module.c

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/*
 * AVR32-specific kernel module loader
 *
 * Copyright (C) 2005-2006 Atmel Corporation
 *
 * GOT initialization parts are based on the s390 version
 *   Copyright (C) 2002, 2003 IBM Deutschland Entwicklung GmbH,
 *                            IBM Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/bug.h>
#include <linux/elf.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleloader.h>
#include <linux/vmalloc.h>

void module_free(struct module *mod, void *module_region)
{
    vfree(mod->arch.syminfo);
    mod->arch.syminfo = NULL;

    vfree(module_region);
}

static inline int check_rela(Elf32_Rela *rela, struct module *module,
                 char *strings, Elf32_Sym *symbols)
{
    struct mod_arch_syminfo *info;

    info = module->arch.syminfo + ELF32_R_SYM(rela->r_info);
    switch (ELF32_R_TYPE(rela->r_info)) {
    case R_AVR32_GOT32:
    case R_AVR32_GOT16:
    case R_AVR32_GOT8:
    case R_AVR32_GOT21S:
    case R_AVR32_GOT18SW:   /* mcall */
    case R_AVR32_GOT16S:    /* ld.w */
        if (rela->r_addend != 0) {
            printk(KERN_ERR
                   "GOT relocation against %s at offset %u with addend\n",
                   strings + symbols[ELF32_R_SYM(rela->r_info)].st_name,
                   rela->r_offset);
            return -ENOEXEC;
        }
        if (info->got_offset == -1UL) {
            info->got_offset = module->arch.got_size;
            module->arch.got_size += sizeof(void *);
        }
        pr_debug("GOT[%3lu] %s\n", info->got_offset,
             strings + symbols[ELF32_R_SYM(rela->r_info)].st_name);
        break;
    }

    return 0;
}

int module_frob_arch_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
                  char *secstrings, struct module *module)
{
    Elf32_Shdr *symtab;
    Elf32_Sym *symbols;
    Elf32_Rela *rela;
    char *strings;
    int nrela, i, j;
    int ret;

    /* Find the symbol table */
    symtab = NULL;
    for (i = 0; i < hdr->e_shnum; i++)
        switch (sechdrs[i].sh_type) {
        case SHT_SYMTAB:
            symtab = &sechdrs[i];
            break;
        }
    if (!symtab) {
        printk(KERN_ERR "module %s: no symbol table\n", module->name);
        return -ENOEXEC;
    }

    /* Allocate room for one syminfo structure per symbol. */
    module->arch.nsyms = symtab->sh_size / sizeof(Elf_Sym);
    module->arch.syminfo = vmalloc(module->arch.nsyms
                   * sizeof(struct mod_arch_syminfo));
    if (!module->arch.syminfo)
        return -ENOMEM;

    symbols = (void *)hdr + symtab->sh_offset;
    strings = (void *)hdr + sechdrs[symtab->sh_link].sh_offset;
    for (i = 0; i < module->arch.nsyms; i++) {
        if (symbols[i].st_shndx == SHN_UNDEF &&
            strcmp(strings + symbols[i].st_name,
               "_GLOBAL_OFFSET_TABLE_") == 0)
            /* "Define" it as absolute. */
            symbols[i].st_shndx = SHN_ABS;
        module->arch.syminfo[i].got_offset = -1UL;
        module->arch.syminfo[i].got_initialized = 0;
    }

    /* Allocate GOT entries for symbols that need it. */
    module->arch.got_size = 0;
    for (i = 0; i < hdr->e_shnum; i++) {
        if (sechdrs[i].sh_type != SHT_RELA)
            continue;
        nrela = sechdrs[i].sh_size / sizeof(Elf32_Rela);
        rela = (void *)hdr + sechdrs[i].sh_offset;
        for (j = 0; j < nrela; j++) {
            ret = check_rela(rela + j, module,
                     strings, symbols);
            if (ret)
                goto out_free_syminfo;
        }
    }

    /*
     * Increase core size to make room for GOT and set start
     * offset for GOT.
     */
    module->core_size = ALIGN(module->core_size, 4);
    module->arch.got_offset = module->core_size;
    module->core_size += module->arch.got_size;

    return 0;

out_free_syminfo:
    vfree(module->arch.syminfo);
    module->arch.syminfo = NULL;

    return ret;
}

static inline int reloc_overflow(struct module *module, const char *reloc_name,
                 Elf32_Addr relocation)
{
    printk(KERN_ERR "module %s: Value %lx does not fit relocation %s\n",
           module->name, (unsigned long)relocation, reloc_name);
    return -ENOEXEC;
}

