CS260 program assignment #3 (30 points, check the schedule for the due date)

Transcription

1 CS260 program assignment #3 (30 points, check the schedule for the due date) This assembly language program simulates virtual memory management. Since you have no access to associative memory, you will need to write a function to simulate a TLB and the rest of the virtual memory techniques discussed in the Virtual Memory chapter in the Course Notes! You earn points by completing the code, as you ll soon see This project requires the files 3VirtMem.asm, and Test3.zip, which contains a library file, an include file (VirtMem.inc) required by 3VirtMem.asm, and test and data files. After you unzip the download, to create 3VirtMem.exe, use ml /Zi 3VirtMem.asm VirtMem.lib to run the program, at the command prompt use 3VirtMem.exe test3.txt to see the sample in Course Notes chap 22, use 3VirtMem.exe /s Chap22.txt to run limited unit testing, use 3VirtMem.exe /u to do a full test, use test3.bat To experiment or debug, you can create a shorter datafile (e.g., shorter.txt). To use it, run 3VirtMem.exe shorter.txt 3VirtMem.exe reads a data file (test3.txt) that contains a series of virtual memory requests. The program honors each virtual memory request using simulated vpframes in working memory. If you care, the format of the data file is explained in the GetData routine in 3VirtMem.asm (or run 3Virtmem.exe /c to display it). 3VirtMem.asm contains the line include VirtMem.inc. At compile time, the contents of VirtMem.inc is used along with the contents of 3VirtMem.asm to produce 3VirtMem.obj. However, 3VirtMem.obj does not contain all the code required for the problem. The rest of the code lives in VirtMem.lib. The linker satisfies the extern statements that appear in 3VirtMem.asm, with the corresponding public statements that I put into the file VirtMem.asm that I used to create VirtMem.lib. Note: I created the file VirtMem.lib by ml /c VirtMem.asm lib Virtmem.lib /ignorecase +VirtMem.obj,lib.lst So, if you start with a completely working program that implements the ideas in the Course Notes, what are you supposed to do to earn 30 points??? The Grades section of 3VirtMem.asm contains the answer. Read it now from the file ; ; ; Grades ; ; This file with the Virtmem.lib is a fully functioning correct program! ; Run the test procedure to verify that this is true! ; ; Each function in this file is defined in a uproc/uendp block. The ; library has a corresponding gsmproc/gsmendp block. The points you earn ; for this problem will depend on which uproc/uendp routines you write ; A: >=27 points; B: >=24 points; C: >=21 points; D: >=18 points; F: < 18 pts. ; You can't earn more than 30 points total...even if you do more... unless... ; if you code ALL the routines worth points, you can earn 31 points. This is known ; as the Ryosuke Niwa Challenge. Ryosuke is the first person to earn 31 even though ; he didn t need the points to earn an A! Why do it??? Because there was an opportunity ; to learn more? Because it was there? If you have to ask why, well, never mind.

2 Currently, 3VirtMem.asm has the main routine and little else. All the calls through out the system go to the library. If the library detects that you wrote code for a function, it calls your code instead of using the library code. To be cool, here s what to do! 1) Setup the editor ;;NOTE: set the editor to use tabs == 8 spaces, and to insert spaces instead of TABS! ;; Otherwise, the results will be impossible for me to read and you'll loose style points!!! ;; If you are using WinMerge, set tabs==8 and insert spaces, also!!! ;; Ragged text is "unacceptable" style subject to a 10% penalty!!! 2) Entirely read 3VirtMem.asm to get the lay of the land. 3) One by one, for each function a.) Between uproc XXXX,pts and uendp XXXX write the code. The documentation for each function includes a description!!!! Read it! Basically it documents (a) where the incoming data is located, (b) where results are returned, and (c) what registers you may trashed. input output ; ENTRY registers (and/or stack) which contain input arguments ; EXIT - registers, and/or stack, and/or flags which contain the results ; REGS - registers which are modified by the function at exit. ; (You may need to use other registers in the function, but you ; must restore their original values when the function exits! ; PUSH on entry, and POP original values on exit. The outside ; world only cares what is changed by your function. Do NOT ; list what registers you use, only those that may have CHANGED!) b.) For example, for function DspCRLF ;************** DspCRLF - Display CR,LF ; ENTRY - none ; EXIT - none ; REGS - FLAGS ; USES - whatever (hints: DspChr, DspStr, PrintStr, MSDOS, etc.) BEFORE AFTER uproc DspCRLF,1 Uses uproc DspCRLF,1 library int 3 ;for debugging ret code push ax int 3 ;for debugging... uendp DspCRLF pop ax ret uendp DspCRLF ` Now, when you re-compile and run 3VirtMem.exe, your DspCRLF is used instead of the library code. c.) Add some throw-away-unit-testing code to exercise your function (this is not always feasible) d.) Re-compile and debug your function when the int 3 breakpoint is hit. e.) When you think it is working, remove the unit test code, and run it with test3.bat to verify that all is well. If it compares exactly, you earn the points for this function! If it doesn t compare exactly, fix the code, or give-up and try later. If you decide to try later, just put ret as the first instruction in the function. Then, go on to the next function, and so on. To re-active your function code, just remove the first instruction ret and the rest of your code becomes active.

