From 171e807fd524928c895ed7090a288352ed8f7cf1 Mon Sep 17 00:00:00 2001 From: Stanislav Kinsbursky Date: Sat, 3 Nov 2012 11:43:05 +1100 Subject: [PATCH] ipc: introduce message queue copy feature This patch is required for checkpoint/restore in userspace. c/r requires some way to get all pending IPC messages without deleting them from the queue (checkpoint can fail and in this case tasks will be resumed, so queue have to be valid). To achive this, new operation flag MSG_COPY for sys_msgrcv() system call was introduced. If this flag was specified, then mtype is interpreted as number of the message to copy. If MSG_COPY is set, then kernel will allocate dummy message with passed size, and then use new copy_msg() helper function to copy desired message (instead of unlinking it from the queue). Notes: 1) Return -ENOSYS if MSG_COPY is specified, but CONFIG_CHECKPOINT_RESTORE is not set. Signed-off-by: Stanislav Kinsbursky Cc: Serge Hallyn Cc: "Eric W. Biederman" Cc: Pavel Emelyanov Cc: Al Viro Cc: KOSAKI Motohiro Cc: Michael Kerrisk Signed-off-by: Andrew Morton --- include/uapi/linux/msg.h | 1 + ipc/msg.c | 50 ++++++++++++++++++++++++++++++++++++++-- ipc/msgutil.c | 38 ++++++++++++++++++++++++++++++ ipc/util.h | 1 + 4 files changed, 88 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/msg.h b/include/uapi/linux/msg.h index 78dbd2f996a3..22d95c6854e0 100644 --- a/include/uapi/linux/msg.h +++ b/include/uapi/linux/msg.h @@ -10,6 +10,7 @@ /* msgrcv options */ #define MSG_NOERROR 010000 /* no error if message is too big */ #define MSG_EXCEPT 020000 /* recv any msg except of specified type.*/ +#define MSG_COPY 040000 /* copy (not remove) all queue messages */ /* Obsolete, used only for backwards compatibility and libc5 compiles */ struct msqid_ds { diff --git a/ipc/msg.c b/ipc/msg.c index cefc24f46e3e..889cc8db3957 100644 --- a/ipc/msg.c +++ b/ipc/msg.c @@ -777,19 +777,48 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, struct msg_msg *msg; int mode; struct ipc_namespace *ns; +#ifdef CONFIG_CHECKPOINT_RESTORE + struct msg_msg *copy = NULL; + unsigned long copy_number = 0; +#endif if (msqid < 0 || (long) bufsz < 0) return -EINVAL; + if (msgflg & MSG_COPY) { +#ifdef CONFIG_CHECKPOINT_RESTORE + + if (msgflg & MSG_COPY) { + copy_number = msgtyp; + msgtyp = 0; + } + + /* + * Create dummy message to copy real message to. + */ + copy = load_msg(buf, bufsz); + if (IS_ERR(copy)) + return PTR_ERR(copy); + copy->m_ts = bufsz; +#else + return -ENOSYS; +#endif + } mode = convert_mode(&msgtyp, msgflg); ns = current->nsproxy->ipc_ns; msq = msg_lock_check(ns, msqid); - if (IS_ERR(msq)) + if (IS_ERR(msq)) { +#ifdef CONFIG_CHECKPOINT_RESTORE + if (msgflg & MSG_COPY) + free_msg(copy); +#endif return PTR_ERR(msq); + } for (;;) { struct msg_receiver msr_d; struct list_head *tmp; + long msg_counter = 0; msg = ERR_PTR(-EACCES); if (ipcperms(ns, &msq->q_perm, S_IRUGO)) @@ -809,8 +838,16 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, if (mode == SEARCH_LESSEQUAL && walk_msg->m_type != 1) { msgtyp = walk_msg->m_type - 1; +#ifdef CONFIG_CHECKPOINT_RESTORE + } else if (msgflg & MSG_COPY) { + if (copy_number == msg_counter) { + msg = copy_msg(walk_msg, copy); + break; + } +#endif } else break; + msg_counter++; } tmp = tmp->next; } @@ -823,6 +860,10 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, msg = ERR_PTR(-E2BIG); goto out_unlock; } +#ifdef CONFIG_CHECKPOINT_RESTORE + if (msgflg & MSG_COPY) + goto out_unlock; +#endif list_del(&msg->m_list); msq->q_qnum--; msq->q_rtime = get_seconds(); @@ -906,8 +947,13 @@ out_unlock: break; } } - if (IS_ERR(msg)) + if (IS_ERR(msg)) { +#ifdef CONFIG_CHECKPOINT_RESTORE + if (msgflg & MSG_COPY) + free_msg(copy); +#endif return PTR_ERR(msg); + } bufsz = msg_handler(buf, msg, bufsz); free_msg(msg); diff --git a/ipc/msgutil.c b/ipc/msgutil.c index 26143d377c95..b281f5cc0057 100644 --- a/ipc/msgutil.c +++ b/ipc/msgutil.c @@ -100,7 +100,45 @@ out_err: free_msg(msg); return ERR_PTR(err); } +#ifdef CONFIG_CHECKPOINT_RESTORE +struct msg_msg *copy_msg(struct msg_msg *src, struct msg_msg *dst) +{ + struct msg_msgseg *dst_pseg, *src_pseg; + int len = src->m_ts; + int alen; + + BUG_ON(dst == NULL); + if (src->m_ts > dst->m_ts) + return ERR_PTR(-EINVAL); + + alen = len; + if (alen > DATALEN_MSG) + alen = DATALEN_MSG; + + dst->next = NULL; + dst->security = NULL; + memcpy(dst + 1, src + 1, alen); + + len -= alen; + dst_pseg = dst->next; + src_pseg = src->next; + while (len > 0) { + alen = len; + if (alen > DATALEN_SEG) + alen = DATALEN_SEG; + memcpy(dst_pseg + 1, src_pseg + 1, alen); + dst_pseg = dst_pseg->next; + len -= alen; + src_pseg = src_pseg->next; + } + + dst->m_type = src->m_type; + dst->m_ts = src->m_ts; + + return dst; +} +#endif int store_msg(void __user *dest, struct msg_msg *msg, int len) { int alen; diff --git a/ipc/util.h b/ipc/util.h index a61e0ca2bffd..eeb79a1fbd83 100644 --- a/ipc/util.h +++ b/ipc/util.h @@ -140,6 +140,7 @@ int ipc_parse_version (int *cmd); extern void free_msg(struct msg_msg *msg); extern struct msg_msg *load_msg(const void __user *src, int len); +extern struct msg_msg *copy_msg(struct msg_msg *src, struct msg_msg *dst); extern int store_msg(void __user *dest, struct msg_msg *msg, int len); extern void recompute_msgmni(struct ipc_namespace *); -- 2.39.5