powerpc/secvar: Warn and error if multiple secvar ops are set

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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230210080401.345462-6-ajd@linux.ibm.com

diff --git a/arch/powerpc/include/asm/secvar.h b/arch/powerpc/include/asm/secvar.h
index 07ba36f..a2b5f22 100644 (file)
--- 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 6a29777..19172a2 100644 (file)
--- 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 ef89861..4c0a3b0 100644 (file)
--- 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[] = {