Make msgbuf_peekbytes() not return leading zeroes.
Introduce new MSGBUF_WRAP flag, indicating that buffer has wrapped at least once and does not keep zeroes from the last msgbuf_clear(). It allows msgbuf_peekbytes() to return only real data, not requiring every consumer to trim the leading zeroes after doing pointless copy. The most visible effect is that kern.msgbuf sysctl now always returns proper zero-terminated string, not only after the first buffer wrap. MFC after: 1 week Sponsored by: iXsystems, Inc.
This commit is contained in:
Alexander Motin
parent
7a382e744b
commit
81dc00331d
@ -69,10 +69,10 @@ msgbuf_init(struct msgbuf *mbp, void *ptr, int size)
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mbp->msg_ptr = ptr;
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mbp->msg_size = size;
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mbp->msg_seqmod = SEQMOD(size);
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msgbuf_clear(mbp);
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mbp->msg_magic = MSG_MAGIC;
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mbp->msg_lastpri = -1;
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mbp->msg_flags = 0;
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msgbuf_clear(mbp);
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mbp->msg_magic = MSG_MAGIC;
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bzero(&mbp->msg_lock, sizeof(mbp->msg_lock));
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mtx_init(&mbp->msg_lock, "msgbuf", NULL, MTX_SPIN);
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}
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@ -123,6 +123,7 @@ msgbuf_clear(struct msgbuf *mbp)
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mbp->msg_wseq = 0;
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mbp->msg_rseq = 0;
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mbp->msg_cksum = 0;
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mbp->msg_flags &= ~MSGBUF_WRAP;
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}
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/*
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@ -145,18 +146,17 @@ msgbuf_getcount(struct msgbuf *mbp)
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*
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* The caller should hold the message buffer spinlock.
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*/
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static void
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msgbuf_do_addchar(struct msgbuf * const mbp, u_int * const seq, const int c)
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msgbuf_do_addchar(struct msgbuf * const mbp, const int c)
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{
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u_int pos;
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/* Make sure we properly wrap the sequence number. */
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pos = MSGBUF_SEQ_TO_POS(mbp, *seq);
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pos = MSGBUF_SEQ_TO_POS(mbp, mbp->msg_wseq);
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mbp->msg_cksum += (u_int)(u_char)c -
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(u_int)(u_char)mbp->msg_ptr[pos];
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mbp->msg_ptr[pos] = c;
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*seq = MSGBUF_SEQNORM(mbp, *seq + 1);
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mbp->msg_wseq = MSGBUF_SEQADD(mbp, mbp->msg_wseq, 1);
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}
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/*
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@ -167,7 +167,9 @@ msgbuf_addchar(struct msgbuf *mbp, int c)
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{
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mtx_lock_spin(&mbp->msg_lock);
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msgbuf_do_addchar(mbp, &mbp->msg_wseq, c);
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msgbuf_do_addchar(mbp, c);
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if (mbp->msg_wseq >= mbp->msg_size)
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mbp->msg_flags |= MSGBUF_WRAP;
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mtx_unlock_spin(&mbp->msg_lock);
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}
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@ -183,7 +185,6 @@ msgbuf_addchar(struct msgbuf *mbp, int c)
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void
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msgbuf_addstr(struct msgbuf *mbp, int pri, const char *str, int filter_cr)
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{
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u_int seq;
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size_t len, prefix_len;
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char prefix[MAXPRIBUF];
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char buf[32];
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@ -205,11 +206,6 @@ msgbuf_addstr(struct msgbuf *mbp, int pri, const char *str, int filter_cr)
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if (pri != -1)
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prefix_len = sprintf(prefix, "<%d>", pri);
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/*
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* Starting write sequence number.
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*/
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seq = mbp->msg_wseq;
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/*
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* Whenever there is a change in priority, we have to insert a
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* newline, and a priority prefix if the priority is not -1. Here
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@ -218,7 +214,7 @@ msgbuf_addstr(struct msgbuf *mbp, int pri, const char *str, int filter_cr)
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* insert a newline before this string.
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*/
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if (mbp->msg_lastpri != pri && (mbp->msg_flags & MSGBUF_NEEDNL) != 0) {
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msgbuf_do_addchar(mbp, &seq, '\n');
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msgbuf_do_addchar(mbp, '\n');
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mbp->msg_flags &= ~MSGBUF_NEEDNL;
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}
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@ -233,7 +229,7 @@ msgbuf_addstr(struct msgbuf *mbp, int pri, const char *str, int filter_cr)
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int j;
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for (j = 0; j < prefix_len; j++)
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msgbuf_do_addchar(mbp, &seq, prefix[j]);
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msgbuf_do_addchar(mbp, prefix[j]);
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}
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if (msgbuf_show_timestamp && needtime == 1 &&
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@ -241,7 +237,7 @@ msgbuf_addstr(struct msgbuf *mbp, int pri, const char *str, int filter_cr)
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snprintf(buf, sizeof(buf), "[%jd] ",
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(intmax_t)time_uptime);
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for (j = 0; buf[j] != '\0'; j++)
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msgbuf_do_addchar(mbp, &seq, buf[j]);
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msgbuf_do_addchar(mbp, buf[j]);
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needtime = 0;
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}
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@ -265,14 +261,10 @@ msgbuf_addstr(struct msgbuf *mbp, int pri, const char *str, int filter_cr)
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else
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mbp->msg_flags |= MSGBUF_NEEDNL;
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msgbuf_do_addchar(mbp, &seq, str[i]);
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msgbuf_do_addchar(mbp, str[i]);
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}
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/*
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* Update the write sequence number for the actual number of
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* characters we put in the message buffer. (Depends on whether
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* carriage returns are filtered.)
