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05-21-2012 09:33 AM
05-21-2012 09:33 AM
System Service Interception on OpenVMS
Hi,
Does anyone know if DEC/Compaq/HP produced any documentation about the System Service Interception API on OpenVMS Alpha?
If so, where or how I can get a copy of the document(s)?
Thanks
John
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05-21-2012 04:02 PM
05-21-2012 04:02 PM
Re: System Service Interception on OpenVMS
I'm sure that John Gillings will give you the details but conceptually it's pretty simple - just provide a new function with the same name as the system service function, and within that new function do a LIB$FIND_IMAGE_SYMBOL to activate the image and locate the sys service function, then call it.
In your own function you can add whatever diagnostics or monitoring that you want to add. Also you can step into your own function from the debugger and get full access whereas with the system service images it's not so easy.
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05-21-2012 08:46 PM - edited 05-21-2012 08:49 PM
05-21-2012 08:46 PM - edited 05-21-2012 08:49 PM
Re: System Service Interception on OpenVMS
Hmm,
What problem are you trying to solve, or just curios?
Ever heard about Google? Wonderful invention! Try it some day?!
it leads me to: http://h71000.www7.hp.com/openvms/journal/v8/ssi.pdf
Of course it helps knowing that that existed, having talked to Ruth about it :-)
And what about $ HELP SET PROC /SSLOG and $ HELP **bleep**/SSLOG.
[edit: stupid computers (programmers).... I'll let you analyze as to why it bleeb my perfectly honorable reply ]
Now if you experiemnt with that, I recommend to SPAWN first, then try.
When I last used it it was not entirely stable.
I also received the following text and code from Harmut B, some 5 years ago.
See below.
Hope this helps,
Hein.
----------------------- Hartmut --------------------------------------------------------
If you want to use just ssi$declare_intercept.
I append a small example, which I tested on I64/V8.3-1H1.
The SSI_BLOCK is filled like
static SSI_BLOCK ssi_block = {
0, 0,
SSI$C_LENGTH, DYN$C_MISC, DYN$C_SSI_BLOCK,
SSI$K_VERSION_QUAD_LIST, 0,
pre, post};
So you will get into your pre() and post() for all system services, once you successfully called the declare routine.
To do processing just for one system service, you need to check against its declared address, as in starlet.h or for example with a "extern int sys$asctim();". Once in your pre() or post() this system service address is in ps_ssadr.
You can make the call to ssi$declare_intercept from your main image. If you don't have control over main, you can place the call in an init routine in a shareable image and let it call during the image initialization via the lib$initialize mechanism.
On Alpha, if your shareable image is not activated with main, that is SYS$SSISHR is not activated with main, then you can't intercept system service calls from main (and all the shareable images it depends on).
Yes, you should be able to do the same with replacing a few system services. You should also be able to use a single generic replacement routine. There you check the passed ps_ssadr against you list and call the original system service as passed in ss_ssadr. I didn't try that, so far, and therefore don't have an example.
You just link against the SYS$SSISHR, that's all.
That's my understanding, it may be incomplete or not 100% correct, but I hope it helps to get you started or even going.
#include <pdscdef.h> #include <ssdef.h> #include <ssidef.h> #include <starlet.h> #include <stdio.h> #include <dyndef.h> #include <descrip.h> static char timbuf[32] ; static $DESCRIPTOR (timbuf_d, timbuf) ; static short int timlen ; static int preasctim; static int postss; static void pre(int *arg_list, int (*ss_ssadr)(), SSI_PDSC *ps_ssadr, int retadr, SSI_BLOCK *ssi_block_ptr) { if ((int(*)())ps_ssadr==sys$asctim) preasctim++;} static void post() {postss++;} static SSI_BLOCK ssi_block = { 0, 0, SSI$C_LENGTH, DYN$C_MISC, DYN$C_SSI_BLOCK, SSI$K_VERSION_QUAD_LIST, 0, pre, post}; main() { int status; printf ("preasctim: %d, postss: %d\n", preasctim, postss); status= ssi$declare_intercept (&ssi_block); if (status!=SS$_NORMAL) printf ("status: 0x%x\n", status); else { printf ("hello ssi\n"); sys$asctim (&timlen,&timbuf_d,0,0); printf ("time: %.*s\n", timlen, timbuf) ; fsync (fileno (stdout)); printf ("preasctim: %d, postss: %d\n", preasctim, postss); } }
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05-22-2012 10:43 AM
05-22-2012 10:43 AM
Re: System Service Interception on OpenVMS
Thanks for the responses.
