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#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <unistd.h>
#define PG 4096UL
static int fails;
#define CHECK(cond, ...) \
do { \
if (!(cond)) { \
fails++; \
printf("remaptest: FAIL line %d: ", __LINE__); \
printf(__VA_ARGS__); \
printf("\n"); \
} \
} while (0)
static char *anon(size_t pages)
{
char *p = mmap(0, pages * PG, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
return p == MAP_FAILED ? 0 : p;
}
static void fill(char *p, size_t pages, int seed)
{
for (size_t i = 0; i < pages; i++)
memset(p + i * PG, seed + (int)i, PG);
}
static int same(const char *p, size_t pages, int seed)
{
for (size_t i = 0; i < pages; i++)
for (size_t j = 0; j < PG; j += 512)
if (p[i * PG + j] != (char)(seed + (int)i))
return 0;
return 1;
}
static int zero(const char *p, size_t len)
{
for (size_t i = 0; i < len; i += 256)
if (p[i])
return 0;
return 1;
}
static int faults(volatile char *p)
{
pid_t pid = fork();
if (pid == 0) {
(void)*p;
_exit(0);
}
int st = 0;
waitpid(pid, &st, 0);
return WIFSIGNALED(st) && WTERMSIG(st) == SIGSEGV;
}
static void grow_in_place(void)
{
char *p = anon(8);
CHECK(p, "mmap 8 pages");
munmap(p + 3 * PG, 5 * PG);
fill(p, 3, 'a');
char *q = mremap(p, 3 * PG, 6 * PG, 0);
CHECK(q == p, "grow in place: %p, wanted %p", q, p);
if (q != p)
return;
CHECK(same(p, 3, 'a'), "grow in place kept the data");
CHECK(zero(p + 3 * PG, 3 * PG), "the new part is zero");
p[6 * PG - 1] = 1;
q = mremap(p, 6 * PG, 2 * PG, 0);
CHECK(q == p, "shrink: %p", q);
CHECK(same(p, 2, 'a'), "shrink kept the data");
CHECK(faults(p + 2 * PG), "the cut-off part is gone");
CHECK(mremap(p, 2 * PG, 2 * PG, 0) == p, "same size: nothing to do");
munmap(p, 2 * PG);
}
static void move(void)
{
char *a = anon(2);
char *b = anon(1);
CHECK(a && b && b + PG == a, "b (%p) sits right below a (%p)", b, a);
fill(b, 1, 'm');
errno = 0;
CHECK(mremap(b, PG, 4 * PG, 0) == MAP_FAILED && errno == ENOMEM, "no room and no MAYMOVE: ENOMEM (%d)", errno);
char *c = mremap(b, PG, 4 * PG, MREMAP_MAYMOVE);
CHECK(c != MAP_FAILED && c != b, "MAYMOVE moved it: %p", c);
if (c == MAP_FAILED)
return;
CHECK(same(c, 1, 'm'), "the moved page kept its bytes");
CHECK(zero(c + PG, 3 * PG), "the rest is zero");
CHECK(faults(b), "nothing left at the old address");
char *spot = anon(4);
munmap(spot, 4 * PG);
char *d = mremap(c, 4 * PG, 2 * PG, MREMAP_MAYMOVE | MREMAP_FIXED, spot);
CHECK(d == spot, "MREMAP_FIXED: %p, wanted %p", d, spot);
if (d == spot)
CHECK(same(d, 1, 'm'), "MREMAP_FIXED kept the bytes");
CHECK(faults(c), "and the old place is empty");
munmap(spot, 2 * PG);
munmap(a, 2 * PG);
}
static void errors(void)
{
char *p = anon(2);
errno = 0;
