Abstract:
A method for verifying the architectural integrity of a newly written or modified instruction set in a limited operating environment is described. More particularly, this methodology is adapted to perform such verification even though the processor under test has only a one or a few instructions in its partially complete instruction set. Such verification is accomplished using a minimum test driver, under control of a test processor, which loads the data necessary to execute the instruction being tested. The test system also provides actual or simulated I/O capabilities. After execution of that instruction, the test driver directs capture of the execution results for appropriate use. As an aid in performing the verification test, the test driver is provided with an invalid command that forces return of control to the test processor. In operation, the processor to be microcoded is tested instruction by instruction, via shared memory, with microcode corrections being made on the same basis to avoid error propagation into the remainder of the instruction set as it is developed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention is concerned with a method for verifying the architectural integrity of a processor having only a limited or partial instruction set. More particularly, this invention is directed to a methodology for performing such verification on a minimal instruction set or on single instructions to control and then cause execution thereof and to then capture the results of execution. 
     2. Description of the Prior Art 
     It is well known that a newly written or significantly modified instruction set for a given processor needs to be tested and proper execution thereof verified before that set can be relied on. Traditionally, software written to verify the operating architectural integrity of such an instruction set has been written as comprehensive programs that were resident in the processor under test. This approach requires a rather complete implementation of the instruction set and an operational input/output (I/O) facility before serious testing can and does begin. 
     Instructions have been tested in the past on an individual basis, but such testing requires one to employ hand loops that are manually entered, generally via an operator&#39;s console. It was found, however, that the number of different drivers which resulted from the many microcode test efforts, made it difficult to standardize such testing or trust its results, even where testing different code portions of the same instruction set. In addition, this non-automated manual entry verification approach was subject to frequent non-microcode error entry and was, therefore, not conducive to efficient testing. 
     Thus, the prior art relating to architectural verification and/or diagnostics is primarily concerned with automated and semi-automated means and methods for discovering microcode or hardware problems after the complete instruction set and I/O routines have been written. Debugging is generally a piecemeal effort that is serial in nature, discovery of a first bug leading to discovery of related or subsequent bugs, requiring large test driver programs to exhaust all possibilities. Commonly assigned U.S. Pat. No. 4,268,902 to Berglund et al and U.S. Pat. No. 4,312,066 to Bantz et al are typical of such prior art approaches. These patents are both directed to diagnostic and debug methods in which a service or diagnostic processor is attached to a fully operational host having a complete instruction set and full I/O capability to test or diagnose the instruction set or to find the cause of a particular host error. Similar approaches are detailed in commonly assigned U.S. Pat. No. 3,618,028 to Johnson et al and U.S. Pat. No. 3,825,901 to Golnek et al. 
     Unfortunately, utilization of these prior art methods required that operational verification of a new or substantially modified instruction set be held in abeyance until the set was completed and full I/O capability provided. In addition, errors made during the development stage, particularly during the early portion thereof, were often propagated through the entire development effort and not found until that effort was completed and verification testing performed. This meant that additional time had to be spent correcting or rewriting all of the code that contained such propagated errors rather than merely correcting an erroneous instruction. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     Accordingly, it is a principal object of the present invention to provide a method for eliminating architectural errors and verifying proper microcode operation by utilizing a minimal driver to verify, as early in the design stage as possible, the operational integrity of single instructions or small combinations thereof in order to avoid propagation of early development errors. 
     It is also a principal object of the present invention to provide such a method wherein the microcode can be implemented in a top down manner to insure complete testing of each instruction and of the test package for proper regression testing of all changes. 
     It is another object of the present invention to provide a method of verifying microcode operational integrity that utilizes a driver program of minimum size which is adapted to control verification testing on an instruction by instruction basis. 
     It is yet another object of the present invention to provide such a method wherein the support processor provided to control verification testing also furnishes actual or simulated I/O services. 
     It is a further object of the present invention to provide a method of verifying the operational integrity of an instruction set or portion thereof wherein the support processor and the processor under test share a common memory. 
     These and other objects of the present invention are achieved by a methodology of verification wherein a minimum test driver, under control of a test processor, loads the data necessary to execute the instruction being tested. After execution of that instruction, the test driver directs capture of the execution results for appropriate use. As an aid in performing the verification test, the test driver is provided with an invalid command that forces return of control to the test processor. The test driver is loaded and run under control of the support processor which provides actual or simulated I/O capabilities. In operation, the processor to be microcoded is tested instruction by instruction, via shared memory, with microcode corrections being made on the same basis to avoid error propagation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described further, by way of a preferred example thereof, with reference to the accompanying drawings wherein like reference numerals have been used in the several views to depict like elements, in which: 
     FIG. 1 schematically illustrates a simplified representation of an instruction set verification configuration that is adapted to be used in accordance with the subject invention; and 
     FIG. 2 depicts a simplified schematic flowchart of the testing of an example instruction set in accordance with the method of the present invention employing the arrangement shown in FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The basic configuration necessary to support the testing of instructions or provide verification of processor architecture, in accordance with the present invention, is shown in FIG. 1. It includes a test support system 10 or TSS and memory 12 which is to be shared by and between the test support system 10 and the processor under test 14 or PUT. The TSS 10 is provided with sufficient storage to at least contain a test control program or TCP, to accommodate the storage shared with the PUT 14 and to retain actual or simulated input/output (I/O) support. I/O support would typically include provision for diskette support, to contain the test cases to be processed, terminal support, preferably video, to input control information and view test results, and printer support, to be used in providing hard copy reports of the test case execution results. In addition to the foregoing, an interprocessor communication bus 16 is provided to facilitate bidirectional exchanges between the TSS 10 and the PUT 12. Finally, the PUT 12 is given minimum capability for providing its own housekeeping functions. It is, therefore, able to load, store and otherwise manipulate its control, general purpose and floating point registers. 
     Given the basic requirements set forth above, the specific verification environment which follows and the assumption that an additional instruction is to be added to the repertoire of the PUT 12, the following will describe how the &#34;new&#34; instruction is to be tested. It will be assumed, for purposes of this description, that the PUT 12 is a System 370 architectured processor, of the type manufactured by International Business Machines Corporation, and that the example instruction to be added is the S/370 instruction `MVCIN`. As used herein, the term &#34;limited instruction set&#34; refers to an instruction set that is rather limited, i.e., not complete. In fact, the limited instruction set of the processor under test in the following description is fixed at one, the single instruction. 
     For those readers who may be unaware of its function, `MVCIN` provides for an inverse move, that is, a storage-to-storage move which places the second operand specified by the instruction in the location of the first operand specified by the instruction, with the left-to-right sequence of the second operand&#39;s bytes inverted as stored. The first operand address designates the leftmost byte of the first operand. The second operand address designates the rightmost byte of the second operand. Both operands have the same length. The result is obtained as if the second operand were processed from right-to-left and the first operand from left-to-right. The second operand may wrap around from low to high memory and the first operand may wrap around from high to low memory. The contents of each byte moved remain unchanged. 
     The immediately following description is that of a test case program which is employed for the purpose of testing and verifying operation of the `MOVE INVERSE` instruction. Many test cases must be developed to exercise every condition expected, executed and produced by the instruction. The control program TCP in the TSS 10 must therefore read each of the following records and insure that the data in each record is correct. The data is then stored in the shared memory 12 for subsequent processing as a result of exercise of the test case. 
     
