grub/lib/i386/relocator.c

/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 2009  Free Software Foundation, Inc.
 *
 *  GRUB is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  GRUB is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <grub/mm.h>
#include <grub/misc.h>

#include <grub/types.h>
#include <grub/err.h>
#include <grub/term.h>

#include <grub/i386/relocator.h>
#include <grub/relocator_private.h>

extern grub_uint8_t grub_relocator32_start;
extern grub_uint8_t grub_relocator32_end;
extern grub_uint8_t grub_relocator_forward_start;
extern grub_uint8_t grub_relocator_forward_end;
extern grub_uint8_t grub_relocator_backward_start;
extern grub_uint8_t grub_relocator_backward_end;

extern void *grub_relocator_backward_dest;
extern void *grub_relocator_backward_src;
extern grub_size_t grub_relocator_backward_chunk_size;

extern void *grub_relocator_forward_dest;
extern void *grub_relocator_forward_src;
extern grub_size_t grub_relocator_forward_chunk_size;

extern grub_uint32_t grub_relocator32_eax;
extern grub_uint32_t grub_relocator32_ebx;
extern grub_uint32_t grub_relocator32_ecx;
extern grub_uint32_t grub_relocator32_edx;
extern grub_uint32_t grub_relocator32_eip;
extern grub_uint32_t grub_relocator32_esp;

#define RELOCATOR_SIZEOF(x)	(&grub_relocator##x##_end - &grub_relocator##x##_start)

grub_size_t grub_relocator_align = 1;
grub_size_t grub_relocator_forward_size;
grub_size_t grub_relocator_backward_size;
grub_size_t grub_relocator_jumper_size = 10;

void
grub_cpu_relocator_init (void)
{
  grub_relocator_forward_size = RELOCATOR_SIZEOF(_forward);
  grub_relocator_backward_size = RELOCATOR_SIZEOF(_backward);
}

void
grub_cpu_relocator_jumper (void *rels, grub_addr_t addr)
{
  grub_uint8_t *ptr;
  ptr = rels;
  /* movl $addr, %eax (for relocator) */
  *(grub_uint8_t *) ptr = 0xb8;
  ptr++;
  *(grub_uint32_t *) ptr = addr;
  ptr += 4;
  /* jmp $addr */
  *(grub_uint8_t *) ptr = 0xe9;
  ptr++;
  *(grub_uint32_t *) ptr = addr - (grub_uint32_t) (ptr + 4);
  ptr += 4;
}

void
grub_cpu_relocator_backward (void *ptr, void *src, void *dest,
			     grub_size_t size)
{
  grub_relocator_backward_dest = dest;
  grub_relocator_backward_src = src;
  grub_relocator_backward_chunk_size = size;

  grub_memmove (ptr,
		&grub_relocator_backward_start,
		RELOCATOR_SIZEOF (_backward));
}

void
grub_cpu_relocator_forward (void *ptr, void *src, void *dest,
			     grub_size_t size)
{
  grub_relocator_forward_dest = dest;
  grub_relocator_forward_src = src;
  grub_relocator_forward_chunk_size = size;

  grub_memmove (ptr,
		&grub_relocator_forward_start,
		RELOCATOR_SIZEOF (_forward));
}

grub_err_t
grub_relocator32_boot (struct grub_relocator *rel,
		       struct grub_relocator32_state state)
{
  grub_addr_t target;
  void *src;
  grub_err_t err;
  grub_addr_t relst;

  err = grub_relocator_alloc_chunk_align (rel, &src, &target, 0,
					  (0xffffffff - RELOCATOR_SIZEOF (32))
					  + 1, RELOCATOR_SIZEOF (32), 16);
  if (err)
    return err;

  grub_relocator32_eax = state.eax;
  grub_relocator32_ebx = state.ebx;
  grub_relocator32_ecx = state.ecx;
  grub_relocator32_edx = state.edx;
  grub_relocator32_eip = state.eip;
  grub_relocator32_esp = state.esp;

  grub_memmove (src, &grub_relocator32_start, RELOCATOR_SIZEOF (32));

  err = grub_relocator_prepare_relocs (rel, target, &relst);
  if (err)
    return err;

  asm volatile ("cli");
  ((void (*) (void)) relst) ();

  /* Not reached.  */
  return GRUB_ERR_NONE;
}