Updated: 11 December 1998

OpenVMS System Services Reference Manual

Related Services

$CANEXH, $DCLEXH, $DELPRC, $EXIT, $FORCEX, $GETJPI, $GETJPIW, $HIBER, $PROCESS_SCAN, $RESUME, $SETPRI, $SETPRN, $SETPRV, $SETRWM, $SUSPND, $WAKE

Condition Values Returned

SS$_ACCVIO	The caller cannot read a specified input string or string descriptor, the privilege list, or the quota list; or the caller cannot write the process identification.
SS$_DUPLNAM	The specified process name duplicates one already specified within that group.
SS$_EXPRCLM	The creation of a detached process failed because the creating process already reached its limit for the creation of detached processes. This limit is established by the MAXDETACH quota in the user authorization file (UAF) of the creating process.
SS$_EXQUOTA	At least one of the following conditions is true: The process has exceeded its quota for the creation of subprocesses. A quota value specified for the creation of a subprocess exceeds the creating process's corresponding quota. The quota is deductible and the remaining quota for the creating process would be less than the minimum.
SS$_INCOMPAT	The remote node is running an incompatible version of the operating system, namely, one that does not support remote process creation.
SS$_INSFMEM	The system dynamic memory is insufficient for the requested operation.
SS$_INVARG	An invalid argument was specified.
SS$_IVLOGNAM	At least one of the following two conditions is true: The specified process name has a length of 0 or has more than 15 characters. The specified image name, input name, output name, or error name has more than 255 characters.
SS$_IVQUOTAL	The quota list is not in the proper format.
SS$_IVSTSFLG	A reserved status flag was specified.
SS$_NODELEAVE	The specified node was removed from the OpenVMS Cluster during the $CREPRC service's execution.
SS$_NOPRIV	The caller violated one of the privilege restrictions.
SS$_NORMAL	The service completed successfully.
SS$_NOSLOT	No process control block is available; in other words, the maximum number of processes that can exist concurrently in the system has been reached.
SS$_NOSUCHNODE	The specified node is not currently a member of the cluster.
SS$_REMRSRC	The remote node has insufficient resources to respond to the request. (Bring this error to the attention of your system manager.)
SS$_UNREACHABLE	The remote node is a member of the cluster but is not accepting requests. This is normal for a brief period early in the system boot process.

Adds a range of demand-zero allocation pages (on VAX systems) or pagelets (on Alpha systems) to a process's virtual address space for the execution of the current image.

Format

SYS$CRETVA inadr ,[retadr] ,[acmode]

C Prototype

int sys$cretva (struct _va_range *inadr, struct _va_range *retadr, unsigned int acmode);

Arguments

inadr

OpenVMS usage:	address_range
type:	longword (unsigned)
access:	read only
mechanism:	by reference

Address of a 2-longword array containing the starting and ending virtual addresses of the pages to be created. If the starting and ending virtual addresses are the same, a single page is created. The addresses are adjusted up or down to fall on CPU-specific page boundaries. Only the virtual page number portion of the virtual address is used; the low order byte-within-page bits are ignored.

retadr

OpenVMS usage:	address_range
type:	longword (unsigned)
access:	write only
mechanism:	by reference--array reference or descriptor

Address of a 2-longword array to receive the starting and ending virtual addresses of the pages created.

On Alpha systems, the retadr argument should be checked by programs for actual allocation. Because the Alpha architecture defines more than one page size, more space might be created than was specified in the retadr argument.

acmode

OpenVMS usage:	access_mode
type:	longword (unsigned)
access:	read only
mechanism:	by value

Access mode and protection for the new pages. The acmode argument is a longword containing the access mode. The $PSLDEF macro defines the following symbols for the four access modes.

Symbol	Access Mode
PSL$C_KERNEL	Kernel
PSL$C_EXEC	Executive
PSL$C_SUPER	Supervisor
PSL$C_USER	User

The most privileged access mode used is the access mode of the caller. The protection of the pages is read/write for the resultant access mode and those more privileged.

Description

The Create Virtual Address Space service adds a range of demand-zero allocation pages to a process's virtual address space for the execution of the current image.

