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
|
#include "common.h"
#include <libsec.h>
#include "dat.h"
/*
* unnatural acts with virtual memory
*/
typedef struct{
int ref;
char *va;
long sz;
}S;
static S s[15]; /* 386 only gives 4 */
static int nstab = nelem(s);
static long ssem = 1;
//static ulong thresh = 10*1024*1024;
static ulong thresh = 1024;
void*
segmalloc(ulong sz)
{
int i, j;
void *va;
if(sz < thresh)
return emalloc(sz);
semacquire(&ssem, 1);
for(i = 0; i < nstab; i++)
if(s[i].ref == 0)
goto found;
notfound:
/* errstr not informative; assume we hit seg limit */
for(j = nstab - 1; j >= i; j--)
if(s[j].ref)
break;
nstab = j;
semrelease(&ssem, 1);
return emalloc(sz);
found:
/*
* the system doesn't leave any room for expansion
*/
va = segattach(SG_CEXEC, "memory", 0, sz + sz/10 + 4096);
if(va == 0)
goto notfound;
s[i].ref++;
s[i].va = va;
s[i].sz = sz;
semrelease(&ssem, 1);
memset(va, 0, sz);
return va;
}
void
segmfree(void *va)
{
char *a;
int i;
a = va;
for(i = 0; i < nstab; i++)
if(s[i].va == a)
goto found;
free(va);
return;
found:
semacquire(&ssem, 1);
s[i].ref--;
s[i].va = 0;
s[i].sz = 0;
semrelease(&ssem, 1);
}
void*
segreallocfixup(int i, ulong sz)
{
char buf[ERRMAX];
void *va, *ova;
rerrstr(buf, sizeof buf);
if(strstr(buf, "segments overlap") == 0)
sysfatal("segibrk: %r");
va = segattach(SG_CEXEC, "memory", 0, sz);
if(va == 0)
sysfatal("segattach: %r");
ova = s[i].va;
fprint(2, "fix memcpy(%p, %p, %lud)\n", va, ova, s[i].sz);
memcpy(va, ova, s[i].sz);
s[i].va = va;
s[i].sz = sz;
segdetach(ova);
return va;
}
void*
segrealloc(void *va, ulong sz)
{
char *a;
int i;
ulong sz0;
fprint(2, "segrealloc %p %lud\n", va, sz);
if(va == 0)
return segmalloc(sz);
a = va;
for(i = 0; i < nstab; i++)
if(s[i].va == a)
goto found;
if(sz >= thresh)
if(a = segmalloc(sz)){
sz0 = msize(va);
memcpy(a, va, sz0);
fprint(2, "memset(%p, 0, %lud)\n", a + sz0, sz - sz0);
memset(a + sz0, 0, sz - sz0);
return a;
}
return realloc(va, sz);
found:
sz0 = s[i].sz;
fprint(2, "segbrk(%p, %p)\n", s[i].va, s[i].va + sz);
va = segbrk(s[i].va, s[i].va + sz);
if(va == (void*)-1 || va < end)
return segreallocfixup(i, sz);
a = va;
if(sz > sz0)
{
fprint(2, "memset(%p, 0, %lud)\n", a + sz0, sz - sz0);
memset(a + sz0, 0, sz - sz0);
}
s[i].va = va;
s[i].sz = sz;
return va;
}
void*
emalloc(ulong n)
{
void *p;
fprint(2, "emalloc %lud\n", n);
p = mallocz(n, 1);
if(!p)
sysfatal("malloc %lud: %r", n);
setmalloctag(p, getcallerpc(&n));
return p;
}
void
main(void)
{
char *p;
int i;
ulong sz;
p = 0;
for(i = 0; i < 6; i++){
sz = i*512;
p = segrealloc(p, sz);
memset(p, 0, sz);
}
segmfree(p);
exits("");
}
|
