[9fans] tip o' the day

[9fans] tip o' the day

[Russ Cox]

Here's a long one.

---------- Forwarded message ----------
From: Russ Cox <russcox@gmail.com>
Date: Thu, 17 Feb 2005 13:41:56 -0500
Subject: Re: png
To: andrey mirtchovski <mirtchov@cpsc.ucalgary.ca>
Cc: anyrhine@cs.helsinki.fi


> mem user overflow
> pool sbrkmem block 115348
> hdr 0a110c09 00000020 00002d1e 00000000 00000000 faf0f100
> tail 0a110c09 00000020 00002d1e 00000000 00000000 faf0f100 | ef1400be
> 00000020
> user data 00 00 00 00  00 00 00 00 | 00 f1 f0 fa  be 00 14 ef
> panic: pool panic
> 8.png 336871: suicide: sys: trap: fault read addr=0x0 pc=0x00006cd5

This says that the block at address 0x115348 has overflowed the
amount written to it.  In the "user data" print, the | marks the place
where the user data should end.  The next magic bytes are "fe f1 f0 fa"
(fee fi fo fum), but a 00 has overwritten the fe.

The size of the block is the second word of the header minus the
16-bit word contained between ef and be in the tail, so 0x20-0x14 = 12
in this case.  That includes the 2 words of tags, so there's really
only 4 bytes.
So you called malloc(4) and then wrote 5 bytes to it.

The header is two words.  The next two are the malloc tags and then
after that comes the real data.  The malloc tags are by default the pc
that last allocated and reallocated the block, so you allocated from 0x2d1e.
Run src -s 0x2d1e /bin/png and you'll have the line that allocated.
If that's a wrapper (e.g., pngmalloc) you can change the wrapper to do

    v = malloc(n);
    setmalloctag(v, getcallerpc(&n));

so that the tag will have the caller of pngmalloc instead of pngmalloc itself.

Russ

Re: [9fans] tip o' the day

[Sergey Reva]

In Acme type 'Indent ON' and then press middle mouse button on it to turn on auto indent

--
http://rs-rlab.narod.ru                            mailto:rs_rlab@mail.ru

Re: [9fans] tip o' the day

[YAMANASHI Takeshi]

having read steve's venti recovery page posted on another thread,
i feel this should go into the tips.

	To get the last valid venti archive score:  fossil/last /dev/sdC0/fossil
--

[9fans] tip o' the day

[Steve Simon]

Added a Tip o' the day page to the wiki with peoples contributions,
I took the liberty of editing peoples text on occasion to make it
clearer in the context of a list rather than an email thread.

I haven't attributed them - if there where an argument Google knows.

-Steve

[9fans] tip o' the day

[Russ Cox]

I was debugging a program with Nashi just now
and he was surprised to find out about snap and
snapfs.

What surprises do you wish someone had told you about?

Russ

P.S. If you keep them to one line, maybe I'll make an
alternate fortune file so you can put
   fortune /sys/lib/plan9.tips
or something in your profile.

Re: [9fans] tip o' the day

[Tim Newsham]

> What surprises do you wish someone had told you about?

   fn cd { builtin cd $* && awd $sysname }

but that should be in the standard distribution now.  I'm
sure there are more, but I can't remember them now.

> Russ

Tim N.

Re: [9fans] tip o' the day

[Fco. J. Ballesteros]

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you can use stub(8) to provide file mount points.
/sys/src/cmd/unix/winplumb lets you plumb to a windows navigator

thanks

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From: Russ Cox <russcox@gmail.com>
To: 9fans <9fans@cse.psu.edu>
Subject: [9fans] tip o' the day
Date: Tue, 8 Feb 2005 03:05:20 -0500
Message-ID: <ee9e417a050208000537d60bcf@mail.gmail.com>

I was debugging a program with Nashi just now
and he was surprised to find out about snap and
snapfs.

What surprises do you wish someone had told you about?

Russ

P.S. If you keep them to one line, maybe I'll make an
alternate fortune file so you can put
   fortune /sys/lib/plan9.tips
or something in your profile.

