/*
 * kallsyms_relocs.c - resolve non-exported symbols
 *
 * Copyright (C) 2018 SUSE
 * Author: Nicolai Stange <nstange@suse.de>
 *
 * 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/kernel.h>
#include <linux/module.h>
#include <linux/kallsyms.h>
#include "kallsyms_relocs.h"

struct find_args
{
	struct klp_kallsyms_reloc reloc;
	unsigned long match_count;
};

static int __find_callback(void *data, const char *name, unsigned long addr)
{
	struct find_args *args = data;

	if (strcmp(args->reloc.symname, name))
		return 0;

	args->match_count++;

	/*
	 * Finish the search when the symbol is found for the desired
	 * position or the position is not defined.
	 */
	if (!args->reloc.sympos || args->match_count == args->reloc.sympos) {
		*args->reloc.addr = (void *)addr;
		return 1;
	}

	return 0;
}

static
int (*klpe_module_kallsyms_on_each_symbol)(const char *modname,
					   int (*fn)(void *, const char *,
						     unsigned long),
					   void *data);

static int __klp_resolve_kallsyms_relocs(struct klp_kallsyms_reloc *relocs,
					 unsigned long count)
{
	unsigned long i;
	struct find_args args;

	for (i = 0; i < count; ++i) {
		*relocs[i].addr = NULL;
		args.reloc = relocs[i];
		args.match_count = 0;

		if (args.reloc.objname) {
			klpe_module_kallsyms_on_each_symbol(args.reloc.objname,
							    __find_callback,
							    &args);
		} else {
			kallsyms_on_each_symbol(__find_callback, &args);
		}

		if (!*relocs[i].addr) {
			if (relocs[i].objname) {
				pr_err("livepatch: symbol %s:%s not resolved\n",
				       relocs[i].objname, relocs[i].symname);
			} else {
				pr_err("livepatch: symbol %s not resolved\n",
				       relocs[i].symname);
			}

			return -ENOENT;
		}
	}

	return 0;
}

struct module *(*klpe_find_module)(const char *name);

/* Bootstrap: resolve non-exported module_kallsyms_on_each_symbol() */
int klp_kallsyms_relocs_init(void)
{
	static struct klp_kallsyms_reloc bootstrap_relocs[] = {
		{ "module_kallsyms_on_each_symbol",
		  (void *)&klpe_module_kallsyms_on_each_symbol },
		{ "find_module", (void *)&klpe_find_module },
	};

	/* Already initialized? */
	if (klpe_module_kallsyms_on_each_symbol)
		return 0;

	/*
	 * All relocations are against symbols from vmlinux, the yet
	 * unresolved klpe_module_kallsyms_on_each_symbol() will not
	 * get invoked and the call below will work fine at this stage
	 * already.
	 */
	return __klp_resolve_kallsyms_relocs(bootstrap_relocs,
					     ARRAY_SIZE(bootstrap_relocs));
}

int klp_resolve_kallsyms_relocs(struct klp_kallsyms_reloc *relocs,
				unsigned long count)
{
	int ret;

	ret = klp_kallsyms_relocs_init();
	if (ret)
		return ret;

	return  __klp_resolve_kallsyms_relocs(relocs, count);
}