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[PATCH v3 6/8] platform/x86: dell-wmi-smbios: Add a sysfs interface for SMBIOS tokens

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  [PATCH v3 6/8] platform/x86: dell-wmi-smbios: Add a sysfs interface for SMBIOS tokens Mario Limonciello <mario.limonciello@dell.com> - 2017-09-28 06:10 +0200
    Re: [PATCH v3 6/8] platform/x86: dell-wmi-smbios: Add a sysfs  interface for SMBIOS tokens Darren Hart <dvhart@infradead.org> - 2017-09-30 04:20 +0200
      Re: [PATCH v3 6/8] platform/x86: dell-wmi-smbios: Add a sysfs  interface for SMBIOS tokens Andy Shevchenko <andy.shevchenko@gmail.com> - 2017-10-01 11:00 +0200

#1741156 — [PATCH v3 6/8] 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-smbios.c                 | 36 ++++++++++++++++++++++
 2 files changed, 52 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..4cbff5ffe380
--- /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-smbios.c b/drivers/platform/x86/dell-smbios.c
index 4174afbade13..ac176953e46e 100644
--- a/drivers/platform/x86/dell-smbios.c
+++ b/drivers/platform/x86/dell-smbios.c
@@ -229,6 +229,34 @@ 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, "%04x\t%04x\t%04x\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_open(struct inode *inode, struct file *file)
 {
 	return nonseekable_open(inode, file);
@@ -367,10 +395,16 @@ static int dell_smbios_wmi_probe(struct wmi_device *wdev)
 		ret = -ENOMEM;
 		goto fail_devfs_buffer;
 	}
+	ret = sysfs_create_group(&wdev->dev.kobj, &smbios_attribute_group);
+	if (ret)
+		goto fail_create_group;
 
 	wmi_dev = wdev;
+	kobject_uevent(&wdev->dev.kobj, KOBJ_CHANGE);
 	return 0;
 
+fail_create_group:
+	free_pages((unsigned long)devfs_buffer, 3);
 fail_devfs_buffer:
 	free_pages((unsigned long)internal_buffer, 3);
 	return ret;
@@ -381,6 +415,8 @@ static int dell_smbios_wmi_remove(struct wmi_device *wdev)
 	wmi_dev = NULL;
 	free_pages((unsigned long)internal_buffer, 3);
 	free_pages((unsigned long)devfs_buffer, 3);
+	sysfs_remove_group(&wdev->dev.kobj, &smbios_attribute_group);
+	kobject_uevent(&wdev->dev.kobj, KOBJ_CHANGE);
 	return 0;
 }
 
-- 
2.14.1

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#1742452 — Re: [PATCH v3 6/8] platform/x86: dell-wmi-smbios: Add a sysfs interface for SMBIOS tokens

On Wed, Sep 27, 2017 at 11:02:18PM -0500, 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.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
> ---
...
> +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, "%04x\t%04x\t%04x\n",

Minor Coding Style nit - spaces around binary operators: 3.1) Spaces

-- 
Darren Hart
VMware Open Source Technology Center

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#1742754 — Re: [PATCH v3 6/8] platform/x86: dell-wmi-smbios: Add a sysfs interface for SMBIOS tokens

On Sat, Sep 30, 2017 at 5:10 AM, Darren Hart <dvhart@infradead.org> wrote:
> On Wed, Sep 27, 2017 at 11:02:18PM -0500, 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.
>>
>> Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
>> ---
> ...
>> +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, "%04x\t%04x\t%04x\n",
>
> Minor Coding Style nit - spaces around binary operators: 3.1) Spaces

Fresh looking to this excerpt gives me an idea that we may actually
predict how many tokens to write beforehand. It makes output also
cleaner in a sense to not disrupt a last token in the middle.

Something like
tokens_to_print = min(da_num_tokens, (PAGE_SIZE  - 1) / 15);
?

-- 
With Best Regards,
Andy Shevchenko

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