module.c

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/*
 *  This program 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 2 of the License, 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 License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *  Copyright (C) 2001 Rusty Russell.
 *  Copyright (C) 2003, 2004 Ralf Baechle ([email protected])
 *  Copyright (C) 2005 Thiemo Seufer
 */

#undef DEBUG

#include <linux/moduleloader.h>
#include <linux/elf.h>
#include <linux/mm.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/jump_label.h>

#include <asm/pgtable.h>    /* MODULE_START */

struct mips_hi16 {
    struct mips_hi16 *next;
    Elf_Addr *addr;
    Elf_Addr value;
};

static LIST_HEAD(dbe_list);
static DEFINE_SPINLOCK(dbe_lock);

#ifdef MODULE_START
void *module_alloc(unsigned long size)
{
    return __vmalloc_node_range(size, 1, MODULE_START, MODULE_END,
                GFP_KERNEL, PAGE_KERNEL, -1,
                __builtin_return_address(0));
}
#endif

int apply_r_mips_none(struct module *me, u32 *location, Elf_Addr v)
{
    return 0;
}

static int apply_r_mips_32_rel(struct module *me, u32 *location, Elf_Addr v)
{
    *location += v;

    return 0;
}

static int apply_r_mips_26_rel(struct module *me, u32 *location, Elf_Addr v)
{
    if (v % 4) {
        pr_err("module %s: dangerous R_MIPS_26 REL relocation\n",
               me->name);
        return -ENOEXEC;
    }

    if ((v & 0xf0000000) != (((unsigned long)location + 4) & 0xf0000000)) {
        printk(KERN_ERR
               "module %s: relocation overflow\n",
               me->name);
        return -ENOEXEC;
    }

    *location = (*location & ~0x03ffffff) |
                ((*location + (v >> 2)) & 0x03ffffff);

    return 0;
}

static int apply_r_mips_hi16_rel(struct module *me, u32 *location, Elf_Addr v)
{
    struct mips_hi16 *n;

    /*
     * We cannot relocate this one now because we don't know the value of
     * the carry we need to add.  Save the information, and let LO16 do the
     * actual relocation.
     */
    n = kmalloc(sizeof *n, GFP_KERNEL);
    if (!n)
        return -ENOMEM;

    n->addr = (Elf_Addr *)location;
    n->value = v;
    n->next = me->arch.r_mips_hi16_list;
    me->arch.r_mips_hi16_list = n;

    return 0;
}

static void free_relocation_chain(struct mips_hi16 *l)
{
    struct mips_hi16 *next;

    while (l) {
        next = l->next;
        kfree(l);
        l = next;
    }
}

static int apply_r_mips_lo16_rel(struct module *me, u32 *location, Elf_Addr v)
{
    unsigned long insnlo = *location;
    struct mips_hi16 *l;
    Elf_Addr val, vallo;

    /* Sign extend the addend we extract from the lo insn.  */
    vallo = ((insnlo & 0xffff) ^ 0x8000) - 0x8000;

    if (me->arch.r_mips_hi16_list != NULL) {
        l = me->arch.r_mips_hi16_list;
        while (l != NULL) {
            struct mips_hi16 *next;
            unsigned long insn;

            /*
             * The value for the HI16 had best be the same.
             */
            if (v != l->value)
                goto out_danger;

            /*
             * Do the HI16 relocation.  Note that we actually don't
             * need to know anything about the LO16 itself, except
             * where to find the low 16 bits of the addend needed
             * by the LO16.
             */
            insn = *l->addr;
            val = ((insn & 0xffff) << 16) + vallo;
            val += v;

