module.c

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/* MN10300 Kernel module helper routines
 *
 * Copyright (C) 2007, 2008, 2009 Red Hat, Inc. All Rights Reserved.
 * Written by Mark Salter ([email protected])
 * - Derived from arch/i386/kernel/module.c
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public Licence as published by
 * the Free Software Foundation; either version 2 of the Licence, or
 * (at your option) any later version.
 *
 * This program 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 Licence for more details.
 *
 * You should have received a copy of the GNU General Public Licence
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include <linux/moduleloader.h>
#include <linux/elf.h>
#include <linux/vmalloc.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/bug.h>

#if 0
#define DEBUGP printk
#else
#define DEBUGP(fmt, ...)
#endif

static void reloc_put16(uint8_t *p, uint32_t val)
{
    p[0] = val & 0xff;
    p[1] = (val >> 8) & 0xff;
}

static void reloc_put24(uint8_t *p, uint32_t val)
{
    reloc_put16(p, val);
    p[2] = (val >> 16) & 0xff;
}

static void reloc_put32(uint8_t *p, uint32_t val)
{
    reloc_put16(p, val);
    reloc_put16(p+2, val >> 16);
}

/*
 * apply a RELA relocation
 */
int apply_relocate_add(Elf32_Shdr *sechdrs,
               const char *strtab,
               unsigned int symindex,
               unsigned int relsec,
               struct module *me)
{
    unsigned int i, sym_diff_seen = 0;
    Elf32_Rela *rel = (void *)sechdrs[relsec].sh_addr;
    Elf32_Sym *sym;
    Elf32_Addr relocation, sym_diff_val = 0;
    uint8_t *location;
    uint32_t value;

    DEBUGP("Applying relocate section %u to %u\n",
           relsec, sechdrs[relsec].sh_info);

    for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
        /* this is where to make the change */
        location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
            + rel[i].r_offset;

        /* this is the symbol the relocation is referring to (note that
         * all undefined symbols have been resolved by the caller) */
        sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
            + ELF32_R_SYM(rel[i].r_info);

        /* this is the adjustment to be made */
        relocation = sym->st_value + rel[i].r_addend;

        if (sym_diff_seen) {
            switch (ELF32_R_TYPE(rel[i].r_info)) {
            case R_MN10300_32:
            case R_MN10300_24:
            case R_MN10300_16:
            case R_MN10300_8:
                relocation -= sym_diff_val;
                sym_diff_seen = 0;
                break;
            default:
                printk(KERN_ERR "module %s: Unexpected SYM_DIFF relocation: %u\n",
                       me->name, ELF32_R_TYPE(rel[i].r_info));
                return -ENOEXEC;
            }
        }

        switch (ELF32_R_TYPE(rel[i].r_info)) {
            /* for the first four relocation types, we simply
             * store the adjustment at the location given */
        case R_MN10300_32:
            reloc_put32(location, relocation);
            break;
        case R_MN10300_24:
            reloc_put24(location, relocation);
            break;
        case R_MN10300_16:
            reloc_put16(location, relocation);
            break;
        case R_MN10300_8:
            *location = relocation;
            break;

            /* for the next three relocation types, we write the
             * adjustment with the address subtracted over the
             * value at the location given */
        case R_MN10300_PCREL32:
            value = relocation - (uint32_t) location;
            reloc_put32(location, value);
            break;
        case R_MN10300_PCREL16:
            value = relocation - (uint32_t) location;
            reloc_put16(location, value);
            break;
        case R_MN10300_PCREL8:
            *location = relocation - (uint32_t) location;
            break;

        case R_MN10300_SYM_DIFF:
            /* This is used to adjust the next reloc as required
             * by relaxation. */
            sym_diff_seen = 1;
            sym_diff_val = sym->st_value;
            break;

        case R_MN10300_ALIGN:
            /* Just ignore the ALIGN relocs.
             * Only interesting if kernel performed relaxation. */
            continue;

        default:
            printk(KERN_ERR "module %s: Unknown relocation: %u\n",
                   me->name, ELF32_R_TYPE(rel[i].r_info));
            return -ENOEXEC;
        }
    }
    if (sym_diff_seen) {
        printk(KERN_ERR "module %s: Nothing follows SYM_DIFF relocation: %u\n",
                       me->name, ELF32_R_TYPE(rel[i].r_info));
        return -ENOEXEC;
    }
    return 0;
}