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grub/grub-core/kern/arm/dl.c

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/* dl.c - arch-dependent part of loadable module support */
/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2013 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/dl.h>
#include <grub/elf.h>
#include <grub/misc.h>
#include <grub/err.h>
#include <grub/mm.h>
#include <grub/i18n.h>
#include <grub/arm/reloc.h>
struct trampoline_arm
{
#define ARM_LOAD_IP 0xe59fc000
#define ARM_BX 0xe12fff1c
#define ARM_MOV_PC 0xe1a0f00c
grub_uint32_t load_ip; /* ldr ip, [pc] */
grub_uint32_t bx; /* bx ip or mov pc, ip*/
grub_uint32_t addr;
};
static grub_uint16_t thumb_template[8] =
{
0x468c, /* mov ip, r1 */
0x4903, /* ldr r1, [pc, #12] ; (10 <.text+0x10>) */
/* Exchange R1 and IP in limited Thumb instruction set.
IP gets negated but we compensate it by C code. */
/* R1 IP */
/* -A R1 */
0x4461, /* add r1, ip */ /* R1-A R1 */
0x4249, /* negs r1, r1 */ /* A-R1 R1 */
0x448c, /* add ip, r1 */ /* A-R1 A */
0x4249, /* negs r1, r1 */ /* R1-A A */
0x4461, /* add r1, ip */ /* R1 A */
0x4760 /* bx ip */
};
struct trampoline_thumb
{
grub_uint16_t template[8];
grub_uint32_t neg_addr;
};
#pragma GCC diagnostic ignored "-Wcast-align"
grub_err_t
grub_arch_dl_get_tramp_got_size (const void *ehdr, grub_size_t *tramp,
grub_size_t *got)
{
const Elf_Ehdr *e = ehdr;
const Elf_Shdr *s;
unsigned i;
*tramp = 0;
*got = 0;
for (i = 0, s = (const Elf_Shdr *) ((grub_addr_t) e + e->e_shoff);
i < e->e_shnum;
i++, s = (const Elf_Shdr *) ((grub_addr_t) s + e->e_shentsize))
if (s->sh_type == SHT_REL)
{
const Elf_Rel *rel, *max;
for (rel = (const Elf_Rel *) ((grub_addr_t) e + s->sh_offset),
max = (const Elf_Rel *) ((grub_addr_t) rel + s->sh_size);
rel + 1 <= max;
rel = (const Elf_Rel *) ((grub_addr_t) rel + s->sh_entsize))
switch (ELF_R_TYPE (rel->r_info))
{
case R_ARM_CALL:
case R_ARM_JUMP24:
{
*tramp += sizeof (struct trampoline_arm);
break;
}
case R_ARM_THM_CALL:
case R_ARM_THM_JUMP24:
case R_ARM_THM_JUMP19:
{
*tramp += sizeof (struct trampoline_thumb);
break;
}
}
}
grub_dprintf ("dl", "trampoline size %x\n", *tramp);
return GRUB_ERR_NONE;
}
/*************************************************
* Runtime dynamic linker with helper functions. *
*************************************************/
grub_err_t
grub_arch_dl_relocate_symbols (grub_dl_t mod, void *ehdr,
Elf_Shdr *s, grub_dl_segment_t seg)
{
Elf_Rel *rel, *max;
for (rel = (Elf_Rel *) ((char *) ehdr + s->sh_offset),
max = (Elf_Rel *) ((char *) rel + s->sh_size);
rel < max;
rel = (Elf_Rel *) ((char *) rel + s->sh_entsize))
{
Elf_Addr *target, sym_addr;
grub_err_t retval;
Elf_Sym *sym;
if (seg->size < rel->r_offset)
return grub_error (GRUB_ERR_BAD_MODULE,
"reloc offset is out of the segment");
target = (void *) ((char *) seg->addr + rel->r_offset);
sym = (Elf_Sym *) ((char *) mod->symtab
+ mod->symsize * ELF_R_SYM (rel->r_info));
sym_addr = sym->st_value;
switch (ELF_R_TYPE (rel->r_info))
{
case R_ARM_ABS32:
{
/* Data will be naturally aligned */
retval = grub_arm_reloc_abs32 (target, sym_addr);
if (retval != GRUB_ERR_NONE)
return retval;
}
break;
case R_ARM_CALL:
case R_ARM_JUMP24:
{
grub_int32_t offset;
sym_addr += grub_arm_jump24_get_offset (target);
offset = sym_addr - (grub_uint32_t) target;
