1 | #define _XOPEN_SOURCE 500
|
---|
2 |
|
---|
3 | #include <sys/types.h>
|
---|
4 | #include <sys/stat.h>
|
---|
5 | #include <fcntl.h>
|
---|
6 | #include <unistd.h>
|
---|
7 | #include <errno.h>
|
---|
8 | #include <stdio.h>
|
---|
9 | #include <string.h>
|
---|
10 | #include <setjmp.h>
|
---|
11 | #include <signal.h>
|
---|
12 | #include <sys/time.h>
|
---|
13 | #include <sys/resource.h>
|
---|
14 |
|
---|
15 | static sigjmp_buf jb;
|
---|
16 |
|
---|
17 | static void sighandler(int signum) {
|
---|
18 | siglongjmp(jb, signum);
|
---|
19 | }
|
---|
20 |
|
---|
21 | int main(int argc, char ** argv) {
|
---|
22 | if (argc != 2) {
|
---|
23 | fprintf(stderr, "Usage: %s TESTFILE\n", argv[0]);
|
---|
24 | return 1;
|
---|
25 | }
|
---|
26 |
|
---|
27 | const char * filename = argv[1];
|
---|
28 |
|
---|
29 | int fd = open(filename, O_CREAT|O_RDWR|O_TRUNC, 0666);
|
---|
30 | if (fd < 0) {
|
---|
31 | perror("open failed");
|
---|
32 | return 1;
|
---|
33 | }
|
---|
34 |
|
---|
35 | struct rlimit rlim;
|
---|
36 | if (getrlimit(RLIMIT_FSIZE, &rlim) < 0) {
|
---|
37 | perror("rlimit");
|
---|
38 | } else {
|
---|
39 | if (rlim.rlim_cur != RLIM_INFINITY)
|
---|
40 | printf("RLIMIT_FSIZE cur = 0x%llx\n", (long long)rlim.rlim_cur);
|
---|
41 | if (rlim.rlim_max != RLIM_INFINITY)
|
---|
42 | printf("RLIMIT_FSIZE max = 0x%llx\n", (long long)rlim.rlim_max);
|
---|
43 | }
|
---|
44 |
|
---|
45 | #define SHIFT (sizeof(off_t) * 8 - 2)
|
---|
46 | volatile off_t off_t_max = (((off_t)1 << SHIFT)-1)|((off_t)1 << SHIFT);
|
---|
47 | off_t pos = lseek(fd, off_t_max, SEEK_SET);
|
---|
48 | if (pos == (off_t)-1) {
|
---|
49 | perror("lseek failed");
|
---|
50 | printf("attempted to set pos to 0x%llx\n", (long long)off_t_max);
|
---|
51 | printf("binary chopping to find actual max:\n");
|
---|
52 | int slo = 0;
|
---|
53 | int shi = SHIFT + 1;
|
---|
54 | while (shi - slo > 1) {
|
---|
55 | int sm = slo + (shi - slo) / 2;
|
---|
56 | off_t m = (off_t)1 << sm;
|
---|
57 | pos = lseek(fd, m, SEEK_SET);
|
---|
58 | if (pos == (off_t)-1) {
|
---|
59 | printf("lseek to 0x%llx fails, errno=%d (%s)\n", (long long)m, errno, strerror(errno));
|
---|
60 | shi = sm;
|
---|
61 | } else {
|
---|
62 | printf("lseek to 0x%llx works\n", (long long)m);
|
---|
63 | slo = sm;
|
---|
64 | }
|
---|
65 | }
|
---|
66 |
|
---|
67 | off_t lo = (off_t)1 << slo;
|
---|
68 | off_t hi = (off_t)1 << shi;
|
---|
69 | while (hi - lo > 1) {
|
---|
70 | off_t m = lo + (hi - lo) / 2;
|
---|
71 | pos = lseek(fd, m, SEEK_SET);
|
---|
72 | if (pos == (off_t)-1) {
|
---|
73 | printf("lseek to 0x%llx fails, errno=%d (%s)\n", (long long)m, errno, strerror(errno));
|
---|
74 | hi = m;
|
---|
75 | } else {
|
---|
76 | printf("lseek to 0x%llx works\n", (long long)m);
|
---|
77 | lo = m;
|
---|
78 | }
|
---|
79 | }
|
---|
80 | off_t_max = lo;
|
---|
