[PATCH v6 07/26] powerpc/secvar: Handle format string in the consumer

[Andrew Donnellan]

From: Russell Currey <rus...@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 <rus...@russell.cc>
Signed-off-by: Andrew Donnellan <a...@linux.ibm.com>
Reviewed-by: Stefan Berger <stef...@linux.ibm.com>

---

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

v3: Enforce format string size limit (ruscur)

v4: Pass the buffer size as an argument, not using a macro (stefanb,
    npiggin)

    Fix error reporting (npiggin)
---
 arch/powerpc/include/asm/secvar.h            |  1 +
 arch/powerpc/kernel/secvar-sysfs.c           | 27 +++++++-------------
 arch/powerpc/platforms/powernv/opal-secvar.c | 25 ++++++++++++++++++
 3 files changed, 35 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/include/asm/secvar.h 
b/arch/powerpc/include/asm/secvar.h
index a2b5f2203dc5..1a2c696a48ad 100644
--- a/arch/powerpc/include/asm/secvar.h
+++ b/arch/powerpc/include/asm/secvar.h
@@ -17,6 +17,7 @@ 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, size_t bufsize);
 };
 
 #ifdef CONFIG_PPC_SECURE_BOOT
diff --git a/arch/powerpc/kernel/secvar-sysfs.c 
b/arch/powerpc/kernel/secvar-sysfs.c
index b786d1005027..e4661559c855 100644
--- a/arch/powerpc/kernel/secvar-sysfs.c
+++ b/arch/powerpc/kernel/secvar-sysfs.c
@@ -21,26 +21,17 @@ 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[32];
+       ssize_t len = secvar_ops->format(tmp, sizeof(tmp));
 
-       rc = of_property_read_string(node, "format", &format);
-       if (rc)
-               goto out;
+       if (len > 0)
+               return sysfs_emit(buf, "%s\n", tmp);
+       else if (len < 0)
+               pr_err("Error %zd reading format string\n", len);
+       else
+               pr_err("Got empty format string from backend\n");
 
-       rc = sysfs_emit(buf, "%s\n", format);
-
-out:
-       of_node_put(node);
-
-       return rc;
+       return -EIO;
 }
 
 
diff --git a/arch/powerpc/platforms/powernv/opal-secvar.c 
b/arch/powerpc/platforms/powernv/opal-secvar.c
index 4c0a3b030fe0..e33bb703ecbc 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, size_t bufsize)
+{
+       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, bufsize, "%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)
-- 
2.39.1