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2008-08-12 Robert Millan <rmh@aybabtu.com>

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* loader/i386/pc/multiboot.c (grub_multiboot_load_elf32): Move part
        of the relocation code from here ...
        (grub_multiboot): ... to here.
        (forward_relocator, backward_relocator): Move from here ...
        * kern/i386/loader.S (grub_multiboot_forward_relocator)
        (grub_multiboot_backward_relocator): ... to here.
        (grub_multiboot_real_boot): Use %edx for entry offset.  Put Multiboot
        magic in %eax.  Use %ebp for jumping (so %edx is not trashed).
        * include/grub/i386/loader.h (grub_multiboot_forward_relocator)
        (grub_multiboot_forward_relocator_end)
        (grub_multiboot_backward_relocator)
        (grub_multiboot_backward_relocator_end): New variables.
This commit is contained in:
robertmh 2008-08-12 15:40:26 +00:00
parent 05f9452b12
commit 371458b576
4 changed files with 113 additions and 56 deletions
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41
kern/i386/loader.S
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@ -132,6 +132,36 @@ VARIABLE(grub_multiboot_payload_dest)
VARIABLE(grub_multiboot_payload_entry_offset)
.long 0
/*
* The relocators below understand the following parameters:
* ecx: Size of the block to be copied.
* esi: Where to copy from (always lowest address, even if we're relocating
* backwards).
* edi: Where to copy to (likewise).
* edx: Offset of the entry point (relative to the beginning of the block).
*/
VARIABLE(grub_multiboot_forward_relocator)
cld
addl %edi, %edx
rep
movsb
jmp *%edx
VARIABLE(grub_multiboot_forward_relocator_end)
VARIABLE(grub_multiboot_backward_relocator)
std
addl %ecx, %esi
addl %ecx, %edi
/* backward movsb is implicitly off-by-one. compensate that. */
incl %ecx
rep
movsb
/* same problem again. */
incl %edi
addl %edi, %edx
jmp *%edx
VARIABLE(grub_multiboot_backward_relocator_end)
FUNCTION(grub_multiboot_real_boot)
/* Push the entry address on the stack. */
pushl %eax
@ -149,11 +179,14 @@ FUNCTION(grub_multiboot_real_boot)
movl EXT_C(grub_multiboot_payload_size), %ecx
movl EXT_C(grub_multiboot_payload_orig), %esi
movl EXT_C(grub_multiboot_payload_dest), %edi
movl EXT_C(grub_multiboot_payload_entry_offset), %eax
movl EXT_C(grub_multiboot_payload_entry_offset), %edx
/* Move the magic value into eax. */
movl $MULTIBOOT_MAGIC2, %eax
/* Jump to the relocator. */
popl %edx
jmp *%edx
popl %ebp
jmp *%ebp
/*
* This starts the multiboot 2 kernel.