I am experimenting with SSI in order to capture the system calls issued by an old application.
I had already found using Google the journals on the subject written by John Gillings and Ruth Goldenberg. Though they are extremely interesting, they did not provide enough practical information since I am not an OpenVMS internals guru.
Ruth did mention at the end of her journal "For information on the use of SSI, please check HP OpenVMS System Documentation home page for forthcoming documentation", but I have not yet been successful in finding this information.
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05-22-2012 02:42 PM
05-22-2012 02:42 PM
Re: System Service Interception on OpenVMS
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05-24-2012 02:43 PM
05-24-2012 02:43 PM
Re: System Service Interception on OpenVMS
I've been able to intercept system services using ssi$declare_interrupt.
On Alpha V8.3, I was only able to get the intercepts to work with RUN/DEBUG (something to do with getting SYS$SSISHR activated).
A few things to look out for. You need to be very careful of recursion. Anything that directly or indirectly invokes a system service from inside the pre or post routine could put you into a recursion loop. You can use a simple static flag in both pre and post routines so they only act on first level calls.
pre(args...) static busy if not busy then busy=true do stuff here... busy=false endif end
I was able to do I/O from the protected code. Counters showed thousands of other invokations even for trivially simple programs (there appears to be some kind of polling from DEBUG)
You can detect specific system services by looking at the PDSC address and comparing with the global symbol (as shown in Hein/Hartmut's the C example). However, I couldn't find a simple way to identify an arbitrary incoming service call. There are obvious brute force mechanisms, but for the huge volume of calls you're likely to get, the lookup needs to be fast.
I was trying to create a generic routine to dump the name and argument list of all system services called. The simplest mechanism I can think of is to dump name/PDSC pairs, based on a shareable image /NAMES list from SYS$PUBLIC_VECTORS, then dump the PDSC of each call, along with the argument list, then post process the listings to resolve the addresses into names.
Use SSI$DECLARE_REPACEMENT PDSC_Of_Target,YourRoutine
to substitute routines (but beware, this is non-trivial!)
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05-24-2012 03:29 PM
05-24-2012 03:29 PM
Re: System Service Interception on OpenVMS
>>> On Alpha V8.3, I was only able to get the intercepts to work with RUN/DEBUG (something to do with getting SYS$SSISHR activated).
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05-24-2012 07:18 PM
05-24-2012 07:18 PM
Re: System Service Interception on OpenVMS
No errors, status is normal, just no execution of the pre and post routines. Example:
$ run/nodebug ssi ELAPSED: 0 00:00:00.00 CPU: 0:00:00.00 BUFIO: 0 DIRIO: 0 FAULTS: 0 Declare: 00000001 Pre: In 00000000 Act 00000000 Post Out 00000000 act 00000000 $ run/debug ssi OpenVMS Alpha Debug64 Version V8.3-016 %DEBUG-I-INITIAL, Language: AMACRO, Module: SYS$MISCDEF DBG> go SSI_PRE 25-MAY-2012 11:53:39.35 SS: 820EBC60 PDSC: 001A08C0 From: 810CC14C Args: 7 00000000 00000080 00000000 00000000 00000000 00000000 00000000 SSI_PRE 25-MAY-2012 11:53:39.35 SS: 82101290 PDSC: 0019F540 From: 810CC184 Args: 1 00000000 SSI_PRE 25-MAY-2012 11:53:39.35 SS: 820EBC60 PDSC: 001A08C0 From: 810CC14C Args: 7 00000000 00000080 00000000 00000000 00000000 00000000 00000000 SSI_PRE 25-MAY-2012 11:53:39.35 SS: 82101290 PDSC: 0019F540 From: 810CC184 Args: 1 00000000 SSI_PRE 25-MAY-2012 11:53:39.35 SS: 82100EF0 PDSC: 0019F420 From: 810CBBD4 Args: 11 00000000 7AD639C0 00000000 7AD639B8 00000000 7AD639B8 00000000 7AD639E8 00000000 00000000 00000000 SSI_PRE 25-MAY-2012 11:53:39.35 SS: 82131AB0 PDSC: 001A0110 From: 810C20C4 Args: 1 00000000 ELAPSED: 0 00:00:00.00 CPU: 0:00:00.00 BUFIO: 2 DIRIO: 0 FAULTS: 0 Declare: 00000001 Pre: In 00000033 Act 00000006 Post Out 00000033 act 00000006 %DEBUG-I-EXITSTATUS, is '%SYSTEM-S-NORMAL, normal successful completion' DBG>
