This fastpath handler filters out events for files with certain prefixes.
To use it:
[root] insmod fastpath-mod.ko # This requires root.
[user] ./fastpath-user /tmp a,b,c & # Root is not needed
[user] touch /tmp/aa # a is in the prefix list (a,b,c), no events
[user] touch /tmp/xx # x is not in the prefix list, generates events
Accessing file xx # this is the output from fastpath_user
Signed-off-by: Song Liu <song@xxxxxxxxxx>
---
MAINTAINERS | 1 +
samples/Kconfig | 20 ++++-
samples/Makefile | 2 +-
samples/fanotify/.gitignore | 1 +
samples/fanotify/Makefile | 5 +-
samples/fanotify/fastpath-mod.c | 138 +++++++++++++++++++++++++++++++
samples/fanotify/fastpath-user.c | 90 ++++++++++++++++++++
7 files changed, 254 insertions(+), 3 deletions(-)
create mode 100644 samples/fanotify/fastpath-mod.c
create mode 100644 samples/fanotify/fastpath-user.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 7ad507f49324..8939a48b2d99 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8658,6 +8658,7 @@ S: Maintained
F: fs/notify/fanotify/
F: include/linux/fanotify.h
F: include/uapi/linux/fanotify.h
+F: samples/fanotify/
FARADAY FOTG210 USB2 DUAL-ROLE CONTROLLER
M: Linus Walleij <linus.walleij@xxxxxxxxxx>
diff --git a/samples/Kconfig b/samples/Kconfig
index b288d9991d27..b0d3dff48bb0 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -149,15 +149,33 @@ config SAMPLE_CONNECTOR
with it.
See also Documentation/driver-api/connector.rst
+config SAMPLE_FANOTIFY
+ bool "Build fanotify monitoring sample"
+ depends on FANOTIFY && CC_CAN_LINK && HEADERS_INSTALL
+ help
+ When enabled, this builds samples for fanotify.
+ There multiple samples for fanotify. Please see the
+ following configs for more details of these
+ samples.
+
config SAMPLE_FANOTIFY_ERROR
bool "Build fanotify error monitoring sample"
- depends on FANOTIFY && CC_CAN_LINK && HEADERS_INSTALL
+ depends on SAMPLE_FANOTIFY
help
When enabled, this builds an example code that uses the
FAN_FS_ERROR fanotify mechanism to monitor filesystem
errors.
See also Documentation/admin-guide/filesystem-monitoring.rst.
+config SAMPLE_FANOTIFY_FASTPATH
+ tristate "Build fanotify fastpath sample"
+ depends on SAMPLE_FANOTIFY && m
+ help
+ When enabled, this builds kernel module that contains a
+ fanotify fastpath handler.
+ The fastpath handler filters out certain filename
+ prefixes for the fanotify user.
+
config SAMPLE_HIDRAW
bool "hidraw sample"
depends on CC_CAN_LINK && HEADERS_INSTALL
diff --git a/samples/Makefile b/samples/Makefile
index b85fa64390c5..108360972626 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -6,7 +6,7 @@ subdir-$(CONFIG_SAMPLE_ANDROID_BINDERFS) += binderfs
subdir-$(CONFIG_SAMPLE_CGROUP) += cgroup
obj-$(CONFIG_SAMPLE_CONFIGFS) += configfs/
obj-$(CONFIG_SAMPLE_CONNECTOR) += connector/
-obj-$(CONFIG_SAMPLE_FANOTIFY_ERROR) += fanotify/
+obj-$(CONFIG_SAMPLE_FANOTIFY) += fanotify/
subdir-$(CONFIG_SAMPLE_HIDRAW) += hidraw
obj-$(CONFIG_SAMPLE_HW_BREAKPOINT) += hw_breakpoint/
obj-$(CONFIG_SAMPLE_KDB) += kdb/
diff --git a/samples/fanotify/.gitignore b/samples/fanotify/.gitignore
index d74593e8b2de..306e1ddec4e0 100644
