12 Nov
2021
12 Nov
'21
5 p.m.
A friend of mine used the word "unexec" for it, which I think is
actually pretty fitting. It's sort of the complement to the exec() call.
Johnny
On 2021-11-12 16:59, Johnny Billquist wrote:
RMS kept the idea alive in Emacs, where even today you
fire up the core
system, load all kind of libraries, and then you do a memory dump, which
is the runnable Emacs image.
? JOhnny
On 2021-11-12 16:06, Thomas DeBellis wrote:
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
It's not uncommon or it least it didn't
used to be.? Here are three
examples:
First, I believe early versions of Smalltalk did exactly this.
Second, at WPI, we implemented two commands called freeze and thaw,
which would take all the information in the currently running job
(AC's, PC, open files, Etc.) and write them into a file.? You could
^C, freeze, come back later, thaw the .ICE file (frozen job, get it?)
and be right where you were.? One common use was when a dial up was
abruptly disconnected by call waiting.? The monitor would notice you
were detached and perform a freeze on your behalf, thus both freeing
up the job slot and not losing your work.? Saved me a bunch of
TECO'ing.? It could have been extended to batch jobs running out of
processor time, but I don't remember if it was.
I liked it so much that I tried to implement it at Columbia for
Tops-20.? Tried...? I think the problem I ran into was that I couldn't
find out timers and get the same fork handles.? Or one of the
problems. Another was security, which I'll discuss below.
Third, at Columbia, it was used extensively in our chronically CPU
starved environment:
? * The EXEC could save the PCL environment (but I think this originally
??? was part of the CMU implementation)
? * The mailing system keeps a binary file of forwarding bindings.? If
??? you edit the text source, the newer write date is noticed and the
??? binary is 'recompiled'
? * I lifted the feature for LPTSPL's LPFORM.INI parser when I realized
??? how often it was getting reparsed (basically after any idle period
??? between jobs)
?From the information security standpoint, you have to consider the
usage of these kinds of files.? Obviously, you wouldn't want to thaw
something with JACCT set unless the existing job had the ability to
get that, was [1,2] without some fairly careful checking.? Ditto
Tops-20, if the fork had capabilities.? I mean, if somebody could get
write access to the binary, then they could potentially compromise
system security with a little strategic FILDDT'ing (or EXAMINE and
DEPOSIT, if it came to that).
A 'legitimately' corrupt binary could also crash the fork on start up,
but I don't recall as we ever fully addressed that.? I think a
checksum would have been the obvious start, but I guess we didn't want
to spend the cycles.
In these days of multi-gigahertz processors, I don't see the children
discussing it much at all.
> ------------------------------------------------------------------------
> On 11/12/21 9:24 AM, Paul Koning wrote:
>
> That's a bit like how RSX-11/D and IAS boot -- by reloading the image
> of memory when you issued the SAV command. Pretty clever: you set
> things up the way you want them to be, and then you make that state
> persistent.
> ????paul
>> ------------------------------------------------------------------------
>>
>>
>> On Nov 11, 2021, at 6:22 PM, Johnny Billquist <bqt at softjar.se>
>> wrote: I must admit that I hadn't considered the possibility of just
>> saving the core. Which of course can accomplish the same thing in a
>> neat way.
>>