CMSC313, Computer Organization & Assembly Language Programming, Spring 2013
Project 4: Indexed Addressing
Due: Tuesday March 12, 2013, 11:59pm
Objective
The objective of this programming project is to gain experience
writing assembly language code using indexed addressing modes.
Background
Your assembly language program for this project will work with a
linked list that is defined in a C program. Each node of the linked list
contains data about an e-book. The data type for a node is declared as:
<![CDATA[
typedef struct book {
char title[48] ;
char author[48] ; // first author
char subject[20] ; // Nonfiction, Fantasy, Mystery, ...
unsigned int year ; // year of e-book release
struct book *next ;
} book ;
]]>
In memory, each struct book occupies a contiguous block of
memory. Each field of the struct is placed right after the
previous one. This can be observed in the gdb debugger. (In
this example, B031 is a struct book):
<![CDATA[
(gdb) print B031
$1 = {title = "Breaking Point", '\000' <repeats 33 times>,
author = "Pamela Clare", '\000' <repeats 35 times>,
subject = "Romance", '\000' <repeats 12 times>, year = 2011,
next = 0x804a2e0}
(gdb) print &B031
$2 = (book *) 0x804a3a0
(gdb) print &B031.title
$3 = (char (*)[48]) 0x804a3a0
(gdb) print &B031.author
$4 = (char (*)[48]) 0x804a3d0
(gdb) print &B031.subject
$5 = (char (*)[20]) 0x804a400
(gdb) print &B031.year
$6 = (unsigned int *) 0x804a414
(gdb) print &B031.next
$7 = (struct book **) 0x804a418
]]>
Using this information we can define offsets for each field of
the struct:
<![CDATA[
; Offsets for fields in struct book.
;
%define TITLE_OFFSET 0
%define AUTHOR_OFFSET 48
%define SUBJECT_OFFSET 96
%define YEAR_OFFSET 116
%define NEXT_OFFSET 120
]]>
For example, if the ESI register holds the address of B031,
then [ESI+YEAR_OFFSET] can be used to reference the year field
of the struct. Similarly, [ESI+ECX+SUBJECT_OFFSET] can
be used to access the i-th character of the subject string
where the value of i is stored in ECX.
The last field of struct book is a pointer --- i.e., an address
-- of another struct book. This field allows us to connect
the nodes into a linked list. In the debugger session above, we can
print out the address of another struct book and notice
that it is the one referenced in the next field of
B031.
<![CDATA[
(gdb) print B031.next
$1 = (struct book *) 0x804a300
(gdb) print &B030
$8 = (book *) 0x804a2e0
]]>
Assignment
Your assignment is to write an assembly language program that traverses
a linked list of struct book's and prints out all the e-books
that have Fantasy as the subject. You must make good use of indexed
addressing modes. You will be graded on how well you use indexed
addressing modes.
Note: some CPU's do not support indexed addressing modes, so it
is always possible to write an assembly language program that
avoids using indexed addressing modes. However, if you submit a program
that does not make good use of indexed addressing modes for this
project, you will lose a significant number of points in your grade.
