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authorNick Terrell <terrelln@fb.com>2020-07-30 22:08:36 +0300
committerIngo Molnar <mingo@kernel.org>2020-07-31 12:49:08 +0300
commit48f7ddf785af24aa380f3282d8d4400883d0099e (patch)
tree2966f60c6983ba2e09c0972da2c3cca51eecf140 /scripts
parent4963bb2b89884bbdb7e33e6a09c159551e9627aa (diff)
downloadlinux-48f7ddf785af24aa380f3282d8d4400883d0099e.tar.xz
init: Add support for zstd compressed kernel
- Add the zstd and zstd22 cmds to scripts/Makefile.lib - Add the HAVE_KERNEL_ZSTD and KERNEL_ZSTD options Architecture specific support is still needed for decompression. Signed-off-by: Nick Terrell <terrelln@fb.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Tested-by: Sedat Dilek <sedat.dilek@gmail.com> Reviewed-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20200730190841.2071656-4-nickrterrell@gmail.com
Diffstat (limited to 'scripts')
-rw-r--r--scripts/Makefile.lib22
1 files changed, 22 insertions, 0 deletions
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 916b2f7f7098..54f7b7eb580b 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -413,6 +413,28 @@ quiet_cmd_xzkern = XZKERN $@
quiet_cmd_xzmisc = XZMISC $@
cmd_xzmisc = cat $(real-prereqs) | $(XZ) --check=crc32 --lzma2=dict=1MiB > $@
+# ZSTD
+# ---------------------------------------------------------------------------
+# Appends the uncompressed size of the data using size_append. The .zst
+# format has the size information available at the beginning of the file too,
+# but it's in a 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 zstd tool think that
+# the file is corrupt. This is expected.
+#
+# zstd uses a maximum window size of 8 MB. zstd22 uses a maximum window size of
+# 128 MB. zstd22 is used for kernel compression because it is decompressed in a
+# single pass, so zstd doesn't need to allocate a window buffer. When streaming
+# decompression is used, like initramfs decompression, zstd22 should likely not
+# be used because it would require zstd to allocate a 128 MB buffer.
+
+quiet_cmd_zstd = ZSTD $@
+ cmd_zstd = { cat $(real-prereqs) | $(ZSTD) -19; $(size_append); } > $@
+
+quiet_cmd_zstd22 = ZSTD22 $@
+ cmd_zstd22 = { cat $(real-prereqs) | $(ZSTD) -22 --ultra; $(size_append); } > $@
+
# ASM offsets
# ---------------------------------------------------------------------------