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linux-user: Properly Handle semun Structure In Cross-Endian Situations

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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 <tommusta@gmail.com>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
This commit is contained in:
Tom Musta 2014-08-12 13:53:34 -05:00 committed by Riku Voipio
parent 5d2fa8ebb4
commit 5464baecf5
1 changed files with 11 additions and 2 deletions
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13
linux-user/syscall.c
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@ -2652,9 +2652,18 @@ static inline abi_long do_semctl(int semid, int semnum, int cmd,
switch( cmd ) { switch( cmd ) {
case GETVAL: case GETVAL:
case SETVAL: 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)); ret = get_errno(semctl(semid, semnum, cmd, arg));
target_su.val = tswap32(arg.val);
break; break;
case GETALL: case GETALL:
case SETALL: case SETALL: