3ebe12439b
This implements the API defined in <linux/decompress/generic.h> which is used for kernel, initramfs, and initrd decompression. This patch together with the first patch is enough for XZ-compressed initramfs and initrd; XZ-compressed kernel will need arch-specific changes. The buffering requirements described in decompress_unxz.c are stricter than with gzip, so the relevant changes should be done to the arch-specific code when adding support for XZ-compressed kernel. Similarly, the heap size in arch-specific pre-boot code may need to be increased (30 KiB is enough). The XZ decompressor needs memmove(), memeq() (memcmp() == 0), and memzero() (memset(ptr, 0, size)), which aren't available in all arch-specific pre-boot environments. I'm including simple versions in decompress_unxz.c, but a cleaner solution would naturally be nicer. Signed-off-by: Lasse Collin <lasse.collin@tukaani.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Alain Knaff <alain@knaff.lu> Cc: Albin Tonnerre <albin.tonnerre@free-electrons.com> Cc: Phillip Lougher <phillip@lougher.demon.co.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
169 lines
5.3 KiB
Plaintext
169 lines
5.3 KiB
Plaintext
#
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# Configuration for initramfs
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#
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config INITRAMFS_SOURCE
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string "Initramfs source file(s)"
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default ""
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help
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This can be either a single cpio archive with a .cpio suffix or a
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space-separated list of directories and files for building the
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initramfs image. A cpio archive should contain a filesystem archive
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to be used as an initramfs image. Directories should contain a
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filesystem layout to be included in the initramfs image. Files
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should contain entries according to the format described by the
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"usr/gen_init_cpio" program in the kernel tree.
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When multiple directories and files are specified then the
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initramfs image will be the aggregate of all of them.
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See <file:Documentation/early-userspace/README> for more details.
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If you are not sure, leave it blank.
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config INITRAMFS_ROOT_UID
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int "User ID to map to 0 (user root)"
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depends on INITRAMFS_SOURCE!=""
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default "0"
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help
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This setting is only meaningful if the INITRAMFS_SOURCE is
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contains a directory. Setting this user ID (UID) to something
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other than "0" will cause all files owned by that UID to be
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owned by user root in the initial ramdisk image.
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If you are not sure, leave it set to "0".
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config INITRAMFS_ROOT_GID
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int "Group ID to map to 0 (group root)"
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depends on INITRAMFS_SOURCE!=""
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default "0"
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help
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This setting is only meaningful if the INITRAMFS_SOURCE is
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contains a directory. Setting this group ID (GID) to something
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other than "0" will cause all files owned by that GID to be
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owned by group root in the initial ramdisk image.
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If you are not sure, leave it set to "0".
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config RD_GZIP
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bool "Support initial ramdisks compressed using gzip" if EMBEDDED
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default y
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depends on BLK_DEV_INITRD
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select DECOMPRESS_GZIP
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help
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Support loading of a gzip encoded initial ramdisk or cpio buffer.
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If unsure, say Y.
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config RD_BZIP2
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bool "Support initial ramdisks compressed using bzip2" if EMBEDDED
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default !EMBEDDED
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depends on BLK_DEV_INITRD
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select DECOMPRESS_BZIP2
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help
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Support loading of a bzip2 encoded initial ramdisk or cpio buffer
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If unsure, say N.
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config RD_LZMA
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bool "Support initial ramdisks compressed using LZMA" if EMBEDDED
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default !EMBEDDED
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depends on BLK_DEV_INITRD
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select DECOMPRESS_LZMA
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help
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Support loading of a LZMA encoded initial ramdisk or cpio buffer
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If unsure, say N.
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config RD_XZ
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bool "Support initial ramdisks compressed using XZ" if EMBEDDED
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default !EMBEDDED
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depends on BLK_DEV_INITRD
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select DECOMPRESS_XZ
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help
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Support loading of a XZ encoded initial ramdisk or cpio buffer.
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If unsure, say N.
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config RD_LZO
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bool "Support initial ramdisks compressed using LZO" if EMBEDDED
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default !EMBEDDED
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depends on BLK_DEV_INITRD
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select DECOMPRESS_LZO
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help
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Support loading of a LZO encoded initial ramdisk or cpio buffer
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If unsure, say N.
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choice
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prompt "Built-in initramfs compression mode" if INITRAMFS_SOURCE!=""
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help
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This option decides by which algorithm the builtin initramfs
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will be compressed. Several compression algorithms are
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available, which differ in efficiency, compression and
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decompression speed. Compression speed is only relevant
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when building a kernel. Decompression speed is relevant at
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each boot.
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If you have any problems with bzip2 or LZMA compressed
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initramfs, mail me (Alain Knaff) <alain@knaff.lu>.
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High compression options are mostly useful for users who are
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low on RAM, since it reduces the memory consumption during
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boot.
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If in doubt, select 'gzip'
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config INITRAMFS_COMPRESSION_NONE
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bool "None"
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help
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Do not compress the built-in initramfs at all. This may
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sound wasteful in space, but, you should be aware that the
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built-in initramfs will be compressed at a later stage
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anyways along with the rest of the kernel, on those
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architectures that support this.
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However, not compressing the initramfs may lead to slightly
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higher memory consumption during a short time at boot, while
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both the cpio image and the unpacked filesystem image will
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be present in memory simultaneously
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config INITRAMFS_COMPRESSION_GZIP
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bool "Gzip"
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depends on RD_GZIP
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help
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The old and tried gzip compression. It provides a good balance
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between compression ratio and decompression speed.
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config INITRAMFS_COMPRESSION_BZIP2
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bool "Bzip2"
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depends on RD_BZIP2
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help
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Its compression ratio and speed is intermediate.
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Decompression speed is slowest among the four. The initramfs
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size is about 10% smaller with bzip2, in comparison to gzip.
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Bzip2 uses a large amount of memory. For modern kernels you
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will need at least 8MB RAM or more for booting.
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config INITRAMFS_COMPRESSION_LZMA
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bool "LZMA"
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depends on RD_LZMA
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help
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The most recent compression algorithm.
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Its ratio is best, decompression speed is between the other
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three. Compression is slowest. The initramfs size is about 33%
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smaller with LZMA in comparison to gzip.
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config INITRAMFS_COMPRESSION_XZ
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bool "XZ"
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depends on RD_XZ
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help
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XZ uses the LZMA2 algorithm. The initramfs size is about 30%
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smaller with XZ in comparison to gzip. Decompression speed
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is better than that of bzip2 but worse than gzip and LZO.
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Compression is slow.
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config INITRAMFS_COMPRESSION_LZO
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bool "LZO"
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depends on RD_LZO
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help
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Its compression ratio is the poorest among the four. The kernel
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size is about 10% bigger than gzip; however its speed
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(both compression and decompression) is the fastest.
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endchoice
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