diff mbox series

[net-next,v7,4/4] eventpoll: Add epoll ioctl for epoll_params

Message ID 20240209211528.51234-5-jdamato@fastly.com (mailing list archive)
State New, archived
Headers show
Series Per epoll context busy poll support | expand

Commit Message

Joe Damato Feb. 9, 2024, 9:15 p.m. UTC
Add an ioctl for getting and setting epoll_params. User programs can use
this ioctl to get and set the busy poll usec time, packet budget, and
prefer busy poll params for a specific epoll context.

Parameters are limited:
  - busy_poll_usecs is limited to <= s32_max
  - busy_poll_budget is limited to <= NAPI_POLL_WEIGHT by unprivileged
    users (!capable(CAP_NET_ADMIN))
  - prefer_busy_poll must be 0 or 1
  - __pad must be 0

Signed-off-by: Joe Damato <jdamato@fastly.com>
Acked-by: Stanislav Fomichev <sdf@google.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
---
 .../userspace-api/ioctl/ioctl-number.rst      |  1 +
 fs/eventpoll.c                                | 72 +++++++++++++++++++
 include/uapi/linux/eventpoll.h                | 13 ++++
 3 files changed, 86 insertions(+)

Comments

Eric Dumazet Feb. 11, 2024, 9:40 a.m. UTC | #1
On Fri, Feb 9, 2024 at 10:15 PM Joe Damato <jdamato@fastly.com> wrote:
>
> Add an ioctl for getting and setting epoll_params. User programs can use
> this ioctl to get and set the busy poll usec time, packet budget, and
> prefer busy poll params for a specific epoll context.
>
> Parameters are limited:
>   - busy_poll_usecs is limited to <= s32_max
>   - busy_poll_budget is limited to <= NAPI_POLL_WEIGHT by unprivileged
>     users (!capable(CAP_NET_ADMIN))
>   - prefer_busy_poll must be 0 or 1
>   - __pad must be 0
>
> Signed-off-by: Joe Damato <jdamato@fastly.com>
> Acked-by: Stanislav Fomichev <sdf@google.com>
> Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
> ---
>  .../userspace-api/ioctl/ioctl-number.rst      |  1 +
>  fs/eventpoll.c                                | 72 +++++++++++++++++++
>  include/uapi/linux/eventpoll.h                | 13 ++++
>  3 files changed, 86 insertions(+)
>
> diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
> index 457e16f06e04..b33918232f78 100644
> --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> @@ -309,6 +309,7 @@ Code  Seq#    Include File                                           Comments
>  0x89  0B-DF  linux/sockios.h
>  0x89  E0-EF  linux/sockios.h                                         SIOCPROTOPRIVATE range
>  0x89  F0-FF  linux/sockios.h                                         SIOCDEVPRIVATE range
> +0x8A  00-1F  linux/eventpoll.h
>  0x8B  all    linux/wireless.h
>  0x8C  00-3F                                                          WiNRADiO driver
>                                                                       <http://www.winradio.com.au/>
> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> index 1b8d01af0c2c..aa58d42737e6 100644
> --- a/fs/eventpoll.c
> +++ b/fs/eventpoll.c
> @@ -37,6 +37,7 @@
>  #include <linux/seq_file.h>
>  #include <linux/compat.h>
>  #include <linux/rculist.h>
> +#include <linux/capability.h>
>  #include <net/busy_poll.h>
>
>  /*
> @@ -494,6 +495,49 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
>         ep->napi_id = napi_id;
>  }
>
> +static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd,
> +                                 unsigned long arg)
> +{
> +       struct eventpoll *ep = file->private_data;
> +       void __user *uarg = (void __user *)arg;
> +       struct epoll_params epoll_params;
> +
> +       switch (cmd) {
> +       case EPIOCSPARAMS:
> +               if (copy_from_user(&epoll_params, uarg, sizeof(epoll_params)))
> +                       return -EFAULT;
> +
> +               /* pad byte must be zero */
> +               if (epoll_params.__pad)
> +                       return -EINVAL;
> +
> +               if (epoll_params.busy_poll_usecs > S32_MAX)
> +                       return -EINVAL;
> +
> +               if (epoll_params.prefer_busy_poll > 1)
> +                       return -EINVAL;
> +
> +               if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT &&
> +                   !capable(CAP_NET_ADMIN))
> +                       return -EPERM;
> +
> +               ep->busy_poll_usecs = epoll_params.busy_poll_usecs;

You need WRITE_ONCE(ep->XXX, val); for all these settings.

> +               ep->busy_poll_budget = epoll_params.busy_poll_budget;
> +               ep->prefer_busy_poll = epoll_params.prefer_busy_poll;
> +               return 0;
> +       case EPIOCGPARAMS:
> +               memset(&epoll_params, 0, sizeof(epoll_params));
> +               epoll_params.busy_poll_usecs = ep->busy_poll_usecs;

You need to use READ_ONCE(ep->XXXXX) for the three reads.


