linux-kernel - [PATCH v3 2/3] powerpc: Fix incorrect stw{, ux, u, x} instructions in __set_pte

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Message-Id: <96354bd77977a6a933fe9020da57629007fdb920.1603358942.git.christophe.leroy@csgroup.eu>
Date:   Thu, 22 Oct 2020 09:29:20 +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>,
        mathieu.desnoyers@...icios.com
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v3 2/3] powerpc: Fix incorrect stw{, ux, u, x} instructions in
 __set_pte_at

From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

The placeholder for instruction selection should use the second
argument's operand, which is %1, not %0. This could generate incorrect
assembly code if the memory addressing of operand %0 is a different
form from that of operand %1.

Also remove the %Un placeholder because having %Un placeholders
for two operands which are based on the same local var (ptep) doesn't
make much sense. By the way, it doesn't change the current behaviour
because "<>" constraint is missing for the associated "=m".

Fixes: 9bf2b5cdc5fe ("powerpc: Fixes for CONFIG_PTE_64BIT for SMP support")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Kumar Gala <galak@...nel.crashing.org>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: linuxppc-dev@...ts.ozlabs.org
Cc: <stable@...r.kernel.org> # v2.6.28+
Acked-by: Segher Boessenkool <segher@...nel.crashing.org>
[chleroy: revised commit log iaw segher's comments and removed %U0]
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
v3: Remove %Un

v2: Changed commit log.
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/include/asm/book3s/32/pgtable.h | 4 ++--
 arch/powerpc/include/asm/nohash/pgtable.h    | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
index 36443cda8dcf..41d8bc6db303 100644
--- a/arch/powerpc/include/asm/book3s/32/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
@@ -522,9 +522,9 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
 	if (pte_val(*ptep) & _PAGE_HASHPTE)
 		flush_hash_entry(mm, ptep, addr);
 	__asm__ __volatile__("\
-		stw%U0%X0 %2,%0\n\
+		stw%X0 %2,%0\n\
 		eieio\n\
-		stw%U0%X0 %L2,%1"
+		stw%X1 %L2,%1"
 	: "=m" (*ptep), "=m" (*((unsigned char *)ptep+4))
 	: "r" (pte) : "memory");
 
diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
index 6277e7596ae5..ac75f4ab0dba 100644
--- a/arch/powerpc/include/asm/nohash/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/pgtable.h
@@ -192,9 +192,9 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
 	 */
 	if (IS_ENABLED(CONFIG_PPC32) && IS_ENABLED(CONFIG_PTE_64BIT) && !percpu) {
 		__asm__ __volatile__("\
-			stw%U0%X0 %2,%0\n\
+			stw%X0 %2,%0\n\
 			eieio\n\
-			stw%U0%X0 %L2,%1"
+			stw%X1 %L2,%1"
 		: "=m" (*ptep), "=m" (*((unsigned char *)ptep+4))
 		: "r" (pte) : "memory");
 		return;
-- 
2.25.0