linux-kernel - [PATCH 4.19 302/346] powerpc: Fix incorrect stw{, ux, u, x} instructions in __set_pte

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Date:   Mon, 28 Dec 2020 13:50:21 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.19 302/346] powerpc: Fix incorrect stw{, ux, u, x} instructions in __set_pte_at

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

commit d85be8a49e733dcd23674aa6202870d54bf5600d upstream.

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".

[chleroy: revised commit log iaw segher's comments and removed %U0]

Fixes: 9bf2b5cdc5fe ("powerpc: Fixes for CONFIG_PTE_64BIT for SMP support")
Cc: <stable@...r.kernel.org> # v2.6.28+
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Acked-by: Segher Boessenkool <segher@...nel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/96354bd77977a6a933fe9020da57629007fdb920.1603358942.git.christophe.leroy@csgroup.eu
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/include/asm/book3s/32/pgtable.h |    4 ++--
 arch/powerpc/include/asm/nohash/pgtable.h    |    4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

--- a/arch/powerpc/include/asm/book3s/32/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
@@ -434,9 +434,9 @@ static inline void __set_pte_at(struct m
 	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");
 
--- a/arch/powerpc/include/asm/nohash/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/pgtable.h
@@ -151,9 +151,9 @@ static inline void __set_pte_at(struct m
 	 */
 	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;