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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>
#ifdef GRUB_UTIL
# include <grub/util/misc.h>
#else
# if !defined(__thumb2__)
# error "Relocations not implemented for A32 ("ARM") instruction set yet!"
# endif
grub_err_t reloc_jump24 (grub_uint32_t *addr, Elf32_Addr sym_addr);
grub_err_t reloc_thm_call (grub_uint16_t *addr, Elf32_Addr sym_addr);
grub_err_t reloc_thm_jump19 (grub_uint16_t *addr, Elf32_Addr sym_addr);
#ifdef DL_DEBUG
static const char *symstrtab;
/*
* This is a bit of a hack, setting the symstrtab pointer to the last STRTAB
* section in the module (which is where symbol names are in the objects I've
* inspected manually).
*/
static void
set_symstrtab (Elf_Ehdr * e)
{
int i;
Elf_Shdr *s;
symstrtab = NULL;
for (i = 0, s = (Elf_Shdr *) ((grub_uint32_t) e + e->e_shoff);
i < e->e_shnum;
i++, s = (Elf_Shdr *) ((grub_uint32_t) s + e->e_shentsize))
if (s->sh_type == SHT_STRTAB)
symstrtab = (void *) ((grub_addr_t) e + s->sh_offset);
}
static const char *
get_symbolname (Elf_Sym * sym)
{
const char *symbolname = symstrtab + sym->st_name;
return (*symbolname ? symbolname : NULL);
}
#endif /* DL_DEBUG */
/*
* R_ARM_ABS32
*
* Simple relocation of 32-bit value (in literal pool)
*/
static grub_err_t
reloc_abs32 (Elf_Word *target, Elf_Addr sym_addr)
{
Elf_Addr tmp;
tmp = *target;
tmp += sym_addr;
*target = tmp;
#if 0 //def GRUB_UTIL
grub_util_info (" %s: reloc_abs32 0x%08x => 0x%08x", __FUNCTION__,
(unsigned int) sym_addr, (unsigned int) tmp);
#endif
return GRUB_ERR_NONE;
}
#endif /* ndef GRUB_UTIL */
/********************************************************************
* Thumb (T32) relocations: *
* *
* 32-bit Thumb instructions can be 16-bit aligned, and are fetched *
* little-endian, requiring some additional fiddling. *
********************************************************************/
/*
* R_ARM_THM_CALL/THM_JUMP24
*
* Relocate Thumb (T32) instruction set relative branches:
* B.W, BL and BLX
*/
grub_err_t
reloc_thm_call (grub_uint16_t *target, Elf32_Addr sym_addr)
{
grub_int32_t offset, offset_low, offset_high;
grub_uint32_t sign, j1, j2, is_blx;
grub_uint32_t insword, insmask;
/* Extract instruction word in alignment-safe manner */
insword = (*target << 16) | (*(target + 1));
insmask = 0xf800d000;
/* B.W/BL or BLX? Affects range and expected target state */
if (((insword >> 12) & 0xd) == 0xc)
is_blx = 1;
else
is_blx = 0;
/* If BLX, target symbol must be ARM (target address LSB == 0) */
if (is_blx && (sym_addr & 1))
{
#ifndef GRUB_UTIL
return grub_error
(GRUB_ERR_BUG, N_("Relocation targeting wrong execution state"));
#else
grub_util_error ("Relocation targeting wrong execution state");
#endif
}
offset_low = -16777216;
offset_high = is_blx ? 16777212 : 16777214;
/* Extract bitfields from instruction words */
sign = (insword >> 26) & 1;
j1 = (insword >> 13) & 1;
j2 = (insword >> 11) & 1;
offset = (sign << 24) | ((~(j1 ^ sign) & 1) << 23) |
((~(j2 ^ sign) & 1) << 22) |
((insword & 0x03ff0000) >> 4) | ((insword & 0x000007ff) << 1);
/* Sign adjust and calculate offset */
if (offset & (1 << 24))
offset -= (1 << 25);
#ifdef GRUB_UTIL
grub_util_info (" sym_addr = 0x%08x", sym_addr);
#endif
#ifdef GRUB_UTIL
offset += sym_addr;
#else
offset += sym_addr - (grub_uint32_t) target;
#endif
#ifdef DEBUG
