Andrew Brown wrote:

> >The following patch adds support for the ddb "dmesg" command to only
> >print the last N bytes of the kernel message buffer.  I've found this
> >useful when debugging a system with a large message buffer, but was
> >interested in only the last few pages of dmesg output.
> 
> neat!
> 
> >Any objections before I commit it?
> 
> not really, but see below anyway.  :)
>
> >@@ -245,10 +246,17 @@ db_dmesg(db_expr_t addr, int haddr, db_e
> > 	mbp = msgbufp;
> > 	bufdata = &mbp->msg_bufc[0];
> > 
> >+	if (haddr && addr <  mbp->msg_bufs)
> 
> extra space.  :)            ^

Picky picky!  Fixed.

> >+		print = addr;
> >+	else
> >+		print = mbp->msg_bufs;
> >+
> > 	for (newl = skip = i = 0, p = bufdata + mbp->msg_bufx;
> > 	    i < mbp->msg_bufs; i++, p++) {
> > 		if (p == bufdata + mbp->msg_bufs)
> > 			p = bufdata;
> >+		if (i < mbp->msg_bufs - print)
> >+			continue;
> 
> you realize that this doesn't take the "\n<.*>" sequences into
> account, yes?

I'm not sure how big a deal this is.  I also could have just started
printing after adding "mbp->msg_bufs - print" to the current message
buffer start, checking for wraparound, etc but that seemed like too
much work.

The way the skip/newl logic works would require a bit of re-ordering
of the existing code.   Unless ... I simply moved the new check to
immediately before the "db_printf("%c", ch);", and that seems to
work ok (but I didn't have any syslog messages in the kernel buffer
to skip over).

> > 		ch = *p;
> > 		/* Skip "\n<.*>" syslog sequences. */
> > 		if (skip) {

Thanks for the feedback,
Simon.
--
Simon Burge                            <simonb@wasabisystems.com>
NetBSD Support and Service:         http://www.wasabisystems.com/