linux-kernel - [PATCH v1 04/12] powerpc/inst: Avoid pointer dereferencing in ppc_inst

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Date:   Wed, 19 May 2021 14:43:31 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        naveen.n.rao@...ux.vnet.ibm.com, jniethe5@...il.com
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v1 04/12] powerpc/inst: Avoid pointer dereferencing in
 ppc_inst_equal()

Avoid casting/dereferencing ppc_inst() as u64* , check each member
of the struct when relevant.

And remove the 0xff initialisation of the suffix for non
prefixed instruction. An instruction with 0xff as a suffix
might be invalid, but still is a prefixed instruction and
has to be considered as this.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/include/asm/inst.h | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/include/asm/inst.h b/arch/powerpc/include/asm/inst.h
index 17f74429d5d6..b49f11c69ed5 100644
--- a/arch/powerpc/include/asm/inst.h
+++ b/arch/powerpc/include/asm/inst.h
@@ -62,7 +62,7 @@ static inline int ppc_inst_primary_opcode(struct ppc_inst x)
 }
 
 #ifdef CONFIG_PPC64
-#define ppc_inst(x) ((struct ppc_inst){ .val = (x), .suffix = 0xff })
+#define ppc_inst(x) ((struct ppc_inst){ .val = (x) })
 
 #define ppc_inst_prefix(x, y) ((struct ppc_inst){ .val = (x), .suffix = (y) })
 
@@ -73,7 +73,7 @@ static inline u32 ppc_inst_suffix(struct ppc_inst x)
 
 static inline bool ppc_inst_prefixed(struct ppc_inst x)
 {
-	return ppc_inst_primary_opcode(x) == OP_PREFIX && ppc_inst_suffix(x) != 0xff;
+	return ppc_inst_primary_opcode(x) == OP_PREFIX;
 }
 
 static inline struct ppc_inst ppc_inst_swab(struct ppc_inst x)
@@ -94,11 +94,6 @@ static inline struct ppc_inst ppc_inst_read(const struct ppc_inst *ptr)
 	}
 }
 
-static inline bool ppc_inst_equal(struct ppc_inst x, struct ppc_inst y)
-{
-	return *(u64 *)&x == *(u64 *)&y;
-}
-
 #else
 
 #define ppc_inst(x) ((struct ppc_inst){ .val = x })
@@ -125,13 +120,17 @@ static inline struct ppc_inst ppc_inst_read(const struct ppc_inst *ptr)
 	return *ptr;
 }
 
+#endif /* CONFIG_PPC64 */
+
 static inline bool ppc_inst_equal(struct ppc_inst x, struct ppc_inst y)
 {
-	return ppc_inst_val(x) == ppc_inst_val(y);
+	if (ppc_inst_val(x) != ppc_inst_val(y))
+		return false;
+	if (!ppc_inst_prefixed(x))
+		return true;
+	return ppc_inst_suffix(x) == ppc_inst_suffix(y);
 }
 
-#endif /* CONFIG_PPC64 */
-
 static inline int ppc_inst_len(struct ppc_inst x)
 {
 	return ppc_inst_prefixed(x) ? 8 : 4;
-- 
2.25.0