1 files changed, 28 insertions, 0 deletions

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 396da16aabf..1c702ca8aac 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -262,6 +262,34 @@ cmd_lzo = (cat $(filter-out FORCE,$^) | \
         lzop -9 && $(call size_append, $(filter-out FORCE,$^))) > $@ || \
         (rm -f $@ ; false)
 
+# XZ
+# ---------------------------------------------------------------------------
+# Use xzkern to compress the kernel image and xzmisc to compress other things.
+#
+# xzkern uses a big LZMA2 dictionary since it doesn't increase memory usage
+# of the kernel decompressor. A BCJ filter is used if it is available for
+# the target architecture. xzkern also appends uncompressed size of the data
+# using size_append. The .xz format has the size information available at
+# the end of the file too, but it's in more complex format and it's good to
+# avoid changing the part of the boot code that reads the uncompressed size.
+# Note that the bytes added by size_append will make the xz tool think that
+# the file is corrupt. This is expected.
+#
+# xzmisc doesn't use size_append, so it can be used to create normal .xz
+# files. xzmisc uses smaller LZMA2 dictionary than xzkern, because a very
+# big dictionary would increase the memory usage too much in the multi-call
+# decompression mode. A BCJ filter isn't used either.
+quiet_cmd_xzkern = XZKERN  $@
+cmd_xzkern = (cat $(filter-out FORCE,$^) | \
+        sh $(srctree)/scripts/xz_wrap.sh && \
+        $(call size_append, $(filter-out FORCE,$^))) > $@ || \
+        (rm -f $@ ; false)
+
+quiet_cmd_xzmisc = XZMISC  $@
+cmd_xzmisc = (cat $(filter-out FORCE,$^) | \
+        xz --check=crc32 --lzma2=dict=1MiB) > $@ || \
+        (rm -f $@ ; false)
+
 # misc stuff
 # ---------------------------------------------------------------------------
 quote:="