--- a/samples/fanotify/.gitignore
+++ b/samples/fanotify/.gitignore
@@ -1 +1,2 @@
fs-monitor
+fastpath-user
diff --git a/samples/fanotify/Makefile b/samples/fanotify/Makefile
index e20db1bdde3b..f5bbd7380104 100644
--- a/samples/fanotify/Makefile
+++ b/samples/fanotify/Makefile
@@ -1,5 +1,8 @@
# SPDX-License-Identifier: GPL-2.0-only
-userprogs-always-y += fs-monitor
+userprogs-always-$(CONFIG_SAMPLE_FANOTIFY_ERROR) += fs-monitor
userccflags += -I usr/include -Wall
+obj-$(CONFIG_SAMPLE_FANOTIFY_FASTPATH) += fastpath-mod.o
+
+userprogs-always-$(CONFIG_SAMPLE_FANOTIFY_FASTPATH) += fastpath-user
diff --git a/samples/fanotify/fastpath-mod.c b/samples/fanotify/fastpath-mod.c
new file mode 100644
index 000000000000..06c4b42ff114
--- /dev/null
+++ b/samples/fanotify/fastpath-mod.c
@@ -0,0 +1,138 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/fsnotify.h>
+#include <linux/fanotify.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/string.h>
+
+struct prefix_item {
+ const char *prefix;
+ struct list_head list;
+};
+
+struct sample_fp_data {
+ /*
+ * str_table contains all the prefixes to ignore. For example,
+ * "prefix1\0prefix2\0prefix3"
+ */
+ char *str_table;
+
+ /* item->prefix points to different prefixes in the str_table. */
+ struct list_head item_list;
+};
+
+static int sample_fp_handler(struct fsnotify_group *group,
+ struct fanotify_fastpath_hook *fp_hook,
+ struct fanotify_fastpath_event *fp_event)
+{
+ const struct qstr *file_name = fp_event->file_name;
+ struct sample_fp_data *fp_data;
+ struct prefix_item *item;
+
+ if (!file_name)
+ return FAN_FP_RET_SEND_TO_USERSPACE;
+ fp_data = fp_hook->data;
+
+ list_for_each_entry(item, &fp_data->item_list, list) {
+ if (strstr(file_name->name, item->prefix) == (char *)file_name->name)
+ return FAN_FP_RET_SKIP_EVENT;
+ }
+
+ return FAN_FP_RET_SEND_TO_USERSPACE;
+}
+
+static int add_item(struct sample_fp_data *fp_data, const char *prev)
+{
+ struct prefix_item *item;
+
+ item = kzalloc(sizeof(*item), GFP_KERNEL);
+ if (!item)
+ return -ENOMEM;
+ item->prefix = prev;
+ list_add_tail(&item->list, &fp_data->item_list);
+ return 0;
+}
+
+static void free_sample_fp_data(struct sample_fp_data *fp_data)
+{
+ struct prefix_item *item, *tmp;
+
+ list_for_each_entry_safe(item, tmp, &fp_data->item_list, list) {
+ list_del_init(&item->list);
+ kfree(item);
+ }
+ kfree(fp_data->str_table);
+ kfree(fp_data);
+}
+
+static int sample_fp_init(struct fanotify_fastpath_hook *fp_hook, const char *args)
+{
+ struct sample_fp_data *fp_data = kzalloc(sizeof(struct sample_fp_data), GFP_KERNEL);
+ char *p, *prev;
+ int ret;
+
+ if (!fp_data)
+ return -ENOMEM;
+
+ /* Make a copy of the list of prefix to ignore */
+ fp_data->str_table = kstrndup(args, FAN_FP_ARGS_MAX, GFP_KERNEL);
+ if (!fp_data->str_table) {
+ ret = -ENOMEM;
+ goto err_out;
+ }
+
+ INIT_LIST_HEAD(&fp_data->item_list);
+ prev = fp_data->str_table;
+ p = fp_data->str_table;
+
+ /* Update the list replace ',' with '\n'*/
+ while ((p = strchr(p, ',')) != NULL) {
+ *p = '\0';
+ ret = add_item(fp_data, prev);
+ if (ret)
+ goto err_out;
+ p = p + 1;
