linux-kernel - [PATCH v4 4/5] sparc: fix accurate exception reporting in copy_to

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Message-Id: <20250905-memcpy_series-v4-4-1ca72dda195b@mkarcher.dialup.fu-berlin.de>
Date: Fri, 05 Sep 2025 00:03:33 +0200
From: Michael Karcher <kernel@...rcher.dialup.fu-berlin.de>
To: Andreas Larsson <andreas@...sler.com>
Cc: sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Michael Karcher <kernel@...rcher.dialup.fu-berlin.de>, 
 John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>, 
 Anthony Yznaga <anthony.yznaga@...cle.com>
Subject: [PATCH v4 4/5] sparc: fix accurate exception reporting in
 copy_to_user for Niagara 4

The referenced commit introduced exception handlers on user-space memory
references in copy_from_user and copy_to_user. These handlers return from
the respective function and calculate the remaining bytes left to copy
using the current register contents. This commit fixes a bad calculation.
This will fix the return value of copy_to_user in a specific faulting case.
The behaviour of memcpy stays unchanged.

Fixes: 957077048009 ("sparc64: Convert NG4copy_{from,to}_user to accurate exception reporting.")
Tested-by: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de> # on Oracle SPARC T4-1
Signed-off-by: Michael Karcher <kernel@...rcher.dialup.fu-berlin.de>
---
 arch/sparc/lib/NG4memcpy.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/sparc/lib/NG4memcpy.S b/arch/sparc/lib/NG4memcpy.S
index 7ad58ebe0d0096ffce4a9a333eb9cc7113c065fe..df0ec1bd194892974899e15dfc0248bb6ebdecf2 100644
--- a/arch/sparc/lib/NG4memcpy.S
+++ b/arch/sparc/lib/NG4memcpy.S
@@ -281,7 +281,7 @@ FUNC_NAME:	/* %o0=dst, %o1=src, %o2=len */
 	subcc		%o5, 0x20, %o5
 	EX_ST(STORE(stx, %g1, %o0 + 0x00), memcpy_retl_o2_plus_o5_plus_32)
 	EX_ST(STORE(stx, %g2, %o0 + 0x08), memcpy_retl_o2_plus_o5_plus_24)
-	EX_ST(STORE(stx, GLOBAL_SPARE, %o0 + 0x10), memcpy_retl_o2_plus_o5_plus_24)
+	EX_ST(STORE(stx, GLOBAL_SPARE, %o0 + 0x10), memcpy_retl_o2_plus_o5_plus_16)
 	EX_ST(STORE(stx, %o4, %o0 + 0x18), memcpy_retl_o2_plus_o5_plus_8)
 	bne,pt		%icc, 1b
 	 add		%o0, 0x20, %o0

-- 
2.50.1