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Additional information on logical name translations and on section name processing is available in the HP OpenVMS Programming Concepts Manual.
| OpenVMS usage: | section_id |
| type: | quadword (unsigned) |
| access: | read only |
| mechanism: | by reference |
The first longword specifies, in the low-order two bits, the matching criteria. Their valid values, the 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. |
The version number is in the second longword and contains two fields: a minor identification in the low-order 24 bits and a major identification in the high-order 8 bits.
If you do not specify ident or specify it as the value 0 (the default), the version number and match control fields default to the value 0.
| OpenVMS usage: | longword_unsigned |
| type: | longword (unsigned) |
| access: | read only |
| mechanism: | by value |
On Alpha and I64 systems, the relpag argument is interpreted as an index into the section file, measured in pagelets for a file-backed section or CPU-specific pages for a PFN-mapped section.
On Alpha, I64, and VAX systems, if you do not specify relpag or specify it as the value 0 (the default), the global section is mapped beginning with the first virtual block in a file-backed section or the first CPU-specific page in a PFN-mapped section.
The Map Global Section service establishes a correspondence between pages (maps) in the virtual address space of the process and physical pages occupied by a global section. The protection mask specified at the time the global section is created determines the type of access (for example, read/write or read only) that a particular process has to the section.When $MGBLSC maps a global section, it adds pages to the virtual address space of the process. The section is mapped from a low address to a high address, whether the section is mapped in the program or control region.
If an error occurs during the mapping of a global section, the return address array, if specified, indicates the pages that were successfully mapped when the error occurred. If no pages were mapped, both longwords of the return address array contain the value --1.
Read access is required. If the SEC$M_WRT flag is specified, write access is required.
The working set quota (WSQUOTA) of the process must be sufficient to accommodate the increased size of the virtual address space when the $MGBLSC service maps a section.
If the section pages are copy-on-reference, the process must also have sufficient paging file quota (PGFLQUOTA).
This system service causes the working set of the calling process to be adjusted to the size specified by the working set quota (WSQUOTA). If the working set size of the process is less than quota, the working set size is increased; if the working set size of the process is greater than quota, the working set size is decreased.
$ADJSTK, $ADJWSL, $CRETVA, $CRMPSC, $DELTVA, $DGBLSC, $EXPREG, $LCKPAG, $LKWSET, $PURGWS, $SETPRT, $SETSTK, $SETSWM, $ULKPAG, $ULWSET, $UPDSEC, $UPDSECW
For more information, see the chapter on memory management in the HP OpenVMS Programming Concepts Manual.
SS$_NORMAL The service completed successfully. SS$_ACCVIO The input address array, the global section name or name descriptor, or the section identification field cannot be read by the caller; or the return address array cannot be written by the caller. SS$_ENDOFFILE The starting virtual block number specified is beyond the logical end-of-file. SS$_EXQUOTA The process exceeded its paging file quota, creating copy-on-reference pages. SS$_INSFWSL The working set limit of the process is not large enough to accommodate the increased virtual address space. SS$_INVARG Invalid argument specified to service. Common sources are the incorrect specification of relpag or the values in the inadr array. SS$_IVLOGNAM The global section name has a length of 0 or has more than 43 characters. SS$_IVSECFLG You set a reserved flag. SS$_IVSECIDCTL The match control field of the global section identification is invalid. SS$_NOPRIV The file protection mask specified when the global section was created prohibits the type of access requested by the caller; or a page in the input address range is in the system address space. SS$_NOSHPTS The region ID of a shared page-table region was specified. SS$_NOSUCHSEC The specified global section does not exist. SS$_PAGOWNVIO A page in the specified input address range is owned by a more privileged access mode. SS$_SECREFOVF The maximum number of references for a global section has been reached (2,147,483,647). SS$_TOOMANYLNAM Logical name translation of the gsdnam string exceeded the allowed depth. SS$_VA_IN_USE The existing underlying page cannot be deleted because it is associated with a buffer object. SS$_VASFULL The virtual address space of the process is full; no space is available in the page tables for the pages created to contain the mapped global section.
On Alpha and I64 systems, establishes a correspondence between pages in the virtual address space of the process and the pages occupied by a global disk file, page file, or demand-zero section and can map to a demand-zero section with shared page tables.This service accepts 64-bit addresses.
