Purpose

Use this macroinstruction to allow an application to return one or more buffers to a storage pool. It is also used to logically return a buffer that has been assigned to multiple owners. The buffer is returned to CSM when the owner of the last buffer image returns it to CSM and a buffer return exit routine was not specified during the initial allocation of the buffer.

Usage

An application can specify the address of a buffer return exit routine that is to receive control when the IVTCSM REQUEST=FREE_BUFFER macroinstruction is issued. See Buffer return exit routine for more information. An application might optionally specify that the buffer return exit address specified when the buffer was obtained is to be overridden, allowing a buffer to be freed back to CSM that was obtained specifying a free routine address. This option is requested by specifying FREETO=CSM; it must be invoked in this manner only by the requester of the buffer that specified a free routine on the GET_BUFFER request. If others use this option, the buffer is not returned to the original owner of the buffer.

The application can optionally specify that the buffer obtained is to be cleared when it is returned to the pool on a FREE_BUFFER request. This allows secure data to be cleared after use.

All IVTCSM REQUEST=GET_BUFFER|ASSIGN_BUFFER macroinstructions must have a corresponding FREE_BUFFER request before the buffer is considered available for reallocation by CSM, or before a buffer return exit routine is invoked for a buffer obtained specifying a buffer return exit routine. This is necessary to ensure that all users have finished using the buffer.

Parameters

name

An optional symbol, starting in column 1, that is the name on the IVTCSM macro invocation. The name must conform to the rules for an ordinary assembler language symbol.

,BUFLIST=buflist

A required input parameter of an area containing a list of buffer entries. The number of entries in the list is specified by BUFNUM. An entry in the list is mapped by IVTBUFL.

The following fields in IVTBUFL are required as input for this request:

• BUFL_VERSION
• BUFL_SOURCE (Required only when SKIPBUF=YES is specified.)
• BUFL_TOKEN

No fields in IVTBUFL are returned as output by CSM for this request.

To code, specify the RS-type address, or address in register (2)-(12), of a field.

,BUFNUM=bufnum

A required input parameter, specifying the number of buffer entries in the list.

To code, specify the RS-type address, or address in register (2)-(12), of a fullword field.

,CLEAR=

An optional parameter, specifying whether the buffer is to be cleared when returned to storage pool. The default is CLEAR=NO.

,CLEAR=NO

Specifies that the buffer is not cleared when returned to the storage pool. If the buffer was originally allocated with a CLEAR value of YES, then CLEAR=NO is ignored by CSM, and the buffer is cleared when returned to the storage pool.

,CLEAR=YES

Specifies that the buffer is to be cleared. Specifying CLEAR=YES does not cause a buffer to be cleared that is returned by a user-specified free routine. However, if CLEAR=YES is specified, the buffer is cleared in the event that it is returned to the storage pool.

,ERRBFLST=errbflst

An optional output parameter, specifying the number of the last buffer entry that was successfully processed when an error is detected during processing of the macroinstruction.

To code, specify the RS-type address, or address in register (2)-(12), of a fullword field.

,FREETO=

An optional parameter, allowing the FREERTN parameter on the IVTCSM REQUEST=GET_BUFFER macroinstruction to be overridden. The default is FREETO=USER.

,FREETO=USER

Specifies that the buffer is to be returned to the free routine specified on the GET_BUFFER request.

,FREETO=CSM

Specifies that the free routine address provided when the buffer was obtained is to be overridden and the buffer is to be returned to the storage pool. This option should be used only by the original owner of the buffer.

,GAP=gap

An optional input parameter, specifying the number of bytes used to separate buffer entries. This parameter allows the buffer entries to be in discontiguous storage. If GAP is not specified, buffer entries are not contiguous.

To code, specify the RS-type address, or address in register (2)-(12), of a fullword field.

,MF=

An optional input parameter that specifies the macro form.

MF=S

Specifies the standard form of the macro, which builds an inline parameter list and generates the macro invocation to transfer control to the service. MF=S is the default.

MF=L

Specifies the list form of the macro. Use the list form together with the execute form of the macro for applications that require reentrant code. The list form defines an area of storage that the execute form uses to store the parameters. Only the PLISTVER parameter can be coded with the list form of the macro.

