On Fri, Oct 06, 2017 at 11:59:58PM -0500, Mario Limonciello wrote:
> It's important for the driver to provide a R/W ioctl to ensure that
> two competing userspace processes don't race to provide or read each
> others data.
>
> This userspace character device will be used to perform SMBIOS calls
> from any applications.
>
> It provides an ioctl that will allow passing the WMI calling
> interface buffer between userspace and kernel space.
>
> This character device is intended to deprecate the dcdbas kernel module
> and the interface that it provides to userspace.
>
> To use the character device the buffer needed for the machine will
> also be needed. This information is exported to a sysfs attribute.
>
> The API for interacting with this interface is defined in documentation
> as well as a uapi header provides the format of the structures.
>
> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxxx>
> ---
> Documentation/ABI/testing/dell-smbios-wmi | 41 ++++++++
> .../ABI/testing/sysfs-platform-dell-smbios-wmi | 10 ++
> MAINTAINERS | 1 +
> drivers/platform/x86/dell-smbios-wmi.c | 104 ++++++++++++++++++---
> drivers/platform/x86/dell-smbios.h | 11 +--
> include/uapi/linux/dell-smbios.h | 42 +++++++++
> 6 files changed, 188 insertions(+), 21 deletions(-)
> create mode 100644 Documentation/ABI/testing/dell-smbios-wmi
> create mode 100644 Documentation/ABI/testing/sysfs-platform-dell-smbios-wmi
> create mode 100644 include/uapi/linux/dell-smbios.h
>
> diff --git a/Documentation/ABI/testing/dell-smbios-wmi b/Documentation/ABI/testing/dell-smbios-wmi
> new file mode 100644
> index 000000000000..e067e955fcc9
> --- /dev/null
> +++ b/Documentation/ABI/testing/dell-smbios-wmi
> @@ -0,0 +1,41 @@
> +What: /dev/wmi/dell-smbios
> +Date: November 2017
> +KernelVersion: 4.15
> +Contact: "Mario Limonciello" <mario.limonciello@xxxxxxxx>
> +Description:
> + Perform SMBIOS calls on supported Dell machines.
> + through the Dell ACPI-WMI interface.
> +
> + IOCTL's and buffer formats are defined in:
> + <uapi/linux/dell-smbios.h>
> +
> + 1) To perform a call from userspace, you'll need to first
> + determine the minimum size of the calling interface buffer
> + for your machine.
> + Platforms that contain larger buffers can return larger
> + objects from the system firmware.
> + Commonly this size is either 4k or 32k.
> +
> + To determine the size of the buffer, refer to:
> + sysfs-platform-dell-smbios-wmi
> +
> + 2) After you've determined the minimum size of the calling
> + interface buffer, you can allocate a structure that represents
> + the structure documented above.
> +
> + 3) In the 'length' object store the size of the buffer you
> + determined above and allocated.
> +
> + 4) In this buffer object, prepare as necessary for the SMBIOS
> + call you're interested in. Typically SMBIOS buffers have
> + "class", "select", and "input" defined to values that coincide
> + with the data you are interested in.
> + Documenting class/select/input values is outside of the scope
> + of this documentation. Check with the libsmbios project for
> + further documentation on these values.
> +
> + 6) Run the call by using ioctl() as described in the header.
> +
> + 7) The output will be returned in the buffer object.
> +
> + 8) Be sure to free up your allocated object.
> diff --git a/Documentation/ABI/testing/sysfs-platform-dell-smbios-wmi b/Documentation/ABI/testing/sysfs-platform-dell-smbios-wmi
> new file mode 100644
> index 000000000000..6a0513703a3c
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-platform-dell-smbios-wmi
> @@ -0,0 +1,10 @@
> +What: /sys/devices/platform/<platform>/buffer_size
> +Date: November 2017
> +KernelVersion: 4.15
> +Contact: "Mario Limonciello" <mario.limonciello@xxxxxxxx>
> +Description:
> + A read-only description of the size of a calling
> + interface buffer that can be passed to Dell
> + firmware.
