initramfs: add support for in-kernel initramfs compressed with LZO

Add the necessary parts to be enable the use of LZO-compressed initramfs
build into the kernel.

Signed-off-by: Albin Tonnerre <albin.tonnerre@free-electrons.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Michal Marek <mmarek@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/usr/initramfs_data.lzo.S b/usr/initramfs_data.lzo.S
new file mode 100644
index 0000000..5921190
--- /dev/null
+++ b/usr/initramfs_data.lzo.S
@@ -0,0 +1,29 @@
+/*
+  initramfs_data includes the compressed binary that is the
+  filesystem used for early user space.
+  Note: Older versions of "as" (prior to binutils 2.11.90.0.23
+  released on 2001-07-14) dit not support .incbin.
+  If you are forced to use older binutils than that then the
+  following trick can be applied to create the resulting binary:
+
+
+  ld -m elf_i386  --format binary --oformat elf32-i386 -r \
+  -T initramfs_data.scr initramfs_data.cpio.gz -o initramfs_data.o
+   ld -m elf_i386  -r -o built-in.o initramfs_data.o
+
+  initramfs_data.scr looks like this:
+SECTIONS
+{
+       .init.ramfs : { *(.data) }
+}
+
+  The above example is for i386 - the parameters vary from architectures.
+  Eventually look up LDFLAGS_BLOB in an older version of the
+  arch/$(ARCH)/Makefile to see the flags used before .incbin was introduced.
+
+  Using .incbin has the advantage over ld that the correct flags are set
+  in the ELF header, as required by certain architectures.
+*/
+
+.section .init.ramfs,"a"
+.incbin "usr/initramfs_data.cpio.lzo"