         ______________________________________Example Test Case Program______________________________________1.   Z&#39;00001&#39; GEN, MVCIN2.   * MOVE INVERSE: MOVE 16 BYTES WITH LAST* BYTE OVERLAP3.   ********** ********** ********** **********4.   * THE FOLLOWING RECORDS ARE USED TO SET* UP THE TEST CASE FOR EXECUTION5.   ********** ********** ********** **********6.   I&#39;E80F1200121E&#39;     * INSTRUCTION7.   G1(00008000)        * INITIALIZE GPR8.   SA&#39;8200&#39;L&#39;16&#39;XAAA . . . AAA&#39;                    * INITIALIZE                      STORAGE9.   SA&#39;8210&#39;L&#39;16&#39;X555 . . . 555&#39;                    * INITIALIZE                      STORAGE10.  P&#39;0008000000005000&#39; * SET PSW11.  RESULTS=            * INITIATE                      EXECUTION12.  ********** ********** ********** **********13.  * THE FOLLOWING RECORDS ARE USED TO COM-* PARE AGAINST THE EXECUTION RESULTS14.  ********** ********** ********** **********15.  SA&#39;8200&#39;L&#39;16&#39;X555 . . . 5AA&#39;16.  SA&#39;8210&#39;L&#39;16&#39;X555 . . . 555&#39;17.  SA&#39;88&#39; L&#39;4&#39;X0002000018.  END19.  ********** ********** ********** **********______________________________________ 
    
     The first line or record of the test case is a control record that indicates the start of a new test case and the need, if any, of setting up test conditions that are unique to the new test case. The next four lines are comments or internal documentation describing the nature and intent of the test case. Line 6 of the test case is the hexidecimal (hereinafter hex) representation of the MOVE INVERSE instruction which is placed in memory in accordance with the address given in the instruction address field of the PSW record. Line 7 indicates the hex value `000080000` to which general purpose register 1 (GPR1) of the PUT 10 is initialized. Lines 8 and 9 initialize locations in the shared memory 12 to the sixteen bit hex values shown. More specifically, these records initialize storage, at locations 8200-820F with a hex value of `AAA...AAA` and locations 8210-821F with a hex value of `555...555`. Line 10 sets a program status word (PSW) for execution, which indicates where in memory the instruction has been placed. In this instance, the instruction address of the PSW is used to locate the address of the test instruction. The location of the PSW in storage is employed to establish the address pointed to by the LOAD PSW instruction in the test control program, see below, at label `PSWADDI`. The RESULTS=record, line 11, indicates to the control program that execution may proceed, that the test case has been sufficiently initialized. Lines 15 and 16 are known valid results, which are stored in shared memory 12, to which the instruction execution results will be compared in order to verify proper execution. They represent the condition of storage subsequent to execution of the test case. Line 17 of the test case is an expected interruption code and instruction length which is used for comparison purposes after execution of the instruction being tested. Line 18 signifies the end of the test case program, that result comparison and reporting can begin. As inferred above, all lines of the test case program that start with an asterisk indicate a comment or separator line used to internally document the test case program itself. 
     A processor under test control program or PUTCP is utilized to provide the facility by which the PUT registers are initialized or loaded. Obviously, any storage initialization requirements can be satisfied via shared memory 12. However, loading the PUT 14 internals requires only a minimum of test support system aid. It should be noted that the mechanism for storing the registers of the PUT 14 is also present in the PUTCP and will be explained hereinafter in greater detail. 
     The PUTCP contains those instructions which must be operational on the PUT 12 in order to proceed with further testing. In this particular example, the processor being microcoded is an IBM S/370, which requires the loading of sixteen general purpose and control registers. While that requirement must, therefore, be accommodated by the PUTCP, this control program is otherwise comprised of a minimum number of instructions. 
     
         __________________________________________________________________________Example Processor Under Test Control Program* THIS PROGRAM IS TO BE LOADED FROM TESTER 10 INTO* THE PRIMARY MAIN STORE FOR SUBSEQUENT EXECUTION.* THIS PROGRAM IS USED TO INITIALIZE AND PROPERLY* CONDITION THE PUT 12 FOR EXECUTION OF THE TEST* CASE AND TO ASSIST IN CAPTURING THE RESULTS OF* TEST CASE EXECUTION.__________________________________________________________________________  ORG  *+X&#39;00400&#39;  USING       *,15BEGIN  B    START1R0     EQU  0RF     EQU  15  DS   0F*      GPR BUFFER AFTER EXECUTIONGPRE   EQU   *GEN0E  DC   X&#39;00000000&#39;                 GENERAL REGISTER 0GEN1E  DC   X&#39;00000000&#39;                 GENERAL REGISTER 1GEN2E  DC   X&#39;00000000&#39;                 GENERAL REGISTER 2GEN3E  DC   X&#39;00000000&#39;                 GENERAL REGISTER 3GEN4E  DC   X&#39;00000000&#39;                 GENERAL REGISTER 4GEN5E  DC   X&#39;00000000&#39;                 GENERAL REGISTER 5GEN6E  DC   X&#39;00000000&#39;                 GENERAL REGISTER 6GEN7E  DC   X&#39;00000000&#39;                 GENERAL REGISTER 7GEN8E  DC   X&#39;00000000&#39;                 GENERAL REGISTER 8GEN9E  DC   X&#39;00000000&#39;                 GENERAL REGISTER 9GENAE  