> +
> + Commonly this size is either 4k or 32k.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 2a99ee9fd883..4940f3c7481b 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -3986,6 +3986,7 @@ M: Mario Limonciello <mario.limonciello@xxxxxxxx>
> L: platform-driver-x86@xxxxxxxxxxxxxxx
> S: Maintained
> F: drivers/platform/x86/dell-smbios-wmi.c
> +F: include/uapi/linux/dell-smbios.h
>
> DELL LAPTOP DRIVER
> M: Matthew Garrett <mjg59@xxxxxxxxxxxxx>
> diff --git a/drivers/platform/x86/dell-smbios-wmi.c b/drivers/platform/x86/dell-smbios-wmi.c
> index 3de8abea38f8..2b78aba68755 100644
> --- a/drivers/platform/x86/dell-smbios-wmi.c
> +++ b/drivers/platform/x86/dell-smbios-wmi.c
> @@ -15,6 +15,7 @@
> #include <linux/mutex.h>
> #include <linux/uaccess.h>
> #include <linux/wmi.h>
> +#include <uapi/linux/dell-smbios.h>
> #include "dell-smbios.h"
> #include "dell-wmi-descriptor.h"
> static DEFINE_MUTEX(call_mutex);
> @@ -29,19 +30,9 @@ struct misc_bios_flags_structure {
>
> #define DELL_WMI_SMBIOS_GUID "A80593CE-A997-11DA-B012-B622A1EF5492"
>
> -struct wmi_extensions {
> - __u32 argattrib;
> - __u32 blength;
> - __u8 data[];
> -} __packed;
> -
> -struct wmi_smbios_buffer {
> - struct calling_interface_buffer std;
> - struct wmi_extensions ext;
> -} __packed;
> -
> struct wmi_smbios_priv {
> struct wmi_smbios_buffer *buf;
> + struct device_attribute buffer_size_attr;
> struct list_head list;
> struct wmi_device *wdev;
> struct device *child;
> @@ -113,6 +104,78 @@ int dell_smbios_wmi_call(struct calling_interface_buffer *buffer)
> return ret;
> }
>
> +static long dell_smbios_wmi_ioctl(struct wmi_device *wdev, unsigned int cmd,
> + unsigned long arg)
> +{
> + struct wmi_smbios_buffer __user *input =
> + (struct wmi_smbios_buffer __user *) arg;
Why not just always define arg as "struct wmi_smbios_buffer __user *"?
No need to pass down a vague type here, right?
Unless you need to better name your structure to show that it is a dell
type only :)
> + struct wmi_smbios_priv *priv;
> + int ret = 0;
> + size_t size;
> +
> + switch (cmd) {
> + case DELL_WMI_SMBIOS_CMD:
> + priv = dev_get_drvdata(&wdev->dev);
> + if (!priv)
> + return -ENODEV;
> + size = sizeof(struct wmi_smbios_buffer);
> + mutex_lock(&call_mutex);
> + if (copy_from_user(priv->buf, input, size)) {
> + dev_dbg(&wdev->dev, "Copy %lu from user failed\n",
> + size);
> + ret = -EFAULT;
> + goto fail_smbios_cmd;
> + }
> + if (priv->buf->length < priv->buffer_size) {
> + dev_err(&wdev->dev,
> + "Buffer %lld too small, need at least %d\n",
> + priv->buf->length, priv->buffer_size);
> + ret = -EINVAL;
> + goto fail_smbios_cmd;
> + }
No checking for too big of a length? Any other fields you should check
for validity? Like too small?
> + if (dell_smbios_call_filter(&wdev->dev, &priv->buf->std)) {
> + dev_err(&wdev->dev, "Invalid call %d/%d:%8x\n",
> + priv->buf->std.class, priv->buf->std.select,
> + priv->buf->std.input[0]);
> + ret = -EFAULT;
> + goto fail_smbios_cmd;
> + }
> + size = priv->buffer_size - sizeof(struct wmi_smbios_buffer);
What if size just went too small and wrapped around? :(
Remember, "All input is evil". Go print that out and put it on the wall
when you are designing this user/kernel api. You can trust no one, you
have to validate _everything_.
> --- /dev/null
> +++ b/include/uapi/linux/dell-smbios.h
> @@ -0,0 +1,42 @@
> +/*
> + * User API for WMI methods for use with dell-smbios
> + *
> + * Copyright (c) 2017 Dell Inc.
> + *
> + * 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.
> + */
> +
> +#ifndef _UAPI_DELL_SMBIOS_H_
> +#define _UAPI_DELL_SMBIOS_H_
> +
> +#include <linux/ioctl.h>
> +#include <linux/wmi.h>
> +
> +/* This structure may be modified by the firmware when we enter
> + * system management mode through SMM, hence the volatiles
> + */
> +struct calling_interface_buffer {
> + __u16 class;
> + __u16 select;
> + volatile __u32 input[4];
> + volatile __u32 output[4];
> +} __packed;
I still don't buy the use of volatile, but oh well, I'm assuming you
properly tested this?
> +struct wmi_extensions {
> + __u32 argattrib;
> + __u32 blength;
> + __u8 data[];
> +} __packed;
> +
> +struct wmi_smbios_buffer {
> + __u64 length;
> + struct calling_interface_buffer std;
> + struct wmi_extensions ext;
> +} __packed;
Much better, right? Now why do you feel you need a compat ioctl for
this structure? If you do, where is that logic?
And I still didn't see where you were verifying the list of commands in
this structure, was that in some other patch?
thanks,
greg k-h