Re: [9fans] tip o' the day

[Steve Simon]

my bad, I meant to offer one

Add this rule to $home/lib/plumbing:

	type is text
	data matches 'Local (.*)'
	plumb to none
	plumb start rc -c $1

so you can attach a remote file server "behind" rio,
IE in all rio windows:

	term% plumb 'Local 9fs machine'

-Steve

Re: [9fans] tip o' the day

[Robert Raschke]

To build a kernel as a mere mortal user (a bit too long for the one
line restriction):

mkdir -p $home/src/kernel/ ^ (pc boot ip port)
for (i in pc boot ip port) {
	bind -c $home/src/kernel/$i $home/src/kernel/$i
	bind -a /sys/src/9/$i $home/src/kernel/$i
}
cd $home/src/kernel/pc
mk 'CONF=pccpuf'

The only thing that irks me with this ever so slightly, is the fact
that in order to make actual changes to existing files in /sys/..., I
need to copy them into my own directory before doing the binding.

Robby

Re: [9fans] tip o' the day

[Steve Simon]

> alternate fortune file so you can put
>    fortune /sys/lib/plan9.tips

Though I thing learning more is "a good thing", I cannot
help but get an image of a paperclip poping up to give me the tip...

-Steve

Re: [9fans] tip o' the day

[Ronald G. Minnich]

On Tue, 8 Feb 2005, Steve Simon wrote:

> Though I thing learning more is "a good thing", I cannot help but get an
> image of a paperclip poping up to give me the tip...

glenda with a chainsaw works for me.

ron

Re: [9fans] tip o' the day

[Catalin(ux aka Dino) BOIE]

On Tue, 8 Feb 2005, Russ Cox wrote:

> I was debugging a program with Nashi just now
> and he was surprised to find out about snap and
> snapfs.
>
> What surprises do you wish someone had told you about?
>
> Russ
>
> P.S. If you keep them to one line, maybe I'll make an
> alternate fortune file so you can put
>   fortune /sys/lib/plan9.tips
> or something in your profile.

Good idea!

P.S. What is the CTRL+C key combination?

---
Catalin(ux aka Dino) BOIE
catab at deuroconsult.ro
http://kernel.umbrella.ro/

Re: [9fans] tip o' the day

[Charles Forsyth]

>P.S. What is the CTRL+C key combination?

Delete.  it was possibly more appropriate when it was labelled `RUBOUT',
as in `get the boys to rub out those processes'.

Re: [9fans] tip o' the day

[Catalin(ux aka Dino) BOIE]

On Tue, 8 Feb 2005, Charles Forsyth wrote:

>> P.S. What is the CTRL+C key combination?
>
> Delete.  it was possibly more appropriate when it was labelled `RUBOUT',
> as in `get the boys to rub out those processes'.

Thanks!

---
Catalin(ux aka Dino) BOIE
catab at deuroconsult.ro
http://kernel.umbrella.ro/

Re: [9fans] tip o' the day

[andrey mirtchovski]

i humbly offer this as contribution:

	http://pages.cpsc.ucalgary.ca/~mirtchov/lanlp9/tips.html

these tips were laboriously assembled by dean prichard and company at
LANL in their Plan 9 days.  i'm only hosting it.

pick and choose what you feel is of value.

andrey

Re: [9fans] tip o' the day

[Ronald G. Minnich]

On Tue, 8 Feb 2005, Russ Cox wrote:

> What surprises do you wish someone had told you about?

if you want to watch how 9p works between client and server, man iostats

It's worth your time to find out what the '1' attribute is on a file

Re: [9fans] tip o' the day

[Sam]

> What surprises do you wish someone had told you about?

The -[sS] flags to /acme/mail/Mail.

Re: [9fans] tip o' the day

[Heiko Dudzus]

>> What surprises do you wish someone had told you about?
>
> The -[sS] flags to /acme/mail/Mail.

Nice, yes, nice.
:)

Re: [9fans] tip o' the day

[Micah Stetson]

bind -c /n/unix/some/awfully/long/path/name /n/shorter

Use files named guide for per-project scratch space in acme.

I'm not sure that's the best one-liner for what I mean.  I used to use
directory windows and unnamed windows made with 'New' for scratch
space in Acme.  Now I create a guide file for the project I'm working
on and use it for temporary notes, commands, and the names of files
that I'm working with.  The commands get an appropriate working
directory, the notes get some context (i.e. what project they go
with), and I don't get warned to save the file when I exit, but I can
still save it if I want to.

