1 /*
2 * Copyright (C) 2012-2017 Red Hat, Inc.
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
12 * the GNU General Public License for more details.
13 *
14 * Description:
15 *
16 * The program is designed to test max_map_count tunable file
17 *
18 * The kernel Documentation say that:
19 * /proc/sys/vm/max_map_count contains the maximum number of memory map
20 * areas a process may have. Memory map areas are used as a side-effect
21 * of calling malloc, directly by mmap and mprotect, and also when
22 * loading shared libraries.
23 *
24 * Each process has his own maps file: /proc/[pid]/maps, and each line
25 * indicates a map entry, so it can caculate the amount of maps by reading
26 * the file lines' number to check the tunable performance.
27 *
28 * The program tries to invoke mmap() endlessly until it triggers MAP_FAILED,
29 * then reads the process's maps file /proc/[pid]/maps, save the line number to
30 * map_count variable, and compare it with /proc/sys/vm/max_map_count,
31 * map_count should be greater than max_map_count by 1;
32 *
33 * Note: On some architectures there is a special vma VSYSCALL, which
34 * is allocated without incrementing mm->map_count variable. On these
35 * architectures each /proc/<pid>/maps has at the end:
36 * ...
37 * ...
38 * ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]
39 *
40 * so we ignore this line during /proc/[pid]/maps reading.
41 */
42
43 #define _GNU_SOURCE
44 #include <sys/wait.h>
45 #include <errno.h>
46 #include <fcntl.h>
47 #include <stdbool.h>
48 #include <stdio.h>
49 #include <stdlib.h>
50 #include <sys/utsname.h>
51 #include "mem.h"
52
53 #define MAP_COUNT_DEFAULT 1024
54 #define MAX_MAP_COUNT 65536L
55
56 /* This is a filter to exclude map entries which aren't accounted
57 * for in the vm_area_struct's map_count.
58 */
filter_map(const char * line)59 static bool filter_map(const char *line)
60 {
61 char buf[BUFSIZ];
62 int ret;
63
64 ret = sscanf(line, "%*p-%*p %*4s %*p %*2d:%*2d %*d %s", buf);
65 if (ret != 1)
66 return false;
67
68 switch (tst_arch.type) {
69 case TST_X86:
70 case TST_X86_64:
71 /* On x86, there's an old compat vsyscall page */
72 if (!strcmp(buf, "[vsyscall]"))
73 return true;
74 break;
75 case TST_IA64:
76 /* On ia64, the vdso is not a proper mapping */
77 if (!strcmp(buf, "[vdso]"))
78 return true;
79 break;
80 case TST_ARM:
81 /* Skip it when run it in aarch64 */
82 if (tst_kernel_bits() == 64)
83 return false;
84
85 /* Older arm kernels didn't label their vdso maps */
86 if (!strncmp(line, "ffff0000-ffff1000", 17))
87 return true;
88 break;
89 default:
90 break;
91 };
92
93 return false;
94 }
95
count_maps(pid_t pid)96 static long count_maps(pid_t pid)
97 {
98 FILE *fp;
99 size_t len;
100 char *line = NULL;
101 char buf[BUFSIZ];
102 long map_count = 0;
103
104 snprintf(buf, BUFSIZ, "/proc/%d/maps", pid);
105 fp = fopen(buf, "r");
106 if (fp == NULL)
107 tst_brk(TBROK | TERRNO, "fopen %s", buf);
108 while (getline(&line, &len, fp) != -1) {
109 /* exclude vdso and vsyscall */
110 if (filter_map(line))
111 continue;
112 map_count++;
113 }
114 fclose(fp);
115
116 return map_count;
117 }
118
max_map_count_test(void)119 static void max_map_count_test(void)
120 {
121 int status;
122 pid_t pid;
123 long max_maps;
124 long map_count;
125 long max_iters;
126 long memfree;
127
128 /*
129 * XXX Due to a possible kernel bug, oom-killer can be easily
130 * triggered when doing small piece mmaps in huge amount even if
131 * enough free memory available. Also it has been observed that
132 * oom-killer often kill wrong victims in this situation, we
133 * decided to do following steps to make sure no oom happen:
134 * 1) use a safe maximum max_map_count value as upper-bound,
135 * we set it 65536 in this case, i.e., we don't test too big
136 * value;
137 * 2) make sure total mapping isn't larger than
138 * CommitLimit - Committed_AS
139 */
140 memfree = SAFE_READ_MEMINFO("CommitLimit:") - SAFE_READ_MEMINFO("Committed_AS:");
141 /* 64 used as a bias to make sure no overflow happen */
142 max_iters = memfree / sysconf(_SC_PAGESIZE) * 1024 - 64;
143 if (max_iters > MAX_MAP_COUNT)
144 max_iters = MAX_MAP_COUNT;
145
146 max_maps = MAP_COUNT_DEFAULT;
147 if (max_iters < max_maps)
148 tst_brk(TCONF, "test requires more free memory");
149
150 while (max_maps <= max_iters) {
151 set_sys_tune("max_map_count", max_maps, 1);
152
153 switch (pid = SAFE_FORK()) {
154 case 0:
155 while (mmap(NULL, 1, PROT_READ,
156 MAP_SHARED | MAP_ANONYMOUS, -1, 0)
157 != MAP_FAILED) ;
158 if (raise(SIGSTOP) != 0)
159 tst_brk(TBROK | TERRNO, "raise");
160 exit(0);
161 default:
162 break;
163 }
164 /* wait child done mmap and stop */
165 SAFE_WAITPID(pid, &status, WUNTRACED);
166 if (!WIFSTOPPED(status))
167 tst_brk(TBROK, "child did not stopped");
168
169 map_count = count_maps(pid);
170 /* Note max_maps will be exceeded by one for
171 * the sysctl setting of max_map_count. This
172 * is the mm failure point at the time of
173 * writing this COMMENT!
174 */
175 if (map_count == (max_maps + 1))
176 tst_res(TPASS, "%ld map entries in total "
177 "as expected.", max_maps);
178 else
179 tst_res(TFAIL, "%ld map entries in total, but "
180 "expected %ld entries", map_count, max_maps);
181
182 /* make child continue to exit */
183 SAFE_KILL(pid, SIGCONT);
184 SAFE_WAITPID(pid, &status, 0);
185
186 max_maps = max_maps << 1;
187 }
188 }
189
190 static struct tst_test test = {
191 .needs_root = 1,
192 .forks_child = 1,
193 .test_all = max_map_count_test,
194 .save_restore = (const struct tst_path_val[]) {
195 {"/proc/sys/vm/overcommit_memory", "0", TST_SR_TBROK},
196 {"/proc/sys/vm/max_map_count", NULL, TST_SR_TBROK},
197 {}
198 },
199 };
200