selftest: acct: Add selftest for the acct() syscall

The acct() system call enables or disables process accounting.
If accounting is turned on, records for each terminating process
are appended to a specified filename as it terminates. An argument of NULL
causes accounting to be turned off.

This patch will add a test for the acct() syscall.
Signed-off-by: Abdulrasaq Lawani <abdulrasaqolawani@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/Makefile

 # SPDX-License-Identifier: GPL-2.0
+TARGETS += acct
 TARGETS += alsa
 TARGETS += amd-pstate
 TARGETS += arm64

tools/testing/selftests/acct/.gitignore

+acct_syscall
+config
+process_log
\ No newline at end of file

tools/testing/selftests/acct/Makefile

+# SPDX-License-Identifier: GPL-2.0
+TEST_GEN_PROGS := acct_syscall
+CFLAGS += -Wall
+
+include ../lib.mk
\ No newline at end of file

tools/testing/selftests/acct/acct_syscall.c

+// SPDX-License-Identifier: GPL-2.0
+
+/* kselftest for acct() system call
+ *  The acct() system call enables or disables process accounting.
+ */
+
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/wait.h>
+
+#include "../kselftest.h"
+
+int main(void)
+{
+	char filename[] = "process_log";
+	FILE *fp;
+	pid_t child_pid;
+	int sz;
+
+	// Setting up kselftest framework
+	ksft_print_header();
+	ksft_set_plan(1);
+
+	// Check if test is run a root
+	if (geteuid()) {
+		ksft_test_result_skip("This test needs root to run!\n");
+		return 1;
+	}
+
+	// Create file to log closed processes
+	fp = fopen(filename, "w");
+
+	if (!fp) {
+		ksft_test_result_error("%s.\n", strerror(errno));
+		ksft_finished();
+		return 1;
+	}
+
+	acct(filename);
+
+	// Handle error conditions
+	if (errno) {
+		ksft_test_result_error("%s.\n", strerror(errno));
+		fclose(fp);
+		ksft_finished();
+		return 1;
+	}
+
+	// Create child process and wait for it to terminate.
+
+	child_pid = fork();
+
+	if (child_pid < 0) {
+		ksft_test_result_error("Creating a child process to log failed\n");
+		acct(NULL);
+		return 1;
+	} else if (child_pid > 0) {
+		wait(NULL);
+		fseek(fp, 0L, SEEK_END);
+		sz = ftell(fp);
+
+		acct(NULL);
+
+		if (sz <= 0) {
+			ksft_test_result_fail("Terminated child process not logged\n");
+			ksft_exit_fail();
+			return 1;
+		}
+
+		ksft_test_result_pass("Successfully logged terminated process.\n");
+		fclose(fp);
+		ksft_exit_pass();
+		return 0;
+	}
+
+	return 1;
+}