[patch 35/39] sh: use generic strncpy()

From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, amodra@gmail.com,
	bin.meng@windriver.com, chenzhou10@huawei.com, dalias@libc.org,
	geert+renesas@glider.be, glaubitz@physik.fu-berlin.de,
	krzk@kernel.org, kuninori.morimoto.gx@renesas.com,
	linux-mm@kvack.org, mm-commits@vger.kernel.org,
	romain.naour@gmail.com, sam@ravnborg.org,
	torvalds@linux-foundation.org, ysato@users.sourceforge.jp
Subject: [patch 35/39] sh: use generic strncpy()
Date: Fri, 14 Aug 2020 17:32:04 -0700	[thread overview]
Message-ID: <20200815003204.lzZYGZKk4%akpm@linux-foundation.org> (raw)
In-Reply-To: <20200814172939.55d6d80b6e21e4241f1ee1f3@linux-foundation.org>

From: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Subject: sh: use generic strncpy()

Current SH will get below warning at strncpy()

In file included from ${LINUX}/arch/sh/include/asm/string.h:3,
                 from ${LINUX}/include/linux/string.h:20,
                 from ${LINUX}/include/linux/bitmap.h:9,
                 from ${LINUX}/include/linux/nodemask.h:95,
                 from ${LINUX}/include/linux/mmzone.h:17,
                 from ${LINUX}/include/linux/gfp.h:6,
                 from ${LINUX}/innclude/linux/slab.h:15,
                 from ${LINUX}/linux/drivers/mmc/host/vub300.c:38:
${LINUX}/drivers/mmc/host/vub300.c: In function 'new_system_port_status':
${LINUX}/arch/sh/include/asm/string_32.h:51:42: warning: array subscript\
  80 is above array bounds of 'char[26]' [-Warray-bounds]
   : "0" (__dest), "1" (__src), "r" (__src+__n)
                                     ~~~~~^~~~

In general, strncpy() should behave like below.

	char dest[10];
	char *src = "12345";

	strncpy(dest, src, 10);
	// dest = {'1', '2', '3', '4', '5',
	           '\0','\0','\0','\0','\0'}

But, current SH strnpy() has 2 issues.
1st is it will access to out-of-memory (= src + 10).
2nd is it needs big fixup for it, and maintenance __asm__
code is difficult.

To solve these issues, this patch simply uses generic strncpy()
instead of architecture specific one.

Link: https://marc.info/?l=linux-renesas-soc&m=157664657013309
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Alan Modra <amodra@gmail.com>
Cc: Bin Meng <bin.meng@windriver.com>
Cc: Chen Zhou <chenzhou10@huawei.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Romain Naour <romain.naour@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/sh/include/asm/string_32.h |   26 --------------------------
 1 file changed, 26 deletions(-)

--- a/arch/sh/include/asm/string_32.h~sh-use-generic-strncpy
+++ a/arch/sh/include/asm/string_32.h
@@ -28,32 +28,6 @@ static inline char *strcpy(char *__dest,
 	return __xdest;
 }
 
-#define __HAVE_ARCH_STRNCPY
-static inline char *strncpy(char *__dest, const char *__src, size_t __n)
-{
-	register char *__xdest = __dest;
-	unsigned long __dummy;
-
-	if (__n == 0)
-		return __xdest;
-
-	__asm__ __volatile__(
-		"1:\n"
-		"mov.b	@%1+, %2\n\t"
-		"mov.b	%2, @%0\n\t"
-		"cmp/eq	#0, %2\n\t"
-		"bt/s	2f\n\t"
-		" cmp/eq	%5,%1\n\t"
-		"bf/s	1b\n\t"
-		" add	#1, %0\n"
-		"2:"
-		: "=r" (__dest), "=r" (__src), "=&z" (__dummy)
-		: "0" (__dest), "1" (__src), "r" (__src+__n)
-		: "memory", "t");
-
-	return __xdest;
-}
-
 #define __HAVE_ARCH_STRCMP
 static inline int strcmp(const char *__cs, const char *__ct)
 {
_

