On Alpha and Integrity server systems, creates a permanent,
memory-resident, global demand-zero section to which processes
can map. Shared page table sections can also be created.
This service accepts 64-bit addresses.
Format
SYS$CREATE_GDZRO gs_name_64 ,ident_64 ,prot ,length_64 ,acmode
,flags [,reserved_length_64] [,rad_mask]
C Prototype
int sys$create_gdzro (void *gs_name_64, struct _secid
*ident_64, unsigned int prot, unsigned
__int64 length_64, unsigned int acmode,
unsigned int flags,...);
1 – 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 the 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. 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.
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.
To view the diagram depicting the mask, see the VSI OpenVMS System
Services Reference Manual.
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 0 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 argument 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
tables does not imply that the global section must have
a length that is an even multiple of CPU-specific page
table pages. The global section might not fully use the
last shared page table 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. 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
flags
OpenVMS usage:mask_longword
type: longword (unsigned)
access: read only
mechanism: by value
Flag mask specifying the type of 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 the flags that are valid for the
$CREATE_GDZRO service:
Flag Description
SEC$M_DZRO Pages are demand-zero pages. By default, this flag
is always present in this service and cannot be
disabled.
SEC$M_GBL Pages form a global section. By default, this flag
is always present in this service and cannot be
disabled.
SEC$M_MRES Pages form a memory-resident section. By default,
this flag is always present in this service and
cannot be disabled.
SEC$M_PERM Global section is permanent. By default, this flag
is always present in this service and cannot be
disabled.
SEC$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_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$_IVSECFLG is returned if any undefined bits are set.
reserved_length_64
OpenVMS usage:byte count
type: quadword (unsigned)
access: write only
mechanism: 32- or 64-bit reference
Length, in bytes, of the global section as currently registered
in the Reserved Memory Registry. The reserved_length_64 argument
is the 32- or 64-bit virtual address of a naturally aligned
quadword into which the service returns the reserved length.
If reserved_length_64 is not specified or is specified as 0, no
reserved length is returned to the caller.
If the memory-resident global section is not registered,
reserved_length_64 is written with the value 0.
rad_mask
OpenVMS usage:mask_quadword
type: quadword (unsigned)
access: read only
mechanism: by value
Use the rad_mask argument to specify from which RADs to allocate
memory. Currently only one bit may be set. The specified RAD
must contain memory. This argument is only a hint. Memory may be
obtained from other RADs if no free memory is available at the
time of allocation.
The rad_mask argument is considered only if the SEC$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.