Quoting [EMAIL PROTECTED] ([EMAIL PROTECTED]):
> [PATCH 02/05]
>
> This patch uses the value written into the next_syscall_data proc file
> as a target id for the next IPC object to be created.
> The following syscalls have a new behavior if next_syscall_data is set:
> . mssget()
> . semget()
> . shmget()
>
> Signed-off-by: Nadia Derbey <[EMAIL PROTECTED]>
>
> ---
> include/linux/next_syscall_data.h | 17 +++++++++++++++--
> ipc/util.c | 38
> ++++++++++++++++++++++++++++++--------
> 2 files changed, 45 insertions(+), 10 deletions(-)
>
> Index: linux-2.6.26-rc5-mm3/include/linux/next_syscall_data.h
> ===================================================================
> --- linux-2.6.26-rc5-mm3.orig/include/linux/next_syscall_data.h
> 2008-07-01 10:25:48.000000000 +0200
> +++ linux-2.6.26-rc5-mm3/include/linux/next_syscall_data.h 2008-07-01
> 11:35:11.000000000 +0200
> @@ -3,7 +3,8 @@
> *
> * Definitions to support fixed data for next syscall to be called. The
> * following is supported today:
> - * . object creation with a predefined id.
> + * . object creation with a predefined id
> + * . for a sysv ipc object
> *
> */
>
> @@ -16,13 +17,25 @@
> * If this structure is pointed to by a task_struct, next syscall to be
> called
> * by the task will have a non-default behavior.
> * For example, it can be used to pre-set the id of the object to be created
> - * by next syscall.
> + * by next syscall. The following syscalls support this feature:
> + * . msgget(), semget(), shmget()
> */
> struct next_syscall_data {
> int ndata;
> long data[NDATA];
> };
>
> +/*
> + * Returns true if tsk has some data set in its next_syscall_data, 0 else
> + */
> +#define next_data_set(tsk) ((tsk)->nsd \
> + ? ((tsk)->nsd->ndata ? 1 : 0) \
> + : 0)
> +
> +#define get_next_data(tsk) ((tsk)->nsd->data[0])
> +
> +
> +
> extern ssize_t get_next_syscall_data(struct task_struct *, char *, size_t);
> extern int set_next_syscall_data(struct task_struct *, char *);
> extern int reset_next_syscall_data(struct task_struct *);
> Index: linux-2.6.26-rc5-mm3/ipc/util.c
> ===================================================================
> --- linux-2.6.26-rc5-mm3.orig/ipc/util.c 2008-07-01 10:25:48.000000000
> +0200
> +++ linux-2.6.26-rc5-mm3/ipc/util.c 2008-07-01 10:41:36.000000000 +0200
> @@ -266,20 +266,42 @@ int ipc_addid(struct ipc_ids* ids, struc
> if (ids->in_use >= size)
> return -ENOSPC;
>
> - err = idr_get_new(&ids->ipcs_idr, new, &id);
> - if (err)
> - return err;
> + if (next_data_set(current)) {
> + /* There is a target id specified, try to use it */
> + int next_id = get_next_data(current);
> + int new_lid = next_id % SEQ_MULTIPLIER;
> +
> + if (next_id !=
> + (new_lid + (next_id / SEQ_MULTIPLIER) * SEQ_MULTIPLIER))
> + return -EINVAL;
You're leaving the next_data info set on error. Should we clear it?
I think it seems more reasonable to clear it on error and just expect
the application, if it wants to retry, re-set it to the desired id
before retry.
> +
> + err = idr_get_new_above(&ids->ipcs_idr, new, new_lid, &id);
> + if (err)
> + return err;
> + if (id != new_lid) {
> + idr_remove(&ids->ipcs_idr, id);
> + return -EBUSY;
> + }
> +
> + new->id = next_id;
> + new->seq = next_id / SEQ_MULTIPLIER;
> + reset_next_syscall_data(current);
> + } else {
> + err = idr_get_new(&ids->ipcs_idr, new, &id);
> + if (err)
> + return err;
> +
> + new->seq = ids->seq++;
> + if (ids->seq > ids->seq_max)
> + ids->seq = 0;
> + new->id = ipc_buildid(id, new->seq);
> + }
>
> ids->in_use++;
>
> new->cuid = new->uid = current->euid;
> new->gid = new->cgid = current->egid;
>
> - new->seq = ids->seq++;
> - if(ids->seq > ids->seq_max)
> - ids->seq = 0;
> -
> - new->id = ipc_buildid(id, new->seq);
> spin_lock_init(&new->lock);
> new->deleted = 0;
> rcu_read_lock();
>
> --
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