From: Tom Musta Date: Tue, 12 Aug 2014 18:53:34 +0000 (-0500) Subject: linux-user: Properly Handle semun Structure In Cross-Endian Situations X-Git-Tag: v2.2.0-rc0~165^2~11 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=5464baecf521d1ca8095604f5a7371443c94226a;p=thirdparty%2Fqemu.git linux-user: Properly Handle semun Structure In Cross-Endian Situations 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 --- diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 08fdd940143..39ab4c79423 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: