OpenVMS System Services Reference Manual

All other bits in the flags argument are reserved for future use by Digital 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.

SS$_VA_NOTPAGALGN The start_va_64 argument is not CPU-specific page aligned.

$CRMPSC

Allows a process to associate (map) a section of its address space with (1) a specified section of a file (a disk file section) or (2) specified physical addresses represented by page frame numbers (a page frame section). This service also allows the process to create either type of section and to specify that the section be available only to the creating process (private section) or to all processes that map to it (global section).

Format

SYS$CRMPSC [inadr] ,[retadr] ,[acmode] ,[flags] ,[gsdnam] ,[ident] ,[relpag] ,[chan] ,[pagcnt] ,[vbn] ,[prot] ,[pfc]

C Prototype

int sys$crmpsc (struct _va_range *inadr, struct _va_range *retadr, unsigned int acmode, unsigned int flags, void *gsdnam, unsigned int relpag, unsigned short int chan, unsigned int pagcnt, unsigned int vbn, unsigned int prot,unsigned int pfc);

ARGUMENTS

inadr

OpenVMS usage: address_range

type: longword (unsigned)

access: read only

mechanism: by reference

Starting and ending virtual addresses into which the section is to be mapped. The inadr argument is the address of a 2-longword array containing, in order, the starting and ending process virtual addresses. Only the virtual page number portion of each virtual address is used to specify which pages are to be mapped; the low-order byte-within-page bits are ignored for this purpose.
The interpretation of the inadr argument depends on the setting of SEC$M_EXPREG in the flags argument and on whether you are using an Alpha or a VAX system. The two system types are discussed separately in this section.
On Alpha systems, if you do not set the SEC$M_EXPREG flag, the inadr argument specifies the starting and ending virtual addresses of the region to be mapped. Addresses in system space are not allowed. The addresses must be aligned on CPU-specific pages; no rounding to CPU-specific pages occurs. The lower address of the inadr argument must be on a CPU-specific page boundary and the higher address of the inadr argument must be 1 less than a CPU-specific boundary, thus forming a range from lowest to highest address bytes. You can use the SYI$_PAGE_SIZE item code in the $GETSYI system service to set the inadr argument to the proper values.
If, on the other hand, you do set the SEC$M_EXPREG flag, indicating that the mapping should take place using the first available space in a particular region, the inadr argument is used only to indicate the desired region: the program region (P0) or the control region (P1).

Caution
Mapping into the P1 region is generally discouraged, but, if done, must be executed with extreme care. Since the user stack is mapped in P1, it is possible that references to the user stack might inadvertently read or write the pages mapped with $CRMPSC.

When the SEC$M_EXPREG flag is set, the second inadr longword is ignored, while bit 30 (the second most significant bit) of the first inadr longword is used to determine the region of choice. If the bit is clear, P0 is chosen; if the bit is set, P1 is chosen. On Alpha systems, bit 31 (the most significant bit) of the first inadr longword must be 0. To ensure compatibility between VAX and Alpha systems when you choose a region, Digital recommends that you specify, for the first inadr longword, any virtual address in the desired region.
In general, the inadr argument should be specified. However, it can be omitted to request a special feature: for permanent global sections, you can omit the inadr argument, or specify it as 0, to request that the section be created but not mapped. Such a request will be granted regardless of the setting of the SEC$M_EXPREG flag. However, to ensure compatibility between VAX and Alpha systems, Digital recommends that the SEC$M_EXPREG flag be clear when the inadr argument is omitted.
On VAX systems, if you do not set the SEC$M_EXPREG flag, the inadr argument specifies the starting and ending virtual addresses of the region to be mapped. Addresses in system space are not allowed. If the starting and ending virtual addresses are the same, a single page is mapped.

Note
If the SEC$M_EXPREG flag is not set, Digital recommends that the inadr argument always specify the entire virtual address range, from starting byte address to ending byte address. This ensures compatibility between VAX and Alpha systems.

If, on the other hand, you do set the SEC$M_EXPREG flag, indicating that the mapping should take place using the first available space in a particular region, the inadr argument is used only to indicate the desired region: the program region (P0) or the control region (P1).

