// SPDX-License-Identifier: GPL-2.0-only OR MIT
/*
 * Copyright (C) 2023 The Falco Authors.
 *
 * This file is dual licensed under either the MIT or GPL 2. See MIT.txt
 * or GPL2.txt for full copies of the license.
 */

#include <helpers/interfaces/fixed_size_event.h>
#include <helpers/interfaces/variable_size_event.h>

/*=============================== EXIT EVENT ===========================*/

SEC("tp_btf/sys_exit")
int BPF_PROG(fsconfig_x, struct pt_regs *regs, long ret) {
	struct auxiliary_map *auxmap = auxmap__get();
	if(!auxmap) {
		return 0;
	}

	auxmap__preload_event_header(auxmap, PPME_SYSCALL_FSCONFIG_X);

	/*=============================== COLLECT PARAMETERS  ===========================*/

	/* Parameter 1: ret (type: PT_ERRNO) */
	auxmap__store_s64_param(auxmap, ret);

	/* Parameter 2: fd (type: PT_FD) */
	/* This is the file-system fd */
	int32_t fd = (int32_t)extract__syscall_argument(regs, 0);
	auxmap__store_s64_param(auxmap, (int64_t)fd);

	/* Parameter 3: cmd (type: PT_ENUMFLAGS32) */
	uint32_t cmd = (uint32_t)extract__syscall_argument(regs, 1);
	uint32_t scap_cmd = fsconfig_cmds_to_scap(cmd);
	auxmap__store_u32_param(auxmap, scap_cmd);

	/* Parameter 4: key (type: PT_CHARBUF) */
	unsigned long key_pointer = extract__syscall_argument(regs, 2);
	auxmap__store_charbuf_param(auxmap, key_pointer, MAX_PARAM_SIZE, USER);

	int aux = extract__syscall_argument(regs, 4);

	if(ret < 0) {
		/* If the syscall fails we push empty params to userspace. */

		/* Parameter 5: value_bytebuf (type: PT_BYTEBUF) */
		auxmap__store_empty_param(auxmap);

		/* Parameter 6: value_charbuf (type: PT_CHARBUF) */
		auxmap__store_empty_param(auxmap);
	} else {
		unsigned long value_pointer = extract__syscall_argument(regs, 3);

		/* According to the command we need to understand what value we have to push to userspace.
		 */
		/* see https://elixir.bootlin.com/linux/latest/source/fs/fsopen.c#L271 */
		switch(scap_cmd) {
		case PPM_FSCONFIG_SET_FLAG:
		case PPM_FSCONFIG_SET_FD:
		case PPM_FSCONFIG_CMD_CREATE:
		case PPM_FSCONFIG_CMD_RECONFIGURE:
			/* Since `value` is NULL we send two empty params. */

			/* Parameter 5: value_bytebuf (type: PT_BYTEBUF) */
			auxmap__store_empty_param(auxmap);

			/* Parameter 6: value_charbuf (type: PT_CHARBUF) */
			auxmap__store_empty_param(auxmap);
			break;

		case PPM_FSCONFIG_SET_STRING:
		case PPM_FSCONFIG_SET_PATH:
		case PPM_FSCONFIG_SET_PATH_EMPTY:
			/* `value` is a NUL-terminated string.
			 * Push `value_charbuf` but not `value_bytebuf` (empty).
			 */

			/* Parameter 5: value_bytebuf (type: PT_BYTEBUF) */
			auxmap__store_empty_param(auxmap);

			/* Parameter 6: value_charbuf (type: PT_CHARBUF) */
			auxmap__store_charbuf_param(auxmap, value_pointer, MAX_PATH, USER);
			break;

		case PPM_FSCONFIG_SET_BINARY:
			/* `value` points to a binary blob and `aux` indicates its size.
			 * Push `value_bytebuf` but not `value_charbuf` (empty).
			 */

			/* Parameter 5: value_bytebuf (type: PT_BYTEBUF) */
			auxmap__store_bytebuf_param(auxmap, value_pointer, aux, USER);

			/* Parameter 6: value_charbuf (type: PT_CHARBUF) */
			auxmap__store_empty_param(auxmap);
			break;

		default:
			/* Parameter 5: value_bytebuf (type: PT_BYTEBUF) */
			auxmap__store_empty_param(auxmap);

			/* Parameter 6: value_charbuf (type: PT_CHARBUF) */
			auxmap__store_empty_param(auxmap);
			break;
		}
	}

	/* Parameter 7: aux (type: PT_INT32) */
	auxmap__store_s32_param(auxmap, aux);

	/*=============================== COLLECT PARAMETERS  ===========================*/

	auxmap__finalize_event_header(auxmap);

	auxmap__submit_event(auxmap);

	return 0;
}

/*=============================== EXIT EVENT ===========================*/
