From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8BB9879D2; Wed, 30 Oct 2024 13:03:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730293410; cv=none; b=B/wY20X2cjZ70T/79dQEEHjtHmWbKyk0Wg5KEvCFagqfudo5LoMSLm7txxEZHb43YC4/m/nCr1QhCH2pMlqwmFvHFr7I+Q6SgVYf3QXMtReT9xreWSa9f/HZ3/vLilvKPJho5D/8vxRTB0NBtYCFg1LonskrdxWRWI3vljCmJ9k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730293410; c=relaxed/simple; bh=4JJuFUF260AEDPKZcNLDY2ITdnV9Hn1qJCgacNVcXI0=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=KuoQSSt7x+HN16s/GTZNaDbqwnP9Fp3ioGCcBWZcuildXasySM95/S+gq8HBNrZKWEYSk/Ff+0r5R6Nx0KBk3N2KQK7UCqQIUSlO7oU01hlTGBJXIdI1QwE8/b8fVOrxOUnavqj/sgK08uJR6H8nrLFwbkuY84xqjVBzIH/ANdg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jsKHhAEj; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jsKHhAEj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9D94FC4CEE3; Wed, 30 Oct 2024 13:03:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730293410; bh=4JJuFUF260AEDPKZcNLDY2ITdnV9Hn1qJCgacNVcXI0=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=jsKHhAEj174ZBAEjCPNWFn6LRcIizGpvb0Letj4m3aOyZxCrxX8rqSggxiZKKNURn TgJVSwQf51t3X3ncQ4qbUM6IMnFVdrjxtIoeAQPK1QiIhVkzyNdtWg58tsnbS9OUJI jzObHEA0sDoRfivOYy1lSOyDt4TkMhtdEXaoAQtPIQxJSflER9aur+P4m+KDKVeILv fALxkd+BqeV9xlU7A4HbWB1cb0T1QjkybbIvZ2asZ65i/wAt6GhmdWkl7UFSXIY+bE 3dEdRbk5znzwbA1xjUBdAoNnUYGMAnutUxbXYZrv814igekFWKRCQEgU0850+XMmr4 SQMk/ee5ZTuUQ== Message-ID: <5b8318018dd316f618eea059f610579a205c05db.camel@kernel.org> Subject: Re: [RFC bpf-next fanotify 2/5] samples/fanotify: Add a sample fanotify fastpath handler From: Jeff Layton To: Song Liu , bpf@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: kernel-team@meta.com, andrii@kernel.org, eddyz87@gmail.com, ast@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, kpsingh@kernel.org, mattbobrowski@google.com, amir73il@gmail.com, repnop@google.com, josef@toxicpanda.com Date: Wed, 30 Oct 2024 09:03:27 -0400 In-Reply-To: <20241029231244.2834368-3-song@kernel.org> References: <20241029231244.2834368-1-song@kernel.org> <20241029231244.2834368-3-song@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; 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text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.52.4 (3.52.4-2.fc40) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2024-10-29 at 16:12 -0700, Song Liu wrote: > This fastpath handler filters out events for files with certain prefixes. > To use it: >=20 > [root] insmod fastpath-mod.ko # This requires root. >=20 > [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 >=20 > Accessing file xx # this is the output from fastpath_user >=20 > Signed-off-by: Song Liu > --- > 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 >=20 > 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/ > =20 > FARADAY FOTG210 USB2 DUAL-ROLE CONTROLLER > M: Linus Walleij > 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 > =20 > +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. > =20 > +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-$(CONFIG_SAMPLE_ANDROID_BINDERFS) +=3D binderfs > subdir-$(CONFIG_SAMPLE_CGROUP) +=3D cgroup > obj-$(CONFIG_SAMPLE_CONFIGFS) +=3D configfs/ > obj-$(CONFIG_SAMPLE_CONNECTOR) +=3D connector/ > -obj-$(CONFIG_SAMPLE_FANOTIFY_ERROR) +=3D fanotify/ > +obj-$(CONFIG_SAMPLE_FANOTIFY) +=3D fanotify/ > subdir-$(CONFIG_SAMPLE_HIDRAW) +=3D hidraw > obj-$(CONFIG_SAMPLE_HW_BREAKPOINT) +=3D hw_breakpoint/ > obj-$(CONFIG_SAMPLE_KDB) +=3D kdb/ > diff --git a/samples/fanotify/.gitignore b/samples/fanotify/.gitignore > index d74593e8b2de..306e1ddec4e0 100644 > --- a/samples/fanotify/.gitignore > +++ b/samples/fanotify/.gitignore > @@ -1 +1,2 @@ > fs-monitor > +fastpath-user > diff --git