2008-07-30 Robert Millan <rmh@aybabtu.com>

* kern/ieee1275/init.c (grub_machine_set_prefix): If `grub_prefix'
        is non-empty, use it to set the `prefix' environment variable instead
        of the usual approach.
        * kern/i386/linuxbios/init.c (make_install_device): Remove function.
        (grub_machine_set_prefix): Use `grub_prefix' to set the `prefix'
        environment variable instead of dummy make_install_device().

        * kern/i386/ieee1275/startup.S: Include `<grub/machine/kernel.h>'.
        (start): Insert a data section, with `grub_prefix' variable.
        * kern/i386/linuxbios/startup.S: Likewise.

        * include/grub/powerpc/ieee1275/kernel.h [!ASM_FILE] (grub_prefix):
        New variable reference.
        * include/grub/i386/ieee1275/kernel.h (GRUB_KERNEL_MACHINE_PREFIX):
        New macro.  Defines offset of `grub_prefix' within startup.S (relative
        to `start').
        (GRUB_KERNEL_MACHINE_DATA_END): New macro.  Defines the end of data
        section within startup.S (relative to `start').
        * include/grub/i386/coreboot/kernel.h: Likewise.

        * util/elf/grub-mkimage.c (add_segments): Receive `prefix' parameter.
        Overwrite grub_prefix with its contents, at the beginning of the
        first segment.
        (main): Understand -p|--prefix.

kern/i386/ieee1275/startup.S

@@ -19,6 +19,7 @@
 #define ASM_FILE	1
 
 #include <grub/symbol.h>
+#include <grub/machine/kernel.h>
 #include <grub/machine/memory.h>
 #include <grub/cpu/linux.h>
 #include <multiboot.h>
@@ -38,6 +39,24 @@
 
 start:
 _start:
+	jmp codestart
+
+	/*
+	 *  This is a special data area at a fixed offset from the beginning.
+	 */
+
+	. = EXT_C(start) + GRUB_KERNEL_MACHINE_PREFIX
+
+VARIABLE(grub_prefix)
+	/* to be filled by grub-mkimage */
+
+	/*
+	 *  Leave some breathing room for the prefix.
+	 */
+
+	. = EXT_C(start) + GRUB_KERNEL_MACHINE_DATA_END
+
+codestart:
 	movl %eax, EXT_C(grub_ieee1275_entry_fn)
 	jmp EXT_C(grub_main)