Difference between revisions of "CSC231 Homwork 2 Solution 2010"
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| + | * To test the programs, the hexadecimal dump of the object file of the original program was compared to the hexadecimal dump of the object file of your version. | ||
| + | * Assume that hw2_mystery.solution.asm is the orginal that you have to recreate, and assume that hw2c.asm is your program: | ||
| + | |||
| + | nasm -f elf hw2c.asm | ||
| + | hexdump -C hw2c.o | tail -190 | head -40 > hw2c.lst | ||
| + | |||
| + | nasm -f elf hw2_mystery.solution.asm | ||
| + | hexdump -C hw2_mystery.solution.o | tail -190 | head -40 > hw2_mystery.solution.lst | ||
| + | |||
| + | diff -y hw2_mystery.solution.lst hw2c.lst | ||
| + | |||
| + | 000001f0 04 00 00 00 08 00 00 00 00 00 00 00 00 00 00 00 | 000001f0 04 00 00 00 08 00 00 00 00 00 00 00 00 00 00 00 | | ||
| + | 00000200 20 6d 61 6b 65 73 20 70 65 72 66 65 63 74 2e 2e | 00000200 20 6d 61 6b 65 73 20 70 65 72 66 65 63 74 2e 2e | | ||
| + | 00000210 2e 70 72 61 63 74 69 63 65 62 75 74 20 6e 6f 62 | 00000210 2e 70 72 61 63 74 69 63 65 62 75 74 20 6e 6f 62 | | ||
| + | 00000220 6f 64 79 27 73 20 73 6f 20 77 68 79 20 3f 0a 0a | 00000220 6f 64 79 27 73 20 73 6f 20 77 68 79 20 3f 0a 0a | | ||
| + | 00000230 b8 04 00 00 00 bb 01 00 00 00 b9 11 00 00 00 ba | 00000230 b8 04 00 00 00 bb 01 00 00 00 b9 11 00 00 00 ba | | ||
| + | 00000240 08 00 00 00 cd 80 b8 ff ff ff ff b8 04 00 00 00 | | 00000240 08 00 00 00 cd 80 b8 04 00 00 00 bb 01 00 00 00 | | ||
| + | 00000250 bb 01 00 00 00 b9 07 00 00 00 b9 00 00 00 00 ba | | 00000250 b9 07 00 00 00 b9 00 00 00 00 ba 10 00 00 00 cd | | ||
| + | 00000260 07 00 00 00 cd 80 ba 11 00 00 00 b8 01 00 00 00 | | 00000260 80 ba 11 00 00 00 b8 01 00 00 00 b8 04 00 00 00 | | ||
| + | 00000270 b8 04 00 00 00 bb 01 00 00 00 b9 07 00 00 00 ba | | 00000270 bb 01 00 00 00 b9 07 00 00 00 ba 0a 00 00 00 cd | | ||
| + | 00000280 0a 00 00 00 cd 80 b8 04 00 00 00 bb 01 00 00 00 | | 00000280 80 b8 04 00 00 00 bb 01 00 00 00 b9 19 00 00 00 | | ||
| + | 00000290 b9 19 00 00 00 ba 0d 00 00 00 cd 80 b8 04 00 00 | | 00000290 ba 0d 00 00 00 cd 80 b8 04 00 00 00 bb 01 00 00 | | ||
| + | 000002a0 00 bb 01 00 00 00 b9 06 00 00 00 ba 0a 00 00 00 | | 000002a0 00 b9 06 00 00 00 ba 0a 00 00 00 41 cd 80 b8 04 | | ||
| + | 000002b0 41 cd 80 b8 04 00 00 00 bb 01 00 00 00 b9 24 00 | | 000002b0 00 00 00 bb 01 00 00 00 b9 24 00 00 00 41 ba 07 | | ||