+ prev = p;
+ }
+
+ ret = add_item(fp_data, prev);
+ if (ret)
+ goto err_out;
+
+ fp_hook->data = fp_data;
+
+ return 0;
+
+err_out:
+ free_sample_fp_data(fp_data);
+ return ret;
+}
+
+static void sample_fp_free(struct fanotify_fastpath_hook *fp_hook)
+{
+ free_sample_fp_data(fp_hook->data);
+}
+
+static struct fanotify_fastpath_ops fan_fp_ignore_a_ops = {
+ .fp_handler = sample_fp_handler,
+ .fp_init = sample_fp_init,
+ .fp_free = sample_fp_free,
+ .name = "ignore-prefix",
+ .owner = THIS_MODULE,
+};
+
+static int __init fanotify_fastpath_sample_init(void)
+{
+ return fanotify_fastpath_register(&fan_fp_ignore_a_ops);
+}
+static void __exit fanotify_fastpath_sample_exit(void)
+{
+ fanotify_fastpath_unregister(&fan_fp_ignore_a_ops);
+}
+
+module_init(fanotify_fastpath_sample_init);
+module_exit(fanotify_fastpath_sample_exit);
+
+MODULE_AUTHOR("Song Liu");
+MODULE_DESCRIPTION("Example fanotify fastpath handler");
+MODULE_LICENSE("GPL");
diff --git a/samples/fanotify/fastpath-user.c b/samples/fanotify/fastpath-user.c
new file mode 100644
index 000000000000..f301c4e0d21a
--- /dev/null
+++ b/samples/fanotify/fastpath-user.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <err.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/fanotify.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+
+static int total_event_cnt;
+
+static void handle_notifications(char *buffer, int len)
+{
+ struct fanotify_event_metadata *event =
+ (struct fanotify_event_metadata *) buffer;
+ struct fanotify_event_info_header *info;
+ struct fanotify_event_info_fid *fid;
+ struct file_handle *handle;
+ char *name;
+ int off;
+
+ for (; FAN_EVENT_OK(event, len); event = FAN_EVENT_NEXT(event, len)) {
+ for (off = sizeof(*event) ; off < event->event_len;
+ off += info->len) {
+ info = (struct fanotify_event_info_header *)
+ ((char *) event + off);
+ switch (info->info_type) {
+ case FAN_EVENT_INFO_TYPE_DFID_NAME:
+ fid = (struct fanotify_event_info_fid *) info;
+ handle = (struct file_handle *)&fid->handle;
+ name = (char *)handle + sizeof(*handle) + handle->handle_bytes;
+
+ printf("Accessing file %s\n", name);
+ total_event_cnt++;
+ break;
+ default:
+ break;
+ }
+ }
+ }
+}
+
+int main(int argc, char **argv)
+{
+ struct fanotify_fastpath_args args = {
+ .name = "ignore-prefix",
+ .version = 1,
+ .flags = 0,
+ };
+ char buffer[BUFSIZ];
+ int fd;
+
+ if (argc < 3) {
+ printf("Usage\n"
+ "\t %s <path to monitor> <prefix to ignore>\n",
+ argv[0]);
+ return 1;
+ }
+
+ args.init_args = (__u64)argv[2];
+ args.init_args_len = strlen(argv[2]) + 1;
+
+ fd = fanotify_init(FAN_CLASS_NOTIF | FAN_REPORT_NAME | FAN_REPORT_DIR_FID, O_RDONLY);
+ if (fd < 0)
+ errx(1, "fanotify_init");
+
+ if (fanotify_mark(fd, FAN_MARK_ADD,
+ FAN_OPEN | FAN_ONDIR | FAN_EVENT_ON_CHILD,
+ AT_FDCWD, argv[1])) {
+ errx(1, "fanotify_mark");
+ }
+
+ if (ioctl(fd, FAN_IOC_ADD_FP, &args))
+ errx(1, "ioctl");
+
+ while (total_event_cnt < 10) {
+ int n = read(fd, buffer, BUFSIZ);
+
+ if (n < 0)
+ errx(1, "read");
+
+ handle_notifications(buffer, n);
+ }
+
+ ioctl(fd, FAN_IOC_DEL_FP);
+ close(fd);
+
+ return 0;
+}
--
2.43.5
