arch/x86/kernel/livepatch.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * livepatch.c - x86-specific Kernel Live Patching Core
 */

#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/livepatch.h>
#include <asm/text-patching.h>

/* Apply per-object alternatives. Based on x86 module_finalize() */
void arch_klp_init_object_loaded(struct klp_patch *patch,
				 struct klp_object *obj)
{
	int cnt;
	struct klp_modinfo *info;
	Elf_Shdr *s, *alt = NULL, *para = NULL;
	void *aseg, *pseg;
	const char *objname;
	char sec_objname[MODULE_NAME_LEN];
	char secname[KSYM_NAME_LEN];

	info = patch->mod->klp_info;
	objname = obj->name ? obj->name : "vmlinux";

	/* See livepatch core code for BUILD_BUG_ON() explanation */
	BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);

	for (s = info->sechdrs; s < info->sechdrs + info->hdr.e_shnum; s++) {
		/* Apply per-object .klp.arch sections */
		cnt = sscanf(info->secstrings + s->sh_name,
			     ".klp.arch.%55[^.].%127s",
			     sec_objname, secname);
		if (cnt != 2)
			continue;
		if (strcmp(sec_objname, objname))
			continue;
		if (!strcmp(".altinstructions", secname))
			alt = s;
		if (!strcmp(".parainstructions", secname))
			para = s;
	}

	if (alt) {
		aseg = (void *) alt->sh_addr;
		apply_alternatives(aseg, aseg + alt->sh_size);
	}

	if (para) {
		pseg = (void *) para->sh_addr;
		apply_paravirt(pseg, pseg + para->sh_size);
	}
}