Emanuele Aliberti wrote:
Alex Ionescu wrote:
I view this as a "misunderstanding with some
design choices", if not
even a "misunderstanding of NT Subsystem design".
Subsystem design is subtle. Cutler is not an ordinary person. Also the
subsystem design was conceived in another era, in CS terms. Cutler and
his group designed it when the OS (beginning-to-ruin) myth was CM Mach
(at the same time, RMS invented Hurd; recently Apple could sell it
rebranded as Mac OS X...).
Mark Lucovsky wrote the subsystem design (smss, csrss), not Cutler, just
a by the way.
The design choice, in short, is the rôle of the "Client/Server
Runtime SubSystem" (CSR=CSRSS.EXE+CSRSRV.DLL) in the design of the
"O.S. Personality" code, that is the emulation code that manages
processes of the same operating system in user mode, making them
belive to run on the emulated O.S.
The Client/Server Runtime SubSystem, which is unfortunately
incorrectly named by Microsoft,
It is funny to note now that what you say here is a thought that
spinned around in my mind for years in the past. My personal answer
was exactly yours.
is actually the Win32 Personality.
Later I discovered a theologian and philosopher - W. Ockam
(1295/1300-1349) - that today most of us (don't) know is the father of
the KIS(S) principle. Do not invent an hypothesis if it *not needed*.
I used to say "Those developers at MS are really eccentric! Why did
they call the Win32 subsystem server CSRSS.EXE? They are really dumb!".
The unnecessary assumption is, of course, that they *incorrectly
named* it.
(Note for others: The KISS principle is "Keep it simple, stupid" or
sometimes "Keep it simple and stupid")
If you really want to argue using Ockam's Razor (note for others:
Ockam's razor basically says that the simplest assumption is usually the
correct one), then I'm afraid I'm the one winning this argument. My
assumption is that CSRSS has always been built to service Win32's needs.
This has much evidence, as you've added and agreed with me, mostly
importantly:
- The fact that other subsystems have their own *ss.exe
- The fact that CSRSS is specially "polluted" for Win32
Your assumption, as far as I could understand, is that CSR was
"originally supposed to be somethign else" and was later "polluted".
Now, what makes more sense and seems the easiest assumption, by using
Ockam's Razor:
- CSR is what all evidence to it points, a Win32 subsystem runtime
manager. (Alex)
- CSR is everything but what it currently seems to be. CSR was actually
designed to be something totally different. It was later polluted and
became what it is now.(Emanuele)
Ockam would agree with theory #1, and your assumption would become the
unnecessary one.
It manages Win32 processes in user-mode, and
allows them to access
kernel features which would pollute the native-mode ntdll.dll, would
they have been included there. Only Win32 processes use csrss and
registration is done in kernel32. Console windows, another Win32-ism
also use csrss.
This is what we observe today in a live system of the NT family. But,
if you see a man that wears a black suit, are you sure he's a priest?
It could be a MiB, or a punk, or simply an old fashioned gentleman.
If he also wears a cross, he could be a punk or priest. Ockam's Razor
would dictate the simplest assumption to be the true one. Therefore, he
is a priest.
For instance, everybody here knows that the dynamic library NTDLL.DLL
exposes the so called "native API", the NT real API. But even you are
diverted by that sweet assonance and commit the mistake of saying it
has the native-mode mark. Indeed its subsystem ID is 3.
When I discovered it, I had a shock, a few years ago.
Does it fit in you picture?
(Note to others: 3 is IMAGE_SUBSYSTEM_WINDOWS_CUI)
I've always found it strange that ntdll.dll has the CUI subsystem, and
not IMAGE_SUBSYSTEM_NATIVE.
Of course, the most plausible reasons for this are that due to some
kernel/loader semantics, it's simply easier to use this flag for X, Y
reasons. Even simpler, perhaps it's just the default used for building
other DLLs. You can note that basesrv.dll and winsrv.dll also have the
same flag set, even though they are not CUI DLLs. I'm not going to go in
some theory that "Oh God, oh God, ntdll has the Win32 Console flag set,
it must be a hidden console DLL!".
Because NT was designed with a set of universal
native APIs, this was
necessary so that routines useful to only one personality wouldn't be
exported as native APIs. For example, fork() is a POSIX-only API, not
Windows 32. Therefore, it was not included in ntdll.dll, even though
the kernel supports it. Instead, it's used by the POSIX subsystem.
The same goes for Console windows and their APIs, which are usable
only in Win32. Access to the video hardware is done in kernel-mode,
but the functions are called through CSRSS.
