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- or 64-bit
string descriptor pointing to this name string.
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 2 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.
When a section is mapped at creation time, the match control
field is ignored. 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.
prot
OpenVMS usage:file_protection
type: longword (unsigned)
access: read only
mechanism: by value
Protection to be applied to the global demand-zero section. The
mask contains four 4-bit fields. Bits are read from right to left
in each field.
Refer to the VSI OpenVMS System Services Reference Manual to view
the diagram depicting the mask.
Cleared bits indicate that read, write, execute, and delete
access, in that order, are granted to the particular category
of user. Only read, write, and execute access are meaningful
for section protection. Delete access bits are ignored. Read
access also grants execute access for those situations where
execute access applies. If zero is specified, read access and
write access are granted to all users.
length_64
OpenVMS usage:byte count
type: quadword (unsigned)
access: read only
mechanism: by value
Length, in bytes, of the global demand-zero section to be
created. The length_64 must be specified as a multiple of the
CPU-specific page size. A length of 0 cannot be specified.
NOTE
Creating a memory-resident global section with shared page
table does not imply that the global section must have an
even multiple of CPU-specific page table pages. The global
section might not fully use the last page table page.
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 page
file 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 to start mapping into the
process's virtual address space. The offset specified must be
a multiple of a CPU-specific page size.
If a shared page table region is specified by the region_id_
64 argument, section_offset_64 must be an even multiple of
the larger of the number of bytes that can be mapped by a CPU-
specific page. For Integrity server systems, the alignment of
section offsets must also be an integer multiple of the page size
used to map VA space at this offset.
VSI recommends that you avoid any partial mapping of memory-
resident sections when you use shared page tables on Integrity
server systems. If you cannot avoid this, set bit 4 in the system
parameter MMG_CTLFLAGS to limit the effective page size to the
number of bytes that can be mapped by a page.
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 access mode is also the read access mode
and the write access mode. The acmode argument is a longword
containing the access mode.
If the memory-resident global section is created with shared
page tables, this is the access mode that is stored in the owner,
read, and write fields of the corresponding shared page table
entries (PTEs).
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. The calling process can delete pages only if those pages
are owned by an access mode equal to or less privileged than the
access mode of the calling process.
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 the type of the global section to be created
as well as its characteristics. 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
$CRMPSC_GDZRO_64 service:
Flag Description
SEC$M_DZRO Pages are demand-zero pages. By default, this flag
is always present in this service and cannot be
disabled.
SEC$M_EXPREG Pages are mapped into the first available space at
the current end of the specified region.
If the /ALLOCATE qualifier was specified when the
global section was registered in the Reserved
Memory Registry, virtually aligned addresses
after the first available space are chosen for
the mapping.
SEC$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_PERM Global section is permanent.
SEC$M_RAD_ When set, the argument rad_mask is used as a mask
HINT of RADs from which to allocate memory. See the rad_
mask argument description for more information.
SEC$M_READ_ Create shared table pages for the section that
ONLY_SHPT allow read access only.
SEC$M_SHMGS Create a shared-memory global section.
SEC$M_SYSGBL Pages form a system global section. By default,
pages form a group global section.
SEC$M_MRES Pages form a memory-resident section. By default,
this page is always present in this service and
cannot be disabled.
SEC$M_WRT Pages form a read/write section. By default, this
flag is always present in this service and cannot
be disabled.
All other bits in the flags argument are reserved for future
use by VSI and should be specified as 0. The condition value
SS$_IVSECFLG is returned if any undefined bits are set or if
an invalid combination of flags is set.
return_va_64
OpenVMS usage:address
type: quadword address
access: write only
mechanism: by 32- or 64-bit reference
The lowest process virtual address into which the global demand-
zero section was mapped. The return_va_64 argument is the 32- or
64-bit virtual address of a naturally aligned quadword into which
the service returns the virtual address.
If a shared page table region is specified by the region_id_64
argument and the SEC$M_EXPREG flag is set, the returned virtual
address is aligned to a CPU-specific page table page boundary.
return_length_64
OpenVMS usage:byte count
type: quadword (unsigned)
access: write only
mechanism: by 32- or 64-bit reference
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.
start_va_64
OpenVMS usage:address
type: quadword address
access: read only
mechanism: by value
The starting virtual address to map the memory-resident 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$_IVSECFLG is returned.
If SEC$M_EXPREG is clear, start_va_64 is nonzero, and a shared
page table region is specified, the specified starting address
must be aligned to a natural page table page boundary; otherwise,
the condition value SS$_VA_NOTPAGALGN is returned.
If the /ALLOCATE qualifier was specified when the memory-resident
global section was registered in the Reserved Memory Registry
and start_va_64 is aligned to a multiple of CPU-specific pages
appropriate for taking advantage of granularity hints then
granularity hints are used to map to the global section:
o On Alpha systems, granularity hints mean multiples of pages,
regardless of page size. The multiples 8, 64, and 512 pages
are architected.
o On Integrity server systems, OpenVMS initially supports page
sizes of 64KB, 256KB, and 4MB instead of granularity hints.
Additional pages sizes will be supported in the future.
If the flag VA$M_SHARED_PTS is set and this argument is
specified, the specified starting address must be aligned to
the larger of a natural page table boundary or to the largest
possible page size used to map the section. If the alignment is
less than a page table boundary, the $CREATE_REGION_64 service
returns an error. If the alignment is less than the largest page
size used in the section, an error might be returned when you
attempt to map the section.
If you do not specify a starting address, OpenVMS automatically
ensures correct alignment.
map_length_64
OpenVMS usage:byte count
type: quadword (unsigned)
access: read only
mechanism: by value
Length of the memory-resident global section to be mapped. The
length specified must be a multiple of CPU-specific pages. If
this argument is not specified or is specified as zero, the
global file section is mapped up to and including the last page
in that section.
If a shared page table region is specified by the region_id_64
argument, map_length_64 must be an even multiple of the number
of bytes that can be mapped by a CPU-specific page table page or
must include the last page within the global section.
reserved_length_64
OpenVMS usage:byte count
type: quadword (unsigned)
access: write only
mechanism: 32- or 64-bit reference
Length, in bytes, of the global section as currently registered
in the Reserved Memory Registry. The reserved_length_64 argument
is the 32- or 64-bit virtual address of a naturally aligned
quadword into which the service returns the reserved length.
If reserved_length_64 is not specified or is specified as 0, no
reserved length is returned to the caller.
If the memory-resident global section is not registered,
reserved_length_64 is written with the value 0.
rad_mask
OpenVMS usage:mask_quadword
type: quadword (unsigned)
access: read only
mechanism: by value
Use the rad_mask argument to specify from which RADs to allocate
memory. Currently only one bit may be set. The specified RAD
must contain memory. This argument is only a hint. Memory may be
obtained from other RADs if no free memory is available at the
time of allocation.
The rad_mask argument is considered only if the SEC$M_RAD_HINT
flag is specified. Otherwise, this argument is ignored.
On a system that does not support resource affinity domains
(RADs), specifying 1 for the rad_mask argument is allowed.
RAD is supported on AlphaServer GS series systems and starting
from OpenVMS Version 8.4, support is extended to NUMA capable
Integrity servers.