Copyright Digital Equipment Corp. All rights reserved.
Arguments
gs_name_64
OpenVMS usage:section_name
type: character-coded text string
access: read only
mechanism: by 32- or 64-bit descriptor-fixed-length string
descriptor
Name of the global section. The gs_name_64 argument is the 32-
or 64-bit virtual address of a naturally aligned 32-bit or 64-bit
string descriptor pointing to this name string.
You can specify any name from 1 to 43 characters. All processes
mapping to the same global section must specify the same name.
Note that the name is case sensitive.
Use of characters valid in logical names is strongly encouraged.
Valid values include alphanumeric characters, the dollar sign
($), and the underscore (_). If the name string begins with an
underscore (_), the underscore is stripped and the resultant
string is considered to be the actual name. Use of the colon (:)
is not permitted.
Names are first subject to a logical name translation, after
the application of the prefix GBL$ to the name. If the result
translates, it is used as the name of the section. If the
resulting name does not translate, the name specified by the
caller is used as the name of the section.
Additional information on logical name translations and
on section name processing is available in the VSI OpenVMS
Programming Concepts Manual.
ident_64
OpenVMS usage:section_id
type: quadword (unsigned)
access: read only
mechanism: by 32- or 64-bit reference
Identification value specifying the version number of a global
section. The ident_64 argument is a quadword containing three
fields. The ident_64 argument is the 32- or 64-bit virtual
address of a naturally aligned quadword that contains the
identification value.
The first longword specifies the matching criteria in its low-
order two bits.
The valid values, symbolic names by which they can be specified,
and their meanings are as follows:
Symbolic
Value Name Match Criteria
0 SEC$K_MATALL Match all versions of the section.
1 SEC$K_MATEQU Match only if major and minor
identifications match.
2 SEC$K_MATLEQ Match if the major identifications are
equal and the minor identification of the
mapper is less than or equal to the minor
identification of the global section.
If you specify the ident_64 argument as 0, the version number and
match control fields default to 0.
The version number is in the second longword. The version number
contains two fields: a minor identification in the low-order 24
bits and a major identification in the high-order 8 bits. You
can assign values for these fields by installation convention to
differentiate versions of global sections. If no version number
is specified when a section is created, processes that specify a
version number when mapping cannot access the global section.
region_id_64
OpenVMS usage:region identifier
type: quadword (unsigned)
access: read only
mechanism: by 32- or 64-bit reference
The region ID associated with the region to map the global
section. The file VADEF.H in SYS$STARLET_C.TLB and the $VADEF
macro in STARLET.MLB define a symbolic name for each of the three
default regions in P0, P1, and P2 space.
The following region IDs are defined:
Symbol Region
VA$C_P0 Program region
VA$C_P1 Control region
VA$C_P2 64-bit program region
Other region IDs, as returned by the $CREATE_REGION_64 service,
can be specified.
section_offset_64
OpenVMS usage:byte offset
type: quadword (unsigned)
access: read only
mechanism: by value
Offset into the global section at which to start mapping into the
process's virtual address space.
If a map to a global disk file section is being requested, the
section_offset_64 argument specifies an even multiple of disk
blocks. If a map to a global page file or demand-zero section is
being requested, the section_offset_64 argument specifies an even
multiple of CPU-specific pages. If zero is specified, the global
section is mapped beginning with the first page of the section.
If the region_id_64 argument specifies a shared page table
region, section_offset_64 must be an even multiple of pages
mapped by a page table page.
length_64
OpenVMS usage:byte count
type: quadword (unsigned)
access: read only
mechanism: by value
Length, in bytes, of the desired mapping of the global disk file
section.
If a map to a global section is being requested, the length_64
argument must specify an even multiple of disk blocks. If a map
to a global page file or demand-zero section is being requested,
the length_64 argument must specify an even multiple of CPU-
specific pages. If zero is specified, the size of the disk file
is used.
If a shared page-table region is specified by the region_id_64
argument, length_64 must be an even multiple of the number of
bytes that can be mapped by a CPU-specific page-table page or
must include the last page within the memory-resident global
section.
acmode
OpenVMS usage:access_mode
type: longword (unsigned)
access: read only
mechanism: by value
Access mode that is to be the owner of the pages created during
the mapping. This is also the read access mode and, if the SEC$M_
WRT flag is specified, the write access mode. The acmode argument
is a longword containing the access mode.
