//*
//*++ USERMOD(TMVT819)     /* REWORK(20100715) */             .
//*++ VER (S218)
//*   FMID(EBB2218)
//*   PRE  (US04999,US06401,US06958)
//* /*
//*   PROBLEM DESCRIPTION(S):
//*     TMVT819 -
//*       Unable to log on to TSO if time sharing region extends
//*       above 8 MB (X'800000').  Logon attempts fail with
//*       msgIKJ601I, msgIEA701I, msgIEA702I, abend305-1,
//*       abend30A-3, abend806-1 and other errors.  After logon
//*       failure, the TSO time sharing controller may be hung
//*       and will not shut down.
//*
//*       TSO region control task quiesce routine IKJEAR02 saves
//*       time sharing region storage allocation address and
//*       length information for a user being swapped out in the
//*       user storage map (UMSM).  Each 24-bit address and length
//*       is divided by 256 (shifted right eight bits).  The
//*       resulting 16-bit value is stored into a two-byte entry
//*       in the UMSM; for each allocation address/length pair,
//*       there is a pair of two-byte UMSM entries.
//*
//*       When a TSO user is swapped back in, the region control
//*       task restore routine IKJEAR03 rebuilds FBQEs from free
//*       space information saved in the UMSM.  Each two-byte UMSM
//*       entry is retrieved by IKJEAR03 using a load halfword
//*       (LH) instruction.  This is not a problem as long as
//*       addresses are less than X'800000'.  Once an address is
//*       X'800000' or greater, however, the two-byte value saved
//*       in the UMSM becomes X'8000' or greater, which looks to
//*       LH like a negative number.  As a result, the presumed
//*       "sign" bit is propagated leftward, so a value that
//*       should have been X'00008000' becomes X'FFFF8000'.  This
//*       value is shifted left eight bits to restore the original
//*       24 bit address, becoming X'FF800000'.  Address
//*       references using the reconstructed value produce the
//*       expected result, but arithmetic operations that assume
//*       X'00' in the high-order byte generate incorrect output.
//*       Reconstructed main storage supervision control blocks
//*       built with arithmetic using the defective values are
//*       invalid, leading to the abend305 and other main storage
//*       supervision errors.
//*
//*       When a time sharing region is started, the region
//*       controller attaches a copy of the logon scheduler and
//*       swaps out the the region as a logon image, which is used
//*       to initialize the region when a new user attempts to log
//*       on.  Invalid MSS control blocks built during restore of
//*       this logon image result in the abend305 during logon.
//*
//*       In addition to IKJEAR03, IKJEAS02 (swap mainline) and
//*       IKJEAT07 (out of core abnormal termination) also use
//*       LH to retrieve UMSM fields without zeroing the high-order
//*       byte of the resulting 24-bit value.
//*
//*       IKJEAR03 (restore), IKJEAS02 (swap mainline) and
//*       IKJEAT07 (out of core abnormal termination) are changed
//*       to ensure that spurrious sign propagation resulting from
//*       retrieving unsigned two-byte UMSM fields using LH is
//*       prevented by zeroing the high-order bits of resulting
//*       values.
//*
//*   COMPONENT:  360S-CI555-EBB2218
//*
//*   APARS FIXED: TMVT819
//*
//*   SPECIAL CONDITIONS:
//*     ACTION:  The TSO time sharing controller region must be
//*       stopped and restarted after installation of this user
//*       modification.
//*
//*     DEPENDENCY:
//*       The OS/VS linkage editor HEWLF064 must be available
//*       to permit IKJEAR03, IKJEAS02 and IKJEAT07 to be expanded
//*       with a patch area.
//*
//*   COMMENTS:
//*     LAST CHANGE:  2010/07/15
//*
//*     THE FOLLOWING MODULES AND/OR MACROS ARE AFFECTED BY THIS USERMOD:
//*
//*     MODULES
//*       IKJEAR03
//*       IKJEAS02
//*       IKJEAT07
//*  */.
//*