LXR linux/arch/x86/kernel/livepatch.c

   1/*
   2 * livepatch.c - x86-specific Kernel Live Patching Core
   3 *
   4 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
   5 * Copyright (C) 2014 SUSE
   6 *
   7 * This program is free software; you can redistribute it and/or
   8 * modify it under the terms of the GNU General Public License
   9 * as published by the Free Software Foundation; either version 2
  10 * of the License, or (at your option) any later version.
  11 *
  12 * This program is distributed in the hope that it will be useful,
  13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 * GNU General Public License for more details.
  16 *
  17 * You should have received a copy of the GNU General Public License
  18 * along with this program; if not, see <http://www.gnu.org/licenses/>.
  19 */
  20
  21#include <linux/module.h>
  22#include <linux/uaccess.h>
  23#include <asm/elf.h>
  24#include <asm/livepatch.h>
  25
  26/**
  27 * klp_write_module_reloc() - write a relocation in a module
  28 * @mod:        module in which the section to be modified is found
  29 * @type:       ELF relocation type (see asm/elf.h)
  30 * @loc:        address that the relocation should be written to
  31 * @value:      relocation value (sym address + addend)
  32 *
  33 * This function writes a relocation to the specified location for
  34 * a particular module.
  35 */
  36int klp_write_module_reloc(struct module *mod, unsigned long type,
  37                           unsigned long loc, unsigned long value)
  38{
  39        size_t size = 4;
  40        unsigned long val;
  41        unsigned long core = (unsigned long)mod->core_layout.base;
  42        unsigned long core_size = mod->core_layout.size;
  43
  44        switch (type) {
  45        case R_X86_64_NONE:
  46                return 0;
  47        case R_X86_64_64:
  48                val = value;
  49                size = 8;
  50                break;
  51        case R_X86_64_32:
  52                val = (u32)value;
  53                break;
  54        case R_X86_64_32S:
  55                val = (s32)value;
  56                break;
  57        case R_X86_64_PC32:
  58                val = (u32)(value - loc);
  59                break;
  60        default:
  61                /* unsupported relocation type */
  62                return -EINVAL;
  63        }
  64
  65        if (loc < core || loc >= core + core_size)
  66                /* loc does not point to any symbol inside the module */
  67                return -EINVAL;
  68
  69        return probe_kernel_write((void *)loc, &val, size);
  70}
  71