iAPX 286 Operating System Writers Guide 1983

REAL MEMORY MANAGEMENTPL/M-286 COMPILER 960-501 date PAGE 216 117 118 119 1DECLARE NULL_PHYS_ADDR LITERALLY '0';DECLARE USED LITERALLY '1',FREE LITERALLY '0';/* Values of boundary tags */DECLARE OKLITERALLY '0',FAILED LITERALLY '8000H';/* Values of exception codes */DECLARE DWRIGHTS LITERALLY '92H' /* For manipulatingspace-management data structures, this moduleneeds these rights parameters: Present, DPL=0,data segment, grow up, writable. */;1*******************************************************//* Space-management data structures. * /20 121 122 123 224 225 226 1DECLARE (FIRST AVLBL,LAST AVLBL,CURR AVLBL)DWORD PUBLIC;/* Physical-address pointers to chain of availablespace. These always point to PRIOR - PARAGRAPH toavoid calculating b~se addresses for MEM_LINKs. * /DECLARE SLOT A SELECTOR PUBLIC,WSLOT A WORD AT (@SLOT A) INITIAL (38H) , /* 7 */SLOT B SELECTOR PUBLIC,WSLOT B WORD AT (@SLOT B) INITIAL (40H) , /* 8 */SLOT C SELECTOR PUB LIC,WSLOT_C WORD AT (@SLOT C) INITIAL (48H) ; /* 9 *//* "Scratch" slots for addressing MEM LINKS. *//* Be sure to reserve these slots with the Builder *//*******************************************************//* Round a size parameter upwards to next" greater *//* or equal (N * BLOCK_MODULUS) :.. 'TAGS_SIZE for some N */ROUND_S IZE: PROCEDURE (A_PTR) PUBLIC REENTRANT;DECLARE A PTR POINTER,ADDR BASED A_PTR DWORD;, AD DR BLOCK MODULUS* (( (ADDR + TAGS SIZE - 1) / BLOCK_MODULUS) + 1)-- TAGS_SIZE;END ROUND_SIZE;1*******************************************************//* Delink from avail able space 1 ist. * /DELINK:PROCEDURE (THIS_SEL) REENTRANT;27 2DECLARE THIS SELTHIS-LINKSELECTOR,BASED THIS SEL STRUCTURE (MEM_LINK);28 2DECLARE PRIOR LINK BASED SLOT CSTRUCTURE (MEM_LINK),Figure 3-9. Code for Memory-Management Example (Cont'd.)3-16 121960-001