[LTP] [PATCH 2/2] Add test for fanotify monitoring of tracing filesystem

[Jan Kara]

On Mon 23-02-26 17:30:28, Cyril Hrubis wrote:
> Hi!
> CCing Jan and Amir.
> 
> > Add a test that will start monitoring the kernel tracing filesystem,
> > write new configuration into tracing sysfiles and then verify
> > that the writes triggered fanotify events.
> > 
> > Signed-off-by: Martin Doucha <mdoucha@suse.cz>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> > ---
> >  runtest/syscalls                              |   1 +
> >  runtest/tracing                               |   1 +
> >  testcases/kernel/syscalls/fanotify/.gitignore |   1 +
> >  .../kernel/syscalls/fanotify/fanotify25.c     | 126 ++++++++++++++++++
> >  4 files changed, 129 insertions(+)
> >  create mode 100644 testcases/kernel/syscalls/fanotify/fanotify25.c
> > 
> > diff --git a/runtest/syscalls b/runtest/syscalls
> > index 2f629e4e4..30224f5b4 100644
> > --- a/runtest/syscalls
> > +++ b/runtest/syscalls
> > @@ -671,6 +671,7 @@ fanotify21 fanotify21
> >  fanotify22 fanotify22
> >  fanotify23 fanotify23
> >  fanotify24 fanotify24
> > +fanotify25 fanotify25
> >  
> >  ioperm01 ioperm01
> >  ioperm02 ioperm02
> > diff --git a/runtest/tracing b/runtest/tracing
> > index d2700ca57..674e2ad97 100644
> > --- a/runtest/tracing
> > +++ b/runtest/tracing
> > @@ -3,6 +3,7 @@ ftrace_regression01	ftrace_regression01.sh
> >  ftrace_regression02	ftrace_regression02.sh
> >  ftrace-stress-test	ftrace_stress_test.sh 90
> >  dynamic_debug01		dynamic_debug01.sh
> > +fanotify25 fanotify25
> >  pt_full_trace_basic pt_test
> >  pt_snapshot_trace_basic pt_test -m
> >  pt_ex_user pt_test -e user
> > diff --git a/testcases/kernel/syscalls/fanotify/.gitignore b/testcases/kernel/syscalls/fanotify/.gitignore
> > index 16af3db85..d6d0599f1 100644
> > --- a/testcases/kernel/syscalls/fanotify/.gitignore
> > +++ b/testcases/kernel/syscalls/fanotify/.gitignore
> > @@ -22,4 +22,5 @@
> >  /fanotify22
> >  /fanotify23
> >  /fanotify24
> > +/fanotify25
> >  /fanotify_child
> > diff --git a/testcases/kernel/syscalls/fanotify/fanotify25.c b/testcases/kernel/syscalls/fanotify/fanotify25.c
> > new file mode 100644
> > index 000000000..c982f3225
> > --- /dev/null
> > +++ b/testcases/kernel/syscalls/fanotify/fanotify25.c
> > @@ -0,0 +1,126 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * Copyright (C) 2026 SUSE LLC
> > + * Author: Petr Pavlu <ppavlu@suse.cz>
> > + * LTP port: Martin Doucha <mdoucha@suse.cz>
> > + */
> > +
> > +/*\
> > + * Verify that fanotify monitoring can be applied to the tracing filesystem
> > + * and write events will be correctly delivered.
