[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 | 39 ++++++++++++++++++++++++++++++--------
2 files changed, 46 insertions(+), 10 deletions(-)
Index: linux-2.6.26-rc8-mm1/include/linux/next_syscall_data.h
===================================================================
--- linux-2.6.26-rc8-mm1.orig/include/linux/next_syscall_data.h 2008-07-08
09:24:38.000000000 +0200
+++ linux-2.6.26-rc8-mm1/include/linux/next_syscall_data.h 2008-07-08
12:12:39.000000000 +0200
@@ -1,7 +1,10 @@
/*
* include/linux/next_syscall_data.h
*
- * Definitions to support fixed data for next syscall to be called.
+ * Definitions to support fixed data for next syscall to be called. The
+ * following is supported today:
+ * . object creation with a predefined id
+ * . for a sysv ipc object
*/
#ifndef _LINUX_NEXT_SYSCALL_DATA_H
@@ -13,13 +16,23 @@
* 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 void reset_next_syscall_data(struct task_struct *);
Index: linux-2.6.26-rc8-mm1/ipc/util.c
===================================================================
--- linux-2.6.26-rc8-mm1.orig/ipc/util.c 2008-07-08 09:05:09.000000000
+0200
+++ linux-2.6.26-rc8-mm1/ipc/util.c 2008-07-08 12:13:40.000000000 +0200
@@ -266,20 +266,43 @@ 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 (unlikely(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;
+ unsigned long new_seq = next_id / SEQ_MULTIPLIER;
+
+ reset_next_syscall_data(current);
+
+ if (next_id != (new_lid + (new_seq * SEQ_MULTIPLIER)))
+ return -EINVAL;
+
+ 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 = new_seq;
+ } 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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