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d4c3e6e1b1
Implement arch_klp_init_object_loaded() for x86, which applies
alternatives/paravirt patches. This fixes the order in which relocations
and alternatives/paravirt patches are applied.
Previously, if a patch module had alternatives or paravirt patches,
these were applied first by the module loader before livepatch can apply
per-object relocations. The (buggy) sequence of events was:
(1) Load patch module
(2) Apply alternatives and paravirt patches to patch module
* Note that these are applied to the new functions in the patch module
(3) Apply per-object relocations to patch module when target module loads.
* This clobbers what was written in step 2
This lead to crashes and corruption in general, since livepatch would
overwrite or step on previously applied alternative/paravirt patches.
The correct sequence of events should be:
(1) Load patch module
(2) Apply per-object relocations to patch module
(3) Apply alternatives and paravirt patches to patch module
This is fixed by delaying paravirt/alternatives patching until after
relocations are applied. Any .altinstructions or .parainstructions
sections are prefixed with ".klp.arch.${objname}" and applied in
arch_klp_init_object_loaded().
Signed-off-by: Jessica Yu <jeyu@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
66 lines
1.9 KiB
C
66 lines
1.9 KiB
C
/*
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* livepatch.c - x86-specific Kernel Live Patching Core
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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/kallsyms.h>
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#include <linux/livepatch.h>
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#include <asm/text-patching.h>
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/* Apply per-object alternatives. Based on x86 module_finalize() */
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void arch_klp_init_object_loaded(struct klp_patch *patch,
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struct klp_object *obj)
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{
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int cnt;
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struct klp_modinfo *info;
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Elf_Shdr *s, *alt = NULL, *para = NULL;
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void *aseg, *pseg;
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const char *objname;
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char sec_objname[MODULE_NAME_LEN];
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char secname[KSYM_NAME_LEN];
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info = patch->mod->klp_info;
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objname = obj->name ? obj->name : "vmlinux";
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/* See livepatch core code for BUILD_BUG_ON() explanation */
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BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
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for (s = info->sechdrs; s < info->sechdrs + info->hdr.e_shnum; s++) {
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/* Apply per-object .klp.arch sections */
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cnt = sscanf(info->secstrings + s->sh_name,
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".klp.arch.%55[^.].%127s",
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sec_objname, secname);
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if (cnt != 2)
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continue;
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if (strcmp(sec_objname, objname))
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continue;
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if (!strcmp(".altinstructions", secname))
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alt = s;
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if (!strcmp(".parainstructions", secname))
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para = s;
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}
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if (alt) {
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aseg = (void *) alt->sh_addr;
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apply_alternatives(aseg, aseg + alt->sh_size);
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}
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if (para) {
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pseg = (void *) para->sh_addr;
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apply_paravirt(pseg, pseg + para->sh_size);
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}
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}
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