Pages are created starting at the address contained in the first longword of the location addressed by the inadr argument and ending with the second longword. The ending address can be lower than the starting address. The retadr argument indicates the byte addresses of the pages created.

If an error occurs while pages are being created, the retadr argument, if specified, indicates the pages that were successfully created before the error occurred. If no pages were created, both longwords of the retadr argument contain the value --1.

If $CRETVA creates pages that already exist, the service deletes those pages if they are not owned by a more privileged access mode than that of the caller. Any such deleted pages are reinitialized as demand-zero pages. For this reason, it is important to use the retadr argument to capture the address range actually created. Because the Alpha architecture has a larger page size than the VAX architecture, more space is potentially affected on Alpha systems.

Required Access or Privileges

None

Required Quota

The paging file quota (PGFLQUOTA) of the process must be sufficient to accommodate the increased size of the virtual address space.

Related Services

$ADJSTK, $ADJWSL, $CRMPSC, $DELTVA, $DGBLSC, $EXPREG, $LCKPAG, $LKWSET, $MGBLSC, $PURGWS, $SETPRT, $SETSTK, $SETSWM, $ULKPAG, $ULWSET, $UPDSEC, $UPDSECW

The Expand Program/Control Region ($EXPREG) service also adds pages to a process's virtual address space.

Note Do not use the $CRETVA system service in conjunction with other user-written procedures or Compaq-supplied procedures (including Run-Time Library procedures). This system service provides no means to communicate a change in virtual address space with other routines. Compaq recommends that you use either $EXPREG or the Run-Time Library procedure Allocate Virtual Memory (LIB$GET_VM) to get memory. You can find documentation on LIB$GET_VM in the OpenVMS RTL Library (LIB$) Manual. When using $DELTVA, you should take care to delete only pages that you have specifically created.

Condition Values Returned

SS$_NORMAL	The service completed successfully.
SS$_ACCVIO	The inadr argument cannot be read by the caller, or the retadr argument cannot be written by the caller.
SS$_EXQUOTA	The process has exceeded its paging file quota.
SS$_INSFWSL	The process's working set limit is not large enough to accommodate the increased size of the virtual address space.
SS$_NOPRIV	A page in the specified range is in the system address space.
SS$_NOSHPTS	A virtual address within a shared page table region was specified.
SS$_PAGOWNVIO	A page in the specified range already exists and cannot be deleted because it is owned by a more privileged access mode than that of the caller.
SS$_VA_IN_USE	The existing underlying page cannot be deleted because it is associated with a buffer object.
SS$_VASFULL	The process's virtual address space is full; no space is available in the page tables for the requested pages.

On Alpha systems, adds a range of demand-zero allocation pages to a process's virtual address space for the execution of the current image. The new pages are added at the virtual address specified by the caller.

This service accepts 64-bit addresses.

Format

SYS$CRETVA_64 region_id_64 ,start_va_64 ,length_64 ,acmode ,flags ,return_va_64 ,return_length_64

C Prototype

int sys$cretva_64 (struct _generic_64 *region_id_64, void *start_va_64, unsigned __int64 length_64, unsigned int acmode, unsigned int flags, void *(*(return_va_64)), unsigned __int64 *return_length_64);

Arguments

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 create the virtual address range. 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. Also, given a particular virtual address, the region ID for the region it is in can be obtained by calling the $GET_REGION_INFO system service specifying the VA$_REGSUM_BY_VA function.

start_va_64

OpenVMS usage:	address
type:	quadword address
access:	read only
mechanism:	by value

The starting address for the created virtual address range. The specified virtual address must be a CPU-specific page aligned address.

length_64

OpenVMS usage:	byte count
type:	quadword (unsigned)
access:	read only
mechanism:	by value

Length of the virtual address space to be created. The length specified must be a multiple of CPU-specific pages.

acmode

OpenVMS usage:	access_mode
type:	longword (unsigned)
access:	read only
mechanism:	by value

Access mode associated with the call to $CRETVA_64. The access mode determines the owner mode of the pages as well as the read and write protection on the pages. 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 $CRETVA_64 service uses whichever of the following access modes is least privileged:

• Access mode specified by the acmode argument
• Access mode of the caller

The protection of the pages is read/write for the resultant access mode and those more privileged.

