Messages in this thread | | | Date | Tue, 30 Nov 1999 18:49:58 -0500 (EST) | From | Chris Wing <> | Subject | [RFC] proposed IPC changes to support 32-bit UIDs |
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Hello. In my latest set of 32-bit UID support patches, I've changed the msgctl(), semctl(), and shmctl() functions to no longer use the same structures for both kernel and user space (for IPC_STAT, IPC_SET, MSG_STAT, SEM_STAT, and SHM_STAT). Instead, the msg_queue, semid_ds, and shmid_ds structures are considered private to the kernel, and there are now 2 sets of structures for communicating with user space:
user_msqid_ds, user_semid_ds, user_shmid_ds and old_user_msqid_ds, old_user_semid_ds, old_user_shmid_ds
The former are used for the "new" IPC_STAT, IPC_SET, et. al, while the latter are used for backwards compatibility (i.e. 16-bit UIDs).
I favored this approach because it made adding 32-bit UID support as simple as possible. I've created functions such as
kernel2user_semid_ds(struct semid_ds *in, struct user_semid_ds *out) kernel2user_ipc_perm(struct ipc_perm *in, struct user_ipc_perm *out) kernel2old_user_ipc_perm(struct ipc_perm *in, struct old_user_ipc_perm *out)
rather than toss all the new code into the already hairy msgctl(), semctl(), and shmctl() functions. This makes the 32-bit UID patch much smaller and easier to manage.
If anyone is interested in looking over this patch, you can find it at: http://www.engin.umich.edu/caen/systems/Linux/code/misc/2.3/19991130/linux-ipc.patch
The patch doesn't define the user_ipc_perm, user_msqid_ds, user_semid_ds, and user_shmid_ds structures; these are defined on an architecture-by-architecture basis for greatest flexibility. You can examine the architectural patches at: http://www.engin.umich.edu/caen/systems/Linux/code/misc/2.3/19991130/ linux-alpha.patch linux-arm.patch linux-i386.patch linux-m68k.patch linux-mips.patch linux-ppc.patch linux-sh.patch linux-sparc.patch
to see the actual definitions.
Questions:
- does anyone think that this is a bad idea?
- should there be more pad space left in the user_ipc_perm, user_msqid_ds, user_semid_ds, and user_shmid_ds structures for future use? At present, I've left 2 machine words worth of pad space in the msqid, semid, and shmid structures, and no extra padding in user_ipc_perm.
Thanks, Chris Wing wingc@engin.umich.edu
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