Micah

Re: [9fans] tip o' the day

[rog]

> bind -c /n/unix/some/awfully/long/path/name /n/shorter

this is even better with mntgen, "global-mutable namespace" hack
(or is it a hack?) and the Local plumb trick mentioned earlier:

(in $home/lib/profile):
	mntgen
	srvfs plumbspace /n
	plumber
	rfork n
	mount -b /srv/plumbspace /n

a little shell script, "local" completes the picture:
	#!/bin/rc
	plumb 'Local ' ^ $"*

then i can do:

	local bind -c /n/unix/some/awfully/long/path/name /n/anything

and /n/anything is immediately visible everywhere (including
in cpu'd shells under /mnt/term) and i can plumb files in it
without any further hassle.

the use of mntgen means that i don't have to restrict myself to
previously existing names.

this is great when constantly dealing with namespaces that
come and go (and particularly since i can import namespaces
directly from Inferno, which means it's easy to gateway across
to Windows machines).

Re: [9fans] tip o' the day

[andrey mirtchovski]

my personal favourite, which i can't live without is the function to start
acme mail in its own rio window (i don't share it with my main acme editor):

it contains my favourite fonts here, but you can make your own file by
starting Mail and issuing a 'Dump' command, then cp-ing acme.dump to
acmemail.dump:

 	plan9% cat /env/'fn#amail'
 	fn amail {acme -l $home^/acmemail.dump}
 	plan9% cat $home/acmemail.dump
 	/usr/andrey
 	/lib/font/bit/10646/7x13/7x13.font
 	/lib/font/bit/10646/7x13/7x13.font
 	          0
 	e          0           0           0           0           1
 	          1          49         143           0           0 /mail/fs/mbox/ Del Snarf | Look Put Mail Delmesg
 	/acme/mail
 	Mail mbox
 	plan9%

andrey

Re: [9fans] tip o' the day

[Ronald G. Minnich]

yikes! These tip of the day things are amazing!

This is so good it seems like it to be on the wiki as well?

ron

Re: [9fans] tip o' the day

[Matthias Teege]

> (in $home/lib/profile):
> 	mntgen
> 	srvfs plumbspace /n
> 	plumber
> 	rfork n
> 	mount -b /srv/plumbspace /n

I don't understand it completly. After that, I try

% 9fs unixbox
% ls /n/unixbox

and get nothing. My profile looks like this

case terminal
	mntgen
	srvfs plumbspace /n
	plumber
	rfork n
	mount -b /srv/plumbspace /n
	upas/fs
	echo -n accelerated > '#m/mousectl'
	echo -n 'res 3' > '#m/mousectl'
	prompt=('term% ' '	')
	fn term%{ $* }
	exec rio -i riostart

What is my mistake? Do I need to mount the unixboxes before lib/profile?

Matthias

Re: [9fans] tip o' the day

[rog]

Matthias:
> > 	mntgen
> > 	srvfs plumbspace /n
> > 	plumber
> > 	rfork n
> > 	mount -b /srv/plumbspace /n
>
> I don't understand it completly.

here's some explanation:
	mntgen
		- creates mountpoints on demand in /n
	srvfs plumbspace /n
		- runs exportfs exporting /n on /srv/plumbspace
	plumber
		- runs the plumber; this runs in the same namespace as the exportfs
			command, so if a command run by the plumber changes its namespace,
			the namespace exported by exportfs will change too.
			(the "Local" rule allows this to happen on command).
	rfork n
		- fork the namespace
	mount -b /srv/plumbspace /n
		- take the namespace exported by exportfs and mount it on /n.
			this makes exportfs's namespace visible, but at one
			level of indirection - any changes to /n made by
			the plumber will now be visible to all. /srv/plumbspace could
			be deleted at this point.

> After that, I try
>
> % 9fs unixbox
> % ls /n/unixbox
>
> and get nothing. My profile looks like this

this is almost certainly because of a problem with exportfs (it
can't keep references to directories that have been walked to but
not opened).  the problem isn't easy to fix without a kernel interface
change, but mntgen has a recent workaround that fixes the problem.

copy mntgen from sources, and i think your problem should go
away.

  cheers,
    rog.

