The sources for this loader can be found in directory
arch/alpha/boot of the Linux kernel source
distribution. It loads the Linux kernel by reading
START_SIZE
bytes starting at disk offset
BOOT_SIZE
+512
(also in bytes). The constants
START_SIZE
and BOOT_SIZE
are defined in
linux/include/asm-alpha/system.h.
START_SIZE
must be at least as big as the kernel image (i.e., the size of the
.text, .data, and .bss segments). Similarly,
BOOT_SIZE
must be at least as big as the image of the
raw bootstrap loader. Both constants should be an integer multiple of the
sector size, which is 512 bytes. The default values are currently 2MB
for START_SIZE
and 16KB for
BOOT_SIZE
. Note
that if you want to boot from a 1.44MB floppy disk, you have to reduce
START_SIZE
to 1400KB and make sure that the kernel you
want to boot is no bigger than that.
To build a raw loader, simply type make rawboot in the top directory of your linux source tree (typically /usr/src/linux). This should produce the following files in arch/alpha/boot:
The first sector on the disk. It contains the offset and size of the next file in the format described above.
The raw boot loader that will load the file below.
The raw kernel image consisting of the .text, .data, and .bss segments of the object file in /usr/src/linux/vmlinux. The extension .nh indicates that this file has no object-file header.
The concatenation of these three files should be written to the disk from which you want to boot. For example, to boot from a floppy, insert an empty floppy disk in, say, /dev/fd0 and then type:
# cat tools/lxboot tools/bootlx vmlinux >/dev/fd0 |
You can then shutdown the system and boot from the floppy by issuing the command boot dva0.