I'm looking at the wait queue changes in 2.3.1, and I noticed that one of the
modified structures is "struct msqid_ds" in include/linux/msg.h.
"struct msqid_ds" is part of the userland-visible ABI; that is why it appears
above the __KERNEL__ line. It is used in file ipc/msg.c, function sys_msgctl,
cases MSG_STAT, IPC_SET, and IPC_STAT. Some of the values copied between
kernel and user space are located after parts of the structure that have
changed size, so they now have different offsets!
I think the canonical fix for this is to have two structures:
struct user_msqid_ds /* userland layout, outside __KERNEL__ */
struct kernel_msqid_ds /* kernel layout, inside __KERNEL__ */
In user_msqid_ds, "wwait" and "rwait" should be void pointers, for
compatibility with 2.2
But I'm not attached to any particular solution. I just want to flag the
problem.
Note: keep an eye on the sparc32 code, which already does one level of
translation (and I believe it works correctly at the moment, good job). Make
sure that it keeps translating to the same structure that sys_msgctl accepts!
Also, I checked out all the other structures affected in 2.3.1, and none
of them triggered me to say "hmmm I remember entering that in my giant
list of ABI Data Types". It's unusual for a wait-queue pointer to be
in an ABI structure.
Michael Elizabeth Chastain
<mailto:mec@shout.net>
"love without fear"
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