DC   X&#39;00000000&#39;                 GENERAL REGISTER 10GENBE  DC   X&#39;00000000&#39;                 GENERAL REGISTER 11GENCE  DC   X&#39;00000000&#39;                 GENERAL REGISTER 12GENDE  DC   X&#39;00000000&#39;                 GENERAL REGISTER 13GENEE  DC   X&#39;00000000&#39;                 GENERAL REGISTER 14GENFE  DC   X&#39;00000000&#39;                 GENERAL REGISTER 15*      GPR BUFFER FOR INITIALIZATIONGPRI   EQU   *GEN0I  DC   X&#39;00000000&#39;                 GENERAL REGISTER 0GEN1I  DC   X&#39;00000000&#39;                 GENERAL REGISTER 1GEN2I  DC   X&#39;00000000&#39;                 GENERAL REGISTER 2GEN3I  DC   X&#39;00000000&#39;                 GENERAL REGISTER 3GEN4I  DC   X&#39;00000000&#39;                 GENERAL REGISTER 4GEN5I  DC   X&#39;00000000&#39;                 GENERAL REGISTER 5GEN6I  DC   X&#39;00000000&#39;                 GENERAL REGISTER 6GEN7I  DC   X&#39;00000000&#39;                 GENERAL REGISTER 7GEN8I  DC   X&#39;00000000&#39;                 GENERAL REGISTER 8GEN9I  DC   X&#39;00000000&#39;                 GENERAL REGISTER 9GENAI  DC   X&#39;00000000&#39;                 GENERAL REGISTER 10GENBI  DC   X&#39;00000000&#39;                 GENERAL REGISTER 11GENCI  DC   X&#39;00000000&#39;                 GENERAL REGISTER 12GENDI  DC   X&#39;00000000&#39;                 GENERAL REGISTER 13GENEI  DC   X&#39;00000000&#39;                 GENERAL REGISTER 14GENFI  DC   X&#39;00000000&#39;                 GENERAL REGISTER 15*      CONTROL REGISTER ACTUAL RESULTSCTLRE   EQU  *CTL0E  DC   X&#39;00000000&#39;                 CONTROL REGISTER 0CTL1E  DC   X&#39;00000000&#39;                 CONTROL REGISTER 1CTL2E  DC   X&#39;00000000&#39;                 CONTROL REGISTER 2CTL3E  DC   X&#39;00000000&#39;                 CONTROL REGISTER 3CTL4E  DC   X&#39;00000000&#39;                 CONTROL REGISTER 4CTL5E  DC   X&#39;00000000&#39;                 CONTROL REGISTER 5CTL6E  DC   X&#39;00000000&#39;                 CONTROL REGISTER 6CTL7E  DC   X&#39;00000000&#39;                 CONTROL REGISTER 7CTL8E  DC   X&#39;00000000&#39;                 CONTROL REGISTER 8CTL9E  DC   X&#39;00000000&#39;                 CONTROL REGISTER 9CTLAE  DC   X&#39;00000000&#39;                 CONTROL REGISTER 10CTLBE  DC   X&#39;00000000&#39;                 CONTROL REGISTER 11CTLCE  DC   X&#39;00000000&#39;                 CONTROL REGISTER 12CTLDE  DC   X&#39;00000000&#39;                 CONTROL REGISTER 13CTLEE  DC   X&#39;00000000&#39;                 CONTROL REGISTER 14CTLFE  DC   X&#39;00000000&#39;                 CONTROL REGISTER 15*      CONTROL REGISTER INITIAL SETTINGSCTLRI  EQU   *CTL0I  DC   X&#39;000000E0&#39;                 CONTROL REGISTER 0CTL1I  DC   X&#39;00000000&#39;                 CONTROL REGISTER 1CTL2I  DC   X&#39;FFFF0000&#39;                 CONTROL REGISTER 2CTL3I  DC   X&#39;00000000&#39;                 CONTROL REGISTER 3CTL4I  DC   X&#39;00000000&#39;                 CONTROL REGISTER 4CTL5I  DC   X&#39;00000000&#39;                 CONTROL REGISTER 5CTL6I  DC   X&#39;00000000&#39;                 CONTROL REGISTER 6CTL7I  DC   X&#39;00000000&#39;                 CONTROL REGISTER 7CTL8I  DC   X&#39;00000000&#39;                 CONTROL REGISTER 8CTL9I  DC   X&#39;00000000&#39;                 CONTROL REGISTER 9CTLAI  DC   X&#39;00000000&#39;                 CONTROL REGISTER 10CTLBI  DC   X&#39;00000000&#39;                 CONTROL REGISTER 11CTLCI  DC   X&#39;00000000&#39;                 CONTROL REGISTER 12CTLDI  DC   X&#39;00000000&#39;                 CONTROL REGISTER 13CTLEI  DC   X&#39;82000000&#39;                 CONTROL REGISTER 14CTLFI  DC   X&#39;00000000&#39;                 CONTROL REGISTER 15  DS   0DPSWADDI  DC   X&#39;00000000&#39;                 INITIAL PSW  DC   A(INTERR)SVCPSWN  DC   X&#39;00080000&#39;                 NEW SVC PSW  DC   A(INTERR)START1 EQU  *  LM   R0,RF,GPRI                 LOAD ALL GPRS  LCTL R0,RF,CTLRI                 LOAD ALL CONTROL REGS  LPSW PSWADDIINTERR EQU  *         SVC INTERRUPT ADDRESS  STM  R0,RF,GPRE                 STORE ALL GPRS  STCTL       RO,RF,CTLRE                 STORE ALL CONTROL REGS  DC   &#39;B20F&#39;    RETURN CONTROL TO THE*                     TESTER VIA A CURRENTLY*                     INVALID INSTRUCTION  END__________________________________________________________________________ 
    
     In addition to loading the above program into shared memory 12, the Test Support System 10 must set certain other memory areas to insure proper execution of the PUT 14. For example, in the given PUTCP, it is assumed that the restart PSW at memory location 0 and SVC PSW at memory location 60, at a minimum, are initialized to their appropriate values. Thus, in the program above, `INTERR` must be the address in the new SVC PSW and `000400` the address in the restart new PSW. It is only necessary that this be done once during the testing procedure. It has been found helpful to intialize other CPU critical areas to values which will provide some trace of erroneous execution. Thus, it would be wise to initialize all new PSW addresses to `INTERR` to insure a store of register values, which values can then be used at a later time in debugging. 
