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[PATCH 06/12] platform/x86: dell-wmi-smbios: Add a sysfs interface for SMBIOS tokens

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  [PATCH 06/12] platform/x86: dell-wmi-smbios: Add a sysfs interface for SMBIOS tokens Mario Limonciello <mario.limonciello@dell.com> - 2017-09-21 16:00 +0200
    Re: [PATCH 06/12] platform/x86: dell-wmi-smbios: Add a sysfs  interface for SMBIOS tokens Pali Rohár <pali.rohar@gmail.com> - 2017-09-25 18:30 +0200
      Re: [PATCH 06/12] platform/x86: dell-wmi-smbios: Add a sysfs  interface for SMBIOS tokens Andy Shevchenko <andy.shevchenko@gmail.com> - 2017-09-25 19:10 +0200
        RE: [PATCH 06/12] platform/x86: dell-wmi-smbios: Add a sysfs  interface for SMBIOS tokens <Mario.Limonciello@dell.com> - 2017-09-25 19:40 +0200

#1736668 — [PATCH 06/12] platform/x86: dell-wmi-smbios: Add a sysfs interface for SMBIOS tokens

Currently userspace tools can access system tokens via the dcdbas
kernel module and a SMI call that will cause the platform to execute
SMM code.

With a goal in mind of deprecating the dcdbas kernel module a different
method for accessing these tokens from userspace needs to be created.

This is intentionally marked to only be readable as root as it can
contain sensitive information about the platform's configuration.

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
---
 .../ABI/testing/sysfs-platform-dell-wmi-smbios     | 16 +++++++++
 drivers/platform/x86/dell-wmi-smbios.c             | 38 ++++++++++++++++++++++
 2 files changed, 54 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-platform-dell-wmi-smbios

diff --git a/Documentation/ABI/testing/sysfs-platform-dell-wmi-smbios b/Documentation/ABI/testing/sysfs-platform-dell-wmi-smbios
new file mode 100644
index 000000000000..6d151f2dffba
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-platform-dell-wmi-smbios
@@ -0,0 +1,16 @@
+What:		/sys/devices/platform/<platform>/tokens
+Date:		October 2017
+KernelVersion:	4.15
+Contact:	"Mario Limonciello" <mario.limonciello@dell.com>
+Description:
+		A read-only description of Dell platform tokens
+		available on the machine.
+
+		The tokens will be displayed in the following
+		machine readable format with each token on a
+		new line:
+
+		ID @ Location : value
+
+		For example token:
+		5 @ 5 : 3
diff --git a/drivers/platform/x86/dell-wmi-smbios.c b/drivers/platform/x86/dell-wmi-smbios.c
index 7f896701fb7b..c3701fdadf7b 100644
--- a/drivers/platform/x86/dell-wmi-smbios.c
+++ b/drivers/platform/x86/dell-wmi-smbios.c
@@ -189,6 +189,34 @@ static void __init find_tokens(const struct dmi_header *dm, void *dummy)
 	}
 }
 
+static ssize_t tokens_show(struct device *dev,
+			   struct device_attribute *attr, char *buf)
+{
+	size_t off = 0;
+	int i;
+
+	for (i = 0; i < da_num_tokens; i++) {
+		if (off > PAGE_SIZE)
+			break;
+		off += scnprintf(buf+off, PAGE_SIZE-off, "%x @ %x : %x\n",
+		da_tokens[i].tokenID, da_tokens[i].location,
+		da_tokens[i].value);
+	}
+
+	return off;
+}
+
+DEVICE_ATTR(tokens, 0400, tokens_show, NULL);
+
+static struct attribute *smbios_attrs[] = {
+	&dev_attr_tokens.attr,
+	NULL
+};
+
+static const struct attribute_group smbios_attribute_group = {
+	.attrs = smbios_attrs,
+};
+
 static int dell_wmi_smbios_probe(struct wmi_device *wdev)
 {
 	int ret;
@@ -206,8 +234,16 @@ static int dell_wmi_smbios_probe(struct wmi_device *wdev)
 		goto fail_buffer;
 	}
 
+	ret = sysfs_create_group(&wdev->dev.kobj, &smbios_attribute_group);
+	if (ret)
+		goto fail_create_group;
+	kobject_uevent(&wdev->dev.kobj, KOBJ_CHANGE);
+
 	return 0;
 
