[PATCH v3 04/24] powerpc/secvar: Handle format string in the consumer

[Andrew Donnellan <ajd@linux.ibm.com>]

From: Russell Currey <ruscur@russell.cc>

The code that handles the format string in secvar-sysfs.c is entirely
OPAL specific, so create a new "format" op in secvar_operations to make
the secvar code more generic.  No functional change.

Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>

---

v2: Use sysfs_emit() instead of sprintf() (gregkh)

v3: Enforce format string size limit (ruscur)
---
 arch/powerpc/include/asm/secvar.h            |  3 +++
 arch/powerpc/kernel/secvar-sysfs.c           | 23 ++++--------------
 arch/powerpc/platforms/powernv/opal-secvar.c | 25 ++++++++++++++++++++
 3 files changed, 33 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/include/asm/secvar.h b/arch/powerpc/include/asm/secvar.h
index 07ba36f868a7..8b6475589120 100644
--- a/arch/powerpc/include/asm/secvar.h
+++ b/arch/powerpc/include/asm/secvar.h
@@ -11,12 +11,15 @@
 #include <linux/types.h>
 #include <linux/errno.h>
 
+#define SECVAR_MAX_FORMAT_LEN	30 // max length of string returned by ->format()
+
 extern const struct secvar_operations *secvar_ops;
 
 struct secvar_operations {
 	int (*get)(const char *key, u64 key_len, u8 *data, u64 *data_size);
 	int (*get_next)(const char *key, u64 *key_len, u64 keybufsize);
 	int (*set)(const char *key, u64 key_len, u8 *data, u64 data_size);
+	ssize_t (*format)(char *buf);
 };
 
 #ifdef CONFIG_PPC_SECURE_BOOT
diff --git a/arch/powerpc/kernel/secvar-sysfs.c b/arch/powerpc/kernel/secvar-sysfs.c
index 462cacc0ca60..d3858eedd72c 100644
--- a/arch/powerpc/kernel/secvar-sysfs.c
+++ b/arch/powerpc/kernel/secvar-sysfs.c
@@ -21,26 +21,13 @@ static struct kset *secvar_kset;
 static ssize_t format_show(struct kobject *kobj, struct kobj_attribute *attr,
 			   char *buf)
 {
-	ssize_t rc = 0;
-	struct device_node *node;
-	const char *format;
-
-	node = of_find_compatible_node(NULL, NULL, "ibm,secvar-backend");
-	if (!of_device_is_available(node)) {
-		rc = -ENODEV;
-		goto out;
-	}
+	char tmp[SECVAR_MAX_FORMAT_LEN];
+	ssize_t len = secvar_ops->format(tmp);
 
-	rc = of_property_read_string(node, "format", &format);
-	if (rc)
-		goto out;
+	if (len <= 0)
+		return -EIO;
 
-	rc = sysfs_emit(buf, "%s\n", format);
-
-out:
-	of_node_put(node);
-
-	return rc;
+	return sysfs_emit(buf, "%s\n", tmp);
 }
 
 
diff --git a/arch/powerpc/platforms/powernv/opal-secvar.c b/arch/powerpc/platforms/powernv/opal-secvar.c
index ef89861569e0..623c6839e66c 100644
--- a/arch/powerpc/platforms/powernv/opal-secvar.c
+++ b/arch/powerpc/platforms/powernv/opal-secvar.c
@@ -98,10 +98,35 @@ static int opal_set_variable(const char *key, u64 ksize, u8 *data, u64 dsize)
 	return opal_status_to_err(rc);
 }
 
+static ssize_t opal_secvar_format(char *buf)
+{
+	ssize_t rc = 0;
+	struct device_node *node;
+	const char *format;
+
+	node = of_find_compatible_node(NULL, NULL, "ibm,secvar-backend");
+	if (!of_device_is_available(node)) {
+		rc = -ENODEV;
+		goto out;
+	}
+
+	rc = of_property_read_string(node, "format", &format);
+	if (rc)
+		goto out;
+
+	rc = snprintf(buf, SECVAR_MAX_FORMAT_LEN, "%s", format);
+
+out:
+	of_node_put(node);
+
+	return rc;
+}
+
 static const struct secvar_operations opal_secvar_ops = {
 	.get = opal_get_variable,
 	.get_next = opal_get_next_variable,
 	.set = opal_set_variable,
+	.format = opal_secvar_format,
 };
 
 static int opal_secvar_probe(struct platform_device *pdev)
-- 
2.39.0