[PATCH v11 2/7] blk-crypto: show supported key types in sysfs

Eric Biggers
2025-02-04T06:03:22Z

From: Eric Biggers <ebiggers@google.com>

Add sysfs files that indicate which type(s) of keys are supported by the
inline encryption hardware associated with a particular request queue:

/sys/block/$disk/queue/crypto/hw_wrapped_keys
/sys/block/$disk/queue/crypto/raw_keys

Userspace can use the presence or absence of these files to decide what
encyption settings to use.

Don't use a single key_type file, as devices might support both key
types at the same time.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
Documentation/ABI/stable/sysfs-block | 20 ++++++++++++++++
block/blk-crypto-sysfs.c | 35 ++++++++++++++++++++++++++++
2 files changed, 55 insertions(+)

diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block
index 0cceb2badc836..890cde28bf90d 100644
--- a/Documentation/ABI/stable/sysfs-block
+++ b/Documentation/ABI/stable/sysfs-block
@@ -227,10 +227,21 @@ Description:
subdirectory contains files which describe the inline encryption
capabilities of the device. For more information about inline
encryption, refer to Documentation/block/inline-encryption.rst.

+What: /sys/block/<disk>/queue/crypto/hw_wrapped_keys
+Date: February 2025
+Contact: linux-block@vger.kernel.org
+Description:
+ [RO] The presence of this file indicates that the device
+ supports hardware-wrapped inline encryption keys, i.e. key blobs
+ that can only be unwrapped and used by dedicated hardware. For
+ more information about hardware-wrapped inline encryption keys,
+ see Documentation/block/inline-encryption.rst.
+
+
What: /sys/block/<disk>/queue/crypto/max_dun_bits
Date: February 2022
Contact: linux-block@vger.kernel.org
Description:
[RO] This file shows the maximum length, in bits, of data unit
@@ -265,10 +276,19 @@ Contact: linux-block@vger.kernel.org
Description:
[RO] This file shows the number of keyslots the device has for
use with inline encryption.

+What: /sys/block/<disk>/queue/crypto/raw_keys
+Date: February 2025
+Contact: linux-block@vger.kernel.org
+Description:
+ [RO] The presence of this file indicates that the device
+ supports raw inline encryption keys, i.e. keys that are managed
+ in raw, plaintext form in software.
+
+
What: /sys/block/<disk>/queue/dax
Date: June 2016
Contact: linux-block@vger.kernel.org
Description:
[RO] This file indicates whether the device supports Direct
diff --git a/block/blk-crypto-sysfs.c b/block/blk-crypto-sysfs.c
index a304434489bac..e832f403f2002 100644
--- a/block/blk-crypto-sysfs.c
+++ b/block/blk-crypto-sysfs.c
@@ -29,10 +29,17 @@ static struct blk_crypto_profile *kobj_to_crypto_profile(struct kobject *kobj)
static struct blk_crypto_attr *attr_to_crypto_attr(struct attribute *attr)
{
return container_of(attr, struct blk_crypto_attr, attr);
}

+static ssize_t hw_wrapped_keys_show(struct blk_crypto_profile *profile,
+ struct blk_crypto_attr *attr, char *page)
+{
+ /* Always show supported, since the file doesn't exist otherwise. */
+ return sysfs_emit(page, "supported\n");
+}
+
static ssize_t max_dun_bits_show(struct blk_crypto_profile *profile,
struct blk_crypto_attr *attr, char *page)
{
return sysfs_emit(page, "%u\n", 8 * profile->max_dun_bytes_supported);
}
@@ -41,24 +48,52 @@ static ssize_t num_keyslots_show(struct blk_crypto_profile *profile,
struct blk_crypto_attr *attr, char *page)
{
return sysfs_emit(page, "%u\n", profile->num_slots);
}

+static ssize_t raw_keys_show(struct blk_crypto_profile *profile,
+ struct blk_crypto_attr *attr, char *page)
+{
+ /* Always show supported, since the file doesn't exist otherwise. */
+ return sysfs_emit(page, "supported\n");
+}
+
#define BLK_CRYPTO_RO_ATTR(_name) \
static struct blk_crypto_attr _name##_attr = __ATTR_RO(_name)

+BLK_CRYPTO_RO_ATTR(hw_wrapped_keys);
BLK_CRYPTO_RO_ATTR(max_dun_bits);
BLK_CRYPTO_RO_ATTR(num_keyslots);
+BLK_CRYPTO_RO_ATTR(raw_keys);
+
+static umode_t blk_crypto_is_visible(struct kobject *kobj,
+ struct attribute *attr, int n)
+{
+ struct blk_crypto_profile *profile = kobj_to_crypto_profile(kobj);
+ struct blk_crypto_attr *a = attr_to_crypto_attr(attr);
+
+ if (a == &hw_wrapped_keys_attr &&
+ !(profile->key_types_supported & BLK_CRYPTO_KEY_TYPE_HW_WRAPPED))
+ return 0;
+ if (a == &raw_keys_attr &&
+ !(profile->key_types_supported & BLK_CRYPTO_KEY_TYPE_RAW))
+ return 0;
+
+ return 0444;
+}

static struct attribute *blk_crypto_attrs[] = {
+ &hw_wrapped_keys_attr.attr,
&max_dun_bits_attr.attr,
&num_keyslots_attr.attr,
+ &raw_keys_attr.attr,
NULL,
};

static const struct attribute_group blk_crypto_attr_group = {
.attrs = blk_crypto_attrs,
+ .is_visible = blk_crypto_is_visible,
};

/*
* The encryption mode attributes. To avoid hard-coding the list of encryption
* modes, these are initialized at boot time by blk_crypto_sysfs_init().
--
2.48.1