memfd.c revision 43bde981ccc57c744f164a9d95d46c7ce8f21808
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2013 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <stdio.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/prctl.h>
#include "util.h"
#include "bus-label.h"
#include "missing.h"
#include "memfd.h"
#include "sd-bus.h"
struct sd_memfd {
int fd;
FILE *f;
};
int sd_memfd_new(sd_memfd **m, const char *name) {
_cleanup_close_ int kdbus = -1;
_cleanup_free_ char *g = NULL;
sd_memfd *n;
assert_return(m, -EINVAL);
kdbus = open("/dev/kdbus/control", O_RDWR|O_NOCTTY|O_CLOEXEC);
if (kdbus < 0)
return -errno;
if (name) {
/* The kernel side is pretty picky about the character
* set here, let's do the usual bus escaping to deal
* with that. */
g = bus_label_escape(name);
if (!g)
return -ENOMEM;
name = g;
} else {
char pr[17] = {};
/* If no name is specified we generate one. We include
* a hint indicating our library implementation, and
* add the thread name to it */
assert_se(prctl(PR_GET_NAME, (unsigned long) pr) >= 0);
if (isempty(pr))
name = "sd";
else {
_cleanup_free_ char *e = NULL;
e = bus_label_escape(pr);
if (!e)
return -ENOMEM;
g = strappend("sd-", e);
if (!g)
return -ENOMEM;
name = g;
}
}
n = new0(struct sd_memfd, 1);
if (!n)
return -ENOMEM;
n->fd = memfd_create(name, 0, MFD_ALLOW_SEALING);
if (n->fd < 0) {
free(n);
return -errno;
}
*m = n;
return 0;
}
int sd_memfd_new_from_fd(sd_memfd **m, int fd) {
sd_memfd *n;
assert_return(m, -EINVAL);
assert_return(fd >= 0, -EINVAL);
/* Check if this is a sealable fd */
if (fcntl(fd, F_GET_SEALS) < 0)
return -ENOTTY;
n = new0(struct sd_memfd, 1);
if (!n)
return -ENOMEM;
n->fd = fd;
*m = n;
return 0;
}
void sd_memfd_free(sd_memfd *m) {
if (!m)
return;
if (m->f)
fclose(m->f);
else
safe_close(m->fd);
free(m);
}
int sd_memfd_get_fd(sd_memfd *m) {
assert_return(m, -EINVAL);
return m->fd;
}
int sd_memfd_get_file(sd_memfd *m, FILE **f) {
assert_return(m, -EINVAL);
assert_return(f, -EINVAL);
if (!m->f) {
m->f = fdopen(m->fd, "r+");
if (!m->f)
return -errno;
}
*f = m->f;
return 0;
}
int sd_memfd_dup_fd(sd_memfd *m) {
int fd;
assert_return(m, -EINVAL);
fd = fcntl(m->fd, F_DUPFD_CLOEXEC, 3);
if (fd < 0)
return -errno;
return fd;
}
int sd_memfd_map(sd_memfd *m, uint64_t offset, size_t size, void **p) {
void *q;
int sealed;
assert_return(m, -EINVAL);
assert_return(size > 0, -EINVAL);
assert_return(p, -EINVAL);
sealed = sd_memfd_get_sealed(m);
if (sealed < 0)
return sealed;
q = mmap(NULL, size, sealed ? PROT_READ : PROT_READ|PROT_WRITE, MAP_PRIVATE, m->fd, offset);
if (q == MAP_FAILED)
return -errno;
*p = q;
return 0;
}
int sd_memfd_set_sealed(sd_memfd *m) {
int r;
assert_return(m, -EINVAL);
r = fcntl(m->fd, F_ADD_SEALS, F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE);
if (r < 0)
return -errno;
return 0;
}
int sd_memfd_get_sealed(sd_memfd *m) {
int r;
assert_return(m, -EINVAL);
r = fcntl(m->fd, F_GET_SEALS);
if (r < 0)
return -errno;
return (r & (F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE)) ==
(F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE);
}
int sd_memfd_get_size(sd_memfd *m, uint64_t *sz) {
int r;
struct stat stat;
assert_return(m, -EINVAL);
assert_return(sz, -EINVAL);
r = fstat(m->fd, &stat);
if (r < 0)
return -errno;
*sz = stat.st_size;
return r;
}
int sd_memfd_set_size(sd_memfd *m, uint64_t sz) {
int r;
assert_return(m, -EINVAL);
r = ftruncate(m->fd, sz);
if (r < 0)
return -errno;
return r;
}
int sd_memfd_new_and_map(sd_memfd **m, const char *name, size_t sz, void **p) {
sd_memfd *n;
int r;
r = sd_memfd_new(&n, name);
if (r < 0)
return r;
r = sd_memfd_set_size(n, sz);
if (r < 0) {
sd_memfd_free(n);
return r;
}
r = sd_memfd_map(n, 0, sz, p);
if (r < 0) {
sd_memfd_free(n);
return r;
}
*m = n;
return 0;
}
int sd_memfd_get_name(sd_memfd *m, char **name) {
char path[sizeof("/proc/self/fd/") + DECIMAL_STR_MAX(int)], buf[FILENAME_MAX+1], *e;
const char *delim, *end;
_cleanup_free_ char *n = NULL;
ssize_t k;
assert_return(m, -EINVAL);
assert_return(name, -EINVAL);
sprintf(path, "/proc/self/fd/%i", m->fd);
k = readlink(path, buf, sizeof(buf));
if (k < 0)
return -errno;
if ((size_t) k >= sizeof(buf))
return -E2BIG;
buf[k] = 0;
delim = strstr(buf, ":[");
if (!delim)
return -EIO;
delim = strchr(delim + 2, ':');
if (!delim)
return -EIO;
delim++;
end = strchr(delim, ']');
if (!end)
return -EIO;
n = strndup(delim, end - delim);
if (!n)
return -ENOMEM;
e = bus_label_unescape(n);
if (!e)
return -ENOMEM;
*name = e;
return 0;
}