[PATCH v3a 0/2] generic and PowerPC accessor functions for arch keystore

[PATCH v3a 0/2] generic and PowerPC accessor functions for arch keystore

[gjoyce]

From: Greg Joyce <gjoyce@linux.vnet.ibm.com>

Changelog v3a:
        - No code changes, but per reviewer requests, adding additional
          mailing lists(keyring, EFI) for wider review.

Architectural neutral functions have been defined for accessing
architecture specific variable store. The neutral functions are
defined as weak so that they may be superseded by platform
specific versions. The functions have been desigined so that 
they can support a large range of platforms/architectures.

PowerPC/pseries versions of these functions provide read/write access
to the non-volatile PLPKS data store.

This functionality allows kernel code such as the block SED opal
driver to store authentication keys in a secure permanent store.

Greg Joyce (2):
  lib: define generic accessor functions for arch specific keystore
  powerpc/pseries: Override lib/arch_vars.c functions

 arch/powerpc/platforms/pseries/Makefile       |   1 +
 .../platforms/pseries/plpks_arch_ops.c        | 167 ++++++++++++++++++
 include/linux/arch_vars.h                     |  23 +++
 lib/Makefile                                  |   2 +-
 lib/arch_vars.c                               |  25 +++
 5 files changed, 217 insertions(+), 1 deletion(-)
 create mode 100644 arch/powerpc/platforms/pseries/plpks_arch_ops.c
 create mode 100644 include/linux/arch_vars.h
 create mode 100644 lib/arch_vars.c


Signed-off-by: Greg Joyce <gjoyce@linux.vnet.ibm.com>
base-commit: ff6992735ade75aae3e35d16b17da1008d753d28
-- 
2.27.0

[PATCH v3a 1/2] lib: generic accessor functions for arch keystore

[gjoyce]

From: Greg Joyce <gjoyce@linux.vnet.ibm.com>

Generic kernel subsystems may rely on platform specific persistent
KeyStore to store objects containing sensitive key material. In such case,
they need to access architecture specific functions to perform read/write
operations on these variables.

Define the generic variable read/write prototypes to be implemented by
architecture specific versions. The default(weak) implementations of
these prototypes return -EOPNOTSUPP unless overridden by architecture
versions.

Signed-off-by: Greg Joyce <gjoyce@linux.vnet.ibm.com>
---
 include/linux/arch_vars.h | 23 +++++++++++++++++++++++
 lib/Makefile              |  2 +-
 lib/arch_vars.c           | 25 +++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/arch_vars.h
 create mode 100644 lib/arch_vars.c

diff --git a/include/linux/arch_vars.h b/include/linux/arch_vars.h
new file mode 100644
index 000000000000..9c280ff9432e
--- /dev/null
+++ b/include/linux/arch_vars.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Platform variable opearations.
+ *
+ * Copyright (C) 2022 IBM Corporation
+ *
+ * These are the accessor functions (read/write) for architecture specific
+ * variables. Specific architectures can provide overrides.
+ *
+ */
+
+#include <linux/kernel.h>
+
+enum arch_variable_type {
+	ARCH_VAR_OPAL_KEY      = 0,     /* SED Opal Authentication Key */
+	ARCH_VAR_OTHER         = 1,     /* Other type of variable */
+	ARCH_VAR_MAX           = 1,     /* Maximum type value */
+};
+
+int arch_read_variable(enum arch_variable_type type, char *varname,
+		       void *varbuf, u_int *varlen);
+int arch_write_variable(enum arch_variable_type type, char *varname,
+			void *varbuf, u_int varlen);
diff --git a/lib/Makefile b/lib/Makefile
index f99bf61f8bbc..b90c4cb0dbbb 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -48,7 +48,7 @@ obj-y += bcd.o sort.o parser.o debug_locks.o random32.o \
 	 bsearch.o find_bit.o llist.o memweight.o kfifo.o \
 	 percpu-refcount.o rhashtable.o \
 	 once.o refcount.o usercopy.o errseq.o bucket_locks.o \
-	 generic-radix-tree.o
+	 generic-radix-tree.o arch_vars.o
 obj-$(CONFIG_STRING_SELFTEST) += test_string.o
 obj-y += string_helpers.o
 obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
diff --git a/lib/arch_vars.c b/lib/arch_vars.c
new file mode 100644
index 000000000000..e6f16d7d09c1
--- /dev/null
+++ b/lib/arch_vars.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Platform variable operations.
+ *
+ * Copyright (C) 2022 IBM Corporation
+ *
+ * These are the accessor functions (read/write) for architecture specific
+ * variables. Specific architectures can provide overrides.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/arch_vars.h>
+
+int __weak arch_read_variable(enum arch_variable_type type, char *varname,
+			      void *varbuf, u_int *varlen)
+{
+	return -EOPNOTSUPP;
+}
+
+int __weak arch_write_variable(enum arch_variable_type type, char *varname,
+			       void *varbuf, u_int varlen)
+{
+	return -EOPNOTSUPP;
+}
-- 
2.27.0