Here are the routines (hopefully my macros are self evident)
Main routine .ENTRY Start,^M<> CALL SSI_START MOVL R0,DeclareStat CALL LIB$INIT_TIMER CALL LIB$SHOW_TIMER CALL SSI_STOP MessageOut <<Declare: !XL Pre: In !XL Act !XL Post Out !XL act !XL> #DeclareStat #In #ActIn #Out #ActOut> RET PRE routine .ENTRY SSI_PRE,^M<R2,R3> arglist args ssadr dsc retadr blk INCL In BLBS Recur,PRESkip MOVL #1,Recur INCL ActIn CALL FormatArgs AllArgs @args_arg(AP) MessageOut <<SSI_PRE !%D SS: !XL PDSC: !XL From: !XL Args: !3UL !AS> - ##0 #ssadr_arg(AP) #dsc_arg(AP) #retadr_arg(AP) #@args_arg(AP) AllArgs> CLRL Recur PRESkip: RET
This obviously has something to do with activation of SYS$SSISHR, but I don't understand the mechanism. I'd guess that most of the time this would be a diagnostic tool, so running under DEBUG would be fairly normal.
Not sure what XPD is, here's what IMAGETREE has to say about the image
$ @imagetree []ssi.exe SSI, executable V1 RWD,RWD,R, SYS$SSISHR, shareable(%X'01',%X'0003E8',MATEQU) X-20 build:XBCA-0080070058 RWED,RWED,RE,RE Installed Open Hdr Shared Prot Lnkbl SYS$BASE_IMAGE, shareable(%X'56',%X'703EFE',MATEQU) ALPHA XBCA-N2O build:XBCA-0080070099 RWED,RWED,RE,RE SYS$SSISHR references 1 image LIBRTL, shareable(%X'01',%X'000001',MATLEQ) X01-001 build:XBCA-0080070005 RWED,RWED,RE,RE Installed Open Hdr SharAddr Lnkbl Resid SYS$PUBLIC_VECTORS, shareable(%X'13',%X'0064E6',MATEQU) X-123 build:XBCA-0080070058 RWED,RWED,RE,RE Installed LIBRTL references 1 image LIBOTS, shareable(%X'01',%X'000003',MATLEQ) LIBOTS V1.5-00 build:XBC4-0080060000 RWED,RWED,RE,RE Installed Open Hdr SharAddr Lnkbl Resid SYS$PUBLIC_VECTORS (repeat) LIBOTS references 1 image SSI references 3 images
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05-25-2012 03:54 AM
05-25-2012 03:54 AM
Re: System Service Interception on OpenVMS
XPD is part of the VMS Objects and Image Tool set. For an image, it lists external procedures and data.
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05-28-2012 08:43 AM
05-28-2012 08:43 AM
Re: System Service Interception on OpenVMS
I have created a shareable executable linked with SYS$SSISHR, and have managed to intercept system services such as SYS$ASCTIM issued from COBOL, but I have found that the RMS system services such as SYS$CONNECT and SYS$RMS_CONNECT are not being intercepted.
Is it not possible to intercept the RMS system services?
By the way, I am currently restricted and struggling with an Alpha running V7.3-2.
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05-29-2012 02:02 AM
05-29-2012 02:02 AM
Re: System Service Interception on OpenVMS
I know, it doesn't help, but it works for me (on OpenVMS V8.3, node EISNER, AlphaServer DS20 500 MHz). I took the Example 3-1 "Use of the Create, Open, and Close Services" from http://h71000.www7.hp.com/doc/731final/4523/4523pro_002.html, changed my example to count sys$connect and created a shareable image with image initialization out of it; I linked the RMS example against it an ran it: the shown count is two.
Sorry, I don't have the time (but you can hire me any time :-) to do more testing and I don't have the same environment as you have: I have no idea why it doesn't work for you and V7.3-2.
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05-29-2012 03:55 PM
05-29-2012 03:55 PM
Re: System Service Interception on OpenVMS
FWIW,
I worked out an ugly way to translate system service PDs into names. I use a macro to build a table of value pairs (PD,descriptor address), like this:
.PSECT Table,RD,WRT,NOEXE,QUAD MaxTbl: .LONG 0 K_MaxTbl=0 SymTbl: .MACRO RTN nam .PSECT Const .ALIGN QUAD S%EXTRACT(0,30,nam): .ASCID /'nam'/ .PSECT Table .ADDRESS 'nam' .ADDRESS S%EXTRACT(0,30,nam) K_MaxTbl=K_MaxTbl+1 .ENDM RTN RTN SYS$QIOW RTN SYS$CLI RTN SYS$ADJSTK RTN SYS$ADJWSL RTN SYS$ALCDNP ...
The list of routine names is taken from SYS$SSISHR entry points. At run time, the table is sorted on PD value at initialisation. To determine a system service name do a binary search for the PD value, which gives the address of the string descriptor.
Regarding JohnRD's question about RMS services. I see a curious behaviour. If I link against SYS$SSISHR without DEBUG and just RUN the image I catch those system services which the image calls directly. Here's the beginning and end of a run of Hein's "STRINGS" program running against itself:
SSI 30-MAY-2012 08:38:35.54 SYS$OPEN From: 00030A98 AP: 1 00000000 SSI 30-MAY-2012 08:38:35.54 SYS$CONNECT From: 00030AC4 AP: 1 00000000 SSI 30-MAY-2012 08:38:35.54 SYS$GET From: 00030B64 AP: 1 00000000 STRINGS SSI 30-MAY-2012 08:38:35.54 SYS$GET From: 00030B64 AP: 1 00000000 SYS$SSISHR_001 LIBRTL_001 LIBOTS_001 SSI 30-MAY-2012 08:38:35.54 SYS$GET From: 00030B64 AP: 1 00000000 SSI 30-MAY-2012 08:38:35.54 SYS$GET From: 00030B64 AP: 1 00000000 ... DSC$K_CLASS_S DSC$K_DTYPE_T START SSI 30-MAY-2012 08:38:35.60 SYS$GET From: 00030B64 AP: 1 00000000 SSI_FINDENTRY SSI_FIXTABLE SSI_STOP SSI_FORMATARGS SSI_START SSI_POST SSI_PRE SSI 30-MAY-2012 08:38:35.60 SYS$GET From: 00030B64 AP: 1 00000000 SSI 30-MAY-2012 08:38:35.60 SYS$CLOSE From: 00030AF4 AP: 1 00000000 SSI Pre: In 000004E3 Act 000001A1 Post: Out 000004E3 act 000001A1
Notice that the output lines (written with LIB$PUT_OUTPUT) don't trigger any traces for the services they obviously call. Also note the counters on the final line. Exactly the same program, run under DEBUG
OpenVMS Alpha Debug64 Version V8.3-016 %DEBUG-I-INITIAL, Language: AMACRO, Module: .MAIN. DBG> go SSI 30-MAY-2012 08:35:50.57 SYS$CLI From: 810BE254 AP: 1 00000000 SSI 30-MAY-2012 08:35:50.57 SYS$OPEN From: 00030A48 AP: 1 00000000 SSI 30-MAY-2012 08:35:50.57 SYS$CONNECT From: 00030A68 AP: 1 00000000 SSI 30-MAY-2012 08:35:50.57 SYS$GET From: 00030AEC AP: 1 00000000 SSI 30-MAY-2012 08:35:50.57 SYS$PUT From: 810C20C4 AP: 1 00000000 STRINGS SSI 30-MAY-2012 08:35:50.57 SYS$GET From: 00030AEC AP: 1 00000000 SSI 30-MAY-2012 08:35:50.57 SYS$PUT From: 810C20C4 AP: 1 00000000 SYS$SSISHR_001 SSI 30-MAY-2012 08:35:50.57 SYS$PUT From: 810C20C4 AP: 1 00000000 LIBRTL_001 SSI 30-MAY-2012 08:35:50.57 SYS$PUT From: 810C20C4 AP: 1 00000000 LIBOTS_001 SSI 30-MAY-2012 08:35:50.57 SYS$GET From: 00030AEC AP: 1 00000000 SSI 30-MAY-2012 08:35:50.57 SYS$GET From: 00030AEC AP: 1 00000000 ... SSI 30-MAY-2012 08:35:52.18 SYS$PUT From: 810C20C4 AP: 1 00000000 DSC$K_CLASS_S SSI 30-MAY-2012 08:35:52.18 SYS$PUT From: 810C20C4 AP: 1 00000000 DSC$K_DTYPE_T SSI 30-MAY-2012 08:35:52.18 SYS$PUT From: 810C20C4 AP: 1 00000000 START SSI 30-MAY-2012 08:35:52.18 SYS$GET From: 00030AEC AP: 1 00000000 SSI 30-MAY-2012 08:35:52.18 SYS$PUT From: 810C20C4 AP: 1 00000000 SSI_FINDENTRY SSI 30-MAY-2012 08:35:52.18 SYS$PUT From: 810C20C4 AP: 1 00000000 SSI_FIXTABLE SSI 30-MAY-2012 08:35:52.18 SYS$PUT From: 810C20C4 AP: 1 00000000 SSI_STOP SSI 30-MAY-2012 08:35:52.18 SYS$PUT From: 810C20C4 AP: 1 00000000 SSI_FORMATARGS SSI 30-MAY-2012 08:35:52.18 SYS$PUT From: 810C20C4 AP: 1 00000000 SSI_START SSI 30-MAY-2012 08:35:52.18 SYS$PUT From: 810C20C4 AP: 1 00000000 SSI_POST SSI 30-MAY-2012 08:35:52.18 SYS$PUT From: 810C20C4 AP: 1 00000000 SSI_PRE SSI 30-MAY-2012 08:35:52.18 SYS$GET From: 00030AEC AP: 1 00000000 SSI 30-MAY-2012 08:35:52.18 SYS$CLOSE From: 00030A8C AP: 1 00000000 SSI Pre: In 000063CD Act 000018F2 Post: Out 000063CD act 000018F2 %DEBUG-I-EXITSTATUS, is '%SYSTEM-S-NORMAL, normal successful completion'
Now we see the SYS$PUTs from LIB$PUT_OUTPUT and the counters are much higher. I guess it depends on when the fixups are done how the SSI effects calls from lower level shareable images. It explains my earlier observation that I got no output, as my test program in that case had no direct system service calls. Could be seen as a feature.
My next puzzle is why the arguments of the RMS services are all 0! Also, DEBUG issues a constant stream of $SETIMR/$WAITFR pairs. I need to work out a simple way to recognise and bypass system service calls originating from DEBUG. The from address should help, but it's non-trivial!
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05-29-2012 06:21 PM
05-29-2012 06:21 PM
Re: System Service Interception on OpenVMS
Proof of concept.
I added a bypass in the PRE routine for "from" address within a particular range.
Running the under DEBUG and using SHOW IMAGE to find the start and end addresses for the DEBUG image and manually DEPOSIT those values into the range check.
I can now set a break point to the active section of the PRE address without sending DEBUG into a recursion loop.
Next step is to find a reasonably clean way to automatically detect the DEBUG image and set the range...
Using this trick with DEBUG I was able to confirm that the argument list SSI gets for the RMS services is indeed count=1 fiist arg=0. Not sure why.
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05-30-2012 01:28 AM
05-30-2012 01:28 AM
Re: System Service Interception on OpenVMS
>>> I guess it depends on when the fixups are done how the SSI effects calls from lower level shareable images.
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05-30-2012 03:31 PM
05-30-2012 03:31 PM
Re: System Service Interception on OpenVMS
>> Or put it another way, if you have a "low level shareable image" linked against sys$public_vectors, you can't fix it up against sys$ssishr
Fair enough, but that doesn't explain the observation. How are we catching system service calls from low level shareable images? Here's the result matrix:
Image Image Liked
Run /NODEBUG /DEBUG
/NODEBUG Direct Only All Calls
/DEBUG All Calls All Calls
Note that in all cases the image itself is linked against SYS$SSISHR (has to be to resolve the calls to DECLARE_INTERCEPT).
My evidence for "All Calls" is I'm catching SS calls with FROM addresses in LIBRTL.
JG> JG> macro/noopt/deb strings+[-]util/lib JG> link strings+ssishr/opt First run, LINK/NODEBUG RUN/NODEBUG. Only one direct call was caught. JG> run strings SSI 31-MAY-2012 07:56:25.74 SYS$GETTIM From: 00030B14 AP: 1 00000000 Please enter filename: SSI Pre: In 00000003 Act 00000001 Post: Out 00000003 act 00000001 Second run LINK/NODEBUG RUN/DEBUG. Direct and indirect calls caught. The block of calls from SYS$CLI to SYS$GET are from LIB$GET_FOREIGN. Note that the LIBRTL addresses are in S0 space - so they're from the resident image. JG> run/debug strings %DEBUG-I-NOGLOBALS, some or all global symbols not accessible OpenVMS Alpha Debug64 Version V8.3-016 %DEBUG-I-INITIAL, Language: AMACRO, Module: STRINGS DBG> go SSI 31-MAY-2012 07:56:54.89 SYS$GETTIM From: 00030B14 AP: 1 00000000 SSI 31-MAY-2012 07:56:54.89 SYS$CLI From: 810BE254 AP: 1 00000000 SSI 31-MAY-2012 07:56:54.89 SYS$SETAST From: 810BEA14 AP: 1 00000000 SSI 31-MAY-2012 07:56:54.89 SYS$READ_THR From: 810BEA2C AP: 1 00000000 SSI 31-MAY-2012 07:56:54.89 SYS$OPEN From: 810BEB68 AP: 1 00000000 SSI 31-MAY-2012 07:56:54.89 SYS$CONNECT From: 810BEC94 AP: 1 00000000 SSI 31-MAY-2012 07:56:54.89 SYS$SETAST From: 810BEDD4 AP: 1 00000000 SSI 31-MAY-2012 07:56:54.89 SYS$GET From: 810BF1E4 AP: 1 00000000 Please enter filename: Exit SSI Pre: In 00000025 Act 00000008 Post: Out 00000025 act 00000008 %DEBUG-I-EXITSTATUS, is '%RMS-E-EOF, end of file detected' DBG> set image librtl DBG> examine 810BE254 %DEBUG-E-INVPD, procedure descriptor at 00000000000E3198 is not valid. LIB$GET_FOREIGN\LIB$GET_FOREIGN\%LINE 545: LDL R5,#X0020(FP) DBG> exit Third run LINK/DEBUG RUN/NODEBUG direct and indirect calls caught. JG> link/debug strings+ssishr/opt JG> run/nodeb strings SSI 31-MAY-2012 07:57:13.40 SYS$GETTIM From: 00030B14 AP: 1 00000000 SSI 31-MAY-2012 07:57:13.40 SYS$CLI From: 810BE254 AP: 1 00000000 SSI 31-MAY-2012 07:57:13.40 SYS$SETAST From: 810BEA14 AP: 1 00000000 SSI 31-MAY-2012 07:57:13.40 SYS$READ_THR From: 810BEA2C AP: 1 00000000 SSI 31-MAY-2012 07:57:13.40 SYS$OPEN From: 810BEB68 AP: 1 00000000 SSI 31-MAY-2012 07:57:13.40 SYS$CONNECT From: 810BEC94 AP: 1 00000000 SSI 31-MAY-2012 07:57:13.40 SYS$SETAST From: 810BEDD4 AP: 1 00000000 SSI 31-MAY-2012 07:57:13.40 SYS$GET From: 810BF1E4 AP: 1 00000000 Please enter filename: Exit SSI Pre: In 00000025 Act 00000008 Post: Out 00000025 act 00000008 %RMS-E-EOF, end of file detected Fourth run LINK/DEBUG RUN/DEBUG direct and indirect calls caught. JG> run/debug strings OpenVMS Alpha Debug64 Version V8.3-016 %DEBUG-I-INITIAL, Language: AMACRO, Module: STRINGS DBG> go SSI 31-MAY-2012 07:57:29.17 SYS$GETTIM From: 00030B14 AP: 1 00000000 SSI 31-MAY-2012 07:57:29.17 SYS$CLI From: 810BE254 AP: 1 00000000 SSI 31-MAY-2012 07:57:29.17 SYS$SETAST From: 810BEA14 AP: 1 00000000 SSI 31-MAY-2012 07:57:29.17 SYS$READ_THR From: 810BEA2C AP: 1 00000000 SSI 31-MAY-2012 07:57:29.17 SYS$OPEN From: 810BEB68 AP: 1 00000000 SSI 31-MAY-2012 07:57:29.17 SYS$CONNECT From: 810BEC94 AP: 1 00000000 SSI 31-MAY-2012 07:57:29.17 SYS$SETAST From: 810BEDD4 AP: 1 00000000 SSI 31-MAY-2012 07:57:29.17 SYS$GET From: 810BF1E4 AP: 1 00000000 Please enter filename: Exit SSI Pre: In 00000025 Act 00000008 Post: Out 00000025 act 00000008 %DEBUG-I-EXITSTATUS, is '%RMS-E-EOF, end of file detected' DBG> set image librtl DBG> examine 810BE254 %DEBUG-E-INVPD, procedure descriptor at 00000000000E3198 is not valid. LIB$GET_FOREIGN\LIB$GET_FOREIGN\%LINE 545: LDL R5,#X0020(FP)
Note that the LIBRTL calls are coming from S0 space, so they're the RESIDENT image (ShareAddr!). How are we catching those, and why does it depend on /DEBUG?