3 Shortcuts: You can use short-cut instructions like shl reg,# and imul reg16,reg16,# to simplify your programming tasks because.186 appears at the top of the Virtmem.inc. Do NOT change VirtMem.inc (the library was compiled with this file). mov ax,1011b shl ax,2 (AX = b) instead of mov cl,2 shl ax,cl mov bx,7 imul ax,bx,3 (AX=0015h) push 12 (000Ch pushed) instead of mov ax,12 push ax How Big are the tables? Assume that both vpframes and virtual pages are 4KB. This means that a program s virtual memory is at most 256 vpages (256 * 4K = 2 8 * 2 2 *2 10 = 2 20 = 1MB, max. addressable space of an Intel 8086) The following values come from the data file and may change each time your program is run. See DosEntry: mov vpagetbl_max,dx ;Save nr. of vpages in virtual memory mov wm_vpframes_cnt,bx ;Save nr. of vpframes in working memory mov tlb_row_cnt,cx ;Save nr. of entries in the expensive TLB Programming notes 1. Make sure you have read and understand Chapter 22 before you change 3VirtMem.asm! 2. Look at the list of functions and see what part they play in the algorithm. 3. We ll use a special debugging trick to test the Not-Recently-Used logic in a controlled fashion. 4. The code dynamically allocates tables based on the input sizes for the virtual page table, TLB, and vpframe maps. 5. Use the next full TLB # strategy to replace the entries in the TLB. 6. Use the next full vpframe # strategy to replace vpframes when all have been used recently. TLB I Vpage # Physical Vpframe # 0?? 0?? 0?? Next full TLB # is in the variable tlb_fullindex See 3VirtMem.asm Working memory Vpframe maps Physical Vpframe index I R 0 0?? 1 0??... D The number of s in the In-Use, Referenced, Dirty maps are defined by wm_vpframes_cnt. Next full vpframe # is in the variable wm_fullindex Virtual Page table (VPtbl) Vpage index P 0 0? 1 0? 2 0? 3 0? 4 0? 5 0? * 0? Physical vpframe # 1 byte per entry 1 P- flag 7 s for vpframe number * Number of entries == program size defined in datafile. Vpage index = 0 program size in vpages minus one! Max program size = 1 MB = 256 * 4K = 8- by 4K

4 7. Basically, through out the system, a virtual page number is a 2-byte value (a word). The vpframe number is a 1-byte value (a byte). 8. The TLB I- is a single byte, a waste of 7 extra s, but, there you have it. 9. The I, R, and D s associated with working memory vpframes, are true single flags, saved in a map (one or more bytes). 10. The Virtual Page Table is an array of bytes most-significant- (msb), the left most, is the P- flag, the remaining 7 s hold the vpframe index. 11. Remember: RTFM. Read the F ine manual. Have fun! Think of Ryosuke Niwa! Helpful hints 1) Think globally. Act locally. Think about the function you are working on and how it fits into the big picture. 2) Regular expressions are great for finding function definitions. Searching for Dsp will show lots of matches. Searching for proc.*dsp (check the regular expression check box) will only show function definitions that contain Dsp in the name! Check the match case checkbox if you care about upper and lower case matching. Think of a question in English stating what you wish to search for. Then use special regular expression symbols to translate your question a. any character. b. the period character \. c. specific character char e.g., a or b etc. d. range of characters [ ] e.g., [_A-Za-z][_A-Za-z0-9]* searches for C++ like variable names (begins with underscore, or letter, followed by zero or letters, digits or underscores e. zero or more occurrences * f. logical OR g. check on-line for examples. However, Crimson Editor doesn t support a lot of fancy searches. 3) When you use F3 to continue a search, sometimes the editor gets stuck and refuses to continue the search even when there are more matches to find (this usually happens near blank lines). Click somewhere and press F3 again. 4) Shift+F3 continues the search backwards. 5) Use int 3 to set breakpoints in all new code. Remove them when you are done testing that code. 6) Search for the regular expression int.*3 to locate int 3 s in your code (matches: int anything 3). 7) Use proc endp to find the next proc OR endp. Good for backing up to the top a function or down to the bottom or to go to the next/previous function. 8) See the Course Notes Index to find Crimson Editor and CodeView topics. They can save a lot of time. An index is your friend. You don t have to know everything, just where to find it! (check the index on the first page, first items on the left under! special! special $......x-xxx etc. using CodeView......x-xxx 9) The DWIM instruction mentioned in class is always handy when you get a mental block. Let me know what special uses you put it to. 10) Remember to use SHL/SHR and IMUL with constants to make life easier!

5 11) Use Crimson Editor s Search Find in Files to find where a name is used/defined. For example, you see GO_MSDOS MEMORY_ALLOCATE in the notes. What the heck is MEMORY_ALLOCATE? Aim the Folder: textbox at your subdirectory containing 3VirtMem.asm, Virtmem.inc, and Errors.inc, click Find. Double click on the highlighted line to see that MEMORY_ALLOCATE is defined in virtmem.inc in the second MSDOS functions. Use the Course Notes Index under MSDOS you ll see 48h allocate memory.. A-189. Turn to page A-189 to get all the details. 12) Don t use CodeView s RUN RESTART option! The only safe thing to do is EXIT entirely to the command line, and then run a fresh copy of CodeView with your program. Why is this? Hint: int x = 4; this is saved in.data void main() { cout << x; x = 7; now RUN RESTART. What do you think x is??? 13) To really give your program a work out, run data file bigtest.txt which produces bigtest.out. 3VirtMem.exe bigtest.txt > pgm.out wm.bat bigtest.out pgm.out

6 Associated Reading The skills for this problem appear in various chapters as shown below. The Virtual Memory algorithm and data structures (ch 22) Arrays (ch 10) maps (ch 9) bytes variable length (ch 12.1, Appendix A) structures (ch 11) IMUL (appendix A.5.1) Macros (ch 8) pushs/pops, PrintStr Interrupts (ch 15) Misc. XCHG (ch 7.1.1) XLAT (ch ) Chapter List Summary 7 (XCHG) 8 (macro) 9 (logical operations) 11 (structure) 12 (seg override) 15 (interrupts) 22 (virtual memory) Appendix A (new/free, IMUL)