Re: [PATCH v3a 1/2] lib: generic accessor functions for arch keystore

[Christophe Leroy]

Le 08/08/2022 à 17:43, gjoyce@linux.vnet.ibm.com a écrit :
> From: Greg Joyce <gjoyce@linux.vnet.ibm.com>
> 
> Generic kernel subsystems may rely on platform specific persistent
> KeyStore to store objects containing sensitive key material. In such case,
> they need to access architecture specific functions to perform read/write
> operations on these variables.
> 
> Define the generic variable read/write prototypes to be implemented by
> architecture specific versions. The default(weak) implementations of
> these prototypes return -EOPNOTSUPP unless overridden by architecture
> versions.
> 
> Signed-off-by: Greg Joyce <gjoyce@linux.vnet.ibm.com>
> ---
>   include/linux/arch_vars.h | 23 +++++++++++++++++++++++
>   lib/Makefile              |  2 +-
>   lib/arch_vars.c           | 25 +++++++++++++++++++++++++
>   3 files changed, 49 insertions(+), 1 deletion(-)
>   create mode 100644 include/linux/arch_vars.h
>   create mode 100644 lib/arch_vars.c
> 
> diff --git a/include/linux/arch_vars.h b/include/linux/arch_vars.h
> new file mode 100644
> index 000000000000..9c280ff9432e
> --- /dev/null
> +++ b/include/linux/arch_vars.h
> @@ -0,0 +1,23 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Platform variable opearations.

Is it platform specific or architecture specific ?

> + *
> + * Copyright (C) 2022 IBM Corporation
> + *
> + * These are the accessor functions (read/write) for architecture specific
> + * variables. Specific architectures can provide overrides.

"variables" is a very generic word which I think doesn't match what you 
want to do.

For me "variables" are local variables and global variables in a C file. 
Here it seems to be something completely different hence the name is 
really meaningfull and misleading.

> + *
> + */
> +
> +#include <linux/kernel.h>
> +
> +enum arch_variable_type {

arch_variable_type ? What's that ? variable types are char, short, long, 
long long, etc ...

> +	ARCH_VAR_OPAL_KEY      = 0,     /* SED Opal Authentication Key */
> +	ARCH_VAR_OTHER         = 1,     /* Other type of variable */
> +	ARCH_VAR_MAX           = 1,     /* Maximum type value */
> +};

Why the hell do you need an enum for two values only ?

> +
> +int arch_read_variable(enum arch_variable_type type, char *varname,
> +		       void *varbuf, u_int *varlen);
> +int arch_write_variable(enum arch_variable_type type, char *varname,
> +			void *varbuf, u_int varlen);
> diff --git a/lib/Makefile b/lib/Makefile
> index f99bf61f8bbc..b90c4cb0dbbb 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -48,7 +48,7 @@ obj-y += bcd.o sort.o parser.o debug_locks.o random32.o \
>   	 bsearch.o find_bit.o llist.o memweight.o kfifo.o \
>   	 percpu-refcount.o rhashtable.o \
>   	 once.o refcount.o usercopy.o errseq.o bucket_locks.o \
> -	 generic-radix-tree.o
> +	 generic-radix-tree.o arch_vars.o
>   obj-$(CONFIG_STRING_SELFTEST) += test_string.o
>   obj-y += string_helpers.o
>   obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
> diff --git a/lib/arch_vars.c b/lib/arch_vars.c
> new file mode 100644
> index 000000000000..e6f16d7d09c1
> --- /dev/null
> +++ b/lib/arch_vars.c

The name is meaningless, too generic.