CHECK(mremap(p + 1, PG, 2 * PG, MREMAP_MAYMOVE) == MAP_FAILED && errno == EINVAL, "unaligned: EINVAL (%d)", errno);
errno = 0;
CHECK(mremap(p, PG, 0, MREMAP_MAYMOVE) == MAP_FAILED && errno == EINVAL, "new_len 0: EINVAL (%d)", errno);
errno = 0;
CHECK(mremap(p, PG, 2 * PG, 64) == MAP_FAILED && errno == EINVAL, "unknown flag: EINVAL (%d)", errno);
errno = 0;
CHECK(mremap(p, PG, 2 * PG, MREMAP_FIXED, p + 8 * PG) == MAP_FAILED && errno == EINVAL,
"FIXED without MAYMOVE: EINVAL (%d)", errno);
errno = 0;
CHECK(mremap(p, 2 * PG, 4 * PG, MREMAP_MAYMOVE | MREMAP_FIXED, p + PG) == MAP_FAILED && errno == EINVAL,
"FIXED onto itself: EINVAL (%d)", errno);
munmap(p, 2 * PG);
errno = 0;
CHECK(mremap(p, PG, 2 * PG, MREMAP_MAYMOVE) == MAP_FAILED && errno == EFAULT, "nothing mapped: EFAULT (%d)", errno);
}
static void file_backed(void)
{
int fd = open("/tmp/remap.dat", O_RDWR | O_CREAT | O_TRUNC, 0644);
CHECK(fd >= 0, "open /tmp/remap.dat");
char page[PG];
for (int i = 0; i < 3; i++) {
memset(page, 'F' + i, PG);
write(fd, page, PG);
}
char *keep = anon(1);
char *f = mmap(0, PG, PROT_READ, MAP_PRIVATE, fd, 0);
(void)keep;
CHECK(f != MAP_FAILED && f[0] == 'F', "file page 0");
char *g = mremap(f, PG, 3 * PG, MREMAP_MAYMOVE);
CHECK(g != MAP_FAILED, "mremap a file mapping");
if (g != MAP_FAILED) {
CHECK(g[0] == 'F' && g[PG] == 'G' && g[2 * PG + 7] == 'H', "moved file pages read the file: %c %c %c", g[0],
g[PG], g[2 * PG + 7]);
munmap(g, 3 * PG);
}
munmap(keep, PG);
close(fd);
unlink("/tmp/remap.dat");
}
static void after_fork(void)
{
char *p = anon(1);
fill(p, 1, 'p');
pid_t pid = fork();
if (pid == 0) {
char *q = mremap(p, PG, 16 * PG, MREMAP_MAYMOVE);
if (q == MAP_FAILED || q[0] != 'p')
_exit(1);
q[0] = 'c';
_exit(q[0] == 'c' ? 0 : 2);
}
int st = 0;
waitpid(pid, &st, 0);
CHECK(WIFEXITED(st) && WEXITSTATUS(st) == 0, "child moved and wrote: status %#x", st);
CHECK(p[0] == 'p', "parent's copy unchanged: %c", p[0]);
munmap(p, PG);
}
static void with_realloc(void)
{
size_t n = 1 << 20;
unsigned *v = malloc(n);
CHECK(v, "malloc 1 MiB");
for (size_t i = 0; i < n / 4; i++)
v[i] = (unsigned)i * 2654435761u;
for (size_t big = 4 << 20; big <= 32 << 20; big *= 2) {
v = realloc(v, big);
CHECK(v, "realloc %zu", big);
if (!v)
return;
size_t bad = 0;
for (size_t i = 0; i < n / 4; i++)
bad += v[i] != (unsigned)i * 2654435761u;
CHECK(bad == 0, "realloc to %zu MiB kept the data (%zu wrong)", big >> 20, bad);
}
v = realloc(v, 2 << 20);
CHECK(v && v[12345] == 12345u * 2654435761u, "realloc down");
free(v);
}
int main(void)
{
grow_in_place();
move();
errors();
file_backed();
after_fork();
with_realloc();
printf("remaptest: %s (%d failed)\n", fails ? "FAILED" : "all passed", fails);
return fails;
}
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