grub_printf(" %s: target=0x%08x, sym_addr=0x%08x, offset=%d\n",
is_blx ? "BLX" : "BL", (unsigned int) target, sym_addr, offset);
#endif
if ((offset < offset_low) || (offset > offset_high))
{
#ifdef GRUB_UTIL
grub_util_error ("Relocation out of range");
#else
return grub_error
(GRUB_ERR_OUT_OF_RANGE, N_("THM_CALL Relocation out of range."));
#endif
}
#ifdef GRUB_UTIL
grub_util_info (" relative destination = 0x%08x",
(unsigned int)target + offset);
#endif
/* Reassemble instruction word */
sign = (offset >> 24) & 1;
j1 = sign ^ (~(offset >> 23) & 1);
j2 = sign ^ (~(offset >> 22) & 1);
insword = (insword & insmask) |
(sign << 26) |
(((offset >> 12) & 0x03ff) << 16) |
(j1 << 13) | (j2 << 11) | ((offset >> 1) & 0x07ff);
/* Write instruction word back in alignment-safe manner */
*target = (insword >> 16) & 0xffff;
*(target + 1) = insword & 0xffff;
#ifdef GRUB_UTIL
#pragma GCC diagnostic ignored "-Wcast-align"
grub_util_info (" *target = 0x%08x", *((unsigned int *)target));
#endif
return GRUB_ERR_NONE;
}
/*
* R_ARM_THM_JUMP19
*
* Relocate conditional Thumb (T32) B<c>.W
*/
grub_err_t
reloc_thm_jump19 (grub_uint16_t *addr, Elf32_Addr sym_addr)
{
grub_int32_t offset;
grub_uint32_t insword, insmask;
/* Extract instruction word in alignment-safe manner */
insword = (*addr) << 16 | *(addr + 1);
insmask = 0xfbc0d800;
/* Extract and sign extend offset */
offset = ((insword >> 26) & 1) << 18
| ((insword >> 11) & 1) << 17
| ((insword >> 13) & 1) << 16
| ((insword >> 16) & 0x3f) << 11
| (insword & 0x7ff);
offset <<= 1;
if (offset & (1 << 19))
offset -= (1 << 20);
/* Adjust and re-truncate offset */
#ifdef GRUB_UTIL
offset += sym_addr;
#else
offset += sym_addr - (grub_uint32_t) addr;
#endif
if ((offset > 1048574) || (offset < -1048576))
{
return grub_error
(GRUB_ERR_OUT_OF_RANGE, N_("THM_JUMP19 Relocation out of range."));
}
offset >>= 1;
offset &= 0x7ffff;
/* Reassemble instruction word and write back */
insword &= insmask;
insword |= ((offset >> 18) & 1) << 26
| ((offset >> 17) & 1) << 11
| ((offset >> 16) & 1) << 13
| ((offset >> 11) & 0x3f) << 16
| (offset & 0x7ff);
*addr = insword >> 16;
*(addr + 1) = insword & 0xffff;
return GRUB_ERR_NONE;
}
/***********************************************************
* ARM (A32) relocations: *
* *
* ARM instructions are 32-bit in size and 32-bit aligned. *
***********************************************************/
/*
* R_ARM_JUMP24
*
* Relocate ARM (A32) B
*/
grub_err_t
reloc_jump24 (grub_uint32_t *addr, Elf32_Addr sym_addr)
{
grub_uint32_t insword;
grub_int32_t offset;
insword = *addr;
offset = (insword & 0x00ffffff) << 2;
if (offset & 0x02000000)
offset -= 0x04000000;
#ifdef GRUB_UTIL
offset += sym_addr;
#else
offset += sym_addr - (grub_uint32_t) addr;
#endif
insword &= 0xff000000;
insword |= (offset >> 2) & 0x00ffffff;
*addr = insword;
return GRUB_ERR_NONE;
}
/*************************************************
* Runtime dynamic linker with helper functions. *
*************************************************/
#ifndef GRUB_UTIL
/*
* find_segment(): finds a module segment matching sh_info
*/
static grub_dl_segment_t
find_segment (grub_dl_segment_t seg, Elf32_Word sh_info)
{
for (; seg; seg = seg->next)
if (seg->section == sh_info)
return seg;
return NULL;
}
/*
* do_relocations():
* Iterate over all relocations in section, calling appropriate functions
* for patching.