> @@ -0,0 +1,25 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Platform variable operations.

platform versus architecture ?

> + *
> + * Copyright (C) 2022 IBM Corporation
> + *
> + * These are the accessor functions (read/write) for architecture specific
> + * variables. Specific architectures can provide overrides.
> + *
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/arch_vars.h>
> +
> +int __weak arch_read_variable(enum arch_variable_type type, char *varname,
> +			      void *varbuf, u_int *varlen)

Sorry, to read a variable, I use READ_ONCE or I read it directly.

> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +int __weak arch_write_variable(enum arch_variable_type type, char *varname,
> +			       void *varbuf, u_int varlen)
> +{
> +	return -EOPNOTSUPP;
> +}

Re: [PATCH v3a 1/2] lib: generic accessor functions for arch keystore

[Michal Suchánek]

On Mon, Aug 08, 2022 at 04:31:06PM +0000, Christophe Leroy wrote:
> 
> 
> Le 08/08/2022 à 17:43, gjoyce@linux.vnet.ibm.com a écrit :
> > From: Greg Joyce <gjoyce@linux.vnet.ibm.com>
> > 
> > Generic kernel subsystems may rely on platform specific persistent
> > KeyStore to store objects containing sensitive key material. In such case,
> > they need to access architecture specific functions to perform read/write
> > operations on these variables.
> > 
> > Define the generic variable read/write prototypes to be implemented by
> > architecture specific versions. The default(weak) implementations of
> > these prototypes return -EOPNOTSUPP unless overridden by architecture
> > versions.
> > 
> > Signed-off-by: Greg Joyce <gjoyce@linux.vnet.ibm.com>
> > ---
> >   include/linux/arch_vars.h | 23 +++++++++++++++++++++++
> >   lib/Makefile              |  2 +-
> >   lib/arch_vars.c           | 25 +++++++++++++++++++++++++
> >   3 files changed, 49 insertions(+), 1 deletion(-)
> >   create mode 100644 include/linux/arch_vars.h
> >   create mode 100644 lib/arch_vars.c
> > 
> > diff --git a/include/linux/arch_vars.h b/include/linux/arch_vars.h
> > new file mode 100644
> > index 000000000000..9c280ff9432e
> > --- /dev/null
> > +++ b/include/linux/arch_vars.h
> > @@ -0,0 +1,23 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Platform variable opearations.
> 
> Is it platform specific or architecture specific ?
> 
> > + *
> > + * Copyright (C) 2022 IBM Corporation
> > + *
> > + * These are the accessor functions (read/write) for architecture specific
> > + * variables. Specific architectures can provide overrides.
> 
> "variables" is a very generic word which I think doesn't match what you 
> want to do.
> 
> For me "variables" are local variables and global variables in a C file. 
> Here it seems to be something completely different hence the name is 
> really meaningfull and misleading.
> 
> > + *
> > + */
> > +
> > +#include <linux/kernel.h>
> > +
> > +enum arch_variable_type {
> 
> arch_variable_type ? What's that ? variable types are char, short, long, 
> long long, etc ...
> 
> > +	ARCH_VAR_OPAL_KEY      = 0,     /* SED Opal Authentication Key */
> > +	ARCH_VAR_OTHER         = 1,     /* Other type of variable */
> > +	ARCH_VAR_MAX           = 1,     /* Maximum type value */
> > +};
> 
> Why the hell do you need an enum for two values only ?
> 
> > +
> > +int arch_read_variable(enum arch_variable_type type, char *varname,
> > +		       void *varbuf, u_int *varlen);
> > +int arch_write_variable(enum arch_variable_type type, char *varname,
> > +			void *varbuf, u_int varlen);
> > diff --git a/lib/Makefile b/lib/Makefile
> > index f99bf61f8bbc..b90c4cb0dbbb 100644
> > --- a/lib/Makefile
> > +++ b/lib/Makefile
> > @@ -48,7 +48,7 @@ obj-y += bcd.o sort.o parser.o debug_locks.o random32.o \
> >   	 bsearch.o find_bit.o llist.o memweight.o kfifo.o \
> >   	 percpu-refcount.o rhashtable.o \
> >   	 once.o refcount.o usercopy.o errseq.o bucket_locks.o \
> > -	 generic-radix-tree.o
> > +	 generic-radix-tree.o arch_vars.o
> >   obj-$(CONFIG_STRING_SELFTEST) += test_string.o
> >   obj-y += string_helpers.o
> >   obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
> > diff --git a/lib/arch_vars.c b/lib/arch_vars.c
> > new file mode 100644
> > index 000000000000..e6f16d7d09c1
> > --- /dev/null
> > +++ b/lib/arch_vars.c
> 
> The name is meaningless, too generic.
> 
> 
> > @@ -0,0 +1,25 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Platform variable operations.
> 
> platform versus architecture ?
> 
> > + *
> > + * Copyright (C) 2022 IBM Corporation
> > + *
> > + * These are the accessor functions (read/write) for architecture specific
> > + * variables. Specific architectures can provide overrides.
> > + *
> > + */
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/arch_vars.h>
> > +
> > +int __weak arch_read_variable(enum arch_variable_type type, char *varname,
> > +			      void *varbuf, u_int *varlen)
> 
> Sorry, to read a variable, I use READ_ONCE or I read it directly.

