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SubjectRe: [RFC PATCH v4 1/3] vfio: platform: add device properties skeleton and user API
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On Wed, 2015-09-09 at 11:17 +0200, Baptiste Reynal wrote:
> From: Antonios Motakis <a.motakis@virtualopensystems.com>
>
> This patch introduces an API that allows to return device properties (OF
> or ACPI) of a device bound to the vfio-platform/vfio-amba driver and the
> skeleton of the implementation for VFIO_PLATFORM. Information about any
> device node bound by VFIO_PLATFORM should be queried via the introduced
> ioctl VFIO_DEVICE_GET_DEV_PROPERTY.
>
> The user needs to know the name and the data type of the property he is
> accessing.
>
> Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
> Signed-off-by: Baptiste Reynal <b.reynal@virtualopensystems.com>
>
> ---
> v3 -> v4:
> - added flags placeholder in vfio_dev_properties
> - ioctl returns -E2BIG if the buffer is too small
> - details VFIO_DEVICE_GET_DEV_PROPERTY documentation
> ---
> drivers/vfio/platform/Makefile | 3 +-
> drivers/vfio/platform/properties.c | 77 +++++++++++++++++++++++++++
> drivers/vfio/platform/vfio_platform_common.c | 35 ++++++++++++
> drivers/vfio/platform/vfio_platform_private.h | 7 +++
> include/uapi/linux/vfio.h | 31 +++++++++++
> 5 files changed, 152 insertions(+), 1 deletion(-)
> create mode 100644 drivers/vfio/platform/properties.c
>
> diff --git a/drivers/vfio/platform/Makefile b/drivers/vfio/platform/Makefile
> index 9ce8afe..37cf5ed 100644
> --- a/drivers/vfio/platform/Makefile
> +++ b/drivers/vfio/platform/Makefile
> @@ -1,5 +1,6 @@
>
> -vfio-platform-y := vfio_platform.o vfio_platform_common.o vfio_platform_irq.o
> +vfio-platform-y := vfio_platform.o vfio_platform_common.o vfio_platform_irq.o \
> + properties.o
>
> obj-$(CONFIG_VFIO_PLATFORM) += vfio-platform.o
> obj-$(CONFIG_VFIO_PLATFORM) += reset/
> diff --git a/drivers/vfio/platform/properties.c b/drivers/vfio/platform/properties.c
> new file mode 100644
> index 0000000..98754c2
> --- /dev/null
> +++ b/drivers/vfio/platform/properties.c
> @@ -0,0 +1,77 @@
> +/*
> + * Copyright (C) 2015 - Virtual Open Systems
> + * Authors: Antonios Motakis <a.motakis@virtualopensystems.com>
> + * Baptiste Reynal <b.reynal@virtualopensystems.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License, version 2, as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/slab.h>
> +#include <linux/vfio.h>
> +#include <linux/property.h>
> +#include "vfio_platform_private.h"
> +
> +static int dev_property_get_strings(struct device *dev, uint32_t *flags,
> + char *name, unsigned *lenp,
> + void __user *datap, unsigned long datasz)
> +{
> + return -EINVAL;
> +}
> +
> +static int dev_property_get_uint(struct device *dev, uint32_t *flags,
> + char *name, uint32_t type, unsigned *lenp,
> + void __user *datap, unsigned long datasz)
> +{
> + return -EINVAL;
> +}
> +
> +int vfio_platform_dev_properties(struct device *dev, uint32_t *flags,
> + uint32_t type, unsigned *lenp,
> + void __user *datap, unsigned long datasz)
> +{
> + char *name;
> + long namesz;
> + int ret;
> +
> + namesz = strnlen_user(datap, datasz);
> + if (!namesz)
> + return -EFAULT;
> + if (namesz > datasz)
> + return -EINVAL;
> +
> + name = kzalloc(namesz, GFP_KERNEL);

What prevents the user from passing an arbitrarily large string here?

> + if (!name)
> + return -ENOMEM;
> + if (strncpy_from_user(name, datap, namesz) <= 0) {
> + kfree(name);
> + return -EFAULT;
> + }
> +
> + switch (type) {
> + case VFIO_DEV_PROPERTY_TYPE_STRINGS:
> + ret = dev_property_get_strings(dev, flags, name, lenp,
> + datap, datasz);
> + break;
> +
> + case VFIO_DEV_PROPERTY_TYPE_U64:
> + case VFIO_DEV_PROPERTY_TYPE_U32:
> + case VFIO_DEV_PROPERTY_TYPE_U16:
> + case VFIO_DEV_PROPERTY_TYPE_U8:
> + ret = dev_property_get_uint(dev, flags, name, type, lenp,
> + datap, datasz);
> + break;
> +
> + default:
> + ret = -EINVAL;
> + }
> +
> + kfree(name);
> + return ret;
> +}
> diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
> index e43efb5..44ba22c 100644
> --- a/drivers/vfio/platform/vfio_platform_common.c
> +++ b/drivers/vfio/platform/vfio_platform_common.c
> @@ -20,6 +20,7 @@
> #include <linux/types.h>
> #include <linux/uaccess.h>
> #include <linux/vfio.h>
> +#include <linux/property.h>
>
> #include "vfio_platform_private.h"
>
> @@ -302,6 +303,34 @@ static long vfio_platform_ioctl(void *device_data,
> return vdev->reset(vdev);
> else
> return -EINVAL;
> + } else if (cmd == VFIO_DEVICE_GET_DEV_PROPERTY) {
> + struct vfio_dev_property info;
> + void __user *datap;
> + unsigned long datasz;
> + int ret;
> +
> + if (!vdev->dev)
> + return -EINVAL;
> +
> + minsz = offsetofend(struct vfio_dev_property, length);
> +
> + if (copy_from_user(&info, (void __user *)arg, minsz))
> + return -EFAULT;
> +
> + if (info.argsz < minsz)
> + return -EINVAL;
> +
> + datap = (void __user *) arg + minsz;
> + datasz = info.argsz - minsz;
> +
> + ret = vfio_platform_dev_properties(vdev->dev, &info.flags,