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 controlling the characteristics of the demand-zero pages created. The flags argument is a longword bit vector in which each bit corresponds to a flag. The $VADEF macro and the VADEF.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 flag that is valid for the $CRETVA_64 service:

Flag	Description
VA$M_NO_OVERMAP	Pages cannot overmap existing address space. By default, pages can overmap existing address space.

All other bits in the flags argument are reserved for future use by Compaq and should be specified as 0. The condition value SS$_IVVAFLG is returned if any undefined bits are set.

return_va_64

OpenVMS usage:	address
type:	quadword (unsigned)
access:	write only
mechanism:	by 32- or 64-bit reference

The lowest process virtual address of the created virtual address range. 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.

return_length_64

OpenVMS usage:	byte count
type:	quadword (unsigned)
access:	write only
mechanism:	by 32- or 64-bit reference

The length of the virtual address range created. 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 in bytes.

Description

The Create Virtual Address Space service is a kernel mode service that can be called from any mode. The service adds a range of demand-zero allocation pages, starting at the virtual address specified by the start_va_64 argument. The pages are added to a process's virtual address space for the execution of the current image. Expansion occurs at the next free available address within the specified region if the range of addresses is beyond the next free available address.

The new pages, which were previously inaccessible to the process, are created as demand-zero pages.

The returned address is always the lowest virtual address in the range of pages created. The returned length is always an unsigned byte count indicating the length of the range of pages created.

Successful return status from $CRETVA means that the specified address space was created of the size specified in the length_64 argument.

If $CRETVA_64 creates pages that already exist, the service deletes those pages if they are not owned by a more privileged access mode than that of the caller. Any such deleted pages are reinitialized as demand-zero pages.

If the condition value SS$_ACCVIO is returned by this service, a value cannot be returned in the memory locations pointed to by the return_va_64 and return_length_64 arguments.

If an address within the specified address range is not within the bounds of the specified region, the condition value SS$_PAGNOTINREG is returned.

If a condition value other than SS$_ACCVIO is returned, the returned address and returned length indicate the pages that were successfully added before the error occurred. If no pages were added, the return_va_64 argument will contain the value --1, and a value cannot be returned in the memory location pointed to by the return_length_64 argument.

Required Privileges

None

Required Quota

The working set quota (WSQUOTA) of the process must be sufficient to accommodate the increased length of the process page table required by the increase in virtual address space.

The process's paging file quota (PGFLQUOTA) must be sufficient to accommodate the increased size of the virtual address space.

Related Services

$CREATE_BUFOBJ_64, $CREATE_REGION_64, $DELETE_REGION_64, $DELTVA_64, $EXPREG_64, $LCKPAG_64, $LKWSET_64, $PURGE_WS, $SETPRT_64, $ULKPAG_64, $ULWSET_64

Condition Values Returned

SS$_NORMAL	The service completed successfully.
SS$_ACCVIO	The return_va_64 or return_length_64 argument cannot be written by the caller.
SS$_EXPGFLQUOTA	The process has exceeded its paging file quota.
SS$_INSFWSL	The process's working set limit is not large enough to accommodate the increased virtual address space.
SS$_IVACMODE	The caller's mode is less privileged than the create mode associated with the region.
SS$_IVREGID	An invalid region ID was specified.
SS$_IVVAFLG	An invalid flag, a reserved flag, or an invalid combination of flags and arguments was specified.
SS$_LEN_NOTPAGMULT	The length_64 argument is not a multiple of CPU-specific pages.
SS$_NOSHPTS	The region ID of a shared page table region was specified.
SS$_PAGNOTINREG	A page in the specified range is not within the specified region.
SS$_PAGOWNVIO	A page in the specified range already exists and cannot be deleted because it is owned by a more privileged access mode than that of the caller.
SS$_REGISFULL	The specified virtual region is full.
SS$_VA_IN_USE	A page in the specified range is already mapped, and the VA$M_NO_OVERLAP flag was set, or the existing underlying page cannot be deleted because it is associated with a buffer object.
SS$_VA_NOTPAGALGN	The start_va_64 argument is not CPU-specific page aligned.

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