a/samples/fanotify/Makefile b/samples/fanotify/Makefile > index e20db1bdde3b..f5bbd7380104 100644 > --- a/samples/fanotify/Makefile > +++ b/samples/fanotify/Makefile > @@ -1,5 +1,8 @@ > # SPDX-License-Identifier: GPL-2.0-only > -userprogs-always-y +=3D fs-monitor > +userprogs-always-$(CONFIG_SAMPLE_FANOTIFY_ERROR) +=3D fs-monitor > =20 > userccflags +=3D -I usr/include -Wall > =20 > +obj-$(CONFIG_SAMPLE_FANOTIFY_FASTPATH) +=3D fastpath-mod.o > + > +userprogs-always-$(CONFIG_SAMPLE_FANOTIFY_FASTPATH) +=3D 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 > +#include > +#include > +#include > +#include > + > +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 =3D 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 =3D fp_hook->data; > + > + list_for_each_entry(item, &fp_data->item_list, list) { > + if (strstr(file_name->name, item->prefix) =3D=3D (char *)file_name->na= me) > + return FAN_FP_RET_SKIP_EVENT; > + } > + > + return FAN_FP_RET_SEND_TO_USERSPACE; > +} The sample is a little underwhelming and everyone hates string parsing in the kernel ;). It'd be nice to see a more real-world use-case for this. Could this be used to implement subtree filtering? I guess you'd have to walk back up the directory tree and see whether it had a given ancestor? > + > +static int add_item(struct sample_fp_data *fp_data, const char *prev) > +{ > + struct prefix_item *item; > + > + item =3D kzalloc(sizeof(*item), GFP_KERNEL); > + if (!item) > + return -ENOMEM; > + item->prefix =3D 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 =3D 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 =3D kstrndup(args, FAN_FP_ARGS_MAX, GFP_KERNEL); > + if (!fp_data->str_table) { > + ret =3D -ENOMEM; > + goto err_out; > + } > + > + INIT_LIST_HEAD(&fp_data->item_list); > + prev =3D fp_data->str_table; > + p =3D fp_data->str_table; > + > + /* Update the list replace ',' with '\n'*/ > + while ((p =3D strchr(p, ',')) !=3D NULL) { > + *p =3D '\0'; > + ret =3D add_item(fp_data, prev); > + if (ret) > + goto err_out; > + p =3D p + 1; > + prev =3D p; > + } > + > + ret =3D add_item(fp_data, prev); > + if (ret) > + goto err_out; > + > + fp_hook->data =3D 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 =3D { > + .fp_handler =3D sample_fp_handler, > + .fp_init =3D sample_fp_init, > + .fp_free =3D sample_fp_free, > + .name =3D "ignore-prefix", > + .owner =3D 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 > +#include > +#include > +#include > +#include > +#include > +#include > + > +static int total_event_cnt; > + > +static void handle_notifications(char *buffer, int len) > +{ > + struct fanotify_event_metadata *event =3D > + (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 =3D FAN_EVENT_NEXT(event, len)) = { > + for (off =3D sizeof(*event) ; off < event->event_len; > + off +=3D info->len) { > + info =3D (struct fanotify_event_info_header *) > + ((char *) event + off); > + switch (info->info_type) { > + case FAN_EVENT_INFO_TYPE_DFID_NAME: > + fid =3D (struct fanotify_event_info_fid *) info; > + handle =3D (struct file_handle *)&fid->handle; > + name =3D (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 =3D { > + .name =3D "ignore-prefix", > + .version =3D 1, > + .flags =3D 0, > + }; > + char buffer[BUFSIZ]; > + int fd; > + > + if (argc < 3) { > + printf("Usage\n" > + "\t %s \n", > + argv[0]); > + return 1; > + } > + > + args.init_args =3D (__u64)argv[2]; > + args.init_args_len =3D strlen(argv[2]) + 1; > + > + fd =3D 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 =3D read(fd, buffer, BUFSIZ); > + > + if (n < 0) > + errx(1, "read"); > + > + handle_notifications(buffer, n); > + } > + > + ioctl(fd, FAN_IOC_DEL_FP); > + close(fd); > + > + return 0; > +} --=20 Jeff Layton