This is supposed to be used for things like the EFI variables and the
already existing powernv secure variables.

Nonetheless, without adding the plumbing for the existing
implementations it is not clear what it's doing, and the interface is
agruably meaningless.

Hence I would either suggest to provide the plumbing necessary for
existing (secure) variable implementations to make use of the interface,
or use private implementations like all the existing platforms do
without exposing the values in any generic way, and leave that to
somebody who is comfortable with designing a working general inteface
for this.

Thanks

Michal

[PATCH v3a 2/2] powerpc/pseries: Override lib/arch_vars.c functions

[gjoyce]

From: Greg Joyce <gjoyce@linux.vnet.ibm.com>

Self Encrypting Drives(SED) make use of POWER LPAR Platform KeyStore
for storing its variables. Thus the block subsystem needs to access
PowerPC specific functions to read/write objects in PLPKS.

Override the default implementations in lib/arch_vars.c file with
PowerPC specific versions.

Signed-off-by: Greg Joyce <gjoyce@linux.vnet.ibm.com>
---
 arch/powerpc/platforms/pseries/Makefile       |   1 +
 .../platforms/pseries/plpks_arch_ops.c        | 167 ++++++++++++++++++
 2 files changed, 168 insertions(+)
 create mode 100644 arch/powerpc/platforms/pseries/plpks_arch_ops.c

diff --git a/arch/powerpc/platforms/pseries/Makefile b/arch/powerpc/platforms/pseries/Makefile
index 14e143b946a3..3a545422eae5 100644
--- a/arch/powerpc/platforms/pseries/Makefile
+++ b/arch/powerpc/platforms/pseries/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_PPC_SPLPAR)	+= vphn.o
 obj-$(CONFIG_PPC_SVM)		+= svm.o
 obj-$(CONFIG_FA_DUMP)		+= rtas-fadump.o
 obj-$(CONFIG_PSERIES_PLPKS) += plpks.o
+obj-$(CONFIG_PSERIES_PLPKS) += plpks_arch_ops.o
 
