bzip2/lzma: make internal initramfs compression configurable

Impact: Avoids silent environment dependency Make builtin initramfs compression an explicit configurable. The previous version would pick a compression based on the binaries which were installed on the system, which could lead to unexpected results. It is now explicitly configured, and not having the appropriate binaries installed on the build host is simply an error. Signed-off-by: Alain Knaff <alain@knaff.lu> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

bzip2/lzma: make internal initramfs compression configurable
Impact: Avoids silent environment dependency Make builtin initramfs compression an explicit configurable. The previous version would pick a compression based on the binaries which were installed on the system, which could lead to unexpected results. It is now explicitly configured, and not having the appropriate binaries installed on the build host is simply an error. Signed-off-by: Alain Knaff <alain@knaff.lu> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Alain Knaff · H. Peter Anvin
1 parent ab59d3b70f
Showing 2 changed files with 68 additions and 12 deletions Side-by-side Diff
usr/Kconfig
usr/Makefile
@@ -71,4 +71,66 @@
 	help
 	  Support loading of a lzma encoded initial ramdisk or cpio buffer
 	  If unsure, say N.
+
+choice
+	prompt "Built-in initramfs compression mode"
+	help
+	  This setting is only meaningful if the INITRAMFS_SOURCE is
+	  set. It decides by which algorithm the INITRAMFS_SOURCE will
+	  be compressed.
+	  Several compression algorithms are available, which differ
+	  in efficiency, compression and decompression speed.
+	  Compression speed is only relevant when building a kernel.
+	  Decompression speed is relevant at each boot.
+
+	  If you have any problems with bzip2 or lzma compressed
+	  initramfs, mail me (Alain Knaff) <alain@knaff.lu>.
+
+	  High compression options are mostly useful for users who
+	  are low on disk space (embedded systems), but for whom ram
+	  size matters less.
+
+	  If in doubt, select 'gzip'
+
+config INITRAMFS_COMPRESSION_NONE
+	bool "None"
+	help
+	  Do not compress the built-in initramfs at all. This may
+	  sound wasteful in space, but, you should be aware that the
+	  built-in initramfs will be compressed at a later stage
+	  anyways along with the rest of the kernel, on those
+	  architectures that support this.
+	  However, not compressing the initramfs may lead to slightly
+	  higher memory consumption during a short time at boot, while
+	  both the cpio image and the unpacked filesystem image will
+	  be present in memory simultaneously
+
+config INITRAMFS_COMPRESSION_GZIP
+	bool "Gzip"
+	depends on RD_GZIP
+	help
+	  The old and tried gzip compression. Its compression ratio is
+	  the poorest among the 3 choices; however its speed (both
+	  compression and decompression) is the fastest.
+
+config INITRAMFS_COMPRESSION_BZIP2
+	bool "Bzip2"
+	depends on RD_BZIP2
+	help
+	  Its compression ratio and speed is intermediate.
+	  Decompression speed is slowest among the three.  The initramfs
+	  size is about 10% smaller with bzip2, in comparison to gzip.
+	  Bzip2 uses a large amount of memory. For modern kernels you
+	  will need at least 8MB RAM or more for booting.
+
+config INITRAMFS_COMPRESSION_LZMA
+	bool "LZMA"
+	depends on RD_LZMA
+	help
+	  The most recent compression algorithm.
+	  Its ratio is best, decompression speed is between the other
+	  two. Compression is slowest.	The initramfs size is about 33%
+	  smaller with LZMA in comparison to gzip.
+
+endchoice
@@ -5,24 +5,18 @@
 klibcdirs:;
 PHONY += klibcdirs
  
-# Find out "preferred" ramdisk compressor. Order of preference is
-#  1. bzip2 efficient, and likely to be present
-#  2. gzip former default
-#  3. lzma
-#  4. none
  
-# None of the above
-suffix_y                   =
+# No compression
+suffix_$(CONFIG_INITRAMFS_COMPRESSION_NONE)   =
  
-# Lzma, but no gzip nor bzip2
-suffix_$(CONFIG_RD_LZMA)   = .lzma
-
 # Gzip, but no bzip2
-suffix_$(CONFIG_RD_GZIP)   = .gz
+suffix_$(CONFIG_INITRAMFS_COMPRESSION_GZIP)   = .gz
  
