[PATCH 5.4 124/189] s390/cpacf: Make use of invalid opcode produce a link error

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5.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Harald Freudenberger <freude@xxxxxxxxxxxxx>

[ Upstream commit 32e8bd6423fc127d2b37bdcf804fd76af3bbec79 ]

Instead of calling BUG() at runtime introduce and use a prototype for a
non-existing function to produce a link error during compile when a not
supported opcode is used with the __cpacf_query() or __cpacf_check_opcode()
inline functions.

Suggested-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
Signed-off-by: Harald Freudenberger <freude@xxxxxxxxxxxxx>
Reviewed-by: Holger Dengler <dengler@xxxxxxxxxxxxx>
Reviewed-by: Juergen Christ <jchrist@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 arch/s390/include/asm/cpacf.h | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/s390/include/asm/cpacf.h b/arch/s390/include/asm/cpacf.h
index fa31f71cf5746..0f6ff2008a159 100644
--- a/arch/s390/include/asm/cpacf.h
+++ b/arch/s390/include/asm/cpacf.h
@@ -161,6 +161,13 @@
 
 typedef struct { unsigned char bytes[16]; } cpacf_mask_t;
 
+/*
+ * Prototype for a not existing function to produce a link
+ * error if __cpacf_query() or __cpacf_check_opcode() is used
+ * with an invalid compile time const opcode.
+ */
+void __cpacf_bad_opcode(void);
+
 static __always_inline void __cpacf_query_rre(u32 opc, u8 r1, u8 r2,
 					      cpacf_mask_t *mask)
 {
@@ -232,7 +239,7 @@ static __always_inline void __cpacf_query(unsigned int opcode,
 		__cpacf_query_rre(CPACF_PRNO, 2, 4, mask);
 		break;
 	default:
-		BUG();
+		__cpacf_bad_opcode();
 	}
 }
 
@@ -257,7 +264,8 @@ static __always_inline int __cpacf_check_opcode(unsigned int opcode)
 	case CPACF_KMA:
 		return test_facility(146);	/* check for MSA8 */
 	default:
-		BUG();
+		__cpacf_bad_opcode();
+		return 0;
 	}
 }
 
-- 
2.43.0







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