Updated: 11 December 1998

Porting VAX MACRO Code to OpenVMS Alpha

The three macros for image initialization-time lockdown follow:

• $LOCK_PAGE_INIT
• $LOCKED_PAGE_END
• $LOCKED_PAGE_START

Required in the initialization routines of an image that is using $LOCKED_PAGE_START and $LOCKED_PAGE_END to delineate areas to be locked at initialization time.

Format

$LOCK_PAGE_INIT [error]

Parameters

[error]

Address to which to branch if one of the $LKWSET calls fail. If this address is reached, R0 reflects the status of the failed call, and R1 contains 0 if the call to lock the code failed, or 1 if that call succeeded but the call to lock the linkage section failed.

Description

$LOCK_PAGE_INIT creates the necessary psects and issues the $LWKSET calls to lock into the working set the code and linkage sections that were declared by $LOCKED_PAGE_START and $LOCKED_PAGE_END. R0 and R1 are destroyed by this macro.

The psects locked by this macro are $LOCK_PAGE_2 and $LOCK_LINKAGE_2. If code sections in other modules, written in other languages, use these psects, they will be locked by an invocation of this macro in a VAX MACRO module.

Marks the end of a section of code that may be locked at image initialization time by the $LOCK_PAGE_INIT macro.

Format

$LOCKED_PAGE_END [link_sect]

Parameters

[link_sect]

Psect to return to if the linkage psect in effect when the $LOCKED_PAGE_START macro was executed was not the default linkage psect, $LINKAGE.

Description

$LOCKED_PAGE_END is used with $LOCKED_PAGE_START to delineate code that may be locked at image initialization time by the $LOCK_PAGE_INIT macro. The code delineated by these macros must contain complete routines---execution cannot fall through either macro, nor can you branch into or out of the locked code. Any attempt to branch into or out of the locked code section or to fall through the macros will be flagged by the compiler with an error.

Marks the start of a section of code that may be locked at image initialization time by the $LOCK_PAGE_INIT macro.

Format

$LOCKED_PAGE_START

There are no parameters for this macro.

Description

$LOCKED_PAGE_START is used with $LOCKED_PAGE_END to delineate code that may be locked at image initialization time by the $LOCK_PAGE_INIT macro. The code delineated by these macros must contain complete routines---execution may not fall through either macro, nor may the locked code be branched into or out of. Any attempt to branch into or out of the locked code section or to fall through the macros will be flagged by the compiler with an error.

The two macros for on-the-fly lockdown follow:

• $LOCK_PAGE
• $UNLOCK_PAGE

Marks the beginning of a section of code to be locked on the fly.

Format

$LOCK_PAGE [error]

Parameters

[error]

Address to branch to if one of the $LKWSET calls fail.

Description

This macro is placed inline in executable code and must be followed by the $UNLOCK_PAGE macro. The $LOCK_PAGE/$UNLOCK_PAGE macro pair creates a separate routine in a separate psect. $LOCK_PAGE locks the pages and linkage section of this separate routine into the working set and JSRs to it. All code between this macro and the matching $UNLOCK_PAGE macro is included in the locked routine and is locked down.

All registers are preserved by this macro unless the error address parameter is present and one of the calls fail. If that happens, R0 reflects the status of the failed call. R1 then contains 0 if the call to lock the code failed or 1 if that call succeeded but the call to lock the linkage section failed.

If the ERROR parameter is used, the ERROR label must be placed outside the scope of the $LOCK_PAGE and $UNLOCK_PAGE pair. This is because the error routine is branched to before calling the subroutine that the $LOCK_PAGE and $UNLOCK_PAGE routines create.

Note that since the locked code is made into a separate routine, any references to local stack storage within the routine will have to be changed, as the stack context is no longer the same. Also, you cannot branch into or out of the locked code from the rest of the routine.

Marks the end of a section of code to be locked on the fly.

Format

$UNLOCK_PAGE [error][,LINK_SECT]

Parameters

[error]

An error address to which to branch if one of the $ULKWSET calls fail.

[link_sect]

Linkage psect to return to if the linkage psect in effect when the $LOCK_PAGE macro was executed was not the default linkage psect, $LINKAGE.

Description

$UNLOCK_PAGE returns from the locked routine created by the $LOCK_PAGE and $UNLOCK_PAGE macro pair and then unlocks the pages and linkage section from the working set. This macro is placed inline in executable code after a $LOCK_PAGE macro.

All registers are preserved by this macro unless the error address parameter is present and one of the calls fail. If that happens, R0 reflects the status of the failed call. R1 then contains 0 if the call to unlock the code failed or 1 if that call succeeded but the call to unlock the linkage section failed.

If the error parameter is used, the error label must be placed outside the scope of the $LOCK_PAGE and $UNLOCK_PAGE pair. This is because the error routine is branched to after returning from the subroutine created by the $LOCK_PAGE and $UNLOCK_PAGE routines.

Copyright © Compaq Computer Corporation 1998. All rights reserved. Legal

5601PRO_013.HTML