Programming Interface Information: This information is NOT intended to be used as Programming Interfaces of z/VM.

#### SEGG

Prolog

Control Block Contents
SEGG DSECT

Storage Layout

Cross Reference (Contains links to field and bit definitions)

#### SEGG Prolog

     NAME       : HCPSEGG
     DESCRIPTION: z/Architecture Segment Table Entry
     DSECT      : SEGG
     Function   : There is one segment table entry for each
                  megabyte of address space.  A segment table is
                  made up of contiguous segment table entries.
                  The format of the segment table entry is
                  ARCHITECTED and cannot be changed in any way
                  which violates the architecture.
     Notes      : The segment table entry does not contain a page
                  table length.  All page tables represent a
                  full megabyte of virtual storage (256 page table entries).

#### SEGG Control Block Content

#### SEGG DSECT

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      SEGG           z/Architecture Segment Table
                                            Entry
    0000    0 Dbl-Word     8 SEGGENTR       Segment table entry
              00000008       SEGGLEN        *-SEGGENTR Length of one STE
    0008    8 Dbl-Word     8 SEGGNEXT (0)   Next segment table entry
    0000    0 Signed       4 SEG64W0        Word 0 of STE Bits 0-31 of PTO
    0004    4 Signed       4 SEG64W1        Word 1 of STE
    0004    4 Bitstring    1 * (2)          Bits 32-47 of PTO
    0006    6 Bitstring    1 SEGGSTA2       Bits 48-52 of PTO, plus the
                                            following three bits:
              .... ..1.      SEGGPROT       X'02' Entire segment is page
                                            protected
    0007    7 Bitstring    1 SEGGSTAT       Segment Table Entry Status
              ..1. ....      SEGGINVL       X'20' Segment Table Entry is
                                            invalid. Bits 0-52 of the segment
                                            table entry do not contain a
                                            valid Page-Table Origin.
              ...1 ....      SEGGCOMN       X'10' Common segment bit
              .... 11..      SEGGTTBT       X'0C' Table Type bits - must be
                                            B'00' 64-bit mask
                                            X'FFFFFFFFFFFFFF800'
              SEGGSTAT       SEGGPTMH       X'FFFFFFFF' Isolate page-table
                                            origin - High
              SEGGSTAT       SEGGPTML       X'FFFFF800' Isolate page-table
                                            origin - Low 64-bit mask
                                            X'FFFFFFFF80000000'
              SEGGSTAT       SEGG2GMH       X'FFFFFFFF' Isolate STE bits
                                            which must be zero in a <2G
                                            STE - High
              .... ....      SEGG2GML       X'80000000' Isolate STE bits
                                            which must be zero in a <2G
                                            STE - Low 64-bit mask
                                            X'0000000000000200' 32-bit high
                                            X'00000000'
              SEGGSTAT       SEGGPROM       X'00000200' Isolate segment page
                                            protect bit 64-bit mask
                                            X'0000000000000020' 32-bit high
                                            X'00000000'
              ..1. ....      SEGGINVM       X'00000020' Isolate invalid bit
                                            64-bit mask X'0000000000000010'
                                            32-bit high X'00000000'
              ...1 ....      SEGGCOMM       X'00000010' Isolate
                                            common-segment bit Notes : Since
                                            segment tables may be longer (up
                                            to 16K) than their boundary
                                            alignment (4K), a STO can not be
                                            computed from an STE address via
                                            a mask.
              ...1 .1..      SEGGSHFT       20 Bits to shift by to convert
                                            between segment number and
                                            virtual address.
              SEGGSTAT       SEGGPTUN       2048 Number of bytes in a
                                            page-table. All page tables are
                                            "full" page tables containing 256
                                            8 byte entries, representing 1M
                                            of virtual storage.
              .... 1.11      SEGGPTUS       11 Number of bits to shift left
                                            in order to multiply by SEGGPTUN.
              .... 1...      SEGGPXNUM      8 Number of bits in a PX
              1111 1111      SEGGPXRIT      X'FF' Mask to isolate a right-
                                            justified PX
              .... 1..1      SEGGPXDS       12-3 Bits to shift to convert
                                            between an isolated page index
                                            and the displacement into the
                                            page table of applicable 8 byte
                                            PTE.

#### SEGG Storage Layout

    *** SEGG - z/Architecture Segment Table Entry
    *
    *     +-------------------------------------------------------+
    *   0 |                       SEGGENTR                        |
    *     +-------------------------------------------------------+
    *
    *** SEGG - z/Architecture Segment Table Entry

    *** Overlay for SEGGENTR in SEGG
    *
    *     +---------------------------+---------------------------+
    *   0 |         SEG64W0           |         SEG64W1           |
    *     +---------------------------+---------------------------+
    *   8
    *
    *** Overlay for SEGGENTR in SEGG

    *** Overlay for SEG64W1 in SEGG
    *
    *                                 +-------------+------+------+
    *   0 ...                       4 |/////////////|:GSTA2|:GSTAT|
    *                                 +-------------+------+------+
    *   8
    *
    *** Overlay for SEG64W1 in SEGG

#### SEGG Cross Reference

    Symbol         Dspl Value
    -------------- ---- -----
    SEGGCOMM       0007 10
    SEGGCOMN       0007 10
    SEGGENTR       0000
    SEGGINVL       0007 20
    SEGGINVM       0007 20
    SEGGLEN        0000 00000008
    SEGGNEXT       0008
    SEGGPROM       0007 SEGGSTAT
    SEGGPROT       0006 02
    SEGGPTMH       0007 SEGGSTAT
    SEGGPTML       0007 SEGGSTAT
    SEGGPTUN       0007 SEGGSTAT
    SEGGPTUS       0007 0B
    SEGGPXDS       0007 09
    SEGGPXNUM      0007 08
    SEGGPXRIT      0007 FF
    SEGGSHFT       0007 14
    SEGGSTAT       0007
    SEGGSTA2       0006
    SEGGTTBT       0007 0C
    SEGG2GMH       0007 SEGGSTAT
    SEGG2GML       0007 00
    SEG64W0        0000
    SEG64W1        0004

This information is based on z/VM V5R2.0. Last updated on 12 Apr 2006 at 17:23:00 EDT.
Copyright IBM Corporation, 1990, 2005