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.
 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

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' SEGGPROT Entire segment is
                                        page protected
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'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

          
*** 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