From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39392) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XIFGc-0004x7-HC for qemu-devel@nongnu.org; Fri, 15 Aug 2014 07:02:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XIFGU-00072N-R4 for qemu-devel@nongnu.org; Fri, 15 Aug 2014 07:01:54 -0400 Received: from [2001:4b98:dc0:45:216:3eff:fe3d:166f] (port=44490 helo=afflict.kos.to) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XIFGU-00071G-Kr for qemu-devel@nongnu.org; Fri, 15 Aug 2014 07:01:46 -0400 From: riku.voipio@linaro.org Date: Fri, 15 Aug 2014 14:01:31 +0300 Message-Id: <05945bb57d1c51a305b40de7d68c1a6b4a00b56d.1408100160.git.riku.voipio@linaro.org> In-Reply-To: References: Subject: [Qemu-devel] [PULL 13/24] linux-user: Properly Handle semun Structure In Cross-Endian Situations List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Peter Maydell , Tom Musta From: Tom Musta The semun union used in the semctl system call contains both an int (val) and pointers. In cross-endian situations on 64 bit targets, the value passed to semctl is an 8 byte (abi_long) value and thus does not have the 4-byte val field in the correct location. In order to rectify this, the other half of the union must be accessed. This is achieved in code by performing a byte swap on the entire 8 byte union, followed by a 4-byte swap of the first half. Also, eliminate an extraneous (dead) line of code that sets target_su.val in the IPC_SET/IPC_GET case. Signed-off-by: Tom Musta Signed-off-by: Riku Voipio --- linux-user/syscall.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 0113250..ba9dfc5 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -2652,9 +2652,18 @@ static inline abi_long do_semctl(int semid, int semnum, int cmd, switch( cmd ) { case GETVAL: case SETVAL: - arg.val = tswap32(target_su.val); + /* In 64 bit cross-endian situations, we will erroneously pick up + * the wrong half of the union for the "val" element. To rectify + * this, the entire 8-byte structure is byteswapped, followed by + * a swap of the 4 byte val field. In other cases, the data is + * already in proper host byte order. */ + if (sizeof(target_su.val) != (sizeof(target_su.buf))) { + target_su.buf = tswapal(target_su.buf); + arg.val = tswap32(target_su.val); + } else { + arg.val = target_su.val; + } ret = get_errno(semctl(semid, semnum, cmd, arg)); - target_su.val = tswap32(arg.val); break; case GETALL: case SETALL: -- 2.0.1