Why the address of flags, I don't see anyone modifying it and there's
nothing defined in the ioctl description for flags being modified on
return. In fact, there are no flags defined yet, it's just a
future-proofing mechanism of the ioctl, so why propagate it at all right
now?

> + info.type, &info.length, datap, datasz);
> +
> + if (copy_to_user((void __user *)arg, &info, minsz))
> + ret = -EFAULT;
> +
> + return ret;
> +
> }
>
> return -ENOTTY;
> @@ -553,6 +582,12 @@ int vfio_platform_probe_common(struct vfio_platform_device *vdev,
>
> vfio_platform_get_reset(vdev, dev);
>
> + /* add device properties flag */
> + if (device_property_present(dev, "name")) {
> + vdev->dev = dev;

It seems precarious to leave ->dev dangling in the else case. This is a
future bug waiting to happen.

> + vdev->flags |= VFIO_DEVICE_FLAGS_DEV_PROPERTIES;
> + }
> +
> mutex_init(&vdev->igate);
>
> return 0;
> diff --git a/drivers/vfio/platform/vfio_platform_private.h b/drivers/vfio/platform/vfio_platform_private.h
> index 1c9b3d5..c75b089 100644
> --- a/drivers/vfio/platform/vfio_platform_private.h
> +++ b/drivers/vfio/platform/vfio_platform_private.h
> @@ -56,6 +56,7 @@ struct vfio_platform_device {
> u32 num_irqs;
> int refcnt;
> struct mutex igate;
> + struct device *dev;
>
> /*
> * These fields should be filled by the bus specific binder
> @@ -89,4 +90,10 @@ extern int vfio_platform_set_irqs_ioctl(struct vfio_platform_device *vdev,
> unsigned start, unsigned count,
> void *data);
>
> +/* device properties support in properties.c */
> +extern int vfio_platform_dev_properties(struct device *dev, uint32_t *flags,
> + uint32_t type, unsigned *lenp,
> + void __user *datap,
> + unsigned long datasz);
> +
> #endif /* VFIO_PLATFORM_PRIVATE_H */
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 9fd7b5d..a1a0eaa 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -164,12 +164,43 @@ struct vfio_device_info {
> #define VFIO_DEVICE_FLAGS_PCI (1 << 1) /* vfio-pci device */
> #define VFIO_DEVICE_FLAGS_PLATFORM (1 << 2) /* vfio-platform device */
> #define VFIO_DEVICE_FLAGS_AMBA (1 << 3) /* vfio-amba device */
> +#define VFIO_DEVICE_FLAGS_DEV_PROPERTIES (1 << 4) /* Device properties */
> __u32 num_regions; /* Max region index + 1 */
> __u32 num_irqs; /* Max IRQ index + 1 */
> };
> #define VFIO_DEVICE_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 7)
>
> /**
> + * VFIO_DEVICE_GET_DEV_PROPERTY - _IOR(VFIO_TYPE, VFIO_BASE + 17,
> + * struct vfio_devtree_info)
> + *
> + * Retrieve a device property, e.g. from a HW description (device tree or ACPI)
> + * if available.
> + * Caller will initialize data[] with a single string with the requested
> + * devicetree property name, and type depending on whether an array of strings
> + * or an array of u32 values is expected. On success, data[] will be filled
> + * with the requested information, either as an array of u32, or with a list
> + * of strings separated by the NULL terminating character.
> + * Return: 0 on success, -errno on failure.
> + * Errors:
> + * E2BIG: the property is too big to fit in the data[] buffer (the required
> + * size is then written into the length field).

I don't know which is more correct, but the
VFIO_DEVICE_GET_PCI_HOT_RESET_INFO uses ENOSPC when the buffer size is
too small. If there's no compelling reason to be different, let's use
it here too.

> + */
> +struct vfio_dev_property {
> + __u32 argsz;
> + __u32 flags; /* Placeholder for future extension */
> + __u32 type;
> +#define VFIO_DEV_PROPERTY_TYPE_STRINGS 0
> +#define VFIO_DEV_PROPERTY_TYPE_U8 1
> +#define VFIO_DEV_PROPERTY_TYPE_U16 2
> +#define VFIO_DEV_PROPERTY_TYPE_U32 3
> +#define VFIO_DEV_PROPERTY_TYPE_U64 4
> + __u32 length; /* Size of data[] */
> + __u8 data[];
> +};
> +#define VFIO_DEVICE_GET_DEV_PROPERTY _IO(VFIO_TYPE, VFIO_BASE + 17)
> +
> +/**
> * VFIO_DEVICE_GET_REGION_INFO - _IOWR(VFIO_TYPE, VFIO_BASE + 8,
> * struct vfio_region_info)
> *





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