Re: [9fans] tip o' the day

[Matthias Teege]

> copy mntgen from sources, and i think your problem should go
> away.

Yes.  I copy mntgen from source and I can see my files ;-) But if I
run "local 9fs unixbox" first and then "local bind -c
/n/unixbox/foo/bar /n/bar" works.

Thanks alot
Matthias

Re: [9fans] tip o' the day

[rog]

> Yes.  I copy mntgen from source and I can see my files ;-) But if I
> run "local 9fs unixbox" first and then "local bind -c
> /n/unixbox/foo/bar /n/bar" works.

yes, that'll work because the namespace is being changed locally
to mntgen.

your previous example was failing to work because the mount was in
your current namespace - through the exportfs "window".  the mount
worked ok, but exportfs didn't keep the reference to the mount-point
around, so mntgen removed the new directory.

the next time the mount point was created by mntgen, it was given a
new qid, and since the kernel uses qids to index its mount table, it
wasn't finding your mount point.

the change i made to mntgen was always to generate the same qid for a
given name; hence although mntgen does delete the name, at least
anything mounted on it will still be visible when it's created again.

the real fix (i think) is to allow fds to refer to non-open files in
the plan 9 syscall interface (hence allowing exportfs to retain
a reference to walked-to directories without opening them),
but that's a significant change, hence unlikely to happen.

i'm sure you didn't want to know that!

  cheers,
    rog.

Re: [9fans] tip o' the day

[Ronald G. Minnich]

On Tue, 15 Feb 2005 rog@vitanuova.com wrote:

> the real fix (i think) is to allow fds to refer to non-open files in the
> plan 9 syscall interface (hence allowing exportfs to retain a reference
> to walked-to directories without opening them), but that's a significant
> change, hence unlikely to happen.

well, overall, it would be actually kind of neat if 9p was reflected right
out to userspace for some of the stuff I do. But boy, that is a change
from open/read/write/close, that's for sure.

ron

Re: [9fans] tip o' the day

[rog]

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actually, technically the changes could be fairly small (and
backwardly compatible).  the problems are those of naming, overall
desirability, and backwards compatibility of those programs that use
the new syscalls.

unless there are ramifications i'm not aware of, which is quite
likely.

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From: "Ronald G. Minnich" <rminnich@lanl.gov>
To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu>
Subject: Re: [9fans] tip o' the day
Date: Tue, 15 Feb 2005 10:26:03 -0700 (MST)
Message-ID: <Pine.LNX.4.58.0502151025180.13209@enigma.lanl.gov>



On Tue, 15 Feb 2005 rog@vitanuova.com wrote:

> the real fix (i think) is to allow fds to refer to non-open files in the
> plan 9 syscall interface (hence allowing exportfs to retain a reference
> to walked-to directories without opening them), but that's a significant
> change, hence unlikely to happen.

well, overall, it would be actually kind of neat if 9p was reflected right
out to userspace for some of the stuff I do. But boy, that is a change
from open/read/write/close, that's for sure.

ron

Re: [9fans] tip o' the day

[McLone]

On Tue, 8 Feb 2005 11:13:59 -0800, Micah Stetson
<micah.stetson@gmail.com> wrote:
> Use files named guide for per-project scratch space in acme.
Good one.

--
wbr,                        |\      _,,,---,,_           dog bless ya!
`                       Zzz /,`.-'`'    -.  ;-;;,_
McLone at GMail dot com    |,4-  ) )-,_. ,\ (  `'-'
  net- and *BSD admin     '---''(_/--'  `-'\_)   ...sorry for emgrish

Re: [9fans] tip o' the day

[Vincent van Gelderen]

fn c {history -D /$1}

(so you can paste the output of
replica/pull somewhere.)