The $PSLDEF macro in STARLET.MLB and the file PSLDEF.H in
SYS$STARLET_C.TLB define the following symbols and their values
for the four access modes:
Value Symbolic Name Access Mode
0 PSL$C_KERNEL Kernel
1 PSL$C_EXEC Executive
2 PSL$C_SUPER Supervisor
3 PSL$C_USER User
The most privileged access mode used is the access mode of the
caller. Address space cannot be created within a region that has
a create mode associated with it that is more privileged than
the caller's mode. The condition value SS$_IVACMODE is returned
if the caller is less privileged than the create mode for the
region.
flags
OpenVMS usage:mask_longword
type: longword (unsigned)
access: read only
mechanism: by value
Flag mask specifying options for the operation. The flags
argument is a longword bit vector in which each bit corresponds
to a flag. The $SECDEF macro and the SECDEF.H file define a
symbolic name for each flag. You construct the flags argument
by performing a logical OR operation on the symbol names for all
desired flags.
The following table describes each flag that is valid for the
$MGBLSC_64 service:
Flag Description
SEC$M_EXPREG Pages are mapped into the first available space at
the current end of the specified region.
If /ALLOCATE was specified when the memory-resident
global section was registered in the Reserved
Memory Registry, virtually aligned addresses
after the first available space are chosen for
the mapping.
It the region_id_64 argument specifies a shared
page-table region, the first available space is
round up to the beginning of the next CPU-specific
page-table page.
SEC$M_GBL Pages form a global section. By default, this flag
is always present in this service and cannot be
disabled.
SEC$M_NO_ Pages cannot overmap existing address space.
OVERMAP
SEC$M_SHMGS On OpenVMS Galaxy systems, create a shared-memory
global section.
SEC$M_SYSGBL The global section map is a system global section.
By default, the section is a group global section.
SEC$M_WRT Map the section with read/write access.
All other bits in the flags argument are reserved for future
use by VSI and should be specified as 0. The condition value
SS$_IVSECFLG is returned if any undefined bits are set or if
an attempt is made to use the SEC$M_PAGFIL flag, which applies
only to the creation of a page-file backed section.
return_va_64
OpenVMS usage:address
type: quadword address
access: write only
mechanism: by 32- or 64-bit reference
The process virtual address into which the global disk or page
file section was mapped. The return_va_64 argument is the 32- or
64-bit virtual address of a naturally aligned quadword into which
the service returns the virtual address.
Upon successful completion of this service, if the
section_offset_64 argument was specified, the virtual address
returned in the return_va_64 argument reflects the offset into
the global section mapped such that the virtual address returned
cannot be aligned on a CPU-specific page boundary. The virtual
address returned will always be on an even virtual disk block
boundary.
return_length_64
OpenVMS usage:byte count
type: quadword (unsigned)
access: write only
mechanism: by 32- or 64-bit reference
The length of the usable virtual address range mapped. The
return_length_64 argument is the 32- or 64-bit virtual address
of a naturally aligned quadword into which the service returns
the length of the virtual address range mapped in bytes.
Upon successful completion of this service, the value in the
return_length_64 argument might differ from the total amount
of virtual address space mapped. The value in the return_va_64
argument plus the value in the return_length_64 argument
indicates the address of the first byte beyond the end of the
mapping of the global disk file section.
If the value in the section_offset_64 argument plus the value in
the length_64 argument did not specify to map the entire global
section, this byte can be located at an even virtual disk block
boundary within the last page of the mapping.
If the section being mapped does not completely fill the last
page used to represent the global disk file section, this byte
can be mapped into your address space; however, it is not backed
up by the disk file.
start_va_64
OpenVMS usage:address
type: quadword address
access: read only
mechanism: by value
The starting virtual address to which to map the global section.
The specified virtual address must be a CPU-specific page-aligned
address. If the flag SEC$M_EXPREG is specified, the start_va_64
argument must not be specified or must be specified as 0. If
SEC$M_EXPREG is set and the start_va_64 argument is nonzero, the
condition value SS$_IVSECFLG is returned.
If the region_id_64 argument specifies a shared page-table
region, start_va_64 must be aligned to a CPU-specific page-table
page boundary.