287 lines
4.2 KiB
HTML
287 lines
4.2 KiB
HTML
<HTML
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><HEAD
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><TITLE
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>The Raw Loader</TITLE
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>SRM Firmware Howto</TH
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CLASS="SECT1"
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><H1
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CLASS="SECT1"
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><A
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NAME="AEN162"
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>4. The Raw Loader</A
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></H1
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><P
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>The sources for this loader can be found in directory
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<TT
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CLASS="LITERAL"
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>arch/alpha/boot</TT
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> of the Linux kernel source
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distribution. It loads the Linux kernel by reading
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<TT
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CLASS="LITERAL"
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>START_SIZE</TT
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> bytes starting at disk offset
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<TT
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CLASS="LITERAL"
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>BOOT_SIZE+512</TT
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> (also in bytes). The constants
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<TT
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CLASS="LITERAL"
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>START_SIZE</TT
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> and <TT
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CLASS="LITERAL"
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>BOOT_SIZE</TT
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> are defined in
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<TT
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CLASS="LITERAL"
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>linux/include/asm-alpha/system.h</TT
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>. <TT
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CLASS="LITERAL"
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>START_SIZE</TT
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>
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must be at least as big as the kernel image (i.e., the size of the
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<TT
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CLASS="LITERAL"
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>.text</TT
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>, <TT
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CLASS="LITERAL"
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>.data</TT
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>, and <TT
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CLASS="LITERAL"
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>.bss</TT
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> segments). Similarly,
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<TT
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CLASS="LITERAL"
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>BOOT_SIZE</TT
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> must be at least as big as the image of the raw
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bootstrap loader. Both constants should be an integer multiple of the
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sector size, which is 512 bytes. The default values are currently 2MB
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for <TT
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CLASS="LITERAL"
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>START_SIZE</TT
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> and 16KB for <TT
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CLASS="LITERAL"
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>BOOT_SIZE</TT
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>. Note
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that if you want to boot from a 1.44MB floppy disk, you have to reduce
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<TT
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CLASS="LITERAL"
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>START_SIZE</TT
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> to 1400KB and make sure that the kernel you
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want to boot is no bigger than that.</P
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><P
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>To build a raw loader, simply type <TT
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CLASS="LITERAL"
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>make rawboot</TT
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> in the top
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directory of your linux source tree (typically
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<TT
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CLASS="LITERAL"
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>/usr/src/linux</TT
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>). This should produce the following files in
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<TT
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CLASS="LITERAL"
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>arch/alpha/boot</TT
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>:</P
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><P
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><P
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></P
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><DIV
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CLASS="VARIABLELIST"
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><DL
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><DT
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><TT
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CLASS="LITERAL"
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>tools/lxboot</TT
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>:</DT
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><DD
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><P
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>The first
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sector on the disk. It contains the offset and size of
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the next file in the format described above.</P
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></DD
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><DT
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><TT
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CLASS="LITERAL"
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>tools/bootlx</TT
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>:</DT
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><DD
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><P
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>The raw boot loader that
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will load the file below.</P
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></DD
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><DT
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><TT
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CLASS="LITERAL"
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>vmlinux.nh</TT
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>:</DT
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><DD
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><P
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>The raw kernel image consisting of
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the <TT
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CLASS="LITERAL"
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>.text</TT
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>, <TT
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CLASS="LITERAL"
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>.data</TT
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>, and <TT
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CLASS="LITERAL"
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>.bss</TT
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> segments of the
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object file in <TT
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CLASS="LITERAL"
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>/usr/src/linux/vmlinux</TT
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>. The
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extension <TT
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CLASS="LITERAL"
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>.nh</TT
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> indicates that this file has no object-file
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header.</P
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></DD
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></DL
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></DIV
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></P
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><P
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>The concatenation of these three files should be written to the
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disk from which you want to boot. For example, to boot from a floppy,
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insert an empty floppy disk in, say, <TT
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CLASS="LITERAL"
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>/dev/fd0</TT
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> and then type:
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<TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="SCREEN"
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># cat tools/lxboot tools/bootlx vmlinux >/dev/fd0</PRE
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></TD
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></TR
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></TABLE
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> </P
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><P
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>You can then shutdown the system and boot from the floppy by
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issuing the command <TT
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CLASS="LITERAL"
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>boot dva0</TT
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>.</P
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></DIV
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><DIV
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ALIGN="center"
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HREF="index.html"
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>Home</A
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>SRM Device Naming</TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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> </TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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>The aboot Loader</TD
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