PM66334: sample program ASMASTXP to validate transactional constraints

Obtain the fix for this APAR.

APAR status

• Closed as new function.

Error description

• sample program ASMASTXP to validate transactional constraints
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of HLASM for z/OS.                 *
  ****************************************************************
  * PROBLEM DESCRIPTION: PM66334 ships a new exit ASMAXTXP       *
  *                      and sample program ASMASTXP to validate *
  *                      constraints for the new transactional   *
  *                      memory instructions at assembly time.   *
  ****************************************************************
  * RECOMMENDATION: Apply the PTF provided                       *
  ****************************************************************
  A new listing exit ASMAXTXP provides functionality to validate
  the constraints associated with the new transactional memory
  instructions.
  For example, the exit validates the total number of instructions
  coded between the TBEGINC and TEND instructions does not
  exceed the specified limit.
  Further details of the constraints can be found in the
  z/Architecture Principles of Operation manual.
  

Problem conclusion

Temporary fix

Comments

• The LISTING exit ASMAXTXP is shipped in SASMMOD1.
  The sample program ASMASTXP is shipped in SASMSAM1.
  The listing exit may issue warning messages as listed below.
  An assembly return code of 4 will be set should the listing
  exit fails any of its tests.
  The "High Level Assembler for z/OS & z/VM & z/VSE
  Programmmer's Guide Release 6" publication (SC26-4941-05)
  will be updated as follows:
  
  --- START OF DOC UPDATES ---
  
      A new appendix will be added:
          Appendix Q. Transactional Memory exit ASMAXTXP
          (z/OS only)
  
      The following text will be added:
          This appendix provides information regarding the use of
          the LISTING exit ASMAXTXP supplied with the High Level
          Assembler.
  
      The section "Function" will be added with the following
      text:
          The LISTING exit ASMAXTXP is used to verify the
          instructions used within a constrained transaction.
          ASMAXTXP performs the following checks for constrained
          transactions:
              1.  The transaction must not exceed more than 32
                  instructions.
              2.  All instructions within the transaction must be
                  within 256 bytes contiguous bytes of storage.
              3.  In addition to all regularly-restricted
                  instructions, i.e. those restricted in a
                  non-constrained transaction, the following
                  instructions are also restricted:
                    a. Any instruction not defined in Chapter 7
                       of the z/Architecture Principles of
                       Operation.
                    b. The only branching instructions are
                       relative branches with a positive relative
                       immediate operand.
                    c. Instructions that cause a classic
                       serialization operation.  Exceptions to
                       this rule include TRANSACTION END and any
                       instructions that cause specific-operand
                       serialization.
                    d. All SS and SSE format instructions.
                    e. A list of individual instructions that may
                       execute in the hardware coprocessor.
  
          Other constraints such as operand alignment and number
          of locations accessed are not possible to check during
          assembly.
  
      The section "Invoking the exit" will be added with the
      following text:
          To invoke the exit, specify the EXIT assembler option
          as follows:
              EXIT(PRTEXIT(ASMAXTXP))
          The sample program ASMASTXP found in SASMSAM1
          can be run with the above assembler option as an
          example of how ASMAXTXP processes constrained
          transactions.
  
      The section "Messages" will be added with the following
      text:
          ASMAXTXP might issue message ASMA701W as follows:
              @ ** ASMA701W LISTING: ASMAXTXP: HLASM R6.0 or
                higher required.
                This message is issued because HLASM R6.0 or
                higher is required to run this exit.
              @ ** ASMA701W LISTING: ASMAXTXP: Could not acquire
                memory.
                An attempt to acquire memory failed and the exit
                could not continue.
              @ ** ASMA701W LISTING: ASMAXTXP: Invalid exit type
                or request type passed to exit.
                ASMAXTXP will only process valid LISTING EXIT
                requests; this message is issued if the listing
                exit request is invalid.
              @ ** ASMA701W LISTING: ASMAXTXP: TBEGINC base
                register nonzero.
                The TBEGINC instruction would cause a
                specification exception if bits in the base
                register field are non-zero.
              @ ** ASMA701W LISTING: ASMAXTXP: TBEGINC second
                operand is invalid.
                The immediate mask value used in the TBEGINC
                instruction does not conform to the instruction's
                specification.
              @ ** ASMA701W LISTING: ASMAXTXP: Transaction
                exceeds total byte limit.
                The transaction length is longer than 256 bytes
                allowed.
              @ ** ASMA701W LISTING: ASMAXTXP: Transaction
                exceeds maximum instruction count (excluding)
                TBEGIN and TEND.
                The number of instructions between the TBEGIN
                and TEND instructions exceeds 32 instructions.
              @ ** ASMA701W LISTING: ASMAXTXP: TBEGINC
                allow-AR-modification control is 0.
                If the allow-AR-modification flag is 0 then the
                exit cannot guarantee that instructions used
                within a transaction will not modify access
                registers.
              @ ** ASMA701W LISTING: ASMAXTXP: Instruction is
                restricted.
                This message is issued if the instruction is
                restricted for example: a privileged instruction,
                modifying ARs / FRs etc.
              @ ** ASMA701W LISTING: ASMAXTXP: Relative branch
                target is zero or negative.
                A relative branch instruction may branch
                backwards in the program. This is invalid in a
                constrained transaction.
              @ ** ASMA701W LISTING: ASMAXTXP: Relative branch
                target exceeds size limit.
                The relative branch will cause program flow to
                leave the constrained transaction without a TEND
                instruction being issued.
              @ ** ASMA701W LISTING: ASMAXTXP: Relative branch
                mask is 0.
                The relative branch instruction will never
                execute because its mask is 0.  ASMAXTXP flags
                this as a warning.
              @ ** ASMA701W LISTING: ASMAXTXP: STCMH with M3
                field = 0 and R1 field = 6 or 7.
                The use of the STCMH instruction becomes
                restricted when the M3 field value is 0
                and the R1 field is 6 or 7.
              @ ** ASMA701W LISTING: ASMAXTXP: Warning: DC/DS
                within transaction.
                A DC or DS assembler instruction has been
                detected during assembly within a constrained
                transaction.  This only occurs if the duplication
                factor on the instruction is non-zero.
              @ ** ASMA701W LISTING: ASMAXTXP: Code section ended
                inside transaction.
                An END statement has been encountered within a
                constrained transaction that has not been
                terminated with a TEND instruction.
  
      The end of the messages issued by ASMAXTXP terminates the
      appendix.
  
  --- END OF DOC UPDATES ---
  
  Additional keywords: PM49761 D/T2827
  

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  UK81557 UK81558 UK81559

Modules/Macros

• ASMAINFO ASMASTXP ASMAXTXP ASMA9Z   HMQ4160J
  

Fix information

• Fixed component name

  HLASM MVS, VM &

• Fixed component ID

  569623400

Applicable component levels

• R160 PSY UK81558

     UP12/09/08 P F209

• R360 PSY UK81557

     UP12/09/30 P 1209

• R689 PSY UK81559

     UP12/09/07 I 1000

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.