+fail_create_group:
+	free_page((unsigned long)buffer);
+
 fail_buffer:
 	kfree(da_tokens);
 	return ret;
@@ -215,8 +251,10 @@ static int dell_wmi_smbios_probe(struct wmi_device *wdev)
 
 static int dell_wmi_smbios_remove(struct wmi_device *wdev)
 {
+	sysfs_remove_group(&wdev->dev.kobj, &smbios_attribute_group);
 	kfree(da_tokens);
 	free_page((unsigned long)buffer);
+	kobject_uevent(&wdev->dev.kobj, KOBJ_CHANGE);
 	return 0;
 }
 
-- 
2.14.1

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#1739153 — Re: [PATCH 06/12] platform/x86: dell-wmi-smbios: Add a sysfs interface for SMBIOS tokens

On Thursday 21 September 2017 08:57:11 Mario Limonciello wrote:
> Currently userspace tools can access system tokens via the dcdbas
> kernel module and a SMI call that will cause the platform to execute
> SMM code.
> 
> With a goal in mind of deprecating the dcdbas kernel module a different
> method for accessing these tokens from userspace needs to be created.
> 
> This is intentionally marked to only be readable as root as it can
> contain sensitive information about the platform's configuration.

Darren, Andy, any comments? I'm not quite sure if such API is suitable
for long term in kernel.

Basically tokens are list of tuples <id, location, value> with
possibility to active them, right?

Does not kernel have some better API for it?

Also, keep in mind security aspect of tokens. They represent e.g. boot
order priority or enable/disable some machine peripheral.

> Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
> ---
>  .../ABI/testing/sysfs-platform-dell-wmi-smbios     | 16 +++++++++
>  drivers/platform/x86/dell-wmi-smbios.c             | 38 ++++++++++++++++++++++
>  2 files changed, 54 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-platform-dell-wmi-smbios
> 
> diff --git a/Documentation/ABI/testing/sysfs-platform-dell-wmi-smbios b/Documentation/ABI/testing/sysfs-platform-dell-wmi-smbios
> new file mode 100644
> index 000000000000..6d151f2dffba
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-platform-dell-wmi-smbios
> @@ -0,0 +1,16 @@
> +What:		/sys/devices/platform/<platform>/tokens
> +Date:		October 2017
> +KernelVersion:	4.15
> +Contact:	"Mario Limonciello" <mario.limonciello@dell.com>
> +Description:
> +		A read-only description of Dell platform tokens
> +		available on the machine.
> +
> +		The tokens will be displayed in the following
> +		machine readable format with each token on a
> +		new line:
> +
> +		ID @ Location : value
> +
> +		For example token:
> +		5 @ 5 : 3
> diff --git a/drivers/platform/x86/dell-wmi-smbios.c b/drivers/platform/x86/dell-wmi-smbios.c
> index 7f896701fb7b..c3701fdadf7b 100644
> --- a/drivers/platform/x86/dell-wmi-smbios.c
> +++ b/drivers/platform/x86/dell-wmi-smbios.c
> @@ -189,6 +189,34 @@ static void __init find_tokens(const struct dmi_header *dm, void *dummy)
>  	}
>  }
>  
> +static ssize_t tokens_show(struct device *dev,
> +			   struct device_attribute *attr, char *buf)
> +{
> +	size_t off = 0;
> +	int i;
> +
> +	for (i = 0; i < da_num_tokens; i++) {
> +		if (off > PAGE_SIZE)
> +			break;
> +		off += scnprintf(buf+off, PAGE_SIZE-off, "%x @ %x : %x\n",
> +		da_tokens[i].tokenID, da_tokens[i].location,
> +		da_tokens[i].value);
> +	}
> +
> +	return off;
> +}
> +
> +DEVICE_ATTR(tokens, 0400, tokens_show, NULL);
> +
> +static struct attribute *smbios_attrs[] = {
> +	&dev_attr_tokens.attr,
> +	NULL
> +};
> +
> +static const struct attribute_group smbios_attribute_group = {
> +	.attrs = smbios_attrs,
> +};
> +
>  static int dell_wmi_smbios_probe(struct wmi_device *wdev)
>  {
>  	int ret;
> @@ -206,8 +234,16 @@ static int dell_wmi_smbios_probe(struct wmi_device *wdev)
>  		goto fail_buffer;
>  	}
>  
> +	ret = sysfs_create_group(&wdev->dev.kobj, &smbios_attribute_group);
> +	if (ret)
> +		goto fail_create_group;
> +	kobject_uevent(&wdev->dev.kobj, KOBJ_CHANGE);
> +
>  	return 0;
>  
> +fail_create_group:
> +	free_page((unsigned long)buffer);
> +
>  fail_buffer:
>  	kfree(da_tokens);
>  	return ret;
> @@ -215,8 +251,10 @@ static int dell_wmi_smbios_probe(struct wmi_device *wdev)
>  
>  static int dell_wmi_smbios_remove(struct wmi_device *wdev)
>  {
> +	sysfs_remove_group(&wdev->dev.kobj, &smbios_attribute_group);
>  	kfree(da_tokens);
>  	free_page((unsigned long)buffer);
> +	kobject_uevent(&wdev->dev.kobj, KOBJ_CHANGE);
>  	return 0;
>  }
>  