Caution
Mapping into the P1 region is generally discouraged, but, if done, must be executed with extreme care. Since the user stack is mapped in P1, it is possible that references to the user stack might inadvertently read or write the pages mapped with $CRMPSC.

When the SEC$M_EXPREG flag is set, the second inadr longword is ignored, while bit 30 (the second most significant bit) of the first inadr longword is used to determine the region of choice. If the bit is clear, P0 is chosen; if the bit is set, P1 is chosen. On VAX systems, bit 31 (the most significant bit) of the first inadr longword is ignored. To ensure compatibility between VAX and Alpha systems when you choose a region, Digital recommends that you specify, for the first inadr longword, any virtual address in the desired region.
In general, the inadr argument should be specified. However, it can be omitted to request a special feature: for permanent global sections, you can omit the inadr argument, or specify it as 0, to request that the section be created but not mapped. You must also ensure that SEC$M_EXPREG is not set in the flags argument. Omitting the inadr argument with SEC$M_EXPREG set is interpreted by VAX systems as a request to map with no region preference. This latter combination of argument settings is strongly discouraged, as the chosen region is indeterminate. To ensure compatibility between VAX and Alpha systems, Digital recommends that the SEC$M_EXPREG flag be clear when the inadr argument is omitted.
retadr

OpenVMS usage: address_range

type: longword (unsigned)

access: write only

mechanism: by reference--array reference

Starting and ending process virtual addresses into which the section was actually mapped by $CRMPSC. The retadr argument is the address of a 2-longword array containing, in order, the starting and ending process virtual addresses.
On Alpha systems, the retadr argument returns starting and ending addresses of the usable range of addresses. This might differ from the total amount mapped. The retadr argument is required when the relpag argument is specified. If the section being mapped does not completely fill the last page used to map the section, the retadr argument indicates the highest address that actually maps the section. If the relpag argument is used to specify an offset into the section, the retadr argument reflects the offset.
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. 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.
flags

OpenVMS usage: mask_longword

type: longword (unsigned)

access: read only

mechanism: by value

Flag mask specifying the type of section to be created or mapped to, as well as its characteristics. The flags argument is a longword bit vector wherein each bit corresponds to a flag. The $SECDEF macro defines 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 and the default value that it supersedes.

Flag Description

SEC$M_GBL Pages form a global section. The default is private section.

SEC$M_CRF Pages are copy-on-reference. By default, pages are shared.

SEC$M_DZRO Pages are demand-zero pages. By default, they are not zeroed when copied. For page file sections, the default is demand zero.

SEC$M_EXPREG Pages are mapped into the first available space. By default, pages are mapped into the range specified by the inadr argument.
See the inadr argument description for a complete explanation of how to set the SEC$M_EXPREG flag.

SEC$M_WRT Pages form a read/write section. By default, pages form a read-only section. For page file sections, the default is writeable.

SEC$M_PERM Global section is permanent. By default, global sections are temporary.

SEC$M_PFNMAP Pages form a page frame section. By default, pages form a disk file section. Pages mapped by SEC$M_PFNMAP are not included in or charged against the process's working set; they are always valid. Do not lock these pages in the working set by using $LKWSET; this can result in a machine check if they are in I/O space.
++On Alpha systems, when the SEC$M_PFNMAP flag is set, the pagcnt and relpag arguments are interpreted in CPU-specific pages, not as pagelets.

SEC$M_SYSGBL Pages form a system global section. By default, pages form a group global section.

SEC$M_PAGFIL Pages form a global page file section. By default, pages form a disk file section. SEC$M_PAGFIL also implies SEC$M_WRT and SEC$M_DZRO.

SEC$M_EXECUTE Pages are mapped if the caller has execute access. This flag takes effect only (1) when specified from executive or kernel mode, (2) when the SEC$M_GBL flag is also specified, and (3) when SEC$M_WRT is not specified. By default $CRMPSC performs a read access check against the section.

SEC$M_NO_OVERMAP Pages cannot overmap existing address space. Note that, by default, pages can overmap existing address space.

