SoW-2019-0002: Dynamic Snapshot

[lttng-tools.git] / tests / utils / testapp / gen-syscall-events / gen-syscall-events.c

/*
 * Copyright (C) 2017 Francis Deslauriers <francis.deslauriers@efficios.com>
 *
 * SPDX-License-Identifier: LGPL-2.1-only
 *
 */

#include <fcntl.h>
#include <stdio.h>
#include <sys/syscall.h>
#include <unistd.h>

#include "utils.h"

#define MAX_LEN 16

static
int open_read_close(const char *path)
{
	int fd, ret;
	char buf[MAX_LEN];
	/*
	 * Start generating syscalls. We use syscall(2) to prevent libc to change
	 * the underlying syscall. e.g. calling openat(2) instead of open(2).
	 */
	fd = syscall(SYS_openat, AT_FDCWD, path, O_RDONLY);
	if (fd < 0) {
		perror("open");
		ret = -1;
		goto error;
	}

	ret = syscall(SYS_read, fd, buf, MAX_LEN);
	if (ret < 0) {
		perror("read");
		ret = -1;
		goto error;
	}

	ret = syscall(SYS_close, fd);
	if (ret == -1) {
		perror("close");
		ret = -1;
		goto error;
	}

error:
	return ret;
}

/*
 * The process waits for the creation of a file passed as argument from an
 * external processes to execute a syscall and exiting. This is useful for tests
 * in combinaison with LTTng's PID tracker feature where we can trace the kernel
 * events generated by our test process only.
 */
int main(int argc, char **argv)
{
	int ret;
	char *start_file;

	if (argc != 2) {
		fprintf(stderr, "Error: Missing argument\n");
		fprintf(stderr, "USAGE: %s PATH_WAIT_FILE\n", argv[0]);
		ret = -1;
		goto error;
	}

	start_file = argv[1];

	/*
	 * Wait for the start_file to be created by an external process
	 * (typically the test script) before executing the syscalls.
	 */
	ret = wait_on_file(start_file);
	if (ret != 0) {
		goto error;
	}

	/*
	 * Start generating syscalls. We use syscall(2) to prevent libc to change
	 * the underlying syscall. e.g. calling openat(2) instead of open(2).
	 */
	ret = open_read_close("/proc/cpuinfo");
	if (ret == -1) {
		ret = -1;
		goto error;
	}

	ret = open_read_close("/proc/cmdline");
	if (ret == -1) {
		ret = -1;
		goto error;
	}

error:
	return ret;
}