/kbuild/kbuild.txt
index 9c230ea71963..dcfeb32e3360 100644
--- a/Documentation/kbuild/kbuild.txt
+++ b/Documentation/kbuild/kbuild.txt
@@ -183,6 +183,15 @@ The output directory is often set using "O=..." on the commandline.
 
 The value can be overridden in which case the default value is ignored.
 
+KBUILD_ABS_SRCTREE
+--------------------------------------------------
+Kbuild uses a relative path to point to the tree when possible. For instance,
+when building in the source tree, the source tree path is '.'
+
+Setting this flag requests Kbuild to use absolute path to the source tree.
+There are some useful cases to do so, like when generating tag files with
+absolute path entries etc.
+
 KBUILD_SIGN_PIN
 --------------------------------------------------
 This variable allows a passphrase or PIN to be passed to the sign-file
diff --git a/Makefile b/Makefile
index 91ad737ff538..357fd3623144 100644
--- a/Makefile
+++ b/Makefile
@@ -244,6 +244,10 @@ else
 	building_out_of_srctree := 1
 endif
 
+ifneq ($(KBUILD_ABS_SRCTREE),)
+srctree := $(abs_srctree)
+endif
+
 objtree		:= .
 VPATH		:= $(srctree)
 
diff --git a/scripts/tags.sh b/scripts/tags.sh
index 7fea4044749b..4e18ae5282a6 100755
--- a/scripts/tags.sh
+++ b/scripts/tags.sh
@@ -17,8 +17,7 @@ ignore="$(echo "$RCS_FIND_IGNORE" | sed 's|\\||g' )"
 # tags and cscope files should also ignore MODVERSION *.mod.c files
 ignore="$ignore ( -name *.mod.c ) -prune -o"
 
-# Do not use full path if we do not use O=.. builds
-# Use make O=. {tags|cscope}
+# Use make KBUILD_ABS_SRCTREE=1 {tags|cscope}
 # to force full paths for a non-O= build
 if [ "${srctree}" = "." -o -z "${srctree}" ]; then
 	tree=