            /*
             * Account for the sign extension that will happen in
             * the low bits.
             */
            val = ((val >> 16) + ((val & 0x8000) != 0)) & 0xffff;

            insn = (insn & ~0xffff) | val;
            *l->addr = insn;

            next = l->next;
            kfree(l);
            l = next;
        }

        me->arch.r_mips_hi16_list = NULL;
    }

    /*
     * Ok, we're done with the HI16 relocs.  Now deal with the LO16.
     */
    val = v + vallo;
    insnlo = (insnlo & ~0xffff) | (val & 0xffff);
    *location = insnlo;

    return 0;

out_danger:
    free_relocation_chain(l);
    me->arch.r_mips_hi16_list = NULL;

    pr_err("module %s: dangerous R_MIPS_LO16 REL relocation\n", me->name);

    return -ENOEXEC;
}

static int (*reloc_handlers_rel[]) (struct module *me, u32 *location,
                Elf_Addr v) = {
    [R_MIPS_NONE]       = apply_r_mips_none,
    [R_MIPS_32]     = apply_r_mips_32_rel,
    [R_MIPS_26]     = apply_r_mips_26_rel,
    [R_MIPS_HI16]       = apply_r_mips_hi16_rel,
    [R_MIPS_LO16]       = apply_r_mips_lo16_rel
};

int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
           unsigned int symindex, unsigned int relsec,
           struct module *me)
{
    Elf_Mips_Rel *rel = (void *) sechdrs[relsec].sh_addr;
    Elf_Sym *sym;
    u32 *location;
    unsigned int i;
    Elf_Addr v;
    int res;

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

    me->arch.r_mips_hi16_list = NULL;
    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 it is referring to */
        sym = (Elf_Sym *)sechdrs[symindex].sh_addr
            + ELF_MIPS_R_SYM(rel[i]);
        if (IS_ERR_VALUE(sym->st_value)) {
            /* Ignore unresolved weak symbol */
            if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
                continue;
            printk(KERN_WARNING "%s: Unknown symbol %s\n",
                   me->name, strtab + sym->st_name);
            return -ENOENT;
        }

        v = sym->st_value;

        res = reloc_handlers_rel[ELF_MIPS_R_TYPE(rel[i])](me, location, v);
        if (res)
            return res;
    }

    /*
     * Normally the hi16 list should be deallocated at this point.  A
     * malformed binary however could contain a series of R_MIPS_HI16
     * relocations not followed by a R_MIPS_LO16 relocation.  In that
     * case, free up the list and return an error.
     */
    if (me->arch.r_mips_hi16_list) {
        free_relocation_chain(me->arch.r_mips_hi16_list);
        me->arch.r_mips_hi16_list = NULL;

        return -ENOEXEC;
    }

    return 0;
}

/* Given an address, look for it in the module exception tables. */
const struct exception_table_entry *search_module_dbetables(unsigned long addr)
{
    unsigned long flags;
    const struct exception_table_entry *e = NULL;
    struct mod_arch_specific *dbe;

    spin_lock_irqsave(&dbe_lock, flags);
    list_for_each_entry(dbe, &dbe_list, dbe_list) {
        e = search_extable(dbe->dbe_start, dbe->dbe_end - 1, addr);
        if (e)
            break;
    }
    spin_unlock_irqrestore(&dbe_lock, flags);

    /* Now, if we found one, we are running inside it now, hence
           we cannot unload the module, hence no refcnt needed. */
    return e;
}

/* Put in dbe list if necessary. */
int module_finalize(const Elf_Ehdr *hdr,
            const Elf_Shdr *sechdrs,
            struct module *me)
{
    const Elf_Shdr *s;
    char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;

    /* Make jump label nops. */
    jump_label_apply_nops(me);

    INIT_LIST_HEAD(&me->arch.dbe_list);
    for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
        if (strcmp("__dbe_table", secstrings + s->sh_name) != 0)
            continue;
        me->arch.dbe_start = (void *)s->sh_addr;
        me->arch.dbe_end = (void *)s->sh_addr + s->sh_size;
        spin_lock_irq(&dbe_lock);
        list_add(&me->arch.dbe_list, &dbe_list);
        spin_unlock_irq(&dbe_lock);
    }
    return 0;
}

void module_arch_cleanup(struct module *mod)
{
    spin_lock_irq(&dbe_lock);
    list_del(&mod->arch.dbe_list);
    spin_unlock_irq(&dbe_lock);
}