     In operation, the testing and verification of the newly added instruction goes forward in the following manner which is schematically represented in FIG. 2. The test case is read from a diskette and each record is verified for accuracy by the Test Support System or TSS 10. If any one of the records is found to be in error, the test case is bypassed, with appropriate alarm of that fact. As in the example test case, the first record is a control record that indicates to the TSS 10 the beginning of a new test case and the need, if any, to set up any test conditions unique to that particular test case. Once PUT 14 storage has been initialized with the minimal control program and the test case data, it is appropriate to have the PUT begin execution. In the present example of a S/370 PUT, control is passed by causing a program restart. While the PUT 14 has control, the TSS 10 waits for execution of the PUTCP to be completed and for control to be passed back to it. 
     The PSW placed in storage address 0 will then be invoked and instructions will begin executing at the address pointed to by the PSW instruction address. The minimal PUTCP entry point is at that address. The general purpose registers are next initialized using the data from the storage areas loaded from the test case records. Similarly, the control registers are also initialized from the storage areas that have been loaded with data from the test case records. Control is then passed to the test case instruction in storage via the LOAD PSW instruction `LPSW`. The test case instructions are then executed. The last instruction executed, placed at the end of the test case by the TSS control program, is a supervisor call `SVC`. When this instruction is executed, it causes the supervisor call PSW to be loaded and execution then proceeds at the PSW instruction address, which in this case is label `INTERR`. At `INTERR`, the general purpose registers are stored back into shared store 12, as are the control registers. 
     The final stage of verification turns control back to the TSS 10. This requires the microcode to recognize some specific instruction as calling for return of control from the PUT 14. It has been determined that the most effective way in which to return control, without having to implement or be responsive to a larger number of instructions in the test control program, is to have the PUT 14 react to an unusual instruction in a predictable manner. More specifically, an invalid instruction is used that, when encountered, forces the PUT 14 to relinquish control. In this particular example, a `B2F0` is utilized as the invalid instruction, which is invoked to trigger the desired return of control. 
     Once control has been returned to the TSS 10, comparison of the results of execution to predetermined values can be initiated and a report concerning such results obtained. The areas of shared storage where data is stored, initially by the TSS 10 and after execution by the PUT 14 for its general purpose and control registers, are known to the TSS 10. In addition, the TSS 10 is also aware of any key areas of architectural significance that might have been cleared or set by itself to a value that would insure that such key areas were not altered by execution of the instruction being tested. With this knowledge, the tester begins to compare the results presented by execution of the test case, records 15 through 17 in this instance, to what was actually present in the PUT&#39;s general purpose and control registers. Architecturally significant areas are now also compared to insure that no changes have occurred therein. All differences between actual and expected results are reported by output thereof to a system printer, the TSS CRT, a diskette or tape, in accordance with the user&#39;s wishes. 
     Although the present invention has been described in the context of a preferred embodiment thereof, it will be readily apparent to those skilled in the appertaining art, that modifications and variations can be made therein without departing from its spirit and scope. Accordingly, it is not intended that the present invention be limited to the specifics of the foregoing description of the preferred embodiment. Instead, the present invention should be considered as being limited solely by the appended claims, which alone are intended to define its scope.