Programming Interface Information:
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IASIT
Control Block Contents
IASIT DSECT
Cross Reference (Contains links to field and bit definitions)
IASIT Prolog
Name : HCPIASIT Description: Internal-Address-Space-Identification Token DSECT : IASIT Function : This DSECT maps an i-ASIT, which is CP's internal identification of an address space. Located by : Any task needing an identification of an address space. Some important fields which contain i-ASITs are: RSANASIT i-ASIT for "null" address space. Created by : HCPSIT%I when translating various representations of address spaces into i-ASITs. Deleted by : Any task which no longer needs the representation. Notes : An i-ASIT is an eight-byte token, doubleword aligned, and * serves as a task's internal representation of a particular * address space. An i-ASIT contains information designating * which address space, information defining the task's * "capability" to access the address space, and information * defining the method of translating addresses for that * task. Since it contains more information than just what * is necessary to identify an address space, an i-ASIT * cannot be directly compared to another i-ASIT to determine * if the same space is designated. A service routine (as * provided by the HCPCMPIA macro) must be used for i-ASIT * comparison purposes. * * The capabilities represented in an i-ASIT are the * following: * * - r-access vs. i-access * - Read/write vs. read/only permission * - For guest instruction-stream references, whether * guest prefixing, guest low-address protection, * and guest fetch-protection override apply. * * Translation of a guest real address into a host real * address is affected by whether or not the address space is * the user's base address space, and whether or not the * user's reference is a primary-space or secondary-space * reference. Prefixing, low-address protection, and * fetch-protection override apply only when the space is the * base, and when the access is a primary-space or * secondary-space reference. * * An i-ASIT must be certified before it can be used for any * purposes. A certified i-ASIT is one that meets the * following criteria: * * - The ASTE sequence number in the i-ASIT matches * the ASTE sequence number in the ASTE (i- or r-access) * *or* * - ASCSEQNO <= ASITSN <= ASTSN (r-access) * * The i-ASIT certification function is provided by either * the HCPASMCI entry point or the HCPACERT macro (to be used * only in cases where performance is a major concern, or the * routine cannot call another routine which uses PFXTMPSV). * Other services which process i-ASITS, such as HCPCMPIA * and HCPCHCR7, handle certification of i-ASITs internally.
IASIT Control Block Content
IASIT DSECT
Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure IASIT Internal-Address-Space-Identifica tion 0000 0 Address 4 IASASTEO (0) Bits 1-25 are the ASTE origin NOTE: This field may ONLY be used in a certified i-ASIT, otherwise, it may point to an ASTE which has no relation to the i-ASIT. 00FFFFC0 IASASTOM X'7FFFFFC0' Mask to apply to IASASTEO to isolate ASTE origin. .... ..1. IASREADM X'00000002' Mask for read-only bit .... ...1 IASFPRVM X'00000001' Mask for force-private-space bit 0000 0 Bitstring 1 * (3) First 3 bytes are ASTE origin 0003 3 Bitstring 1 IASFLAGS Authorization/capability flags .... .1.. IASRACC X'04' When set, task has r-access to the address space. .... ..1. IASREAD X'02' When set, task has read-only access to space. .... ...1 IASFPRIV X'01' Force-Private-Space bit When set, guest prefixing, low-address protection, and fetch-protection override do not apply. When not set, they do apply. 0004 4 Signed 4 IASASTSN I-ASIT ASTE sequence number. It is compared with ASTE sequence number in ASTE. 00000008 IASLEN *-IASIT Length in bytes of an i-ASIT 00000001 IASSIZE (IASLEN+7)/8 Size in doublewords of an i-ASIT
IASIT Storage Layout
*** IASIT - Internal-Address-Space-Identification * * +--------------------+------+---------------------------+ * 0 |////////////////////|:FLAGS| IASASTSN | * +--------------------+------+---------------------------+ * 8 * *** IASIT - Internal-Address-Space-Identification
IASIT Cross Reference
Symbol Dspl Value -------------- ---- ----- IASASTEO 0000 IASASTOM 0000 00FFFFC0 IASASTSN 0004 IASFLAGS 0003 IASFPRIV 0003 01 IASFPRVM 0000 01 IASLEN 0004 00000008 IASRACC 0003 04 IASREAD 0003 02 IASREADM 0000 02 IASSIZE 0004 00000001
Last updated on 5 Jun 2001 at 13:53:49 EDT.
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