#define get_u16(loc)        (*((uint16_t *)loc))
#define put_u16(loc, val)   (*((uint16_t *)loc) = (val))

int apply_relocate_add(Elf32_Shdr *sechdrs, const char *strtab,
               unsigned int symindex, unsigned int relindex,
               struct module *module)
{
    Elf32_Shdr *symsec = sechdrs + symindex;
    Elf32_Shdr *relsec = sechdrs + relindex;
    Elf32_Shdr *dstsec = sechdrs + relsec->sh_info;
    Elf32_Rela *rel = (void *)relsec->sh_addr;
    unsigned int i;
    int ret = 0;

    for (i = 0; i < relsec->sh_size / sizeof(Elf32_Rela); i++, rel++) {
        struct mod_arch_syminfo *info;
        Elf32_Sym *sym;
        Elf32_Addr relocation;
        uint32_t *location;
        uint32_t value;

        location = (void *)dstsec->sh_addr + rel->r_offset;
        sym = (Elf32_Sym *)symsec->sh_addr + ELF32_R_SYM(rel->r_info);
        relocation = sym->st_value + rel->r_addend;

        info = module->arch.syminfo + ELF32_R_SYM(rel->r_info);

        /* Initialize GOT entry if necessary */
        switch (ELF32_R_TYPE(rel->r_info)) {
        case R_AVR32_GOT32:
        case R_AVR32_GOT16:
        case R_AVR32_GOT8:
        case R_AVR32_GOT21S:
        case R_AVR32_GOT18SW:
        case R_AVR32_GOT16S:
            if (!info->got_initialized) {
                Elf32_Addr *gotent;

                gotent = (module->module_core
                      + module->arch.got_offset
                      + info->got_offset);
                *gotent = relocation;
                info->got_initialized = 1;
            }

            relocation = info->got_offset;
            break;
        }

        switch (ELF32_R_TYPE(rel->r_info)) {
        case R_AVR32_32:
        case R_AVR32_32_CPENT:
            *location = relocation;
            break;
        case R_AVR32_22H_PCREL:
            relocation -= (Elf32_Addr)location;
            if ((relocation & 0xffe00001) != 0
                && (relocation & 0xffc00001) != 0xffc00000)
                return reloc_overflow(module,
                              "R_AVR32_22H_PCREL",
                              relocation);
            relocation >>= 1;

            value = *location;
            value = ((value & 0xe1ef0000)
                 | (relocation & 0xffff)
                 | ((relocation & 0x10000) << 4)
                 | ((relocation & 0x1e0000) << 8));
            *location = value;
            break;
        case R_AVR32_11H_PCREL:
            relocation -= (Elf32_Addr)location;
            if ((relocation & 0xfffffc01) != 0
                && (relocation & 0xfffff801) != 0xfffff800)
                return reloc_overflow(module,
                              "R_AVR32_11H_PCREL",
                              relocation);
            value = get_u16(location);
            value = ((value & 0xf00c)
                 | ((relocation & 0x1fe) << 3)
                 | ((relocation & 0x600) >> 9));
            put_u16(location, value);
            break;
        case R_AVR32_9H_PCREL:
            relocation -= (Elf32_Addr)location;
            if ((relocation & 0xffffff01) != 0
                && (relocation & 0xfffffe01) != 0xfffffe00)
                return reloc_overflow(module,
                              "R_AVR32_9H_PCREL",
                              relocation);
            value = get_u16(location);
            value = ((value & 0xf00f)
                 | ((relocation & 0x1fe) << 3));
            put_u16(location, value);
            break;
        case R_AVR32_9UW_PCREL:
            relocation -= ((Elf32_Addr)location) & 0xfffffffc;
            if ((relocation & 0xfffffc03) != 0)
                return reloc_overflow(module,
                              "R_AVR32_9UW_PCREL",
                              relocation);
            value = get_u16(location);
            value = ((value & 0xf80f)
                 | ((relocation & 0x1fc) << 2));
            put_u16(location, value);
            break;
        case R_AVR32_GOTPC:
            /*
             * R6 = PC - (PC - GOT)
             *
             * At this point, relocation contains the
             * value of PC.  Just subtract the value of
             * GOT, and we're done.
             */
            pr_debug("GOTPC: PC=0x%x, got_offset=0x%lx, core=0x%p\n",
                 relocation, module->arch.got_offset,
                 module->module_core);
            relocation -= ((unsigned long)module->module_core
                       + module->arch.got_offset);
            *location = relocation;
            break;
        case R_AVR32_GOT18SW:
            if ((relocation & 0xfffe0003) != 0
                && (relocation & 0xfffc0003) != 0xffff0000)
                return reloc_overflow(module, "R_AVR32_GOT18SW",
                             relocation);
            relocation >>= 2;
            /* fall through */
        case R_AVR32_GOT16S:
            if ((relocation & 0xffff8000) != 0
                && (relocation & 0xffff0000) != 0xffff0000)
                return reloc_overflow(module, "R_AVR32_GOT16S",
                              relocation);
            pr_debug("GOT reloc @ 0x%x -> %u\n",
                 rel->r_offset, relocation);
            value = *location;
            value = ((value & 0xffff0000)
                 | (relocation & 0xffff));
            *location = value;
            break;

        default:
            printk(KERN_ERR "module %s: Unknown relocation: %u\n",
                   module->name, ELF32_R_TYPE(rel->r_info));
            return -ENOEXEC;
        }
    }

    return ret;
}

int module_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
            struct module *module)
{
    vfree(module->arch.syminfo);
    module->arch.syminfo = NULL;

    return 0;
}