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
|
/*
* Standalone run-time system test.
*
* This program checks that stack overflow checking works and that it
* interacts properly with heap extension.
*
* Copyright (C) 1991 Advanced RISC Machines Limited.
*/
#include "rtstand.h"
extern void __swi(0) put_char(int ch);
extern void __swi(2) put_string(char *string);
/* First, we make a function to claim a large(-ish) stack frame.
* Some obfuscation in case the compiler optimises us away...
*/
static int stack(int n, int v) {
/* claim n KB of stack */
int x[256],i;
if (n > 1) v = stack(n-1, v);
for (i = 0; i < 256; ++i) x[i] = v + i;
return x[0] + x[255];
}
/* Now we roll our own decimal output function - strictly %d format...
*/
static void puti(int n) {
if (n < 0) {
put_char('-');
n = -n;
}
if (n > 9) {
int n1 = n / 10;
n = n % 10;
puti(n1);
}
put_char(n + '0');
}
/* ...and a hex outputter... strictly %#.8X format.
*/
static void puth(unsigned n) {
int j;
put_string("0X");
for (j = 0; j < 8; ++j) {
put_char("0123456789ABCDEF"[n >> 28]);
n <<= 4;
}
}
/* Finally, we sit in a loop extending the heap and claiming ever bigger
* stack franes until something gives. Probably, the heap will give first,
* as currently tuned, and the program will announce "memory exhausted".
* If you tune it differently, it can be made to fail will a stack overflow
* run-time error. Try compiling this -DSTACK_OVERFLOW to provoke it.
*/
int main(int argc, char *argv[]) {
unsigned size, ask, got, total;
void *base;
put_string("kernel memory management test\r\n");
size = 4; /* KB */
ask = 0;
for (total = 0;;) {
put_string("force stack to "); puti(size); put_string("KB\r\n");
stack(size, 0);
put_string("request "); puti(ask); put_string(" words of heap - ");
got = __rt_alloc(ask, &base);
total += got;
put_string("allocate "); puti(got);
put_string(" words at "); puth((unsigned)base); put_string("\r\n");
if (got < ask) break;
ask += got / 2;
#ifdef STACK_OVERFLOW
size *= 2;
#else
size += 4;
#endif
}
put_string("memory exhausted, ");
puti(total); put_string(" words of heap, ");
puti(size); put_string("KB of stack\r\n");
return 0;
}
|