A very good example, but a less precise description. NtCreateProcess
is an API that is more abstract than Win32 CreateProcess and than
POSIX fork/exec. As it is more abstract, the respective less general
semantics can be implemented using it. As Casper pointed out, more
general, more abstract, means more complex.
Which is why the Native API isn't the default API, because programming
with it would be much more complicated. Win32 is a good thing in that
regard.
Now, CSRSS is in a way a Client/Server Subsystem,
because it's merely
a 4KB host to CSR Servers, which implement parts of the Win32
behaviour. The 3 servers currently used are: basesrv.dll, which
handles SxS (Side by Side assemblies, a Windows XP feature), VDM
(16-bit emulation) and stuff like Process/Thread creation,
winsrv.dll, which handles some graphical things and
windowmessage-related functionality (such as hardware event
dispatching) plus all the Console code (winsrv is internally split
into 2 CSR Servers). I think a big problem here is that ea believes
that CSRSS is the place where you would add a POSIX subsystem. This
isn't the case. CSRSS is reserved for Win32 CSR Servers.
Of course, not in the instance where basesrv.dll and winsrv.dll are
loaded.
Not in ANY instance!
I think the csrss.exe + csrsrv.dll (the core) were the
original CSR.
Assumption assumption! csrsrv.dll is merely the real implementation of
CSRSS, and provides a common API for all the CSR servers (base and
winsrv). You are *convinced* that CSR+csrsrv.dll were designed to allow
other subsystems to be implemented as DLLs. No, no, no! It was *never*
that way. You mention the proof yourself: csrsrv.dll does things like
setting up the Win32 Base Name Objects directories and other
win32-specific things!
Of course the os2ss and psxss MS sold us don't use
it.
I don't think they "sell" them; psxss is free, and os2ss was part of
Windows. And the reason they don't use it is because they're -not
supposed to-!
They couldn't, because the current CSR core was
intentionally
"polluted" to support only basesrv.dll and winsrv.dll. But it is not
our fault.
Another assumption. How about assuming that CSR was intentionally
CREATED for Win32.
Also I dont think the Win32 server should run in more than one instance.
All subsystems run in more then one instance if multiple Session IDs are
used. This is by the very own design of "Sessions" in NT. Sessions are
completely seperate entities. They run their own set of programs, have
their own desktops, windowstations, windows, etc. Even their -memory- is
seperated. Memory in one session is usually seperated from memory in
another session. Even the Paged and Nonpaged Pools are seperated! It
makes perfect sense that even subsystems are seperated. Plus, this is a
feature that I personally LOVE. It allows me to debug csrss.exe on a
-live- system, simply by connecting to another session. Without this
wonderful design, such abilities would be lost. Also, assume csrss.exe
crashes in one session. The others sessions are still ok. There are a
myriad of reasons why having an isolated environment for each session is
a good thing. It's why windows terminal services are probably one of the
best features of NT.
When you look at the process list, in a TS machine,
those many
csrss.exe you see are (but one) μSessions of the Win32 server (the
mother is the one with lowest PID). Imagine Linus' face if you propose
to load a new instance of the Linux kernel each time you login...
I really wouldn't associate csrss.exe with the Linux kernel. If this was
a high-school debate I could easily attack you personally because you
just made that comparison ;)
well it is exactly what happens when you connect from
a TS client
(win32k.sys is loaded again).
Win32k is made to load into every session by DESIGN, and it comes with a
share of benefits. Did you also know that other drivers can be made
session-specific as well?
I don't know how you define that way of
programming: perhaps, in a
sentence, "Does it compile? Let's sell it!". Well, two.
I think you define it as "secure, isolated, scalable design". Which is
quite different from Linux's monolithic, unscalable design.
Now, let's move on...what actually loads CSRSS? This is called SMSS,
the Session Manager SubSystem. The Session Manager handles all the
subsystems that are installed on an NT Machine. By default, this
means CSRSS, the Win32 subsystem. If you install SFU 3.5, or are
using Windows Server 2003 R2, you will also get psxss.exe.
The original PSXSS.EXE was, as you know, a nice trick. MS had to show
that NT was POSIX 1003.1 compliant, to get DOD contracts.
Possibly true, although it sounds like a conspiracy theory. I'm sure a
big part of POSIX compliance was also compatibility, and also to prove
that NT is a solid design. Remember that NT was originally built for
non-x86 CPUs only because Cutler thought it was the best way to catch
bugs and make a solid OS. Subsystems were a design choice in NT for a
long time.
But, of course, it should do it fast and could not
show "too much".
