-
Notifications
You must be signed in to change notification settings - Fork 46
/
313index-bounds-check.subx
102 lines (94 loc) · 3.44 KB
/
313index-bounds-check.subx
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
# Helper to check an array's bounds, and to abort if they're violated.
# Really only intended to be called from code generated by mu.subx.
== code
__check-mu-array-bounds: # index: int, elem-size: int, arr-size: int, function-name: (addr array byte), array-name: (addr array byte)
# . prologue
55/push-ebp
89/<- %ebp 4/r32/esp
# . save registers
50/push-eax
51/push-ecx
52/push-edx
# . not bothering saving ebx; it's only clobbered if we're going to abort
# ecx = arr-size
8b/-> *(ebp+0x10) 1/r32/ecx
# var overflow/edx: int = 0
ba/copy-to-edx 0/imm32
# var offset/eax: int = index * elem-size
8b/-> *(ebp+8) 0/r32/eax
f7 4/subop/multiply-eax-with *(ebp+0xc)
# check for overflow
81 7/subop/compare %edx 0/imm32
0f 85/jump-if-!= __check-mu-array-bounds:overflow/disp32
# check bounds
39/compare %eax 1/r32/ecx
0f 82/jump-if-unsigned< $__check-mu-array-bounds:end/disp32 # negative index should always abort
# abort if necessary
(write-buffered Stderr "fn ")
(write-buffered Stderr *(ebp+0x14))
(write-buffered Stderr ": offset ")
(write-int32-hex-buffered Stderr %eax)
(write-buffered Stderr " is too large for array '")
(write-buffered Stderr *(ebp+0x18))
(write-buffered Stderr "'\n")
(flush Stderr)
# exit(1)
bb/copy-to-ebx 1/imm32
e8/call syscall_exit/disp32
# never gets here
$__check-mu-array-bounds:end:
# . restore registers
5a/pop-to-edx
59/pop-to-ecx
58/pop-to-eax
# . epilogue
89/<- %esp 5/r32/ebp
5d/pop-to-ebp
c3/return
__check-mu-array-bounds:overflow:
# "fn " function-name ": offset to array '" array-name "' overflowed 32 bits\n"
(write-buffered Stderr "fn ")
(write-buffered Stderr *(ebp+0x14))
(write-buffered Stderr ": offset to array '")
(write-buffered Stderr *(ebp+0x18))
(write-buffered Stderr "' overflowed 32 bits\n")
(flush Stderr)
# exit(1)
bb/copy-to-ebx 1/imm32
e8/call syscall_exit/disp32
# never gets here
# potential alternative
#? __bounds-check: # msg: (addr array byte)
#? (write-buffered Stderr "abort: array bounds exceeded in fn ")
#? 8b/-> *(esp+4) 0/r32/eax # we're going to abort, so just clobber away
#? (write-buffered Stderr %eax)
#? (write-buffered Stderr Newline)
#? # exit(1)
#? bb/copy-to-ebx 1/imm32
#? e8/call syscall_exit/disp32
# to be called as follows:
# var/reg <- index arr/rega: (addr array T), idx/regi: int
# | if size-of(T) is 1, 2, 4 or 8
# => # temporarily save array size to reg to check bounds
# "8b/-> *" rega " " reg "/r32"
# "c1/shift 5/subop/right %" reg " " log2(size-of(T)) "/imm32"
# "3b/compare " reg "/r32 *" rega
# "68/push \"" function "\"/imm32" # pass function name to error message
# "0f 8d/jump-if->= __bounds_check/disp32"
# "81 0/subop/add %esp 4/imm32" # drop function name
# # actually save the index addr in reg
# "8d/copy-address *(" rega "+" regi "<<" log2(size-of(T)) "+4) " reg "/r32"
__mu-abort-null-index-base-address:
(write-buffered Stderr "null address in 'index'\n")
(flush Stderr)
# exit(1)
bb/copy-to-ebx 1/imm32
e8/call syscall_exit/disp32
# never gets here
__mu-abort-null-get-base-address:
(write-buffered Stderr "null address in 'get'\n")
(flush Stderr)
# exit(1)
bb/copy-to-ebx 1/imm32
e8/call syscall_exit/disp32
# never gets here