| + | 000002c0 00 00 41 ba 07 00 00 00 41 cd 80 b8 04 00 00 00 | | 000002c0 00 00 00 41 cd 80 b8 04 00 00 00 bb 01 00 00 00 | | ||
| + | 000002d0 bb 01 00 00 00 b9 11 00 00 00 ba 08 00 00 00 cd | | 000002d0 b9 0e 00 00 00 ba 0b 00 00 00 cd 80 b8 04 00 00 | | ||
| + | 000002e0 80 b8 04 00 00 00 bb 01 00 00 00 b9 2d 00 00 00 | | 000002e0 00 bb 01 00 00 00 b9 2d 00 00 00 ba 03 00 00 00 | | ||
| + | 000002f0 ba 03 00 00 00 cd 80 b8 01 00 00 00 bb 00 00 00 | | 000002f0 cd 80 b8 01 00 00 00 bb 00 00 00 00 cd 80 00 00 | | ||
| + | 00000300 00 cd 80 00 00 00 00 00 00 00 00 00 00 00 00 00 | | 00000300 00 54 68 65 20 4e 65 74 77 69 64 65 20 41 73 73 | | ||
| + | |||
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Revision as of 10:13, 7 October 2010
--D. Thiebaut 21:35, 6 October 2010 (UTC)
Number Systems
Angela Zhu
231a-ab
hw2b.txt
CSC 231
Sept. 29, 2010
Decimal: 135
Hexadecimal: 87
Binary: 1000 0111
Decimal: 1001
Hexadecimal: 3E9
Binary: 0011 1110 1001
Decimal: 255
Hexadecimal: FF
Binary: 1111 1111
Decimal: 2561
Hexadecimal: A01
Binary: 1010 0000 0001
Decimal: 65535
Hexadecimal: FFFF
Binary: 1111 1111 1111 1111
Decimal: 63640
Hexadecimal: F898
Binary: 1111 1000 1001 1000
Decimal: 31
Hexadecimal: 1F
Binary: 1 1111
Decimal: 2290649224
Hexadecimal: 88888888
Binary: 1000 1000 1000 1000 1000 1000 1000 1000
Logic Design
- To test the validity of boolean function, a simple Python program can be of great help.
#! /bin/env python
# truthtable.py
# D. Thiebaut
# how a simple python program can generate the
# truth table of a boolean function
#
def xor( a, b ):
return a and (not b) or (not a ) and b
def candidate( b3, b2, b1, b0 ):
return b2 and b3 and not (b0 and b1) \
or b0 and b1 and not (b2 and b3) \
or xor( b0, b1) and xor( b2, b3 )
def main():
print " a b c d | f "
print "------------+------"
for a in [ 0, 1 ]:
for b in [ 0, 1 ]:
for c in [ 0, 1 ]:
for d in [ 0, 1 ]:
x = candidate( a, b, c, d )
print "%3d%3d%3d%3d |%3d" % \
( a, b, c, d, x )
main()
Mystery Program
- The program prints a quote attributed to Kurt Cobain: "Practice makes perfect... but nobody's perfect... so why practice?"
1 ;;; hw2c.asm
2 ;;; Alec Goebel
3 ;;;
4 ;;; reverse engineered from provided hex dump.
5 ;;; Prints "practice makes perfect...but nobody's perfect...so why practice?\n\n"
6 ;;;
7 ;;; to assemble:
8 ;;;
9 ;;; nasm -f elf -F stabs hw2c.asm
10 ;;; ld -o program hw2c.o
11 ;;;
12 ;;; to run
13 ;;; $ ./hw2c
14 ;;; practice makes perfect...but nobody's perfect...so why practice?
