[PATCH v6 05/26] powerpc/secvar: Warn and error if multiple secvar ops are set

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

From: Russell Currey <ruscur@russell.cc>

The secvar code only supports one consumer at a time.

Multiple consumers aren't possible at this point in time, but we'd want
it to be obvious if it ever could happen.

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

---

v4: Return an error and don't actually try to set secvar_operations if the
    warning is triggered (npiggin)

v5: Drop "extern" to fix a checkpatch check (snowpatch)

v6: Return -EBUSY rather than -1 (stefanb)
---
 arch/powerpc/include/asm/secvar.h            |  4 ++--
 arch/powerpc/kernel/secvar-ops.c             | 10 ++++++++--
 arch/powerpc/platforms/powernv/opal-secvar.c |  4 +---
 3 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/include/asm/secvar.h b/arch/powerpc/include/asm/secvar.h
index 07ba36f868a7..a2b5f2203dc5 100644
--- a/arch/powerpc/include/asm/secvar.h
+++ b/arch/powerpc/include/asm/secvar.h
@@ -21,11 +21,11 @@ struct secvar_operations {
 
 #ifdef CONFIG_PPC_SECURE_BOOT
 
-extern void set_secvar_ops(const struct secvar_operations *ops);
+int set_secvar_ops(const struct secvar_operations *ops);
 
 #else
 
-static inline void set_secvar_ops(const struct secvar_operations *ops) { }
+static inline int set_secvar_ops(const struct secvar_operations *ops) { return 0; }
 
 #endif
 
diff --git a/arch/powerpc/kernel/secvar-ops.c b/arch/powerpc/kernel/secvar-ops.c
index 6a29777d6a2d..19172a2804f0 100644
--- a/arch/powerpc/kernel/secvar-ops.c
+++ b/arch/powerpc/kernel/secvar-ops.c
@@ -8,10 +8,16 @@
 
 #include <linux/cache.h>
 #include <asm/secvar.h>
+#include <asm/bug.h>
 
-const struct secvar_operations *secvar_ops __ro_after_init;
+const struct secvar_operations *secvar_ops __ro_after_init = NULL;
 
-void set_secvar_ops(const struct secvar_operations *ops)
+int set_secvar_ops(const struct secvar_operations *ops)
 {
+	if (WARN_ON_ONCE(secvar_ops))
+		return -EBUSY;
+
 	secvar_ops = ops;
+
+	return 0;
 }
diff --git a/arch/powerpc/platforms/powernv/opal-secvar.c b/arch/powerpc/platforms/powernv/opal-secvar.c
index ef89861569e0..4c0a3b030fe0 100644
--- a/arch/powerpc/platforms/powernv/opal-secvar.c
+++ b/arch/powerpc/platforms/powernv/opal-secvar.c
@@ -113,9 +113,7 @@ static int opal_secvar_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
-	set_secvar_ops(&opal_secvar_ops);
-
-	return 0;
+	return set_secvar_ops(&opal_secvar_ops);
 }
 
 static const struct of_device_id opal_secvar_match[] = {
-- 
2.39.1