linux-kernel - [PATCH 5/6] powerpc/secvar: Extend sysfs to include config vars

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Message-Id: <20221228072943.429266-6-ruscur@russell.cc>
Date:   Wed, 28 Dec 2022 18:29:42 +1100
From:   Russell Currey <ruscur@...sell.cc>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     gregkh@...uxfoundation.org, gcwilson@...ux.ibm.com,
        linux-kernel@...r.kernel.org, nayna@...ux.ibm.com,
        ajd@...ux.ibm.com, zohar@...ux.ibm.com, mpe@...erman.id.au,
        Russell Currey <ruscur@...sell.cc>
Subject: [PATCH 5/6] powerpc/secvar: Extend sysfs to include config vars

The forthcoming pseries consumer of the secvar API wants to expose a
number of config variables.  Allowing secvar implementations to provide
their own sysfs attributes makes it easy for consumers to expose what
they need to.

This is not being used by the OPAL secvar implementation at present, and
the config directory will not be created if no attributes are set.

Signed-off-by: Russell Currey <ruscur@...sell.cc>
---
I played around with adding an API call to facilitate a more generic
key/value interface for config variables and it seemed like unnecessary
complexity.  I think this is cleaner.  If there was ever a secvar
interface other than sysfs we'd have to rework it, though.

 arch/powerpc/include/asm/secvar.h  |  3 +++
 arch/powerpc/kernel/secvar-sysfs.c | 40 ++++++++++++++++++++++++++----
 2 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/secvar.h b/arch/powerpc/include/asm/secvar.h
index 92d2c051918b..250e7066b6da 100644
--- a/arch/powerpc/include/asm/secvar.h
+++ b/arch/powerpc/include/asm/secvar.h
@@ -10,6 +10,7 @@
 
 #include <linux/types.h>
 #include <linux/errno.h>
+#include <linux/sysfs.h>
 
 extern const struct secvar_operations *secvar_ops;
 
@@ -27,10 +28,12 @@ struct secvar_operations {
 #ifdef CONFIG_PPC_SECURE_BOOT
 
 extern void set_secvar_ops(const struct secvar_operations *ops);
+extern void set_secvar_config_attrs(const struct attribute **attrs);
 
 #else
 
 static inline void set_secvar_ops(const struct secvar_operations *ops) { }
+static inline void set_secvar_config_attrs(const struct attribute **attrs) { }
 
 #endif
 
diff --git a/arch/powerpc/kernel/secvar-sysfs.c b/arch/powerpc/kernel/secvar-sysfs.c
index ea408763dc78..0c3790345403 100644
--- a/arch/powerpc/kernel/secvar-sysfs.c
+++ b/arch/powerpc/kernel/secvar-sysfs.c
@@ -15,9 +15,17 @@
 
 #define NAME_MAX_SIZE	   1024
 
+const struct attribute **secvar_config_attrs __ro_after_init = NULL;
+
 static struct kobject *secvar_kobj;
 static struct kset *secvar_kset;
 
+void set_secvar_config_attrs(const struct attribute **attrs)
+{
+	WARN_ON_ONCE(secvar_config_attrs);
+	secvar_config_attrs = attrs;
+}
+
 static ssize_t format_show(struct kobject *kobj, struct kobj_attribute *attr,
 			   char *buf)
 {
@@ -134,6 +142,16 @@ static int update_kobj_size(void)
 	return 0;
 }
 
+static int secvar_sysfs_config(struct kobject *kobj)
+{
+	struct attribute_group config_group = {
+		.name = "config",
+		.attrs = (struct attribute **)secvar_config_attrs,
+	};
+
+	return sysfs_create_group(kobj, &config_group);
+}
+
 static int secvar_sysfs_load(void)
 {
 	char *name;
@@ -196,26 +214,38 @@ static int secvar_sysfs_init(void)
 
 	rc = sysfs_create_file(secvar_kobj, &format_attr.attr);
 	if (rc) {
-		kobject_put(secvar_kobj);
-		return -ENOMEM;
+		pr_err("secvar: Failed to create format object\n");
+		rc = -ENOMEM;
+		goto err;
 	}
 
 	secvar_kset = kset_create_and_add("vars", NULL, secvar_kobj);
 	if (!secvar_kset) {
 		pr_err("secvar: sysfs kobject registration failed.\n");
-		kobject_put(secvar_kobj);
-		return -ENOMEM;
+		rc = -ENOMEM;
+		goto err;
 	}
 
 	rc = update_kobj_size();
 	if (rc) {
 		pr_err("Cannot read the size of the attribute\n");
-		return rc;
+		goto err;
+	}
+
+	if (secvar_config_attrs) {
+		rc = secvar_sysfs_config(secvar_kobj);
+		if (rc) {
+			pr_err("secvar: Failed to create config directory\n");
+			goto err;
+		}
 	}
 
 	secvar_sysfs_load();
 
 	return 0;
+err:
+	kobject_put(secvar_kobj);
+	return rc;
 }
 
 late_initcall(secvar_sysfs_init);
-- 
2.38.1