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
|
// SPDX-License-Identifier: GPL-2.0
/*
* Test that loads/stores expand the stack segment, or trigger a SEGV, in
* various conditions.
*
* Based on test code by Tom Lane.
*/
#undef NDEBUG
#include <assert.h>
#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <sys/resource.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#define _KB (1024)
#define _MB (1024 * 1024)
volatile char *stack_top_ptr;
volatile unsigned long stack_top_sp;
volatile char c;
enum access_type {
LOAD,
STORE,
};
/*
* Consume stack until the stack pointer is below @target_sp, then do an access
* (load or store) at offset @delta from either the base of the stack or the
* current stack pointer.
*/
__attribute__ ((noinline))
int consume_stack(unsigned long target_sp, unsigned long stack_high, int delta, enum access_type type)
{
unsigned long target;
char stack_cur;
if ((unsigned long)&stack_cur > target_sp)
return consume_stack(target_sp, stack_high, delta, type);
else {
// We don't really need this, but without it GCC might not
// generate a recursive call above.
stack_top_ptr = &stack_cur;
#ifdef __powerpc__
asm volatile ("mr %[sp], %%r1" : [sp] "=r" (stack_top_sp));
#else
asm volatile ("mov %%rsp, %[sp]" : [sp] "=r" (stack_top_sp));
#endif
// Kludge, delta < 0 indicates relative to SP
if (delta < 0)
target = stack_top_sp + delta;
else
target = stack_high - delta + 1;
volatile char *p = (char *)target;
if (type == STORE)
*p = c;
else
c = *p;
// Do something to prevent the stack frame being popped prior to
// our access above.
getpid();
}
return 0;
}
static int search_proc_maps(char *needle, unsigned long *low, unsigned long *high)
{
unsigned long start, end;
static char buf[4096];
char name[128];
FILE *f;
int rc;
f = fopen("/proc/self/maps", "r");
if (!f) {
perror("fopen");
return -1;
}
while (fgets(buf, sizeof(buf), f)) {
rc = sscanf(buf, "%lx-%lx %*c%*c%*c%*c %*x %*d:%*d %*d %127s\n",
&start, &end, name);
if (rc == 2)
continue;
if (rc != 3) {
printf("sscanf errored\n");
rc = -1;
break;
}
if (strstr(name, needle)) {
*low = start;
*high = end - 1;
rc = 0;
break;
}
}
fclose(f);
return rc;
}
int child(unsigned int stack_used, int delta, enum access_type type)
{
unsigned long low, stack_high;
assert(search_proc_maps("[stack]", &low, &stack_high) == 0);
assert(consume_stack(stack_high - stack_used, stack_high, delta, type) == 0);
printf("Access OK: %s delta %-7d used size 0x%06x stack high 0x%lx top_ptr %p top sp 0x%lx actual used 0x%lx\n",
type == LOAD ? "load" : "store", delta, stack_used, stack_high,
stack_top_ptr, stack_top_sp, stack_high - stack_top_sp + 1);
return 0;
}
static int test_one(unsigned int stack_used, int delta, enum access_type type)
{
pid_t pid;
int rc;
pid = fork();
if (pid == 0)
exit(child(stack_used, delta, type));
assert(waitpid(pid, &rc, 0) != -1);
if (WIFEXITED(rc) && WEXITSTATUS(rc) == 0)
return 0;
// We don't expect a non-zero exit that's not a signal
assert(!WIFEXITED(rc));
printf("Faulted: %s delta %-7d used size 0x%06x signal %d\n",
type == LOAD ? "load" : "store", delta, stack_used,
WTERMSIG(rc));
return 1;
}
// This is fairly arbitrary but is well below any of the targets below,
// so that the delta between the stack pointer and the target is large.
#define DEFAULT_SIZE (32 * _KB)
static void test_one_type(enum access_type type, unsigned long page_size, unsigned long rlim_cur)
{
assert(test_one(DEFAULT_SIZE, 512 * _KB, type) == 0);
// powerpc has a special case to allow up to 1MB
assert(test_one(DEFAULT_SIZE, 1 * _MB, type) == 0);
#ifdef __powerpc__
// This fails on powerpc because it's > 1MB and is not a stdu &
// not close to r1
assert(test_one(DEFAULT_SIZE, 1 * _MB + 8, type) != 0);
#else
assert(test_one(DEFAULT_SIZE, 1 * _MB + 8, type) == 0);
#endif
#ifdef __powerpc__
// Accessing way past the stack pointer is not allowed on powerpc
assert(test_one(DEFAULT_SIZE, rlim_cur, type) != 0);
#else
// We should be able to access anywhere within the rlimit
assert(test_one(DEFAULT_SIZE, rlim_cur, type) == 0);
#endif
// But if we go past the rlimit it should fail
assert(test_one(DEFAULT_SIZE, rlim_cur + 1, type) != 0);
// Above 1MB powerpc only allows accesses within 4224 bytes of
// r1 for accesses that aren't stdu
assert(test_one(1 * _MB + page_size - 128, -4224, type) == 0);
#ifdef __powerpc__
assert(test_one(1 * _MB + page_size - 128, -4225, type) != 0);
#else
assert(test_one(1 * _MB + page_size - 128, -4225, type) == 0);
#endif
// By consuming 2MB of stack we test the stdu case
assert(test_one(2 * _MB + page_size - 128, -4224, type) == 0);
}
static int test(void)
{
unsigned long page_size;
struct rlimit rlimit;
page_size = getpagesize();
getrlimit(RLIMIT_STACK, &rlimit);
printf("Stack rlimit is 0x%lx\n", rlimit.rlim_cur);
printf("Testing loads ...\n");
test_one_type(LOAD, page_size, rlimit.rlim_cur);
printf("Testing stores ...\n");
test_one_type(STORE, page_size, rlimit.rlim_cur);
printf("All OK\n");
return 0;
}
#ifdef __powerpc__
#include "utils.h"
int main(void)
{
return test_harness(test, "stack_expansion_ldst");
}
#else
int main(void)
{
return test();
}
#endif
|