A data file is provided for you. This data file must be copied
on the GL filesystem to your account. The file resides in:
<![CDATA[
/afs/umbc.edu/users/c/h/chang/pub/cs313/data4.o
]]>
When you assemble your program, you must include data4.o
when you issue the ld command. That is, your compilation
command should look like:
<![CDATA[
linux2% nasm -f elf -g fantasy.asm
linux2% ld fantasy.o data4.o
]]>
The records in the data4.o file contain the information for
these e-books:
<![CDATA[
Breaking Point, Pamela Clare, Romance, 2011
Vow, Kim Carpenter, Nonfiction, 2012
1491, Charles C. Mann, Nonfiction, 2006
Three Weeks with My Brother, Nicholas Sparks, Nonfiction, 2004
The 10 Habits of Happy Mothers, Meg Meeker, M.D., Nonfiction, 2011
We Need to Talk About Kevin, Lionel Shriver, Fiction, 2011
The Prague Cemetery, Umberto Eco, Fiction, 2011
Black Dahlia & White Rose, Joyce Carol Oates, Fiction, 2012
Glad Tidings, Debbie Macomber, Romance, 2012
A Summer Affair, Elin Hilderbrand, Romance, 2008
Dead until Dark, Charlaine Harris, Fantasy, 2001
Between the Dark and the Daylight, Richard Marsh, Mystery, 2012
Good Girls Don't, Victoria Dahl, Romance, 2011
Inheritance, Christopher Paolini, Fantasy, 2011
Best Staged Plans, Claire Cook, Fiction, 2011
The Gap Year, Sarah Bird, Humor, 2011
The Affair Next Door, Anna Katherine Green, Mystery, 2012
Crossed, Ally Condie, Romance, 2011
Eclipse, Stephenie Meyer, Romance, 2007
New Moon, Stephenie Meyer, Romance, 2007
The Third Gate, Lincoln Child, Fantasy, 2012
1225 Christmas Tree Lane, Debbie Macomber, Romance, 2011
Murder on Astor Place, Victoria Thompson, Mystery, 2009
Heaven is for Real, Todd Burpo, Nonfiction, 2011
15 Seconds, Andrew Gross, Thriller, 2012
Harry Potter and the Chamber of Secrets, J.K. Rowling, Fantasy, 2012
1Q84, Haruki Murakami, Fiction, 2011
The Affair, Lee Child, Mystery, 2011
The Girl With the Dragon Tattoo, Stieg Larsson, Mystery, 2011
Explosive Eighteen, Janet Evanovich, Mystery, 2011
The Help, Kathryn Stockett, Fiction, 2009
]]>
A correct program should print out all the Fantasy books:
<![CDATA[
Dead until Dark, Charlaine Harris, Fantasy, 2001
Inheritance, Christopher Paolini, Fantasy, 2011
The Third Gate, Lincoln Child, Fantasy, 2012
Harry Potter and the Chamber of Secrets, J.K. Rowling, Fantasy, 2012
]]>
The data4.o file also contains a pointer named library
that points to the first node in the linked list. Thus, one of your
first instructions should be:
<![CDATA[
mov esi, [library]
]]>
When you are ready to look at the next node of the linked list, you can
just say:
<![CDATA[
mov esi, [esi+NEXT_OFFSET]
]]>
Implementation Notes
- You need to declare library as an external label in your
assembly language program:
<![CDATA[
extern library
]]>
- This linked list does not have a "dummy" header node. The
library pointer references the first node directly.
- The next field of the last node in the linked list
holds the value 0. That is how you will know that you have
reached the end of the linked list.
- When you print a string field of struct book (i.e.,
title, author and subject), you should NOT
copy these strings to a new memory location, since these strings
are already in memory. You should tell the WRITE system call where these
strings reside.
- Note that the strings in struct book are C-style NULL
terminated strings. You will need to find out how long each string is
before you make the system call to WRITE. (You can also
use indexed addressing, here.)
- Your project submission will be graded with a different data file.
So, you should make sure that your code works when it's given a
different linked list.
- You can use your prt_dec subroutine from Project 3
to print out the year field. If your prt_dec
subroutine does not work, then just don't print the year field.
- You may find the LEA instruction useful. (LEA = Load Effective
Address.) The LEA instruction stores what would have been the
address in the source operand into the destination operand. For example,
<![CDATA[
lea edi, [ESI+SUBJECT_OFFSET]
]]>
will move ESI + SUBJECT_OFFSET and store it in EDI.
Turning in your program
Use the UNIX submit command on the GL system to turn in
your project. You should submit 2 files: your assembly
language program and a typescript file of a sample run of your program.
You do not need to submit the data4.o file.
The UNIX command to do this should look something like:
submit cs313 proj4 fantasy.asm typescript
Last Modified:
26 Mar 2013 05:56:32 EDT
by
Richard Chang
to Spring 2013 CMSC 313 Homepage