SYS$MGBLSC_64 gs_name_64 ,ident_64 ,region_id_64 ,section_offset_64 ,length_64 ,acmode ,flags ,return_va_64 ,return_length_64
[,start_va_64]
int sys$mgblsc_64 (void *gsdnam_64, struct _secid *ident_64, struct _generic_64 *region_id_64, unsigned __int64 section_offset_64, unsigned __int64 length_64, unsigned int acmode, unsigned int flags, void *(*(return_va_64)), unsigned __int64 *return_length_64,...);
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 HP 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:
Value Symbolic 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_OVERMAP Pages cannot overmap existing address space. 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$M_WRT Map the section with read/write access. All other bits in the flags argument are reserved for future use by HP and should be specified as 0. The condition value SS$_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.
The Map to Global Section service establishes a correspondence between pages in the virtual address space of the process and pages occupied by a global disk file, page file, or memory-resident demand-zero section. This service adds pages to the virtual address space of the process.If a global disk file or page file backed section is being mapped, invalid page table entries are placed in the process page table.
If a memory-resident global section is being mapped, global pages are not charged against the process's working set quota when the virtual memory is referenced and the global pages are not charged against the process's pagefile quota.
If the memory-resident global section was not registered in the Reserved Memory Registry or /NOALLOCATE was specified when the global section was registered, invalid page table entries are placed in the process page table.
If the memory-resident global section was registered in the Reserved Memory Registry and /ALLOCATE was specified when the memory-resident global section was registered, valid page table entries are placed in the process page tables.
If a global disk file or page file backed section is being mapped, and the flag SEC$M_EXPREG is set, the first free virtual address within the specified region is used to start mapping to the global section.
To use the shared page tables associated with a memory-resident global section, you must first create a shared page table region (with SYS$CREATE_REGION_64). To map to the memory-resident global section using the shared page tables you must do the following:
- Specify a shared page table region in the region_id_64 argument.
- Specify SEC$M_WRT in the flags argument.
- Set the flag SEC$M_EXPREG or provide a CPU-specific page-table page-aligned virtual address in the start_va_64 argument.
- Specify a CPU-specific page-table page-aligned value for the section_offset_64 argument or zero.
- Specify a value for the map_length_64 argument that is an even multiple of bytes mapped by a CPU-specific page-table page, or include the last page of the section or zero.
See the description of $CREATE_REGION_64 for information about calculating virtual addresses that are aligned to a CPU-specific page table page boundary.
A memory-resident global section can be mapped with shared page tables or private page tables. The following table lists the factors associated with determining whether the mapping occurs with shared page tables or private page tables:
Global Section Created with Shared Page Tables Shared Page-Table Region Specified by region_id_64 Type of Page Tables Used in Mapping No No Private No Yes Private Yes No Private Yes Yes Shared In general, if the flag SEC$M_EXPREG is set, the first free virtual address within the specified region is used to map to the global section.
If the flag SEC$M_EXPREG is set, a memory-resident global section is being mapped and the region_id_64 argument indicates a shared page-table region, the first free virtual address within the specified region is rounded up to a CPU-specific page-table page boundary and used to map to the global section.
If the flag SEC$M_EXPREG is set and the /ALLOCATE qualifier was specified with the SYSMAN command RESERVED_MEMORY ADD for the memory-resident global section, the first free virtual address within the specified region is rounded up to the same virtual alignment as the physical alignment of the preallocated pages and used to map to the global section. Granularity hints are set appropriately for each process private page-table entry (PTE).
In general, if the flag SEC$M_EXPREG is clear, the virtual address in the start_va_64 argument is used to map to the global section.
If the flag SEC$M_EXPREG is clear and a memory-resident global section is being mapped, the value specified in the start_va_64 argument can determine if the mapping is possible and if granularity hints are used in the private page tables. If a shared page-table region is specified by the region_id_64 argument, the virtual address specified by the start_va_64 argument must be on an even CPU-specific page-table page boundary or an error is returned by this service. If the region_id_64 argument does not specify a shared page-table region and the /ALLOCATE qualifier was specified with the SYSMAN command RESERVED_MEMORY ADD for this global section, granularity hints are used only if the virtual alignment of start_va_64 is appropriate for the use of granularity hints:
- On Alpha systems, granularity hints mean multiples of pages, regardless of page size. The multiples 8, 64, and 512 pages are architected.
- On I64 systems, OpenVMS initially supports page sizes of 64KB, 256KB, and 4MB instead of granularity hints. Additional pages sizes will be supported in the future.
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