> +               epoll_params.busy_poll_budget = ep->busy_poll_budget;
> +               epoll_params.prefer_busy_poll = ep->prefer_busy_poll;
> +               if (copy_to_user(uarg, &epoll_params, sizeof(epoll_params)))
> +                       return -EFAULT;
> +               return 0;
> +       default:
> +               return -ENOIOCTLCMD;
> +       }
> +}
>
diff mbox series

Patch

diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
index 457e16f06e04..b33918232f78 100644
--- a/Documentation/userspace-api/ioctl/ioctl-number.rst
+++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
@@ -309,6 +309,7 @@  Code  Seq#    Include File                                           Comments
 0x89  0B-DF  linux/sockios.h
 0x89  E0-EF  linux/sockios.h                                         SIOCPROTOPRIVATE range
 0x89  F0-FF  linux/sockios.h                                         SIOCDEVPRIVATE range
+0x8A  00-1F  linux/eventpoll.h
 0x8B  all    linux/wireless.h
 0x8C  00-3F                                                          WiNRADiO driver
                                                                      <http://www.winradio.com.au/>
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 1b8d01af0c2c..aa58d42737e6 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -37,6 +37,7 @@ 
 #include <linux/seq_file.h>
 #include <linux/compat.h>
 #include <linux/rculist.h>
+#include <linux/capability.h>
 #include <net/busy_poll.h>
 
 /*
@@ -494,6 +495,49 @@  static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
 	ep->napi_id = napi_id;
 }
 
+static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd,
+				  unsigned long arg)
+{
+	struct eventpoll *ep = file->private_data;
+	void __user *uarg = (void __user *)arg;
+	struct epoll_params epoll_params;
+
+	switch (cmd) {
+	case EPIOCSPARAMS:
+		if (copy_from_user(&epoll_params, uarg, sizeof(epoll_params)))
+			return -EFAULT;
+
+		/* pad byte must be zero */
+		if (epoll_params.__pad)
+			return -EINVAL;
+
+		if (epoll_params.busy_poll_usecs > S32_MAX)
+			return -EINVAL;
+
+		if (epoll_params.prefer_busy_poll > 1)
+			return -EINVAL;
+
+		if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT &&
+		    !capable(CAP_NET_ADMIN))
+			return -EPERM;
+
+		ep->busy_poll_usecs = epoll_params.busy_poll_usecs;
+		ep->busy_poll_budget = epoll_params.busy_poll_budget;
+		ep->prefer_busy_poll = epoll_params.prefer_busy_poll;
+		return 0;
+	case EPIOCGPARAMS:
+		memset(&epoll_params, 0, sizeof(epoll_params));
+		epoll_params.busy_poll_usecs = ep->busy_poll_usecs;
+		epoll_params.busy_poll_budget = ep->busy_poll_budget;
+		epoll_params.prefer_busy_poll = ep->prefer_busy_poll;
+		if (copy_to_user(uarg, &epoll_params, sizeof(epoll_params)))
+			return -EFAULT;
+		return 0;
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+
 #else
 
 static inline bool ep_busy_loop(struct eventpoll *ep, int nonblock)
@@ -505,6 +549,12 @@  static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
 {
 }
 
+static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd,
+				  unsigned long arg)
+{
+	return -EOPNOTSUPP;
+}
+
 #endif /* CONFIG_NET_RX_BUSY_POLL */
 
 /*
@@ -864,6 +914,26 @@  static void ep_clear_and_put(struct eventpoll *ep)
 		ep_free(ep);
 }
 
+static long ep_eventpoll_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	int ret;
+
+	if (!is_file_epoll(file))
+		return -EINVAL;
+
+	switch (cmd) {
+	case EPIOCSPARAMS:
+	case EPIOCGPARAMS:
+		ret = ep_eventpoll_bp_ioctl(file, cmd, arg);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
 static int ep_eventpoll_release(struct inode *inode, struct file *file)
 {
 	struct eventpoll *ep = file->private_data;
@@ -970,6 +1040,8 @@  static const struct file_operations eventpoll_fops = {
 	.release	= ep_eventpoll_release,
 	.poll		= ep_eventpoll_poll,
 	.llseek		= noop_llseek,
+	.unlocked_ioctl	= ep_eventpoll_ioctl,
+	.compat_ioctl   = compat_ptr_ioctl,
 };
 
 /*
diff --git a/include/uapi/linux/eventpoll.h b/include/uapi/linux/eventpoll.h
index cfbcc4cc49ac..4f4b948ef381 100644
--- a/include/uapi/linux/eventpoll.h
+++ b/include/uapi/linux/eventpoll.h
@@ -85,4 +85,17 @@  struct epoll_event {
 	__u64 data;
 } EPOLL_PACKED;
 
+struct epoll_params {
+	__u32 busy_poll_usecs;
+	__u16 busy_poll_budget;
+	__u8 prefer_busy_poll;
+
+	/* pad the struct to a multiple of 64bits */
+	__u8 __pad;
+};
+
+#define EPOLL_IOC_TYPE 0x8A
+#define EPIOCSPARAMS _IOW(EPOLL_IOC_TYPE, 0x01, struct epoll_params)
+#define EPIOCGPARAMS _IOR(EPOLL_IOC_TYPE, 0x02, struct epoll_params)
+
 #endif /* _UAPI_LINUX_EVENTPOLL_H */