PM76008: IDF: STMTSTEP THROUGH LRL INSTRUCTION CORRUPTS REGISTER DISPLAY

A fix is available

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APAR status

  • Closed as program error.

Error description

  • IDF: STMTSTEP through LRL instruction corrupts register display
    
    .
    Problem description
    Hi... LRL is another instruction that doesn't work under
    STMTSTEP
    through IDF. It corrupts the target register. Then, because IDF
    uses
    the displayed values in the registers, the execution that
    follows the
    LRL is incorrect. Here's some sample code to illustrate the
    point:
    
             TITLE 'DEMO OF IDF BUG'
    MYPROG   CSECT
    *
             STM   14,12,12(13)
             BASR  11,0
             AHI   11,-6
             USING MYPROG,11
    *
    * TO REPRODUCE THIS PROBLEM:
    *
    * ISSUE THE REGS COMMAND TO DISPLAY THE REGISTERS.
    * STMTSTEP FROM THE LRL TO THE NOPR. R3 DISPLAYS
    * INCORRECTLY AS X'0A610001', INSTEAD OF X'00000001'.
    * (X'0A61' IS SVC 97. NOT A COINCIDENCE, I ASSUME!)
    * ADDITIONALLY, THE LR INSTRUCTION CAUSES R2 TO
    * CONTAIN THE WRONG VALUE (BECAUSE R3 CONTAINS THE
    * WRONG VALUE).
    *
    * HOWEVER, IF YOU SET A *BREAKPOINT* ON THE NOPR
    * INSTRUCTION AND THEN ISSUE A RUN COMMAND (INSTEAD
    * OF DOING A STMTSTEP THROUGH THE LRL INSTRUCTION),
    * THEN BOTH R3 AND R2 ARE CORRECT.
    *
             LRL   3,=F'1'
             LR    2,3
    *
             NOPR  0
    *
             LM    14,12,12(13)
             SR    15,15
             BR    14
    *
    FULLWORD DC    F'1'
    *
             END
    

Local fix

  • None at this time...
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED: Users of ASMIDF from High Level Assembler    *
    *                 Toolkit feature for z/OS, z/VM and z/VSE     *
    ****************************************************************
    * PROBLEM DESCRIPTION: ASMIDF processing of LRL and other      *
    *                      non-branch instructions with relative   *
    *                      long operands is incorrect in step      *
    *                      mode, because the referenced data is    *
    *                      overlaid with a breakpoint.             *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    ASMIDF assumed for historical reasons that a relative operand
    was always a branch target, so for execution in step mode it
    always set a breakpoint at the operand address.  The code
    was then enhanced for z/Architecture to recognize that LARL
    and EXRL were not branches, but many additional non-branch
    relative instructions were added later to z/Architecture, such
    as LRL.  ASMIDF incorrectly treated these as possible branches
    as well, so it set a breakpoint at the operand address, which
    overwrote the data to be referenced by the instruction.  Before
    checking operands, ASMIDF should check whether the instruction
    is a branch, as there is no need to set additional breakpoints
    for other types of instruction.
    

Problem conclusion

  • ASMIDF now checks the instruction type flags to determine
    whether the instruction is a branch, so that non-branch relative
    long instructions will function correctly in step mode.  This
    includes the following instructions: CGFRL, CGHRL, CGRL, CHRL,
    CLGFRL, CLHHRL, CLGRL, CLHRL, CLRL, CRL, LGFRL, LGHRL, LGRL,
    LHRL, LLGFRL, LLGHRL, LLHRL, LRL, PFDRL, STGRL, STHRL, STRL.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PM76008

  • Reported component name

    HLASM TOOLKIT

  • Reported component ID

    569623401

  • Reported release

    16A

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-10-26

  • Closed date

    2012-12-14

  • Last modified date

    2013-04-23

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

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

    UK90334 UK90335 UK90336

Modules/Macros

  • ASMMSTRT ASMMUTL6 ASMMUTL7
    

Fix information

  • Fixed component name

    HLASM TOOLKIT

  • Fixed component ID

    569623401

Applicable component levels

  • R16A PSY UK90334

       UP12/12/18 P F212

  • R36A PSY UK90335

       UP12/12/17 P 1212

  • R6IM PSY UK90336

       UP12/12/17 P E512

Fix is available

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Document information


More support for:

z/OS family

Software version:

16A

Operating system(s):

z/OS

Reference #:

PM76008

Modified date:

2013-04-23

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