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*/
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mbp->msg_wseq = seq;
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if (mbp->msg_wseq >= mbp->msg_size)
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mbp->msg_flags |= MSGBUF_WRAP;
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/*
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* Set the last priority.
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@ -302,9 +294,9 @@ msgbuf_getchar(struct msgbuf *mbp)
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return (-1);
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}
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if (len > mbp->msg_size)
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mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
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mbp->msg_rseq = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_size);
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c = (u_char)mbp->msg_ptr[MSGBUF_SEQ_TO_POS(mbp, mbp->msg_rseq)];
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mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + 1);
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mbp->msg_rseq = MSGBUF_SEQADD(mbp, mbp->msg_rseq, 1);
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mtx_unlock_spin(&mbp->msg_lock);
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@ -329,7 +321,7 @@ msgbuf_getbytes(struct msgbuf *mbp, char *buf, int buflen)
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return (0);
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}
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if (len > mbp->msg_size) {
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mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
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mbp->msg_rseq = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_size);
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len = mbp->msg_size;
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}
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pos = MSGBUF_SEQ_TO_POS(mbp, mbp->msg_rseq);
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@ -337,7 +329,7 @@ msgbuf_getbytes(struct msgbuf *mbp, char *buf, int buflen)
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len = min(len, (u_int)buflen);
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bcopy(&mbp->msg_ptr[pos], buf, len);
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mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + len);
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mbp->msg_rseq = MSGBUF_SEQADD(mbp, mbp->msg_rseq, len);
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mtx_unlock_spin(&mbp->msg_lock);
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@ -363,7 +355,10 @@ msgbuf_peekbytes(struct msgbuf *mbp, char *buf, int buflen, u_int *seqp)
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if (buf == NULL) {
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/* Just initialise *seqp. */
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*seqp = MSGBUF_SEQNORM(mbp, mbp->msg_wseq - mbp->msg_size);
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if (mbp->msg_flags & MSGBUF_WRAP)
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*seqp = MSGBUF_SEQSUB(mbp, mbp->msg_wseq, mbp->msg_size);
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else
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*seqp = 0;
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mtx_unlock_spin(&mbp->msg_lock);
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return (0);
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}
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@ -375,14 +370,14 @@ msgbuf_peekbytes(struct msgbuf *mbp, char *buf, int buflen, u_int *seqp)
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return (0);
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}
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if (len > mbp->msg_size) {
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*seqp = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
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*seqp = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_size);
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len = mbp->msg_size;
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}
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pos = MSGBUF_SEQ_TO_POS(mbp, *seqp);
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len = min(len, mbp->msg_size - pos);
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len = min(len, (u_int)buflen);
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bcopy(&mbp->msg_ptr[MSGBUF_SEQ_TO_POS(mbp, *seqp)], buf, len);
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*seqp = MSGBUF_SEQNORM(mbp, *seqp + len);
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*seqp = MSGBUF_SEQADD(mbp, *seqp, len);
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mtx_unlock_spin(&mbp->msg_lock);
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@ -50,6 +50,7 @@ struct msgbuf {
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int msg_lastpri; /* saved priority value */
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u_int msg_flags;
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#define MSGBUF_NEEDNL 0x01 /* set when newline needed */
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#define MSGBUF_WRAP 0x02 /* buffer has wrapped around */
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struct mtx msg_lock; /* mutex to protect the buffer */
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};
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@ -57,8 +58,10 @@ struct msgbuf {
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#define MSGBUF_SEQNORM(mbp, seq) (((seq) + (mbp)->msg_seqmod) % \
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(mbp)->msg_seqmod)
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#define MSGBUF_SEQ_TO_POS(mbp, seq) ((seq) % (mbp)->msg_size)
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/* Subtract sequence numbers. Note that only positive values result. */
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#define MSGBUF_SEQSUB(mbp, seq1, seq2) (MSGBUF_SEQNORM((mbp), (seq1) - (seq2)))
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/* Add/subtract normalized sequence numbers. Normalized values result. */
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#define MSGBUF_SEQADD(mbp, seq1, seq2) (((seq1) + (seq2)) % (mbp)->msg_seqmod)
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#define MSGBUF_SEQSUB(mbp, seq1, seq2) ((seq1) >= (seq2) ? (seq1) - (seq2) : \
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(seq1) + (mbp)->msg_seqmod - (seq2))
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#ifdef _KERNEL
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extern int msgbufsize;
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