> > + */
> > +
> > +#define _GNU_SOURCE
> > +#include "tst_test.h"
> > +#include "lapi/mount.h"
> > +
> > +#ifdef HAVE_SYS_FANOTIFY_H
> > +#include "fanotify.h"
> > +
> > +#define MNTPOINT "/sys/kernel/tracing"
> > +#define EVENTS_SYSFILE MNTPOINT "/kprobe_events"
> > +
> > +static const struct traceconfig {
> > +	const char *filename;
> > +	const char *wdata;
> > +} trace_cmds[] = {
> > +	{EVENTS_SYSFILE, "p:ltp_load_module_0 load_module"},
> > +	{MNTPOINT "/events/kprobes/ltp_load_module_0/enable", "1"},
> > +	{MNTPOINT "/events/kprobes/ltp_load_module_0/enable", "0"},
> > +	{EVENTS_SYSFILE, "-:ltp_load_module_0"},
> > +	{}
> > +};
> > +
> > +static int fan_fd = -1;
> > +static int unmount_needed;
> > +
> > +static void setup(void)
> > +{
> > +	if (tst_fs_type(MNTPOINT) != TST_TRACEFS_MAGIC) {
> > +		SAFE_MOUNT("tracefs", MNTPOINT, "tracefs",
> > +			MS_NODEV | MS_NOEXEC | MS_NOSUID, NULL);
> > +		unmount_needed = 1;
> > +	}
> > +
> > +	if (access(EVENTS_SYSFILE, F_OK))
> > +		tst_brk(TCONF, "Kprobe events not supported by kernel");
> > +
> > +	fan_fd = SAFE_FANOTIFY_INIT(FAN_CLASS_NOTIF | FAN_NONBLOCK, O_RDONLY);
> > +	SAFE_FANOTIFY_MARK(fan_fd, FAN_MARK_ADD | FAN_MARK_MOUNT, FAN_MODIFY,
> > +		-1, MNTPOINT);
> > +}
> > +
> > +static void do_child(void)
> > +{
> > +	int i, fd, events, ret;
> > +	pid_t pid = getpid();
> > +	struct fanotify_event_metadata buf;
> > +
> > +	for (i = 0, events = 0; trace_cmds[i].filename; i++) {
> > +		fd = SAFE_OPEN(trace_cmds[i].filename, O_WRONLY, 0644);
> > +		SAFE_WRITE(1, fd, trace_cmds[i].wdata,
> > +			strlen(trace_cmds[i].wdata));
> > +		SAFE_CLOSE(fd);
> > +
> > +		while ((ret = read(fan_fd, &buf, sizeof(buf))) > 0) {
> > +			if (buf.pid != pid)
> > +				continue;
> > +
> > +			if (!(buf.mask & FAN_MODIFY)) {
> > +				tst_res(TFAIL, "Unexpected event %llx",
> > +					buf.mask);
> > +				continue;
> > +			}
> > +
> > +			events++;
> > +		}
> > +
> > +		if (ret < 0 && errno != EAGAIN)
> > +			tst_res(TFAIL | TERRNO, "fanotify read() failed");
> > +	}
> > +
> > +	if (events == i)
> > +		tst_res(TPASS, "Received %d events", events);
> > +	else
> > +		tst_res(TFAIL, "Received %d events, expected %d", events, i);
> > +}
> > +
> > +static void run(void)
> > +{
> > +	/*
> > +	 * Fork a child to do the actual trace writes, otherwise tracefs
> > +	 * would be busy until the current process exits and it would become
> > +	 * impossible to unmount in cleanup().
> > +	 */
> > +	if (!SAFE_FORK()) {
> > +		do_child();
> > +		SAFE_CLOSE(fan_fd);
> > +		exit(0);
> > +	}
> > +}
> > +
> > +static void cleanup(void)
> > +{
> > +	if (fan_fd >= 0)
> > +		SAFE_CLOSE(fan_fd);
> > +
> > +	if (unmount_needed)
> > +		SAFE_UMOUNT(MNTPOINT);
> > +}
> > +
> > +static struct tst_test test = {
> > +	.test_all = run,
> > +	.setup = setup,
> > +	.cleanup = cleanup,
> > +	.needs_root = 1,
> > +	.forks_child = 1,
> > +	.taint_check = TST_TAINT_W | TST_TAINT_D,
> > +	.needs_kconfigs = (const char *[]) {
> > +		"CONFIG_TRACING",
> > +		NULL
> > +	}
> > +};
> > +
> > +#else
> > +	TST_TEST_TCONF("system doesn't have required fanotify support");
> > +#endif
> > -- 
> > 2.52.0
> > 
> > 
> > -- 
> > Mailing list info: https://lists.linux.it/listinfo/ltp
> 
> -- 
> Cyril Hrubis
> chrubis@suse.cz
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR