Re: Is a page protected?--how to determine
OK, I'll bite. Why do you need to determine? If you have any reason to think that the page is protected (presumably because you did it or might have done it), then you can just unprotect it. A page does not need to be protected in order to successfully unprotect. Note that protection is not a count it is a toggle. Two protects followed by one unprotect leaves the page not protected.. Peter Relson z/OS Core Technology Design -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
On Wed, 25 Jul 2007 07:27:15 -0400, Peter Relson [EMAIL PROTECTED] wrote: OK, I'll bite. Why do you need to determine? If you have any reason to think that the page is protected (presumably because you did it or might have done it), then you can just unprotect it. A page does not need to be protected in order to successfully unprotect. Note that protection is not a count it is a toggle. Two protects followed by one unprotect leaves the page not protected.. Peter Relson z/OS Core Technology Design -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html The need is based on stuff that can be put into key-0 CSA -or- into dynamic LPA during install time, and is briefly updated after it has been put into CSA or dynamic LPA. Since the dynamic LPA is protected, it needs to be unprotected and then reprotected, but the CSA needs neither. Hence the 'need to determine'. Thank you. Paul Schuster -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
On Wed, 25 Jul 2007 12:08:42 -0500 Paul Schuster [EMAIL PROTECTED] wrote: :On Wed, 25 Jul 2007 07:27:15 -0400, Peter Relson [EMAIL PROTECTED] wrote: : :OK, I'll bite. Why do you need to determine? : :If you have any reason to think that the page is protected (presumably :because you did it or might have done it), then you can just unprotect it. :A page does not need to be protected in order to successfully unprotect. :Note that protection is not a count it is a toggle. Two protects :followed by one unprotect leaves the page not protected.. :The need is based on stuff that can be put into key-0 CSA -or- into dynamic :LPA during install time, and is briefly updated after it has been put into :CSA or dynamic LPA. Since the dynamic LPA is protected, it needs to be :unprotected and then reprotected, but the CSA needs neither. Hence the :'need to determine'. I wonder if ASM/VSM checks for modified page-protected LPA. -- Binyamin Dissen [EMAIL PROTECTED] http://www.dissensoftware.com Director, Dissen Software, Bar Grill - Israel Should you use the mailblocks package and expect a response from me, you should preauthorize the dissensoftware.com domain. I very rarely bother responding to challenge/response systems, especially those from irresponsible companies. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
-Original Message- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Binyamin Dissen Sent: Wednesday, July 25, 2007 12:28 PM To: IBM-MAIN@BAMA.UA.EDU Subject: Re: Is a page protected?--how to determine On Wed, 25 Jul 2007 12:08:42 -0500 Paul Schuster [EMAIL PROTECTED] wrote: :On Wed, 25 Jul 2007 07:27:15 -0400, Peter Relson [EMAIL PROTECTED] wrote: : :OK, I'll bite. Why do you need to determine? : :If you have any reason to think that the page is protected (presumably :because you did it or might have done it), then you can just unprotect it. :A page does not need to be protected in order to successfully unprotect. :Note that protection is not a count it is a toggle. Two protects :followed by one unprotect leaves the page not protected.. :The need is based on stuff that can be put into key-0 CSA -or- into dynamic :LPA during install time, and is briefly updated after it has been put into :CSA or dynamic LPA. Since the dynamic LPA is protected, it needs to be :unprotected and then reprotected, but the CSA needs neither. Hence the :'need to determine'. I wonder if ASM/VSM checks for modified page-protected LPA. -- Binyamin Dissen [EMAIL PROTECTED] From what I remember from the deep-dark-past, LPA is never paged-out. So if something modifies an LPA page, then it must also do a PGFIX so that the frame in which it resides is never used for anything else. I remember a type 3 SVC which did an initialization of itself upon the first execution. The updated data area within the SVC code had to be page fixed and the comment was or else the data is lost if the frame is ever reused due to low activity. -- John McKown Senior Systems Programmer HealthMarkets Keeping the Promise of Affordable Coverage Administrative Services Group Information Technology The information contained in this e-mail message may be privileged and/or confidential. It is for intended addressee(s) only. If you are not the intended recipient, you are hereby notified that any disclosure, reproduction, distribution or other use of this communication is strictly prohibited and could, in certain circumstances, be a criminal offense. If you have received this e-mail in error, please notify the sender by reply and delete this message without copying or disclosing it. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
How do you define a brief update? Especially in computer time with the current processors? Better technique would be to reload the module into dynamic LPA than turn off protection, modify, turn on protection, I would think. Wayne Driscoll Product Developer JME Software LLC NOTE: All opinions are strictly my own. -Original Message- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Paul Schuster Sent: Wednesday, July 25, 2007 12:09 PM To: IBM-MAIN@BAMA.UA.EDU Subject: Re: Is a page protected?--how to determine On Wed, 25 Jul 2007 07:27:15 -0400, Peter Relson [EMAIL PROTECTED] wrote: OK, I'll bite. Why do you need to determine? If you have any reason to think that the page is protected (presumably because you did it or might have done it), then you can just unprotect it. A page does not need to be protected in order to successfully unprotect. Note that protection is not a count it is a toggle. Two protects followed by one unprotect leaves the page not protected.. Peter Relson z/OS Core Technology Design -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html The need is based on stuff that can be put into key-0 CSA -or- into dynamic LPA during install time, and is briefly updated after it has been put into CSA or dynamic LPA. Since the dynamic LPA is protected, it needs to be unprotected and then reprotected, but the CSA needs neither. Hence the 'need to determine'. Thank you. Paul Schuster -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
The MVS monitors I know about that support storage viewing and alteration allow for this. Some like TMONMVS automatically fix an LPA pages which is being modified. SYSVIEW is aware of the status and will prompt you to page fix it yourself DUMP025W ALTER not valid, address 0933B002 is page protected but not fixed using the pgfix command. Best Regards, Sam Knutson, GEICO Performance and Availability Management mailto:[EMAIL PROTECTED] (office) 301.986.3574 Think big, act bold, start simple, grow fast... -Original Message- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of McKown, John Sent: Wednesday, July 25, 2007 1:55 PM To: IBM-MAIN@BAMA.UA.EDU Subject: Re: Is a page protected?--how to determine From what I remember from the deep-dark-past, LPA is never paged-out. So if something modifies an LPA page, then it must also do a PGFIX so that the frame in which it resides is never used for anything else. I remember a type 3 SVC which did an initialization of itself upon the first execution. The updated data area within the SVC code had to be page fixed and the comment was or else the data is lost if the frame is ever reused due to low activity. -- John McKown Senior Systems Programmer HealthMarkets Keeping the Promise of Affordable Coverage Administrative Services Group Information Technology This email/fax message is for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized review, use, disclosure or distribution of this email/fax is prohibited. If you are not the intended recipient, please destroy all paper and electronic copies of the original message. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
That's why some (older) vendor code was required to be loaded into FLPA with no page protect. Jon L. Veilleux [EMAIL PROTECTED] (860) 636-2683 -Original Message- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of McKown, John Sent: Wednesday, July 25, 2007 1:55 PM To: IBM-MAIN@BAMA.UA.EDU Subject: Re: Is a page protected?--how to determine -Original Message- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Binyamin Dissen Sent: Wednesday, July 25, 2007 12:28 PM To: IBM-MAIN@BAMA.UA.EDU Subject: Re: Is a page protected?--how to determine On Wed, 25 Jul 2007 12:08:42 -0500 Paul Schuster [EMAIL PROTECTED] wrote: :On Wed, 25 Jul 2007 07:27:15 -0400, Peter Relson [EMAIL PROTECTED] wrote: : :OK, I'll bite. Why do you need to determine? : :If you have any reason to think that the page is protected (presumably :because you did it or might have done it), then you can just unprotect it. :A page does not need to be protected in order to successfully unprotect. :Note that protection is not a count it is a toggle. Two protects :followed by one unprotect leaves the page not protected.. :The need is based on stuff that can be put into key-0 CSA -or- into dynamic :LPA during install time, and is briefly updated after it has been put into :CSA or dynamic LPA. Since the dynamic LPA is protected, it needs to be :unprotected and then reprotected, but the CSA needs neither. Hence the :'need to determine'. I wonder if ASM/VSM checks for modified page-protected LPA. -- Binyamin Dissen [EMAIL PROTECTED] From what I remember from the deep-dark-past, LPA is never paged-out. So if something modifies an LPA page, then it must also do a PGFIX so that the frame in which it resides is never used for anything else. I remember a type 3 SVC which did an initialization of itself upon the first execution. The updated data area within the SVC code had to be page fixed and the comment was or else the data is lost if the frame is ever reused due to low activity. -- John McKown Senior Systems Programmer HealthMarkets Keeping the Promise of Affordable Coverage Administrative Services Group Information Technology The information contained in this e-mail message may be privileged and/or confidential. It is for intended addressee(s) only. If you are not the intended recipient, you are hereby notified that any disclosure, reproduction, distribution or other use of this communication is strictly prohibited and could, in certain circumstances, be a criminal offense. If you have received this e-mail in error, please notify the sender by reply and delete this message without copying or disclosing it. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html This e-mail may contain confidential or privileged information. If you think you have received this e-mail in error, please advise the sender by reply e-mail and then delete this e-mail immediately. Thank you. Aetna -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Is a page protected?--how to determine
Hello: I have a need to determine if an address in storage is page protected in order to determine if a PGSER UNPROTECT needs to be done. The best I have tried and seen in earlier posts is to look for a CC=1 on a TPROT backed up with an ESTAE. Are there any other methods to do this? Thank you. Paul Schuster -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
Paul, You are in the right way. I think this is the same technique used in NUCLEUS by CSECT IEAVEVAL but with a FRR instead. Regards, Philippe Leite z/OS Systems Programmer Portugal On Tue, 24 Jul 2007 01:32:43 -0500, Paul Schuster [EMAIL PROTECTED] wrote: Hello: I have a need to determine if an address in storage is page protected in order to determine if a PGSER UNPROTECT needs to be done. The best I have tried and seen in earlier posts is to look for a CC=1 on a TPROT backed up with an ESTAE. Are there any other methods to do this? Thank you. Paul Schuster -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
Chapter 10 of the pops manual. IVSK instruction will tell you the key, access control bits, and fetch protection bit of a page. - Original Message - From: Paul Schuster [EMAIL PROTECTED] Newsgroups: bit.listserv.ibm-main To: IBM-MAIN@BAMA.UA.EDU Sent: Tuesday, July 24, 2007 1:32 AM Subject: Is a page protected?--how to determine Hello: I have a need to determine if an address in storage is page protected in order to determine if a PGSER UNPROTECT needs to be done. The best I have tried and seen in earlier posts is to look for a CC=1 on a TPROT backed up with an ESTAE. Are there any other methods to do this? Thank you. Paul Schuster -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
David, Actually, ISVK cannot tell you if a page is protected or not, it only shows you the storage key and fetch bit. The Page protection bit (bit 54) is in Page Table Entry and Segment Table Entry. Best regards, Philippe Leite z/OS Systems Programmer Portugal On Tue, 24 Jul 2007 07:28:15 -0500, David Day [EMAIL PROTECTED] wrote: Chapter 10 of the pops manual. IVSK instruction will tell you the key, access control bits, and fetch protection bit of a page. - Original Message - From: Paul Schuster [EMAIL PROTECTED] Newsgroups: bit.listserv.ibm-main To: IBM-MAIN@BAMA.UA.EDU Sent: Tuesday, July 24, 2007 1:32 AM Subject: Is a page protected?--how to determine Hello: I have a need to determine if an address in storage is page protected in order to determine if a PGSER UNPROTECT needs to be done. The best I have tried and seen in earlier posts is to look for a CC=1 on a TPROT backed up with an ESTAE. Are there any other methods to do this? Thank you. Paul Schuster -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
-Original Message- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Paul Schuster Sent: Tuesday, July 24, 2007 12:33 AM To: IBM-MAIN@BAMA.UA.EDU Subject: Is a page protected?--how to determine Hello: I have a need to determine if an address in storage is page protected in order to determine if a PGSER UNPROTECT needs to be done. The best I have tried and seen in earlier posts is to look for a CC=1 on a TPROT backed up with an ESTAE. Are there any other methods to do this? Thank you. Paul Schuster Use a loop with IVSK and TPROT for key 0. Something like this: L R2,page_address LOOP BR 0 purge cache IVSK R0,R2 page-in TPROT 0(R2),0 test for key zero storability BO LOOP oops, paged-out. try again BNZ PROT page protected, LAP, read-only data space BZ NO_PROT not protected Testing for key zero storability will catch page protection, or low address protection, or read-only data space. You may want to provide special filtering for those weird cases. Jeffrey D. Smith Principal Product Architect Farsight Systems Corporation 700 KEN PRATT BLVD. #204-159 LONGMONT, CO 80501-6452 303-774-9381 direct 303-484-6170 FAX http://www.farsight-systems.com/ -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
I guess I read what I wanted to read, and not what the original question was. Try to take more time in the future before replying. Paul, hope I didn't send you on a wild goose chase. --Dave Day - Original Message - From: Philippe Leite [EMAIL PROTECTED] Newsgroups: bit.listserv.ibm-main To: IBM-MAIN@BAMA.UA.EDU Sent: Tuesday, July 24, 2007 8:22 AM Subject: Re: Is a page protected?--how to determine David, Actually, ISVK cannot tell you if a page is protected or not, it only shows you the storage key and fetch bit. The Page protection bit (bit 54) is in Page Table Entry and Segment Table Entry. Best regards, Philippe Leite z/OS Systems Programmer Portugal On Tue, 24 Jul 2007 07:28:15 -0500, David Day [EMAIL PROTECTED] wrote: Chapter 10 of the pops manual. IVSK instruction will tell you the key, access control bits, and fetch protection bit of a page. - Original Message - From: Paul Schuster [EMAIL PROTECTED] Newsgroups: bit.listserv.ibm-main To: IBM-MAIN@BAMA.UA.EDU Sent: Tuesday, July 24, 2007 1:32 AM Subject: Is a page protected?--how to determine Hello: I have a need to determine if an address in storage is page protected in order to determine if a PGSER UNPROTECT needs to be done. The best I have tried and seen in earlier posts is to look for a CC=1 on a TPROT backed up with an ESTAE. Are there any other methods to do this? Thank you. Paul Schuster -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
In a message dated 7/24/2007 1:33:11 A.M. Central Daylight Time, [EMAIL PROTECTED] writes: I have a need to determine if an address in storage is page protected in order to determine if a PGSER UNPROTECT needs to be done. One way, not necessarily the most elegant, is to establish an ESTAE or FRR, put your program into key 0, and do an OI into any byte in the page with an operand of X'00'. This instruction will not change the byte being accessed, but if the page is page protected your OI will produce a S0C4 which you trap and from which you recover in your recovery routine. If the page is not page protected, the next instruction after the OI will execute. Bill Fairchild Plainfield, IL ** Get a sneak peek of the all-new AOL at http://discover.aol.com/memed/aolcom30tour -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
-Original Message- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of (IBM Mainframe Discussion List) Sent: Tuesday, July 24, 2007 8:07 AM To: IBM-MAIN@BAMA.UA.EDU Subject: Re: Is a page protected?--how to determine In a message dated 7/24/2007 1:33:11 A.M. Central Daylight Time, [EMAIL PROTECTED] writes: I have a need to determine if an address in storage is page protected in order to determine if a PGSER UNPROTECT needs to be done. One way, not necessarily the most elegant, is to establish an ESTAE or FRR, put your program into key 0, and do an OI into any byte in the page with an operand of X'00'. This instruction will not change the byte being accessed, but if the page is page protected your OI will produce a S0C4 which you trap and from which you recover in your recovery routine. If the page is not page protected, the next instruction after the OI will execute. Bill Fairchild very bad idea in general. if the page is not protected, then you don't know what other processes are updating that page nor how they serialize their updates. the OI is not an interlocked update and may cause corruption when another CPU is concurrently modifying that byte. Jeffrey D. Smith Principal Product Architect Farsight Systems Corporation 700 KEN PRATT BLVD. #204-159 LONGMONT, CO 80501-6452 303-774-9381 direct 303-484-6170 FAX http://www.farsight-systems.com/ -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
-Original Message- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Paul Schuster Sent: Tuesday, July 24, 2007 12:33 AM To: IBM-MAIN@BAMA.UA.EDU Subject: Is a page protected?--how to determine Hello: I have a need to determine if an address in storage is page protected in order to determine if a PGSER UNPROTECT needs to be done. The best I have tried and seen in earlier posts is to look for a CC=1 on a TPROT backed up with an ESTAE. Are there any other methods to do this? Thank you. Paul Schuster In addition to what else has been posted, be very careful about unprotecting a page that your application did not explicitly protect. An application that uses IARVSERV to share pages with COPY_ON_WRITE will implicitly page-protect the shared pages. When a unit of work attempts to store into the protected page, the system catches the PIC 0004 and copies the contents to another real frame. Then the page table entry is modified to point to the new real frame and the unit of work is redispatched to try the update again; this time succeeding. The unit of work never sees the PIC 0004. If you explicitly unprotect such a shared page, then you will screw up shared pages scheme. Jeffrey D. Smith Principal Product Architect Farsight Systems Corporation 700 KEN PRATT BLVD. #204-159 LONGMONT, CO 80501-6452 303-774-9381 direct 303-484-6170 FAX http://www.farsight-systems.com/ -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
In a message dated 7/24/2007 10:56:09 A.M. Central Daylight Time, [EMAIL PROTECTED] writes: very bad idea in general. if the page is not protected, then you don't know what other processes are updating that page nor how they serialize their updates. the OI is not an interlocked update and may cause corruption when another CPU is concurrently modifying that byte. OK. Find some other instruction that will not corrupt storage by serializing properly on the storage and which instruction will NOT really change anything in the storage. My main idea was to execute an instruction that does not really change anything but yet the instruction processing microcode tests the byte to be accessed for write capability in that page. I do not understand how my instruction that does not change any of the 8 bits in a byte can possibly corrupt any bytes anywhere near that one byte regardless of what other CPUs or I/O operations are doing concurrently. Here's another bad idea: find the page table entry for the page in question and test the page protect bit in that entry. Bill Fairchild Plainfield, IL ** Get a sneak peek of the all-new AOL at http://discover.aol.com/memed/aolcom30tour -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
-Original Message- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of (IBM Mainframe Discussion List) Sent: Tuesday, July 24, 2007 10:05 AM To: IBM-MAIN@BAMA.UA.EDU Subject: Re: Is a page protected?--how to determine In a message dated 7/24/2007 10:56:09 A.M. Central Daylight Time, [EMAIL PROTECTED] writes: very bad idea in general. if the page is not protected, then you don't know what other processes are updating that page nor how they serialize their updates. the OI is not an interlocked update and may cause corruption when another CPU is concurrently modifying that byte. OK. Find some other instruction that will not corrupt storage by serializing properly on the storage and which instruction will NOT really change anything in the storage. My main idea was to execute an instruction that does not really change anything but yet the instruction processing microcode tests the byte to be accessed for write capability in that page. I do not understand how my instruction that does not change any of the 8 bits in a byte can possibly corrupt any bytes anywhere near that one byte regardless of what other CPUs or I/O operations are doing concurrently. Because the fetch and the store are separated in time. Another CPU or an I/O operation can store into the byte *after* your CPU fetches the byte but *before* your CPU stores the byte. The other CPU update will be wiped out by your CPU subsequent store into the byte. If the application does not know how the page owner is serializing access to the page, there is no way to attempt a safe store into the page to detect protection. Jeffrey D. Smith Principal Product Architect Farsight Systems Corporation 700 KEN PRATT BLVD. #204-159 LONGMONT, CO 80501-6452 303-774-9381 direct 303-484-6170 FAX http://www.farsight-systems.com/ -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
There's no obvious way for an unauthorized program to discover that information. If you're a supervisor state program you can issue a TPROT with a key of 0. If the condition code is 1 then the page is protected. The interpretation of the other condition codes is left as an exercise to the reader. Note also that there is the usual time of check to time of reference defect with any such check. Why would you want to unprotect a protected page anyway? That would seem to be a hideously bad idea if it's not your own page, and if it -is- your own page, you ought to already know whether it's protected or not. CC -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Is a page protected?--how to determine
In a message dated 7/24/2007 11:14:10 A.M. Central Daylight Time, [EMAIL PROTECTED] writes: Because the fetch and the store are separated in time. Another CPU or an I/O operation can store into the byte *after* your CPU fetches the byte but *before* your CPU stores the byte. The other CPU update will be wiped out by your CPU subsequent store into the byte. Very clear. Thanks for the enlightenment. Bill Fairchild Plainfield, IL ** Get a sneak peek of the all-new AOL at http://discover.aol.com/memed/aolcom30tour -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
