91 lines
2.5 KiB
C
91 lines
2.5 KiB
C
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/*
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* livepatch.c - x86-specific Kernel Live Patching Core
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*
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* Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
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* Copyright (C) 2014 SUSE
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/module.h>
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#include <linux/uaccess.h>
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#include <asm/cacheflush.h>
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#include <asm/page_types.h>
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#include <asm/elf.h>
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#include <asm/livepatch.h>
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/**
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* klp_write_module_reloc() - write a relocation in a module
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* @mod: module in which the section to be modified is found
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* @type: ELF relocation type (see asm/elf.h)
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* @loc: address that the relocation should be written to
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* @value: relocation value (sym address + addend)
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*
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* This function writes a relocation to the specified location for
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* a particular module.
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*/
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int klp_write_module_reloc(struct module *mod, unsigned long type,
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unsigned long loc, unsigned long value)
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{
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int ret, numpages, size = 4;
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bool readonly;
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unsigned long val;
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unsigned long core = (unsigned long)mod->module_core;
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unsigned long core_ro_size = mod->core_ro_size;
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unsigned long core_size = mod->core_size;
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switch (type) {
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case R_X86_64_NONE:
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return 0;
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case R_X86_64_64:
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val = value;
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size = 8;
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break;
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case R_X86_64_32:
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val = (u32)value;
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break;
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case R_X86_64_32S:
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val = (s32)value;
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break;
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case R_X86_64_PC32:
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val = (u32)(value - loc);
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break;
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default:
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/* unsupported relocation type */
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return -EINVAL;
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}
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if (loc < core || loc >= core + core_size)
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/* loc does not point to any symbol inside the module */
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return -EINVAL;
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if (loc < core + core_ro_size)
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readonly = true;
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else
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readonly = false;
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/* determine if the relocation spans a page boundary */
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numpages = ((loc & PAGE_MASK) == ((loc + size) & PAGE_MASK)) ? 1 : 2;
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if (readonly)
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set_memory_rw(loc & PAGE_MASK, numpages);
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ret = probe_kernel_write((void *)loc, &val, size);
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if (readonly)
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set_memory_ro(loc & PAGE_MASK, numpages);
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return ret;
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}
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