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

From: Russell Currey <redacted>

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 <redacted>
Co-developed-by: Andrew Donnellan <redacted>
Signed-off-by: Andrew Donnellan <redacted>

---

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[] = {