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/*
* 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;
}
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