This decency shows how they got two prizes with one shot. PSX is not a
vertical subsystem, but a side subsystem, or a second-level
personality. In fact it requires the Win32 subsystem running to work.
Ah, finally we get to a point where I'll agree you with you on
pollution! Yes, POSIX only works with Win32 loaded. But can we easily
work around this later on, when we have a POSIX subystem? Sure! Does it
have anything to do with CSR? NO!
The first prize is that you show NT is a POSIX system.
The second
prize is that you can not drop Win32 to run your POSIX system. Market
and market, not computer science.
Yes, Microsoft was probably afraid of allowing NT to run in POSIX-only
mode, but we can pull it off much later once that's needed.
This recalls me that recently MS was sentenced, because it is
impossible to remove IE from Windows. A recurring trick.
Well, when NT was first publically shipped its job was to run Win32
applications. Allowing Win32 to be removed might've caused many
technical/support headaches apart from the marketing stuff. I wouldn't
jump to conspiracy theories right away. The design of NT is much
different from the shell/ie.
On older Windows, you can also have os2ss.exe.
These are the POSIX
and OS/2 subsystems.
Once again, let's look back. OS/2 was the original user mode API
Cutler was sked by MS to make available on top of the NT core. As
Windows 3.0 was a worldwide success and the alliance with IBM broke,
they had to switch to Win32. As there was a common ancestor, do you
think they rewrote the CSR from ground up? It is more likely that they
freezed the CSR used by OS/2 and, after a lazy copy & paste, extended
it ("polluted it") to build what we today say it should be named
w32ss.exe.
I think I see what you mean, yes, CSR back in those days was probably
the OS/2 subsystem. How is that better though? It still wasn't a GENERIC
subsystem loader (SMSS is that). They merely took out the OS/2
"pollution" and added win32 "pollution". Then they added the OS/2
"pollution" back into what became os2ss.exe. In that sense, CSR was
always "polluted" by whatever the subsystem it was holding was supposed
to be. Now it's a win32 subsystem, and has been that way for 15 years.
They have nothing to do with CSR at all, and they
are actually, in
themselves, CSRSSes for their own subsystems.
This is by design, an evil design... ;) Would have MS shown how easy
is writing your own subsystem in a moment when they had to face IBM
OS/2 rival API? My friends, close every gate, every window, every hole
and harmour the Win32 server!
Slippery slope fallacy/conspiracy theory. It was simply the design that
every subsystem woudl have its own "CSR EXE" followed by server DLLs.
This is the naming mistake I was talking about;
Microsoft should have
named csrss as w32ss.exe.
Ockam! ;)
Not really, if viewed from the historical perspective, it makes sense
why it was never renamed as such. Assuming that CSR was something else
then the original OS/2 subsystem for a very short while is much more flawed.
So, SMSS is the first process that will load, and it will then load
the subsystems, say csrss psxss and os2ss. These subsystems will then
load server dlls which expose functionality that can be called from
user-mode processes.
SM is a super server. But then, if it is so super, why does it humble
itself in defining DOS devices
This was moved to CSRSS.
, in loading a process of one of its controlled
children (I refer to
WINLOGON.EXE)... If that is not "pollution", maybe a nuclear bomb
exploded somewhere in the vicinity. :(
And this is the second point I agree with you, the second design mistake
of NT. Smss's "initial command" is to run winlogon, and that really
creates a problem where win32 becomes -required-. However, instead of
thinking this was some marketing ploy, I think that NT was getting close
to shipping, and doing it this way was a much easier solution for the
prime goal: Win32. So yes, it's a bad design decision:
BTW: It has a "bug", in that if you define an "inital debugger", the
initial command will be replaced by "initial debugger.exe winlogon", so
that winlogon can be launched with a debugger. Stick your
native/posix/whatever program as the initial debugger, and ignore the
winlogon command line, and you've beaten the flaw ;) The string is
configurable in the registry, IIRC. Once again, this is something we can
do better in ReactOS after the windows stuff works normally.
As I'm writing this, my Win2K3 machine is
running posix grep and
working perfectly. It's not touchign CSRSS at all, nor should it have
to. CSRSS is a win32 subsystem.
CSRSS.EXE+CSRSRV.DLL, as they load BASESRV.DLL and WINSRV.DLL, *are*
the Win32 personality subsystem server.
That's what I meant.
