module.c

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/*
 *  Port on Texas Instruments TMS320C6x architecture
 *
 *  Copyright (C) 2005, 2009, 2010, 2011 Texas Instruments Incorporated
 *  Author: Thomas Charleux ([email protected])
 *
 *  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/moduleloader.h>
#include <linux/elf.h>
#include <linux/vmalloc.h>
#include <linux/kernel.h>

static inline int fixup_pcr(u32 *ip, Elf32_Addr dest, u32 maskbits, int shift)
{
    u32 opcode;
    long ep = (long)ip & ~31;
    long delta = ((long)dest - ep) >> 2;
    long mask = (1 << maskbits) - 1;

    if ((delta >> (maskbits - 1)) == 0 ||
        (delta >> (maskbits - 1)) == -1) {
        opcode = *ip;
        opcode &= ~(mask << shift);
        opcode |= ((delta & mask) << shift);
        *ip = opcode;

        pr_debug("REL PCR_S%d[%p] dest[%p] opcode[%08x]\n",
             maskbits, ip, (void *)dest, opcode);

        return 0;
    }
    pr_err("PCR_S%d reloc %p -> %p out of range!\n",
           maskbits, ip, (void *)dest);

    return -1;
}

/*
 * apply a RELA relocation
 */
int apply_relocate_add(Elf32_Shdr *sechdrs,
               const char *strtab,
               unsigned int symindex,
               unsigned int relsec,
               struct module *me)
{
    Elf32_Rela *rel = (void *) sechdrs[relsec].sh_addr;
    Elf_Sym *sym;
    u32 *location, opcode;
    unsigned int i;
    Elf32_Addr v;
    Elf_Addr offset = 0;

    pr_debug("Applying relocate section %u to %u with offset 0x%x\n",
         relsec, sechdrs[relsec].sh_info, offset);

    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 - offset;

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

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

        switch (ELF32_R_TYPE(rel[i].r_info)) {
        case R_C6000_ABS32:
            pr_debug("RELA ABS32: [%p] = 0x%x\n", location, v);
            *location = v;
            break;
        case R_C6000_ABS16:
            pr_debug("RELA ABS16: [%p] = 0x%x\n", location, v);
            *(u16 *)location = v;
            break;
        case R_C6000_ABS8:
            pr_debug("RELA ABS8: [%p] = 0x%x\n", location, v);
            *(u8 *)location = v;
            break;
        case R_C6000_ABS_L16:
            opcode = *location;
            opcode &= ~0x7fff80;
            opcode |= ((v & 0xffff) << 7);
            pr_debug("RELA ABS_L16[%p] v[0x%x] opcode[0x%x]\n",
                 location, v, opcode);
            *location = opcode;
            break;
        case R_C6000_ABS_H16:
            opcode = *location;
            opcode &= ~0x7fff80;
            opcode |= ((v >> 9) & 0x7fff80);
            pr_debug("RELA ABS_H16[%p] v[0x%x] opcode[0x%x]\n",
                 location, v, opcode);
            *location = opcode;
            break;
        case R_C6000_PCR_S21:
            if (fixup_pcr(location, v, 21, 7))
                return -ENOEXEC;
            break;
        case R_C6000_PCR_S12:
            if (fixup_pcr(location, v, 12, 16))
                return -ENOEXEC;
            break;
        case R_C6000_PCR_S10:
            if (fixup_pcr(location, v, 10, 13))
                return -ENOEXEC;
            break;
        default:
            pr_err("module %s: Unknown RELA relocation: %u\n",
                   me->name, ELF32_R_TYPE(rel[i].r_info));
            return -ENOEXEC;
        }
    }

    return 0;
}