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Programming Interface Information:
This information is NOT intended to be used as Programming Interfaces of z/VM. |
SEGG
Control Block Contents
SEGG DSECT
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
Copyright IBM Corporation, 1990, 2005