diff options
Diffstat (limited to 'arch/x86/kernel/livepatch.c')
| -rw-r--r-- | arch/x86/kernel/livepatch.c | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/arch/x86/kernel/livepatch.c b/arch/x86/kernel/livepatch.c new file mode 100644 index 000000000000..ff3c3101d003 --- /dev/null +++ b/arch/x86/kernel/livepatch.c @@ -0,0 +1,90 @@ +/* + * 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; +} |