81 | printf("Max lseekable off_t = 0x%llx\n", (long long)off_t_max);
|
---|
82 | pos = lseek(fd, off_t_max + 1, SEEK_SET);
|
---|
83 | if (pos != -1)
|
---|
84 | printf("Odd, +1 now works\n");
|
---|
85 | pos = lseek(fd, off_t_max, SEEK_SET);
|
---|
86 | if (pos == -1)
|
---|
87 | printf("Odd, found limit now fails\n");
|
---|
88 | }
|
---|
89 |
|
---|
90 | if (pos != off_t_max) {
|
---|
91 | fprintf(stderr, "warning: lseek to 0x%llx actually set pos to 0x%llx\n", (long long)off_t_max, (long long)pos);
|
---|
92 | }
|
---|
93 |
|
---|
94 | if (pwrite(fd, "hello\n", 6, 2) < 0) {
|
---|
95 | perror("pwrite failed");
|
---|
96 | return 1;
|
---|
97 | }
|
---|
98 |
|
---|
99 | pos = lseek(fd, 0, SEEK_CUR);
|
---|
100 | if (pos != off_t_max) {
|
---|
101 | fprintf(stderr, "warning: pwrite changed file pos to 0x%llx\n", (long long)pos);
|
---|
102 | }
|
---|
103 |
|
---|
104 | char buf[10];
|
---|
105 | ssize_t r = pread(fd, buf, 10, 0);
|
---|
106 | if (r < 0) {
|
---|
107 | fprintf(stderr, "fd=%d\n", fd);
|
---|
108 | perror("pread failed");
|
---|
109 | return 1;
|
---|
110 | }
|
---|
111 |
|
---|
112 | if (r != 8) {
|
---|
113 | int i;
|
---|
114 | fprintf(stderr, "pread() read %lld bytes, expected 8\ngot:", (long long)r);
|
---|
115 | for (i = 0; i != (int)r; ++i) {
|
---|
116 | fprintf(stderr, " 0x%02x", (unsigned char)buf[i]);
|
---|
117 | }
|
---|
118 | fprintf(stderr, "\n");
|
---|
119 | return 1;
|
---|
120 | }
|
---|
121 |
|
---|
122 | if (memcmp(buf, "\0\0hello\n", 8) != 0) {
|
---|
123 | int i;
|
---|
124 | fprintf(stderr, "pread() didn't read the expected data back\ngot:");
|
---|
125 | for (i = 0; i != 8; ++i) {
|
---|
126 | fprintf(stderr, " 0x%02x", (unsigned char)buf[i]);
|
---|
127 | }
|
---|
128 | fprintf(stderr, "\n");
|
---|
129 | return 1;
|
---|
130 | }
|
---|
131 |
|
---|
132 | if (sigsetjmp(jb, 1) == 0) {
|
---|
133 | signal(SIGXFSZ, sighandler);
|
---|
134 | r = write(fd, "", 1);
|
---|
135 | if (r >= 0) {
|
---|
136 | fprintf(stderr, "warning: write() succeeded, writing %lld bytes\n", (long long)r);
|
---|
137 | pos = lseek(fd, 0, SEEK_END);
|
---|
138 | fprintf(stderr, "lseek SEEK_END now returns 0x%llx (off_t_max was 0x%llx)\n", (long long)pos, (long long)off_t_max);
|
---|
139 | } else {
|
---|
140 | fprintf(stderr, "info: write() failed with errno=%d (%s)\n", errno, strerror(errno));
|
---|
141 | }
|
---|
142 | } else {
|
---|
143 | fprintf(stderr, "info: write() cause SIGXFSZ to be raised\n");
|
---|
144 | }
|
---|
145 |
|
---|
146 | pos = lseek(fd, 0, SEEK_CUR);
|
---|
147 | if (pos != off_t_max) {
|
---|
148 | fprintf(stderr, "warning: write changed file pos to 0x%llx\n", (long long)pos);
|
---|
149 | }
|
---|
150 |
|
---|
151 | fprintf(stderr, "Cool, that basically worked - please report the info and/or warnings given above\n");
|
---|
152 | return 0;
|
---|
153 | }
|
---|