Cheers,
	Vincent

Re: [9fans] tip o' the day

[Tim Newsham]

Here are some simple shortcuts I find useful during development.

fn f { du -a $* | sed 's/^.*	//g' }    <-- that whitespace is a tab
 	Tree enumerator (simple "find") useful for many purposes

fn s { lc *.[chsyl] }
 	List out the sources in the current directory.  Similar
 	to an example in the rc paper if I remember correctly.

fn gn { grep -n $* /dev/null }
 	Grep, but force listing of filename:lineno so you
 	can click on an entry to jump to it in an editor.

fn g { grep -n $* *.[chsyl] /dev/null }
 	gn on all sources in the current directory

(how about a plumber command that ran grep -n on the files
in the current directory and the include directory?  Then
you could plumb words to it in acme with mouse chording to
quickly crossreference keywords in the src tree.  I tried
goofing with that once but failed pretty miserably).

Tim N.

Re: [9fans] tip o' the day

[Russ Cox]

> fn gn { grep -n $* /dev/null }
>         Grep, but force listing of filename:lineno so you
>         can click on an entry to jump to it in an editor.
>
> fn g { grep -n $* *.[chsyl] /dev/null }
>         gn on all sources in the current directory

rob and i use this as /bin/g.  it handles both of these:

% cat /bin/g
#!/bin/rc

flags=()
while(! ~ $#* 1 && ~ $1 -* && ! ~ $1 --){
	flags=($flags $1);
	shift
}
if(~ $1 --)
	shift

switch($#*){
case 0
	echo 'usage: g [flags] pattern [files]' >[1=2]
	exit usage
case 1
	pattern=$1
	files=(`{ls *.[bcChm] *.cc *.py *.tex *.ms *.java >[2]/dev/null})
case *
	pattern=$1
	shift
	files=($*)
}
grep -n $flags -- $pattern $files /dev/null
%

> (how about a plumber command that ran grep -n on the files
> in the current directory and the include directory?  Then
> you could plumb words to it in acme with mouse chording to
> quickly crossreference keywords in the src tree.  I tried
> goofing with that once but failed pretty miserably).

i don't see why you'd involve the plumber.  just write
a script.

i find i almost never want to grep both local files and
/sys/include.  i either run g or sig.

% sig memmove
	void* memmove(void *s1, void *s2, long n)
%

russ

Re: [9fans] tip o' the day

[Tim Newsham]

> % sig memmove
> 	void* memmove(void *s1, void *s2, long n)

Ahh, there's a "wish someone had told me earlier" right there!
(Also the "src" command).  Although this doesnt get me everything
that I get from grepping ("sig OREAD" and "sig Disk" dont get
me information about OREAD or struct Disk).

> russ

Tim N.

Re: [9fans] tip o' the day

[andrey mirtchovski]

accessing the dump of another file system:

% 9fs sources
% 9fs sourcesdump
% history -d sourcesdump /n/sources/plan9/sys/src/cmd/ls.c
Jul  1 20:32:24 MDT 2004 /n/sources/plan9/sys/src/cmd/ls.c 5400 [jmk]
Jul  1 20:32:24 MDT 2004 /n/sourcesdump/2005/0215/plan9/sys/src/cmd/ls.c 5400 [jmk]
Dec 30 07:07:14 MST 2003 /n/sourcesdump/2004/0701/plan9/sys/src/cmd/ls.c 5388 [presotto]
Jun 15 11:46:59 MDT 2003 /n/sourcesdump/2003/1230/plan9/sys/src/cmd/ls.c 5284 [rsc]
Mar  2 16:59:32 MST 2003 /n/sourcesdump/2003/0615/plan9/sys/src/cmd/ls.c 5378 [rsc]
Feb 17 11:10:18 MST 2003 /n/sourcesdump/2003/0302/plan9/sys/src/cmd/ls.c 5440 [rsc]
Nov 11 10:09:11 MST 2002 /n/sourcesdump/2003/0217/plan9/sys/src/cmd/ls.c 5609 [rsc]
%

sourcesdump is hardcoded in the 9fs script, but is essentially a mount of
main/archive :)

andrey

Re: [9fans] tip o' the day

[Russ Cox]

> accessing the dump of another file system:
>
> % 9fs sources
> % 9fs sourcesdump
> % history -d sourcesdump /n/sources/plan9/sys/src/cmd/ls.c

even easier now:

9fs sources
history /n/sources/plan9/sys/src/cmd/ls.c