linux-kernel - [PATCH AUTOSEL 5.15 28/68] parisc: Fix extraction of hash lock bits in syscall.S

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Date:   Tue, 30 Nov 2021 09:46:24 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     John David Anglin <dave.anglin@...l.net>,
        Helge Deller <deller@....de>, Sasha Levin <sashal@...nel.org>,
        James.Bottomley@...senPartnership.com, svens@...ckframe.org,
        masahiroy@...nel.org, linux-parisc@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 28/68] parisc: Fix extraction of hash lock bits in syscall.S

From: John David Anglin <dave.anglin@...l.net>

[ Upstream commit df2ffeda6370a77011902e7c9d7a1eb1cbffed4f ]

The extru instruction leaves the most significant 32 bits of the target
register in an undefined state on PA 2.0 systems. If any of these bits
are nonzero, this will break the calculation of the lock pointer.

Fix by using extrd,u instruction via extru_safe macro on 64-bit kernels.

Signed-off-by: John David Anglin <dave.anglin@...l.net>
Signed-off-by: Helge Deller <deller@....de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/parisc/kernel/syscall.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S
index 3f24a0af1e047..06542f2598d50 100644
--- a/arch/parisc/kernel/syscall.S
+++ b/arch/parisc/kernel/syscall.S
@@ -572,7 +572,7 @@ lws_compare_and_swap:
 	ldo	R%lws_lock_start(%r20), %r28
 
 	/* Extract eight bits from r26 and hash lock (Bits 3-11) */
-	extru  %r26, 28, 8, %r20
+	extru_safe  %r26, 28, 8, %r20
 
 	/* Find lock to use, the hash is either one of 0 to
 	   15, multiplied by 16 (keep it 16-byte aligned)
@@ -762,7 +762,7 @@ cas2_lock_start:
 	ldo	R%lws_lock_start(%r20), %r28
 
 	/* Extract eight bits from r26 and hash lock (Bits 3-11) */
-	extru  %r26, 28, 8, %r20
+	extru_safe  %r26, 28, 8, %r20
 
 	/* Find lock to use, the hash is either one of 0 to
 	   15, multiplied by 16 (keep it 16-byte aligned)
-- 
2.33.0