++Alpha specific

gsdnam

OpenVMS usage: section_name

type: character-coded text string

access: read only

mechanism: by descriptor--fixed-length string descriptor

Name of the global section. The gsdnam argument is the address of a character string descriptor pointing to this name string.
For group global sections, the operating system interprets the UIC group as part of the global section name; thus, the names of global sections are unique to UIC groups.
ident

OpenVMS usage: section_id

type: quadword (unsigned)

access: read only

mechanism: by reference

Identification value specifying the version number of a global section and, for processes mapping to an existing global section, the criteria for matching the identification. The ident argument is the address of a quadword structure containing three fields.
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.
The first longword specifies, in its low-order two bits, the matching criteria. The valid values, symbolic names by which they can be specified, and their meanings are as follows.

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 do not specify the ident argument or specify it as 0 (the default), the version number and match control fields default to 0.
relpag

OpenVMS usage: longword_unsigned

type: longword (unsigned)

access: read only

mechanism: by value

Relative page number within the global section of the first page in the section to be mapped. The relpag argument is a longword containing this page number.
On Alpha systems, the relpag argument is interpreted as an index into the section file, measured in pagelets for a file-backed section or in CPU-specific pages for a PFN-mapped section.
On Alpha and VAX systems, you use this argument only for global sections. If you do not specify the relpag argument or specify it as 0 (the default), the global section is mapped beginning with the first virtual block in the file.
chan

OpenVMS usage: channel

type: word (unsigned)

access: read only

mechanism: by value

Number of the channel on which the file has been accessed. The chan argument is a word containing this number.
The file must have been accessed with the OpenVMS RMS macro $OPEN; the file options parameter (FOP) in the FAB must indicate a user file open (UFO keyword). The access mode at which the channel was opened must be equal to or less privileged than the access mode of the caller.
pagcnt

OpenVMS usage: longword_unsigned

type: longword (unsigned)

access: read only

mechanism: by value

Number of pages (on VAX systems) or pagelets (on Alpha systems) in the section. The pagcnt argument is a longword containing this number.
On Alpha systems, if the SEC$M_PFNMAP flag bit is set, the pagcnt argument is interpreted as CPU-specific pages, not as pagelets.
On Alpha and VAX systems, the specified page count is compared with the number of blocks in the section file; if they are different, the lower value is used. If you do not specify the page count or specify it as 0 (the default), the size of the section file is used. However, for physical page frame sections, this argument must not be 0.
vbn

OpenVMS usage: longword_unsigned

type: longword (unsigned)

access: read only

mechanism: by value

Virtual block number in the file that marks the beginning of the section. The vbn argument is a longword containing this number. If you do not specify the vbn argument or specify it as 0 (the default), the section is created beginning with the first virtual block in the file.
If you specified page frame number mapping (by setting the SEC$M_PFNMAP flag), the vbn argument specifies the CPU-specific page frame number where the section begins in memory.
Table SYS-6 shows which arguments are required and which are optional for three different uses of the $CRMPSC service.

Table SYS-6 Required and Optional Arguments for the$CRMPSC Service
Argument Create/Map
Global Section Map Global&185;
Section Create/Map
Private Section

inadr Optional² Required Required

retadr Optional Optional Optional

acmode Optional Optional Optional

flags

SEC$M_GBL Required Ignored Not used

SEC$M_CRF³ Optional Not used Optional

SEC$M_DZRO³ Optional Not used Optional

SEC$M_EXPREG Optional Optional Optional

SEC$M_PERM Optional² Not used Not used

SEC$M_PFNMAP Optional Not used Optional

SEC$M_SYSGBL Optional Optional Not used

SEC$M_WRT Optional Optional Optional

SEC$M_PAGFIL Optional Not used Not used

gsdnam Required Required Not used

ident Optional Optional Not used

relpag³ Optional Optional Not used

chan³ Required Required

pagcnt Required Required

vbn³ Optional Optional

prot Optional Not used

pfc³ Optional Optional

¹The Map Global Section ($MGBLSC) service maps an existing global section.
²See the description of inadr for the rules governing the omission of the argument.
³For physical page frame sections: vbn specifies the starting page frame number; chan must be 0; pfc is not used; and the SEC$M_CRF and SEC$M_DZRO flag bit settings are invalid. For page file sections, chan must be 0 and pfc not used.

prot

OpenVMS usage: file_protection

type: longword (unsigned)

access: read only

mechanism: by value

Protection to be applied to the global page file and PFN sections. For file-backed sections, the protection is taken from the backing file and the prot argument is ignored.