Here's what the call stack looks like inside SSI_PRE when called through LIBRTL
DBG> show calls
module name routine name line rel PC abs PC
SHARE$SIMPLE 000000000000098C 000000000003098C
SHARE$SYS$SSISHR 0000000000010C64 000000000018CC64
SHARE$SYS$SSISHR 0000000000011884 000000000018D884
*LIB$GET_INPUT DO_GET 1851 0000000000000548 FFFFFFFF810BEB68
----- the above looks like a null frame in the same scope as the frame below
*LIB$GET_INPUT ? ?
*LIB$GET_INPUT LIB$GET_INPUT
1569 000000000000020C FFFFFFFF810BE82C
----- the above looks like a null frame in the same scope as the frame below
*LIB$GET_INPUT ? ?
%DEBUG-E-INVPD, procedure descriptor at 00000000000E3198 is not valid.
*LIB$GET_FOREIGN
LIB$GET_FOREIGN
601 0000000000000294 FFFFFFFF810BE414
----- the above looks like a null frame in the same scope as the frame below
*LIB$GET_FOREIGN ? ?
SHARE$SIMPLE 0000000000000AF8 0000000000030AF8
FFFFFFFF8038BDD4 FFFFFFFF8038BDD4
(Another ugly hack to work out where DEBUG is... I'm using LIB$FIND_IMAGE_SYMBOL to locate both symbols exported from the DEBUG shareable image. I've determined their offsets from the beginning and end of the image and hard coded them as constants. At run time, I add (or subtract) the offsets from both symbols, sanity check that both symbols yield the same results and use the resulting range to exclude FROM addresses from processing in the PRE routine. This is obviously dependent on the version of DEBUG)
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05-31-2012 03:21 AM
05-31-2012 03:21 AM
Re: System Service Interception on OpenVMS
>>> Note that the LIBRTL calls are coming from S0 space, so they're the RESIDENT image (ShareAddr!). How are we catching those, and why does it depend on /DEBUG?
I no longer have access to the sources so I can't read the real documentation. I re-read Ruth's paper on ssi and she proves me wrong, fixups aren't always fixed :-(
However, that didn't match what I saw, so far, but wait ...
Usually LIBRTL is installed /resident and /share=addr. So it seems a reasonable assumption that "coming from S0" means, it also uses shared address data. But in general /resident is independent of shared address data. So the asumption is not always true. Shared address data means sharing the linkage sections and pre-applying fixups during INSTALLation of the image. As you show, you can intercept system services from LIBRTL: either you have a private and modified copy of the shared address data in P0 or /DEBUG does some magic. It seems to be the first.
$
It seems that the image activator can't change the shared data of the installed images and didn't bother to tell us about it. I miss the real documentation, here. Also, if you run /DEBUG you get private copies of all the P1 sections, including the shared data. You can verify that from SDA and you will also see that code is still in S0 space.
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06-13-2012 12:32 AM
06-13-2012 12:32 AM
Re: System Service Interception on OpenVMS
What are the chances of HP ever publishing the documentation on SSI?
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06-13-2012 07:33 PM
06-13-2012 07:33 PM
Re: System Service Interception on OpenVMS
>What are the chances of HP ever publishing the documentation on SSI?
If no one formally asks for it, ZERO. HP is a very metrics driven culture. The days of people being able to do things just because it's the right thing to do are long gone. Everything must have a measurable payoff.
Even if you formally ask, I think it's a long shot. The folk who actually know this stuff are also long gone :-(
That said, here's another (tiny) piece of the puzzle. It looks to me like the argument list passed to the PRE action routine is an array of QUADWORDS, not a VAX type argument list (longwords). That explains my puzzle of the 0 arguments to RMS services. Interpreting the argument list as quadwords gives more plausible values.
Please lodge a formal request for the documentation against your HP services contract.