15 ;;;
16 ;;; $
17 ;;; -------------------------------------------------------------------
18
19 EXIT equ 1
20 WRITE equ 4
21 STDOUT equ 1
22
23 ;; ------------------------------------------------------------
24 ;; data areas
25 ;; ------------------------------------------------------------
26
27 section .data
28
29 00000000 206D616B657320 makes db " makes "
30 00000007 706572666563742E2E- prct db "perfect...practice"
31 00000010 2E7072616374696365
32 00000019 627574206E6F626F64- nbdy db "but nobody's so why "
33 00000022 79277320736F207768-
34 0000002B 7920
35 0000002D 3F0A0A qst db "?", 10, 10
36
37
38 ;; ------------------------------------------------------------
39 ;; code area
40 ;; ------------------------------------------------------------
41
42 section .text
43 global _start
44
45 _start:
46
47 ;; write 'practice' on STDOUT
48 00000000 B804000000 mov eax,WRITE
49 00000005 BB01000000 mov ebx,STDOUT
50 0000000A B9[11000000] mov ecx,prct+10
51 0000000F BA08000000 mov edx,8
52 00000014 CD80 int 0x80
53
54 ;; pointless instruction
55 00000016 B8FFFFFFFF mov eax,0xffffffff
56
57 ;; write ' makes ' on STDOUT
58 0000001B B804000000 mov eax,WRITE
59 00000020 BB01000000 mov ebx,STDOUT
60 00000025 B9[07000000] mov ecx,prct ;; pointless
61 0000002A B9[00000000] mov ecx,makes
62 0000002F BA07000000 mov edx,7
63 00000034 CD80 int 0x80
64
65 ;; write 'perfect...' on STDOUT
66 00000036 BA[11000000] mov edx,prct+10 ;; pointless
67 0000003B B801000000 mov eax,1 ;; pointless
68 00000040 B804000000 mov eax,WRITE
69 00000045 BB01000000 mov ebx,STDOUT
70 0000004A B9[07000000] mov ecx,prct
71 0000004F BA0A000000 mov edx,10
72 00000054 CD80 int 0x80
73
74 ;; write "but nobody's " on STDOUT
75 00000056 B804000000 mov eax,WRITE
76 0000005B BB01000000 mov ebx,STDOUT
77 00000060 B9[19000000] mov ecx,nbdy
78 00000065 BA0D000000 mov edx,13
79 0000006A CD80 int 0x80
80
81 ;; write "perfect..." to STDOUT
82 0000006C B804000000 mov eax,WRITE
83 00000071 BB01000000 mov ebx,STDOUT
84 00000076 B9[06000000] mov ecx,prct-1
85 0000007B BA0A000000 mov edx,10
86 00000080 41 inc ecx
87 00000081 CD80 int 0x80
88
89 ;; write "so why " to STDOUT
90 00000083 B804000000 mov eax,WRITE
91 00000088 BB01000000 mov ebx,STDOUT
92 0000008D B9[24000000] mov ecx,nbdy+11
93 00000092 41 inc ecx
94 00000093 BA07000000 mov edx,7
95 00000098 41 inc ecx
96 00000099 CD80 int 0x80
97
98 ;; write "practice" to STDOUT
99 0000009B B804000000 mov eax,WRITE
100 000000A0 BB01000000 mov ebx,STDOUT
101 000000A5 B9[11000000] mov ecx,prct+10
102 000000AA BA08000000 mov edx,8
103 000000AF CD80 int 0x80
104
105 ;; write "?\n\n"
106 000000B1 B804000000 mov eax,WRITE
107 000000B6 BB01000000 mov ebx,STDOUT
108 000000BB B9[2D000000] mov ecx,qst
109 000000C0 BA03000000 mov edx,3
110 000000C5 CD80 int 0x80
111
112 ;; exit()
113 000000C7 B801000000 mov eax,EXIT
114 000000CC BB00000000 mov ebx,0
115 000000D1 CD80 int 0x80 ; final system call
- To test the programs, the hexadecimal dump of the object file of the original program was compared to the hexadecimal dump of the object file of your version.
