module.c

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/*  Kernel module help for x86.
    Copyright (C) 2001 Rusty Russell.

    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
*/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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>
#include <linux/mm.h>
#include <linux/gfp.h>
#include <linux/jump_label.h>

#include <asm/page.h>
#include <asm/pgtable.h>

#if 0
#define DEBUGP(fmt, ...)                \
    printk(KERN_DEBUG fmt, ##__VA_ARGS__)
#else
#define DEBUGP(fmt, ...)                \
do {                            \
    if (0)                      \
        printk(KERN_DEBUG fmt, ##__VA_ARGS__);  \
} while (0)
#endif

void *module_alloc(unsigned long size)
{
    if (PAGE_ALIGN(size) > MODULES_LEN)
        return NULL;
    return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
                GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC,
                -1, __builtin_return_address(0));
}

#ifdef CONFIG_X86_32
int apply_relocate(Elf32_Shdr *sechdrs,
           const char *strtab,
           unsigned int symindex,
           unsigned int relsec,
           struct module *me)
{
    unsigned int i;
    Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
    Elf32_Sym *sym;
    uint32_t *location;

    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 it is referring to.  Note that all
           undefined symbols have been resolved.  */
        sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
            + ELF32_R_SYM(rel[i].r_info);

        switch (ELF32_R_TYPE(rel[i].r_info)) {
        case R_386_32:
            /* We add the value into the location given */
            *location += sym->st_value;
            break;
        case R_386_PC32:
            /* Add the value, subtract its position */
            *location += sym->st_value - (uint32_t)location;
            break;
        default:
            pr_err("%s: Unknown relocation: %u\n",
                   me->name, ELF32_R_TYPE(rel[i].r_info));
            return -ENOEXEC;
        }
    }
    return 0;
}
#else /*X86_64*/
int apply_relocate_add(Elf64_Shdr *sechdrs,
           const char *strtab,
           unsigned int symindex,
           unsigned int relsec,
           struct module *me)
{
    unsigned int i;
    Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
    Elf64_Sym *sym;
    void *loc;
    u64 val;

    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 */
        loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
            + rel[i].r_offset;

        /* This is the symbol it is referring to.  Note that all
           undefined symbols have been resolved.  */
        sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
            + ELF64_R_SYM(rel[i].r_info);

        DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
               (int)ELF64_R_TYPE(rel[i].r_info),
               sym->st_value, rel[i].r_addend, (u64)loc);

        val = sym->st_value + rel[i].r_addend;

        switch (ELF64_R_TYPE(rel[i].r_info)) {
        case R_X86_64_NONE:
            break;
        case R_X86_64_64:
            *(u64 *)loc = val;
            break;
        case R_X86_64_32:
            *(u32 *)loc = val;
            if (val != *(u32 *)loc)
                goto overflow;
            break;
        case R_X86_64_32S:
            *(s32 *)loc = val;
            if ((s64)val != *(s32 *)loc)
                goto overflow;
            break;
        case R_X86_64_PC32:
            val -= (u64)loc;
            *(u32 *)loc = val;
#if 0
            if ((s64)val != *(s32 *)loc)
                goto overflow;
#endif
            break;
        default:
            pr_err("%s: Unknown rela relocation: %llu\n",
                   me->name, ELF64_R_TYPE(rel[i].r_info));
            return -ENOEXEC;
        }
    }
    return 0;

overflow:
    pr_err("overflow in relocation type %d val %Lx\n",
           (int)ELF64_R_TYPE(rel[i].r_info), val);
    pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
           me->name);
    return -ENOEXEC;
}
#endif

int module_finalize(const Elf_Ehdr *hdr,
            const Elf_Shdr *sechdrs,
            struct module *me)
{
    const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL,
        *para = NULL;
    char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;

    for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
        if (!strcmp(".text", secstrings + s->sh_name))
            text = s;
        if (!strcmp(".altinstructions", secstrings + s->sh_name))
            alt = s;
        if (!strcmp(".smp_locks", secstrings + s->sh_name))
            locks = s;
        if (!strcmp(".parainstructions", secstrings + s->sh_name))
            para = s;
    }

    if (alt) {
        /* patch .altinstructions */
        void *aseg = (void *)alt->sh_addr;
        apply_alternatives(aseg, aseg + alt->sh_size);
    }
    if (locks && text) {
        void *lseg = (void *)locks->sh_addr;
        void *tseg = (void *)text->sh_addr;
        alternatives_smp_module_add(me, me->name,
                        lseg, lseg + locks->sh_size,
                        tseg, tseg + text->sh_size);
    }

    if (para) {
        void *pseg = (void *)para->sh_addr;
        apply_paravirt(pseg, pseg + para->sh_size);
    }

    /* make jump label nops */
    jump_label_apply_nops(me);

    return 0;
}

void module_arch_cleanup(struct module *mod)
{
    alternatives_smp_module_del(mod);
}