/* * 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_ro_size = mod->core_ro_size;	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; 	if (loc < core + core_ro_size)		readonly = true;	else		readonly = false; 	/* 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;}