- Assume that hw2_mystery.solution.asm is the orginal that you have to recreate, and assume that hw2c.asm is your program:
nasm -f elf hw2c.asm hexdump -C hw2c.o | tail -190 | head -40 > hw2c.lst nasm -f elf hw2_mystery.solution.asm hexdump -C hw2_mystery.solution.o | tail -190 | head -40 > hw2_mystery.solution.lst diff -y hw2_mystery.solution.lst hw2c.lst
000001f0 04 00 00 00 08 00 00 00 00 00 00 00 00 00 00 00 | 000001f0 04 00 00 00 08 00 00 00 00 00 00 00 00 00 00 00 | 00000200 20 6d 61 6b 65 73 20 70 65 72 66 65 63 74 2e 2e | 00000200 20 6d 61 6b 65 73 20 70 65 72 66 65 63 74 2e 2e | 00000210 2e 70 72 61 63 74 69 63 65 62 75 74 20 6e 6f 62 | 00000210 2e 70 72 61 63 74 69 63 65 62 75 74 20 6e 6f 62 | 00000220 6f 64 79 27 73 20 73 6f 20 77 68 79 20 3f 0a 0a | 00000220 6f 64 79 27 73 20 73 6f 20 77 68 79 20 3f 0a 0a | 00000230 b8 04 00 00 00 bb 01 00 00 00 b9 11 00 00 00 ba | 00000230 b8 04 00 00 00 bb 01 00 00 00 b9 11 00 00 00 ba | 00000240 08 00 00 00 cd 80 b8 ff ff ff ff b8 04 00 00 00 | | 00000240 08 00 00 00 cd 80 b8 04 00 00 00 bb 01 00 00 00 | 00000250 bb 01 00 00 00 b9 07 00 00 00 b9 00 00 00 00 ba | | 00000250 b9 07 00 00 00 b9 00 00 00 00 ba 10 00 00 00 cd | 00000260 07 00 00 00 cd 80 ba 11 00 00 00 b8 01 00 00 00 | | 00000260 80 ba 11 00 00 00 b8 01 00 00 00 b8 04 00 00 00 | 00000270 b8 04 00 00 00 bb 01 00 00 00 b9 07 00 00 00 ba | | 00000270 bb 01 00 00 00 b9 07 00 00 00 ba 0a 00 00 00 cd | 00000280 0a 00 00 00 cd 80 b8 04 00 00 00 bb 01 00 00 00 | | 00000280 80 b8 04 00 00 00 bb 01 00 00 00 b9 19 00 00 00 | 00000290 b9 19 00 00 00 ba 0d 00 00 00 cd 80 b8 04 00 00 | | 00000290 ba 0d 00 00 00 cd 80 b8 04 00 00 00 bb 01 00 00 | 000002a0 00 bb 01 00 00 00 b9 06 00 00 00 ba 0a 00 00 00 | | 000002a0 00 b9 06 00 00 00 ba 0a 00 00 00 41 cd 80 b8 04 | 000002b0 41 cd 80 b8 04 00 00 00 bb 01 00 00 00 b9 24 00 | | 000002b0 00 00 00 bb 01 00 00 00 b9 24 00 00 00 41 ba 07 | 000002c0 00 00 41 ba 07 00 00 00 41 cd 80 b8 04 00 00 00 | | 000002c0 00 00 00 41 cd 80 b8 04 00 00 00 bb 01 00 00 00 | 000002d0 bb 01 00 00 00 b9 11 00 00 00 ba 08 00 00 00 cd | | 000002d0 b9 0e 00 00 00 ba 0b 00 00 00 cd 80 b8 04 00 00 | 000002e0 80 b8 04 00 00 00 bb 01 00 00 00 b9 2d 00 00 00 | | 000002e0 00 bb 01 00 00 00 b9 2d 00 00 00 ba 03 00 00 00 | 000002f0 ba 03 00 00 00 cd 80 b8 01 00 00 00 bb 00 00 00 | | 000002f0 cd 80 b8 01 00 00 00 bb 00 00 00 00 cd 80 00 00 | 00000300 00 cd 80 00 00 00 00 00 00 00 00 00 00 00 00 00 | | 00000300 00 54 68 65 20 4e 65 74 77 69 64 65 20 41 73 73 |