Think about it like the program run by the Architect in Matrix: when
you double click on Microsoft Word's icon and the process is
created, it happily belives to run under Windows, it can see the
familiar libraries, it can call CreateFile and get back a reasonable
file. In fact, CreateFile calls NtCreateFile and so on. Microsoft
Word lives in a fake World. ;)
The two opposite directions the CSR can turn for are:
- be a process totally bound to the Windows personality
Which it's -supposed- to be. CSR is W32SS.
If we clone Windows NT, this is correct.
ReactOS is a Windows NT clone.
But dumping is illegal.
- be a general purpose process, a facility for
any kind of personality
Other personalities don't need CSR! They have PSX and OS2 and VMS and
etc...
The pieces of code MS sold us match this definition. I ask myself: is
this a technical limitation, or imposed by market staff?
How about a design choice? One which makes a lot of sense to me.
As Gunnar saw, probably there is a common set of facilities you need
every time you write a personality server. I would like to write it
once for them all (If I could, but you showed you are much more
skilled than me!).
The common set of facilities are exposed by SMSS callbacks and a smlib!
I've written about that in a previous email.
Casper, as already noted, pointed out it is a complex
piece of code to
write. You are required to write the equivalent of the abstract
NtCreateProcess, to be called by the Windows personality server and by
the POSIX personality server and by the OS/2 server and by the...
One of these abstract callbacks is SbCreateProcess. I plan to implement
the Sb callbacks and SMSS later this year. (Nice bit of trivia:
SbApiPort and SmApiPort are quite different! One relates to SMSS (Sm)
itself, the other handles the common subsystem (Sb) functionality which
you seem to want).
My question is: is it worth writing such a live run-time code? (DLLs
are "dead code", because they live un the context of the process that
loads them; vice versa, a subsystem is a "live DLL", because it lives
before the process that will use it; if you like biology, there is the
same difference between a virus and a bacterium).
More on demand.
Another issue which ea has brought up is that NT is somehow to
"connected" to Win32.
Well, Alex, I repeatedly used the adjective "polluted", which does not
mean "connected". I meant they put helper pieces of code, here and
there, to make the Win32 server's life easier. If you want a more
technical equivalent of "polluted", read it "less general, less
abstract". Casper is definitely right!
Polluted, connected, I still disagree. There is almost nothing in NT
which makes Win32's life easier, apart from some win32k.sys stuff. Yes,
there are certaintly some things which help out win32, but that's
because NT is PRIMARLY DESIGNED to be a Win32 OS. By definition, so must
ReactOS, at least until 1.0 when our goal, to clone Windows NT, is
reached. After that, we are free to explore other areas, if
compatibility can remain intact.
I beg to differ. I've spent a week working on
a sample native
application. It currently can display running processes, drivers,
create a new process and create/delete/list files. Here are some
screenshots:
http://members.tripod.com/WinAlOS/rtlcli.png
http://members.tripod.com/WinAlOS/rtlcli2.png
http://members.tripod.com/WinAlOS/rtlcli3.png
Note that there is no CSR, no win32k.sys loaded. NT is running in its
rawest form. You need less then 16MB of memory (notice that the
processes are using <1MB, the rest is up to the drivers, which you
can disable) and about the same amount of diskspace. This works
perfectly in Windows 2003 without any need to "separate win32".
I actually didn't understand if Russinovich was paid by MS to show that,
I feel a bit insulted. What does Russniovich have to do with anything?
The screenshots above show a program which I alone have worked on, and
that no other "NT hacker" has attempted in doing before.
or if he actually could get there alone, the real NT
hacker! Because,
if you look at what that really means, you get a strange feeling.
I have no idea what you're talking about. There are many more
knowledgable people in NT then Mark. They just don't get the media/MS
attention he does. If he's the "real" NT hacker then what are Skwing,
Filip, KJK::Hyperion, yourself and I?
First, the rumors that pollution (Win32/Win64 infiltration) is gone to
a point where the old NT-designed core is less stable, are immediatley
silenced. Russinovich, indipendently (and with the naive "Oooh" by
some MS engineers...), showed it!
Actually, I think I just did by writing that program. I once again don't
see what the -hell- Russinovich has to do with me. And no, MS didn't pay
me to write that program.
Second, in a hidden and really smart way, you promote the equivalence
CSR=Windows: "Note that there is no CSR, no win32k.sys loaded.".
Yeah, CSR+Win32k.sys == Windows.
Bill is a genius! I love him.
Bill is an idiot, but a very good businessman. Cutler and Mark are
geniuses, and if it wasn't for, especially, Cutler's angry attitude and
specific design goals for NT, win32 would probably be in ntoskrnl.exe
With best regards,
Best regards,
Alex Ionescu