if ((sym_addr & 1) || !grub_arm_jump24_check_offset (offset))
{
struct trampoline_arm *tp = mod->trampptr;
mod->trampptr = tp + 1;
tp->load_ip = ARM_LOAD_IP;
tp->bx = (sym_addr & 1) ? ARM_BX : ARM_MOV_PC;
tp->addr = sym_addr + 8;
offset = (grub_uint8_t *) tp - (grub_uint8_t *) target - 8;
}
if (!grub_arm_jump24_check_offset (offset))
return grub_error (GRUB_ERR_BAD_MODULE,
"trampoline out of range");
grub_arm_jump24_set_offset (target, offset);
}
break;
case R_ARM_THM_CALL:
case R_ARM_THM_JUMP24:
{
/* Thumb instructions can be 16-bit aligned */
grub_int32_t offset;
sym_addr += grub_arm_thm_call_get_offset ((grub_uint16_t *) target);
grub_dprintf ("dl", " sym_addr = 0x%08x\n", sym_addr);
if (ELF_ST_TYPE (sym->st_info) != STT_FUNC)
sym_addr |= 1;
offset = sym_addr - (grub_uint32_t) target;
grub_dprintf("dl", " BL*: target=%p, sym_addr=0x%08x, offset=%d\n",
target, sym_addr, offset);
if (!(sym_addr & 1) || (offset < -0x200000 || offset >= 0x200000))
{
struct trampoline_thumb *tp = mod->trampptr;
mod->trampptr = tp + 1;
grub_memcpy (tp->template, thumb_template, sizeof (tp->template));
tp->neg_addr = -sym_addr - 4;
offset = ((grub_uint8_t *) tp - (grub_uint8_t *) target - 4) | 1;
}
if (offset < -0x200000 || offset >= 0x200000)
return grub_error (GRUB_ERR_BAD_MODULE,
"trampoline out of range");
grub_dprintf ("dl", " relative destination = %p\n",
(char *) target + offset);
retval = grub_arm_thm_call_set_offset ((grub_uint16_t *) target, offset);
if (retval != GRUB_ERR_NONE)
return retval;
}
break;
/* Happens when compiled with -march=armv4. Since currently we need
at least armv5, keep bx as-is.
*/
case R_ARM_V4BX:
break;
case R_ARM_THM_MOVW_ABS_NC:
case R_ARM_THM_MOVT_ABS:
{
grub_uint32_t offset;
offset = grub_arm_thm_movw_movt_get_value((grub_uint16_t *) target);
offset += sym_addr;
if (ELF_R_TYPE (rel->r_info) == R_ARM_THM_MOVT_ABS)
offset >>= 16;
else
offset &= 0xffff;
grub_arm_thm_movw_movt_set_value((grub_uint16_t *) target, offset);
}
break;
case R_ARM_THM_JUMP19:
{
/* Thumb instructions can be 16-bit aligned */
grub_int32_t offset;
sym_addr += grub_arm_thm_jump19_get_offset ((grub_uint16_t *) target);
if (ELF_ST_TYPE (sym->st_info) != STT_FUNC)
sym_addr |= 1;
offset = sym_addr - (grub_uint32_t) target;
if (!grub_arm_thm_jump19_check_offset (offset)
|| !(sym_addr & 1))
{
struct trampoline_thumb *tp = mod->trampptr;
mod->trampptr = tp + 1;
grub_memcpy (tp->template, thumb_template, sizeof (tp->template));
tp->neg_addr = -sym_addr - 4;
offset = ((grub_uint8_t *) tp - (grub_uint8_t *) target - 4) | 1;
}
if (!grub_arm_thm_jump19_check_offset (offset))
return grub_error (GRUB_ERR_BAD_MODULE,
"trampoline out of range");
grub_arm_thm_jump19_set_offset ((grub_uint16_t *) target, offset);
}
break;
default:
return grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
N_("relocation 0x%x is not implemented yet"),
ELF_R_TYPE (rel->r_info));
}
}
return GRUB_ERR_NONE;
}
/*
* Check if EHDR is a valid ELF header.
*/
grub_err_t
grub_arch_dl_check_header (void *ehdr)
{
Elf_Ehdr *e = ehdr;
/* Check the magic numbers. */
if (e->e_ident[EI_CLASS] != ELFCLASS32
|| e->e_ident[EI_DATA] != ELFDATA2LSB || e->e_machine != EM_ARM)
return grub_error (GRUB_ERR_BAD_OS,
N_("invalid arch-dependent ELF magic"));
return GRUB_ERR_NONE;
}
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