 obj-$(CONFIG_SUSPEND)		+= suspend.o
 obj-$(CONFIG_PPC_VAS)		+= vas.o vas-sysfs.o
diff --git a/arch/powerpc/platforms/pseries/plpks_arch_ops.c b/arch/powerpc/platforms/pseries/plpks_arch_ops.c
new file mode 100644
index 000000000000..fdea3322f696
--- /dev/null
+++ b/arch/powerpc/platforms/pseries/plpks_arch_ops.c
@@ -0,0 +1,167 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * POWER Platform arch specific code for SED
+ * Copyright (C) 2022 IBM Corporation
+ *
+ * Define operations for generic kernel subsystems to read/write keys
+ * from POWER LPAR Platform KeyStore(PLPKS).
+ *
+ * List of subsystems/usecase using PLPKS:
+ * - Self Encrypting Drives(SED)
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/ioctl.h>
+#include <uapi/linux/sed-opal.h>
+#include <linux/sed-opal.h>
+#include <linux/arch_vars.h>
+#include "plpks.h"
+
+/*
+ * variable structure that contains all SED data
+ */
+struct plpks_sed_object_data {
+	u_char version;
+	u_char pad1[7];
+	u_long authority;
+	u_long range;
+	u_int  key_len;
+	u_char key[32];
+};
+
+/*
+ * ext_type values
+ *     00        no extension exists
+ *     01-1F     common
+ *     20-3F     AIX
+ *     40-5F     Linux
+ *     60-7F     IBMi
+ */
+
+/*
+ * This extension is optional for version 1 sed_object_data
+ */
+struct sed_object_extension {
+	u8 ext_type;
+	u8 rsvd[3];
+	u8 ext_data[64];
+};
+
+#define PKS_SED_OBJECT_DATA_V1          1
+#define PKS_SED_MANGLED_LABEL           "/default/pri"
+#define PLPKS_SED_COMPONENT             "sed-opal"
+
+#define PLPKS_ARCHVAR_POLICY            WORLDREADABLE
+#define PLPKS_ARCHVAR_OS_COMMON         4
+
+/*
+ * Read the variable data from PKS given the label
+ */
+int arch_read_variable(enum arch_variable_type type, char *varname,
+		       void *varbuf, u_int *varlen)
+{
+	struct plpks_var var;
+	struct plpks_sed_object_data *data;
+	u_int offset = 0;
+	char *buf = (char *)varbuf;
+	int ret;
+
+	var.name = varname;
+	var.namelen = strlen(varname);
+	var.policy = PLPKS_ARCHVAR_POLICY;
+	var.os = PLPKS_ARCHVAR_OS_COMMON;
+	var.data = NULL;
+	var.datalen = 0;
+
+	switch (type) {
+	case ARCH_VAR_OPAL_KEY:
+		var.component = PLPKS_SED_COMPONENT;
+#ifdef OPAL_AUTH_KEY
+		if (strcmp(OPAL_AUTH_KEY, varname) == 0) {
+			var.name = PKS_SED_MANGLED_LABEL;
+			var.namelen = strlen(varname);
+		}
+#endif
+		offset = offsetof(struct plpks_sed_object_data, key);
+		break;
+	case ARCH_VAR_OTHER:
+		var.component = "";
+		break;
+	}
+
+	ret = plpks_read_os_var(&var);
+	if (ret != 0)
+		return ret;
+
+	if (offset > var.datalen)
+		offset = 0;
+
+	switch (type) {
+	case ARCH_VAR_OPAL_KEY:
+		data = (struct plpks_sed_object_data *)var.data;
+		*varlen = data->key_len;
+		break;
+	case ARCH_VAR_OTHER:
+		*varlen = var.datalen;
+		break;
+	}
+
+	if (var.data) {
+		memcpy(varbuf, var.data + offset, var.datalen - offset);
+		buf[*varlen] = '\0';
+		kfree(var.data);
+	}
+
+	return 0;
+}
+
+/*
+ * Write the variable data to PKS given the label
+ */
+int arch_write_variable(enum arch_variable_type type, char *varname,
+			void *varbuf, u_int varlen)
+{
+	struct plpks_var var;
+	struct plpks_sed_object_data data;
+	struct plpks_var_name vname;
+
+	var.name = varname;
+	var.namelen = strlen(varname);
+	var.policy = PLPKS_ARCHVAR_POLICY;
+	var.os = PLPKS_ARCHVAR_OS_COMMON;
+	var.datalen = varlen;
+	var.data = varbuf;
+
+	switch (type) {
+	case ARCH_VAR_OPAL_KEY:
+		var.component = PLPKS_SED_COMPONENT;
+#ifdef OPAL_AUTH_KEY
+		if (strcmp(OPAL_AUTH_KEY, varname) == 0) {
+			var.name = PKS_SED_MANGLED_LABEL;
+			var.namelen = strlen(varname);
+		}
+#endif
+		var.datalen = sizeof(struct plpks_sed_object_data);
+		var.data = (u8 *)&data;
+
+		/* initialize SED object */
+		data.version = PKS_SED_OBJECT_DATA_V1;
+		data.authority = 0;
+		data.range = 0;
+		data.key_len = varlen;
+		memcpy(data.key, varbuf, varlen);
+		break;
+	case ARCH_VAR_OTHER:
+		var.component = "";
+		break;
+	}
+
+	/* variable update requires delete first */
+	vname.namelen = var.namelen;
+	vname.name = var.name;
+	(void)plpks_remove_var(var.component, var.os, vname);
+
+	return plpks_write_var(var);
+}
-- 
2.27.0