 # Bzip2
-suffix_$(CONFIG_RD_BZIP2)  = .bz2
+suffix_$(CONFIG_INITRAMFS_COMPRESSION_BZIP2)  = .bz2
  
+# Lzma
+suffix_$(CONFIG_INITRAMFS_COMPRESSION_LZMA)   = .lzma
  
 # Generate builtin.o based on initramfs_data.o
 obj-$(CONFIG_BLK_DEV_INITRD) := initramfs_data$(suffix_y).o
...	...	@@ -71,4 +71,66 @@
71	71	help
72	72	Support loading of a lzma encoded initial ramdisk or cpio buffer
73	73	If unsure, say N.
	74	+
	75	+choice
	76	+ prompt "Built-in initramfs compression mode"
	77	+ help
	78	+ This setting is only meaningful if the INITRAMFS_SOURCE is
	79	+ set. It decides by which algorithm the INITRAMFS_SOURCE will
	80	+ be compressed.
	81	+ Several compression algorithms are available, which differ
	82	+ in efficiency, compression and decompression speed.
	83	+ Compression speed is only relevant when building a kernel.
	84	+ Decompression speed is relevant at each boot.
	85	+
	86	+ If you have any problems with bzip2 or lzma compressed
	87	+ initramfs, mail me (Alain Knaff) <alain@knaff.lu>.
	88	+
	89	+ High compression options are mostly useful for users who
	90	+ are low on disk space (embedded systems), but for whom ram
	91	+ size matters less.
	92	+
	93	+ If in doubt, select 'gzip'
	94	+
	95	+config INITRAMFS_COMPRESSION_NONE
	96	+ bool "None"
	97	+ help
	98	+ Do not compress the built-in initramfs at all. This may
	99	+ sound wasteful in space, but, you should be aware that the
	100	+ built-in initramfs will be compressed at a later stage
	101	+ anyways along with the rest of the kernel, on those
	102	+ architectures that support this.
	103	+ However, not compressing the initramfs may lead to slightly
	104	+ higher memory consumption during a short time at boot, while
	105	+ both the cpio image and the unpacked filesystem image will
	106	+ be present in memory simultaneously
	107	+
	108	+config INITRAMFS_COMPRESSION_GZIP
	109	+ bool "Gzip"
	110	+ depends on RD_GZIP
	111	+ help
	112	+ The old and tried gzip compression. Its compression ratio is
	113	+ the poorest among the 3 choices; however its speed (both
	114	+ compression and decompression) is the fastest.
	115	+
	116	+config INITRAMFS_COMPRESSION_BZIP2
	117	+ bool "Bzip2"
	118	+ depends on RD_BZIP2
	119	+ help
	120	+ Its compression ratio and speed is intermediate.
	121	+ Decompression speed is slowest among the three. The initramfs
	122	+ size is about 10% smaller with bzip2, in comparison to gzip.
	123	+ Bzip2 uses a large amount of memory. For modern kernels you
	124	+ will need at least 8MB RAM or more for booting.
	125	+
	126	+config INITRAMFS_COMPRESSION_LZMA
	127	+ bool "LZMA"
	128	+ depends on RD_LZMA
	129	+ help
	130	+ The most recent compression algorithm.
	131	+ Its ratio is best, decompression speed is between the other
	132	+ two. Compression is slowest. The initramfs size is about 33%
	133	+ smaller with LZMA in comparison to gzip.
	134	+
	135	+endchoice
...	...	@@ -5,24 +5,18 @@
5	5	klibcdirs:;
6	6	PHONY += klibcdirs
7	7
8		-# Find out "preferred" ramdisk compressor. Order of preference is
9		-# 1. bzip2 efficient, and likely to be present
10		-# 2. gzip former default
11		-# 3. lzma
12		-# 4. none
13	8
14		-# None of the above
15		-suffix_y =
	9	+# No compression
	10	+suffix_$(CONFIG_INITRAMFS_COMPRESSION_NONE) =
16	11
17		-# Lzma, but no gzip nor bzip2
18		-suffix_$(CONFIG_RD_LZMA) = .lzma
19		-
20	12	# Gzip, but no bzip2
21		-suffix_$(CONFIG_RD_GZIP) = .gz
	13	+suffix_$(CONFIG_INITRAMFS_COMPRESSION_GZIP) = .gz
22	14
23	15	# Bzip2
24		-suffix_$(CONFIG_RD_BZIP2) = .bz2
	16	+suffix_$(CONFIG_INITRAMFS_COMPRESSION_BZIP2) = .bz2
25	17
	18	+# Lzma
	19	+suffix_$(CONFIG_INITRAMFS_COMPRESSION_LZMA) = .lzma
26	20
27	21	# Generate builtin.o based on initramfs_data.o
28	22	obj-$(CONFIG_BLK_DEV_INITRD) := initramfs_data$(suffix_y).o