-- 
Pali Rohár
pali.rohar@gmail.com

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#1739182 — Re: [PATCH 06/12] platform/x86: dell-wmi-smbios: Add a sysfs interface for SMBIOS tokens

On Mon, Sep 25, 2017 at 7:23 PM, Pali Rohár <pali.rohar@gmail.com> wrote:
> On Thursday 21 September 2017 08:57:11 Mario Limonciello wrote:
>> Currently userspace tools can access system tokens via the dcdbas
>> kernel module and a SMI call that will cause the platform to execute
>> SMM code.
>>
>> With a goal in mind of deprecating the dcdbas kernel module a different
>> method for accessing these tokens from userspace needs to be created.
>>
>> This is intentionally marked to only be readable as root as it can
>> contain sensitive information about the platform's configuration.
>
> Darren, Andy, any comments? I'm not quite sure if such API is suitable
> for long term in kernel.

I would try to avoid sysfs interfaces for some particular devices.
Besides we are creating a character device. Would it be suitable there?

> Basically tokens are list of tuples <id, location, value> with
> possibility to active them, right?
>
> Does not kernel have some better API for it?

I think the best what kernel may provide is a CSV-like format with or
without title line and different delimiter (TAB/space/etc).

>
> Also, keep in mind security aspect of tokens. They represent e.g. boot
> order priority or enable/disable some machine peripheral.

For IOCTLs we may use capabilities.
In sysfs case we may zero output based on capabilities or some other factors.

-- 
With Best Regards,
Andy Shevchenko

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#1739191 — RE: [PATCH 06/12] platform/x86: dell-wmi-smbios: Add a sysfs interface for SMBIOS tokens

> -----Original Message-----
> From: Andy Shevchenko [mailto:andy.shevchenko@gmail.com]
> Sent: Monday, September 25, 2017 1:04 PM
> To: Pali Rohár <pali.rohar@gmail.com>
> Cc: Limonciello, Mario <Mario_Limonciello@Dell.com>; dvhart@infradead.org;
> LKML <linux-kernel@vger.kernel.org>; Platform Driver <platform-driver-
> x86@vger.kernel.org>; quasisec@google.com
> Subject: Re: [PATCH 06/12] platform/x86: dell-wmi-smbios: Add a sysfs interface
> for SMBIOS tokens
> 
> On Mon, Sep 25, 2017 at 7:23 PM, Pali Rohár <pali.rohar@gmail.com> wrote:
> > On Thursday 21 September 2017 08:57:11 Mario Limonciello wrote:
> >> Currently userspace tools can access system tokens via the dcdbas
> >> kernel module and a SMI call that will cause the platform to execute
> >> SMM code.
> >>
> >> With a goal in mind of deprecating the dcdbas kernel module a different
> >> method for accessing these tokens from userspace needs to be created.
> >>
> >> This is intentionally marked to only be readable as root as it can
> >> contain sensitive information about the platform's configuration.
> >
> > Darren, Andy, any comments? I'm not quite sure if such API is suitable
> > for long term in kernel.
> 
> I would try to avoid sysfs interfaces for some particular devices.
> Besides we are creating a character device. Would it be suitable there?

If the character device having 2 different ioctls for different needs is
acceptable I'm happy to adjust the series to do this instead.

> 
> > Basically tokens are list of tuples <id, location, value> with
> > possibility to active them, right?
> >

I didn't add a way to activate them through this, it was only for
reading purpose.  Activating them should be possible through the
SMBIOS calling interface though.

> > Does not kernel have some better API for it?
> 
> I think the best what kernel may provide is a CSV-like format with or
> without title line and different delimiter (TAB/space/etc).
> 
> >
> > Also, keep in mind security aspect of tokens. They represent e.g. boot
> > order priority or enable/disable some machine peripheral.
> 
> For IOCTLs we may use capabilities.
> In sysfs case we may zero output based on capabilities or some other factors.
> 

Can you recommend what capabilities you would prefer to see this based upon?

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