Use MF=E to specify the execute form of the macro. Use the execute form together with the list form of the macro for applications that require reentrant code. The execute form of the macro stores the parameters into the storage area defined by the list form, and generates the macro invocation to transfer control to the service.

Use MF=M together with the list and execute forms of the macro for service routines that need to provide different options according to user-provided input. Use the list form to define a storage area; use the modify form to set the appropriate options; then use the execute form to call the service.

,list addr

The name of a storage area to contain the parameters. For MF=S, MF=E, and MF=M, this can be an RS-type address or an address in register (1)-(12).

,attr

An optional input string 1 - 60 characters in length that you use to force boundary alignment of the parameter list. Use a value of 0F to force the parameter list to a word boundary, or 0D to force the parameter list to a doubleword boundary. If you do not code attr, the system provides a value of 0D.

,COMPLETE

Specifies that the system is to check for required parameters and supply defaults for omitted optional parameters.

,NOCHECK

Specifies that the system is not to check for required parameters and is not to supply defaults for omitted optional parameters.

Guidelines: Use the modify and execute forms of IVTCSM in the following order:

1. Use IVTCSM ...MF=(M,list-addr,COMPLETE) specifying appropriate parameters, including all required ones.
2. Use IVTCSM ...MF=(M,list-addr,NOCHECK), specifying the parameters that you want to change.
3. Use IVTCSM ...MF=(E,list-addr,NOCHECK), to execute the macro.

,PLISTVER=

An optional input parameter that specifies the version of the macro. PLISTVER determines which parameter list the system generates. PLISTVER is an optional input parameter on all forms of the macro, including the list form. When using PLISTVER, specify it on all macro forms used for a request and with the same value on all of the macro forms. The values are:

IMPLIED_VERSION

The lowest version that allows all parameters specified on the request to be processed. If you omit the PLISTVER parameter, IMPLIED_VERSION is the default.

MAX

Code this value if you want the parameter list to be the largest size currently possible. This size might increase from release to release and affect the amount of storage that your program needs.

If you can tolerate the size change, IBM® recommends that you always specify PLISTVER=MAX on the list form of the macro. Specifying MAX ensures that the list-form parameter list is always long enough to hold all the parameters you might specify on the execute form; in this way, MAX ensures that the parameter list does not overwrite nearby storage.

0

Code this value if you use the currently available parameters

To code, specify one of the following values:

• IMPLIED_VERSION
• MAX
• A decimal value of 0

,RETCODE=retcode

An optional output parameter into which the return code is to be copied from GPR 15.

To code, specify the RS-type address of a fullword field, or register (2)-(12).

,RSNCODE=rsncode

An optional output parameter into which the reason code is to be copied from GPR 0.

To code, specify the RS-type address of a fullword field, or register (2)-(12).

,SKIPBUF=

An optional parameter, specifying whether all entries in the buffer list should be processed. The default is SKIPBUF=NO.

,SKIPBUF=NO

Specifies that all the entries in the buffer list are processed. No entries are skipped. The BUFL_SOURCE value is not examined.

,SKIPBUF=YES

Specifies that the only entries in the buffer list that have a BUFL_SOURCE value indicating the user's non-CSM storage (BUFL_UDSPACE or BUFL_USTOR) are skipped.

,THREAD=thread

An optional input parameter, specifying a unique identifier that is placed in the CSM trace entry to correlate trace records with the application that is requesting the buffers. It is the CSM user's responsibility to ensure that this value is different from the THREAD value specified by other users of the CSM. One way this can be achieved is by specifying an ECSA control block for THREAD.

To code, specify the RS-type address, or address in register (2)-(12), of a 4-character field.

,UTILRTN=utilrtn

An optional input parameter that is issued from a utility routine. Specify the utility routine caller's address to be placed in the CSM trace entry. If this parameter is omitted, only the address of the CSM request issuer is placed in the CSM trace entry. This parameter is relevant only to the tracing process. It should be specified only if the CSM user requires identification of the caller of a utility routine in the CSM trace entry.

To code, specify the RS-type address, or address in register (2)-(12), of a fullword field.

Return codes