linux-kernel - [PATCH v2 10/20] m68k: get rid of zeroing destination on error in csum_and_copy_from

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Message-Id: <20200724012546.302155-10-viro@ZenIV.linux.org.uk>
Date:   Fri, 24 Jul 2020 02:25:36 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: [PATCH v2 10/20] m68k: get rid of zeroing destination on error in csum_and_copy_from_user()

From: Al Viro <viro@...iv.linux.org.uk>

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 arch/m68k/lib/checksum.c | 79 +++++++++---------------------------------------
 1 file changed, 15 insertions(+), 64 deletions(-)

diff --git a/arch/m68k/lib/checksum.c b/arch/m68k/lib/checksum.c
index 3aeca261f622..7e6afeae6217 100644
--- a/arch/m68k/lib/checksum.c
+++ b/arch/m68k/lib/checksum.c
@@ -236,82 +236,33 @@ csum_and_copy_from_user(const void __user *src, void *dst, int len)
 		"clrl %5\n\t"
 		"addxl %5,%0\n\t"	/* add X bit */
 	     "7:\t"
-		"clrl %5\n"		/* no error - clear return value */
-	     "8:\n"
 		".section .fixup,\"ax\"\n"
 		".even\n"
-		/* If any exception occurs zero out the rest.
-		   Similarities with the code above are intentional :-) */
+		/* If any exception occurs, return 0 */
 	     "90:\t"
-		"clrw %3@+\n\t"
-		"movel %1,%4\n\t"
-		"lsrl #5,%1\n\t"
-		"jeq 1f\n\t"
-		"subql #1,%1\n"
-	     "91:\t"
-		"clrl %3@+\n"
-	     "92:\t"
-		"clrl %3@+\n"
-	     "93:\t"
-		"clrl %3@+\n"
-	     "94:\t"
-		"clrl %3@+\n"
-	     "95:\t"
-		"clrl %3@+\n"
-	     "96:\t"
-		"clrl %3@+\n"
-	     "97:\t"
-		"clrl %3@+\n"
-	     "98:\t"
-		"clrl %3@+\n\t"
-		"dbra %1,91b\n\t"
-		"clrw %1\n\t"
-		"subql #1,%1\n\t"
-		"jcc 91b\n"
-	     "1:\t"
-		"movel %4,%1\n\t"
-		"andw #0x1c,%4\n\t"
-		"jeq 1f\n\t"
-		"lsrw #2,%4\n\t"
-		"subqw #1,%4\n"
-	     "99:\t"
-		"clrl %3@+\n\t"
-		"dbra %4,99b\n\t"
-	     "1:\t"
-		"andw #3,%1\n\t"
-		"jeq 9f\n"
-	     "100:\t"
-		"clrw %3@+\n\t"
-		"tstw %1\n\t"
-		"jeq 9f\n"
-	     "101:\t"
-		"clrb %3@+\n"
-	     "9:\t"
-#define STR(X) STR1(X)
-#define STR1(X) #X
-		"moveq #-" STR(EFAULT) ",%5\n\t"
-		"jra 8b\n"
+		"clrl %0\n"
+		"jra 7b\n"
 		".previous\n"
 		".section __ex_table,\"a\"\n"
 		".long 10b,90b\n"
-		".long 11b,91b\n"
-		".long 12b,92b\n"
-		".long 13b,93b\n"
-		".long 14b,94b\n"
-		".long 15b,95b\n"
-		".long 16b,96b\n"
-		".long 17b,97b\n"
-		".long 18b,98b\n"
-		".long 19b,99b\n"
-		".long 20b,100b\n"
-		".long 21b,101b\n"
+		".long 11b,90b\n"
+		".long 12b,90b\n"
+		".long 13b,90b\n"
+		".long 14b,90b\n"
+		".long 15b,90b\n"
+		".long 16b,90b\n"
+		".long 17b,90b\n"
+		".long 18b,90b\n"
+		".long 19b,90b\n"
+		".long 20b,90b\n"
+		".long 21b,90b\n"
 		".previous"
 		: "=d" (sum), "=d" (len), "=a" (src), "=a" (dst),
 		  "=&d" (tmp1), "=d" (tmp2)
 		: "0" (sum), "1" (len), "2" (src), "3" (dst)
 	    );
 
-	return tmp2 ? 0 : sum;
+	return sum;
 }
 
 EXPORT_SYMBOL(csum_and_copy_from_user);
-- 
2.11.0