Re: [PATCH v3a 2/2] powerpc/pseries: Override lib/arch_vars.c functions

[Christophe Leroy]

Le 08/08/2022 à 17:43, gjoyce@linux.vnet.ibm.com a écrit :
> From: Greg Joyce <gjoyce@linux.vnet.ibm.com>
> 
> Self Encrypting Drives(SED) make use of POWER LPAR Platform KeyStore
> for storing its variables. Thus the block subsystem needs to access
> PowerPC specific functions to read/write objects in PLPKS.
> 
> Override the default implementations in lib/arch_vars.c file with
> PowerPC specific versions.
> 
> Signed-off-by: Greg Joyce <gjoyce@linux.vnet.ibm.com>
> ---
>   arch/powerpc/platforms/pseries/Makefile       |   1 +
>   .../platforms/pseries/plpks_arch_ops.c        | 167 ++++++++++++++++++
>   2 files changed, 168 insertions(+)
>   create mode 100644 arch/powerpc/platforms/pseries/plpks_arch_ops.c
> 
> diff --git a/arch/powerpc/platforms/pseries/Makefile b/arch/powerpc/platforms/pseries/Makefile
> index 14e143b946a3..3a545422eae5 100644
> --- a/arch/powerpc/platforms/pseries/Makefile
> +++ b/arch/powerpc/platforms/pseries/Makefile
> @@ -29,6 +29,7 @@ obj-$(CONFIG_PPC_SPLPAR)	+= vphn.o
>   obj-$(CONFIG_PPC_SVM)		+= svm.o
>   obj-$(CONFIG_FA_DUMP)		+= rtas-fadump.o
>   obj-$(CONFIG_PSERIES_PLPKS) += plpks.o
> +obj-$(CONFIG_PSERIES_PLPKS) += plpks_arch_ops.o
>   
>   obj-$(CONFIG_SUSPEND)		+= suspend.o
>   obj-$(CONFIG_PPC_VAS)		+= vas.o vas-sysfs.o
> diff --git a/arch/powerpc/platforms/pseries/plpks_arch_ops.c b/arch/powerpc/platforms/pseries/plpks_arch_ops.c
> new file mode 100644
> index 000000000000..fdea3322f696
> --- /dev/null
> +++ b/arch/powerpc/platforms/pseries/plpks_arch_ops.c
> @@ -0,0 +1,167 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * POWER Platform arch specific code for SED
> + * Copyright (C) 2022 IBM Corporation
> + *
> + * Define operations for generic kernel subsystems to read/write keys
> + * from POWER LPAR Platform KeyStore(PLPKS).
> + *
> + * List of subsystems/usecase using PLPKS:
> + * - Self Encrypting Drives(SED)
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
> +#include <linux/ioctl.h>
> +#include <uapi/linux/sed-opal.h>
> +#include <linux/sed-opal.h>
> +#include <linux/arch_vars.h>
> +#include "plpks.h"
> +
> +/*
> + * variable structure that contains all SED data
> + */
> +struct plpks_sed_object_data {
> +	u_char version;
> +	u_char pad1[7];
> +	u_long authority;
> +	u_long range;
> +	u_int  key_len;
> +	u_char key[32];
> +};
> +
> +/*
> + * ext_type values
> + *     00        no extension exists
> + *     01-1F     common
> + *     20-3F     AIX
> + *     40-5F     Linux
> + *     60-7F     IBMi
> + */
> +
> +/*
> + * This extension is optional for version 1 sed_object_data
> + */
> +struct sed_object_extension {
> +	u8 ext_type;
> +	u8 rsvd[3];
> +	u8 ext_data[64];
> +};
> +
> +#define PKS_SED_OBJECT_DATA_V1          1
> +#define PKS_SED_MANGLED_LABEL           "/default/pri"
> +#define PLPKS_SED_COMPONENT             "sed-opal"
> +
> +#define PLPKS_ARCHVAR_POLICY            WORLDREADABLE
> +#define PLPKS_ARCHVAR_OS_COMMON         4
> +
> +/*
> + * Read the variable data from PKS given the label
> + */
> +int arch_read_variable(enum arch_variable_type type, char *varname,
> +		       void *varbuf, u_int *varlen)

'enum arch_variable_type' is pointlessly long. And it only has two 
possible values, so should be a 'bool'


> +{
> +	struct plpks_var var;
> +	struct plpks_sed_object_data *data;
> +	u_int offset = 0;

Would be better to set it to 0 in the code that handles ARCH_VAR_OTHER 
and leave it unitialised here.