*/
static grub_err_t
do_relocations (Elf_Shdr * relhdr, Elf_Ehdr * e, grub_dl_t mod)
{
grub_dl_segment_t seg;
Elf_Rel *rel;
Elf_Sym *sym;
int i, entnum;
entnum = relhdr->sh_size / sizeof (Elf_Rel);
/* Find the target segment for this relocation section. */
seg = find_segment (mod->segment, relhdr->sh_info);
if (!seg)
return grub_error (GRUB_ERR_EOF, N_("relocation segment not found"));
rel = (Elf_Rel *) ((grub_addr_t) e + relhdr->sh_offset);
/* Step through all relocations */
for (i = 0, sym = mod->symtab; i < entnum; i++)
{
Elf_Addr *target, sym_addr;
int relsym, reltype;
grub_err_t retval;
if (seg->size < rel[i].r_offset)
return grub_error (GRUB_ERR_BAD_MODULE,
"reloc offset is out of the segment");
relsym = ELF_R_SYM (rel[i].r_info);
reltype = ELF_R_TYPE (rel[i].r_info);
target = (Elf_Word *) ((grub_addr_t) seg->addr + rel[i].r_offset);
sym_addr = sym[relsym].st_value;
#ifdef DL_DEBUG
grub_printf ("%s: 0x%08x -> %s @ 0x%08x\n", __FUNCTION__,
(grub_addr_t) sym_addr, get_symbolname (sym), sym->st_value);
#endif
switch (reltype)
{
case R_ARM_ABS32:
{
/* Data will be naturally aligned */
retval = reloc_abs32 (target, sym_addr);
if (retval != GRUB_ERR_NONE)
return retval;
}
break;
case R_ARM_JUMP24:
{
retval = reloc_jump24 (target, sym_addr);
if (retval != GRUB_ERR_NONE)
return retval;
}
break;
case R_ARM_THM_CALL:
case R_ARM_THM_JUMP24:
{
/* Thumb instructions can be 16-bit aligned */
retval = reloc_thm_call ((grub_uint16_t *) target, sym_addr);
if (retval != GRUB_ERR_NONE)
return retval;
}
break;
case R_ARM_THM_JUMP19:
{
/* Thumb instructions can be 16-bit aligned */
retval = reloc_thm_jump19 ((grub_uint16_t *) target, sym_addr);
if (retval != GRUB_ERR_NONE)
return retval;
}
break;
default:
return grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
N_("relocation 0x%x is not implemented yet"),
reltype);
}
}
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;
}
/*
* Verify that provided ELF header contains reference to a symbol table
*/
static int
has_symtab (Elf_Ehdr * e)
{
int i;
Elf_Shdr *s;
for (i = 0, s = (Elf_Shdr *) ((grub_uint32_t) e + e->e_shoff);
i < e->e_shnum;
i++, s = (Elf_Shdr *) ((grub_uint32_t) s + e->e_shentsize))
if (s->sh_type == SHT_SYMTAB)
return 1;
return 0;
}
/*
* grub_arch_dl_relocate_symbols():
* Only externally visible function in this file.
* Locates the relocations section of the ELF object, and calls
* do_relocations() to deal with it.
*/
grub_err_t
grub_arch_dl_relocate_symbols (grub_dl_t mod, void *ehdr)
{
Elf_Ehdr *e = ehdr;
Elf_Shdr *s;
unsigned i;
if (!has_symtab (e))
return grub_error (GRUB_ERR_BAD_MODULE, N_("no symbol table"));
#ifdef DL_DEBUG
set_symstrtab (e);
#endif
#define FIRST_SHDR(x) ((Elf_Shdr *) ((grub_addr_t)(x) + (x)->e_shoff))
#define NEXT_SHDR(x, y) ((Elf_Shdr *) ((grub_addr_t)(y) + (x)->e_shentsize))
for (i = 0, s = FIRST_SHDR (e); i < e->e_shnum; i++, s = NEXT_SHDR (e, s))
{
grub_err_t ret;
switch (s->sh_type)
{
case SHT_REL:
{
/* Relocations, no addends */
ret = do_relocations (s, e, mod);
if (ret != GRUB_ERR_NONE)
return ret;
}
break;
case SHT_NULL:
case SHT_PROGBITS:
case SHT_SYMTAB:
case SHT_STRTAB:
case SHT_NOBITS:
case SHT_ARM_ATTRIBUTES:
break;
case SHT_RELA:
default:
{
grub_printf ("unhandled section_type: %d (0x%08x)\n",
s->sh_type, s->sh_type);
return GRUB_ERR_NOT_IMPLEMENTED_YET;
};
}
}
#undef FIRST_SHDR
#undef NEXT_SHDR
return GRUB_ERR_NONE;
}
#endif /* ndef GRUB_UTIL */
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