1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
|
global exit_code
exit_code = main()
exit(exit_code)
function main
local secret_number
local guess
global 32 input_line
local p_line
p_line = &input_line
secret_number = getrand(100)
puts(.str_intro)
:guess_loop
puts(.str_guess)
syscall(0, 0, p_line, 30)
guess = stoi(p_line)
if guess < secret_number goto too_low
if guess > secret_number goto too_high
puts(.str_got_it)
return 0
:too_low
puts(.str_too_low)
goto guess_loop
:too_high
puts(.str_too_high)
goto guess_loop
:str_intro
string I'm thinking of a number.
byte 10
byte 0
:str_guess
string Guess what it is:
byte 32
byte 0
:str_got_it
string You got it!
byte 10
byte 0
:str_too_low
string Too low!
byte 10
byte 0
:str_too_high
string Too high!
byte 10
byte 0
; get a "random" number from 0 to x using the system clock
function getrand
argument x
global 16 getrand_time
local ptime
local n
ptime = &getrand_time
syscall(228, 0, ptime) ; clock_gettime(CLOCK_REALTIME, ptime)
ptime += 8 ; nanoseconds at offset 8 in struct timespec
n = *4ptime
n %= x
return n
; returns a pointer to a null-terminated string containing the number given
function itos
global 32 itos_string
argument x
local c
local p
p = &itos_string
p += 30
:itos_loop
c = x % 10
c += '0
*1p = c
x /= 10
if x == 0 goto itos_loop_end
p -= 1
goto itos_loop
:itos_loop_end
return p
; returns the number at the start of the given string
function stoi
argument s
local p
local n
local c
n = 0
p = s
:stoi_loop
c = *1p
if c < '0 goto stoi_loop_end
if c > '9 goto stoi_loop_end
n *= 10
n += c - '0
p += 1
goto stoi_loop
:stoi_loop_end
return n
function strlen
argument s
local p
p = s
:strlen_loop
if *1p == 0 goto strlen_loop_end
p += 1
goto strlen_loop
:strlen_loop_end
return p - s
function fputs
argument fd
argument s
local length
length = strlen(s)
syscall(1, fd, s, length)
return
function puts
argument s
fputs(1, s)
return
function fputn
argument fd
argument n
local s
s = itos(n)
fputs(fd, s)
return
function exit
argument status_code
syscall(0x3c, status_code)
function syscall
; I've done some testing, and this should be okay even if
; rbp-56 goes beyond the end of the stack.
; mov rax, [rbp-16]
byte 0x48
byte 0x8b
byte 0x85
byte 0xf0
byte 0xff
byte 0xff
byte 0xff
; mov rdi, rax
byte 0x48
byte 0x89
byte 0xc7
; mov rax, [rbp-24]
byte 0x48
byte 0x8b
byte 0x85
byte 0xe8
byte 0xff
byte 0xff
byte 0xff
; mov rsi, rax
byte 0x48
byte 0x89
byte 0xc6
; mov rax, [rbp-32]
byte 0x48
byte 0x8b
byte 0x85
byte 0xe0
byte 0xff
byte 0xff
byte 0xff
; mov rdx, rax
byte 0x48
byte 0x89
byte 0xc2
; mov rax, [rbp-40]
byte 0x48
byte 0x8b
byte 0x85
byte 0xd8
byte 0xff
byte 0xff
byte 0xff
; mov r10, rax
byte 0x49
byte 0x89
byte 0xc2
; mov rax, [rbp-48]
byte 0x48
byte 0x8b
byte 0x85
byte 0xd0
byte 0xff
byte 0xff
byte 0xff
; mov r8, rax
byte 0x49
byte 0x89
byte 0xc0
; mov rax, [rbp-56]
byte 0x48
byte 0x8b
byte 0x85
byte 0xc8
byte 0xff
byte 0xff
byte 0xff
; mov r9, rax
byte 0x49
byte 0x89
byte 0xc1
; mov rax, [rbp-8]
byte 0x48
byte 0x8b
byte 0x85
byte 0xf8
byte 0xff
byte 0xff
byte 0xff
; syscall
byte 0x0f
byte 0x05
return
|