> +	char *buf = (char *)varbuf;
> +	int ret;
> +
> +	var.name = varname;
> +	var.namelen = strlen(varname);
> +	var.policy = PLPKS_ARCHVAR_POLICY;
> +	var.os = PLPKS_ARCHVAR_OS_COMMON;
> +	var.data = NULL;
> +	var.datalen = 0;
> +
> +	switch (type) {

A switch for a boolean value is pointless. Just do if/else, it will be a 
lot more readable.

> +	case ARCH_VAR_OPAL_KEY:
> +		var.component = PLPKS_SED_COMPONENT;
> +#ifdef OPAL_AUTH_KEY

#ifdefs in C files should be avoided, refer 
https://docs.kernel.org/process/coding-style.html#conditional-compilation

> +		if (strcmp(OPAL_AUTH_KEY, varname) == 0) {
> +			var.name = PKS_SED_MANGLED_LABEL;
> +			var.namelen = strlen(varname);
> +		}
> +#endif
> +		offset = offsetof(struct plpks_sed_object_data, key);
> +		break;
> +	case ARCH_VAR_OTHER:
> +		var.component = "";
> +		break;
> +	}
> +
> +	ret = plpks_read_os_var(&var);
> +	if (ret != 0)
> +		return ret;
> +
> +	if (offset > var.datalen)
> +		offset = 0;
> +
> +	switch (type) {
> +	case ARCH_VAR_OPAL_KEY:
> +		data = (struct plpks_sed_object_data *)var.data;
> +		*varlen = data->key_len;
> +		break;
> +	case ARCH_VAR_OTHER:
> +		*varlen = var.datalen;
> +		break;
> +	}
> +
> +	if (var.data) {
> +		memcpy(varbuf, var.data + offset, var.datalen - offset);
> +		buf[*varlen] = '\0';
> +		kfree(var.data);
> +	}
> +
> +	return 0;
> +}
> +
> +/*
> + * Write the variable data to PKS given the label
> + */
> +int arch_write_variable(enum arch_variable_type type, char *varname,
> +			void *varbuf, u_int varlen)
> +{
> +	struct plpks_var var;
> +	struct plpks_sed_object_data data;
> +	struct plpks_var_name vname;
> +
> +	var.name = varname;
> +	var.namelen = strlen(varname);
> +	var.policy = PLPKS_ARCHVAR_POLICY;
> +	var.os = PLPKS_ARCHVAR_OS_COMMON;
> +	var.datalen = varlen;
> +	var.data = varbuf;
> +
> +	switch (type) {
> +	case ARCH_VAR_OPAL_KEY:
> +		var.component = PLPKS_SED_COMPONENT;
> +#ifdef OPAL_AUTH_KEY
> +		if (strcmp(OPAL_AUTH_KEY, varname) == 0) {
> +			var.name = PKS_SED_MANGLED_LABEL;
> +			var.namelen = strlen(varname);
> +		}
> +#endif
> +		var.datalen = sizeof(struct plpks_sed_object_data);
> +		var.data = (u8 *)&data;
> +
> +		/* initialize SED object */
> +		data.version = PKS_SED_OBJECT_DATA_V1;
> +		data.authority = 0;
> +		data.range = 0;
> +		data.key_len = varlen;
> +		memcpy(data.key, varbuf, varlen);
> +		break;
> +	case ARCH_VAR_OTHER:
> +		var.component = "";
> +		break;
> +	}

That part of code seem to have a lot in common with 
arch_read_variable(), can you refactor ?

> +
> +	/* variable update requires delete first */
> +	vname.namelen = var.namelen;
> +	vname.name = var.name;
> +	(void)plpks_remove_var(var.component, var.os, vname);

Do you really need that cast to (void) ?

> +
> +	return plpks_write_var(var);
> +}