SEGG | Back to Index page

| Prolog Control Block Contents SEGG DSECT Storage Layout Cross Reference (Contains links to field and bit definitions) |
Programming Interface Information: This information is NOT intended to be used as Programming Interfaces of z/VM.

SEGG Prolog | Top of page

     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.
     RELOCATION CONSIDERATIONS : None
     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 | Top of page

     SEGG DSECT
    Top of page

    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 SEG64W10       Bits 32-39 of PTO or SFAA
    0005    5 Bitstring    1 SEG64W11       Bits 40-47 of PTO or Bits 40-43
                                            of SFAA, plus bit 44-46 reserved
                                            bit 47 - ACCF-validity control
    0006    6 Bitstring    1 SEGGSTA2       Bits 48-52 of PTO, plus the
                                            following bits: non-EDAT: bits
                                            48-52 of PTO, plus bit 53 -
                                            ignored bit 54 - Page protection
                                            bit bit 55 - ignored EDAT: bit
                                            48-51 Access-Control bits bit 52
                                            - Fetch Protection bit 53 - 0,
                                            use non-EDAT fmt 1, use EDAT
                                            format bit 54 - DAT protection
                                            bit bit 55 - IEP protection bit
              1111 ....      SEGGACC        X'F0' SEGGACC Access-Control bits
              .... 1...      SEGGFETP       X'08' SEGGFETP Fetch-Protection
                                            bit
              .... .1..      SEGGFORM       X'04' SEGGFORM Format Control bit
              .... ..1.      SEGGPROT       X'02' SEGGPROT Entire segment is
                                            page protected
              .... ...1      SEGGIEP        X'01' SEGGIEP Entire segment is
                                            IEP protected (When FC=1)
    0007    7 Bitstring    1 SEGGSTAT       Segment Table Entry Status
              ..1. ....      SEGGINVL       X'20' SEGGINVL 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' SEGGCOMN Common segment bit
              .... 11..      SEGGTTBT       X'0C' SEGGTTBT Table Type bits -
                                            must be B'00' 64-bit mask
                                            X'FFFFFFFFFFFFFF800'
              SEGGSTAT       SEGGPTMH       X'FFFFFFFF' SEGGPTMH Isolate
                                            page-table origin - High
              SEGGSTAT       SEGGPTML       X'FFFFF800' SEGGPTML Isolate
                                            page-table origin - Low 64-bit
                                            mask X'FFFFFFFF80000000'
              SEGGSTAT       SEGG2GMH       X'FFFFFFFF' SEGG2GMH Isolate STE
                                            bits which must be zero in a
                                            <2G STE - High
              .... ....      SEGG2GML       X'80000000' SEGG2GML 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' SEGGPROM Isolate
                                            segment page protect bit 64-bit
                                            mask X'0000000000000100' 32-bit
                                            high X'00000000'
              SEGGSTAT       SEGGIEPM       X'00000100' SEGGIEPM Isolate
                                            segment IEP protect bit (when
                                            FC=1) 64-bit mask
                                            X'0000000000000020' 32-bit high
                                            X'00000000'
              ..1. ....      SEGGINVM       X'00000020' SEGGINVM Isolate
                                            invalid bit 64-bit mask
                                            X'0000000000000010' 32-bit high
                                            X'00000000'
              ...1 ....      SEGGCOMM       X'00000010' SEGGCOMM 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 SEGGSHFT Bits to shift by to
                                            convert between segment number
                                            and virtual address.
              SEGGSTAT       SEGGPTUN       2048 SEGGPTUN 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 SEGGPTUS Number of bits to
                                            shift left in order to multiply
                                            by SEGGPTUN.
              .... 1...      SEGGPXNUM      8 SEGGPXNUM Number of bits in a
                                            PX
              1111 1111      SEGGPXRIT      X'FF' SEGGPXRIT Mask to isolate a
                                            right- justified PX
              .... 1..1      SEGGPXDS       12-3 SEGGPXDS 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 | Top of page

    *** 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 |:64W10|:64W11|:GSTA2|:GSTAT|
    *                                 +------+------+------+------+
    *   8
    *
    *** Overlay for SEG64W1 in SEGG

SEGG Cross Reference | Top of page

    Symbol         Dspl Value
    -------------- ---- -----
    SEGGACC        0006 F0
    SEGGCOMM       0007 10
    SEGGCOMN       0007 10
    SEGGENTR       0000
    SEGGFETP       0006 08
    SEGGFORM       0006 04
    SEGGIEP        0006 01
    SEGGIEPM       0007 SEGGSTAT
    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
    SEG64W10       0004
    SEG64W11       0005

This information is based on z/VM 7.2.0 Last updated on 24 Jun 2020 at 09:30:25 EDT.
Copyright IBM Corporation, 1990, 2020