Previous | Next | Contents | [Home] | [Comments] | [Ordering info] | [Help]
  4527P017.HTM
  OSSG Documentation
  22-NOV-1996 12:59:08.47
Copyright © Digital Equipment Corporation 1996. All Rights Reserved.

Legal

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.
SS$_VA_NOTPAGALGN	The start_va_64 argument is not CPU-specific page aligned.

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

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

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

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

Flag	Description
SEC$M_GBL	Pages form a global section. The default is private section.
SEC$M_CRF	Pages are copy-on-reference. By default, pages are shared.
SEC$M_DZRO	Pages are demand-zero pages. By default, they are not zeroed when copied. For page file sections, the default is demand zero.
SEC$M_EXPREG	Pages are mapped into the first available space. By default, pages are mapped into the range specified by the inadr argument. See the inadr argument description for a complete explanation of how to set the SEC$M_EXPREG flag.
SEC$M_WRT	Pages form a read/write section. By default, pages form a read-only section. For page file sections, the default is writeable.
SEC$M_PERM	Global section is permanent. By default, global sections are temporary.
SEC$M_PFNMAP	Pages form a page frame section. By default, pages form a disk file section. Pages mapped by SEC$M_PFNMAP are not included in or charged against the process's working set; they are always valid. Do not lock these pages in the working set by using $LKWSET; this can result in a machine check if they are in I/O space. ++On Alpha systems, when the SEC$M_PFNMAP flag is set, the pagcnt and relpag arguments are interpreted in CPU-specific pages, not as pagelets.
SEC$M_SYSGBL	Pages form a system global section. By default, pages form a group global section.
SEC$M_PAGFIL	Pages form a global page file section. By default, pages form a disk file section. SEC$M_PAGFIL also implies SEC$M_WRT and SEC$M_DZRO.
SEC$M_EXECUTE	Pages are mapped if the caller has execute access. This flag takes effect only (1) when specified from executive or kernel mode, (2) when the SEC$M_GBL flag is also specified, and (3) when SEC$M_WRT is not specified. By default $CRMPSC performs a read access check against the section.
SEC$M_NO_OVERMAP	Pages cannot overmap existing address space. Note that, by default, pages can overmap existing address space.

OpenVMS usage:	section_name
type:	character-coded text string
access:	read only
mechanism:	by descriptor--fixed-length string descriptor

OpenVMS usage:	section_id
type:	quadword (unsigned)
access:	read only
mechanism:	by reference

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.

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

OpenVMS usage:	channel
type:	word (unsigned)
access:	read only
mechanism:	by value

Argument	Create/Map Global Section	Map Global&185; Section	Create/Map Private Section
inadr	Optional²	Required	Required

retadr	Optional	Optional	Optional

acmode	Optional	Optional	Optional

flags
SEC$M_GBL	Required	Ignored	Not used
SEC$M_CRF³	Optional	Not used	Optional
SEC$M_DZRO³	Optional	Not used	Optional
SEC$M_EXPREG	Optional	Optional	Optional
SEC$M_PERM	Optional²	Not used	Not used
SEC$M_PFNMAP	Optional	Not used	Optional
SEC$M_SYSGBL	Optional	Optional	Not used
SEC$M_WRT	Optional	Optional	Optional
SEC$M_PAGFIL	Optional	Not used	Not used

gsdnam	Required	Required	Not used

ident	Optional	Optional	Not used

relpag³	Optional	Optional	Not used

chan³	Required		Required

pagcnt	Required		Required

vbn³	Optional		Optional

prot	Optional		Not used

pfc³	Optional		Optional

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