text: /*
   * livepatch.c - x86-specific Kernel Live Patching Core
   *
   * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
   * Copyright (C) 2014 SUSE
   *
   * 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, see <http://www.gnu.org/licenses/>.
   */
  
  #include <linux/module.h>
  #include <linux/uaccess.h>
  #include <asm/cacheflush.h>
  #include <asm/page_types.h>
  #include <asm/elf.h>
  #include <asm/livepatch.h>
  
  /**
   * klp_write_module_reloc() - write a relocation in a module
   * @mod:	module in which the section to be modified is found
   * @type:	ELF relocation type (see asm/elf.h)
   * @loc:	address that the relocation should be written to
   * @value:	relocation value (sym address + addend)
   *
   * This function writes a relocation to the specified location for
   * a particular module.
   */
  int klp_write_module_reloc(struct module *mod, unsigned long type,
  			   unsigned long loc, unsigned long value)
  {
  	int ret, numpages, size = 4;
  	bool readonly;
  	unsigned long val;
  	unsigned long core = (unsigned long)mod->module_core;
  	unsigned long core_size = mod->core_size;
  
  	switch (type) {
  	case R_X86_64_NONE:
  		return 0;
  	case R_X86_64_64:
  		val = value;
  		size = 8;
  		break;
  	case R_X86_64_32:
  		val = (u32)value;
  		break;
  	case R_X86_64_32S:
  		val = (s32)value;
  		break;
  	case R_X86_64_PC32:
  		val = (u32)(value - loc);
  		break;
  	default:
  		/* unsupported relocation type */
  		return -EINVAL;
  	}
  
  	if (loc < core || loc >= core + core_size)
  		/* loc does not point to any symbol inside the module */
  		return -EINVAL;
  
  	readonly = false;
  
  #ifdef CONFIG_DEBUG_SET_MODULE_RONX
  	if (loc < core + mod->core_ro_size)
  		readonly = true;
  #endif
  
  	/* determine if the relocation spans a page boundary */
  	numpages = ((loc & PAGE_MASK) == ((loc + size) & PAGE_MASK)) ? 1 : 2;
  
  	if (readonly)
  		set_memory_rw(loc & PAGE_MASK, numpages);
  
  	ret = probe_kernel_write((void *)loc, &val, size);
  
  	if (readonly)
  		set_memory_ro(loc & PAGE_MASK, numpages);
  
  	return ret;
  }
  