src/basic/memfd-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright 2013 Lennart Poettering
   6
   7   systemd is free software; you can redistribute it and/or modify it
   8   under the terms of the GNU Lesser General Public License as published by
   9   the Free Software Foundation; either version 2.1 of the License, or
  10   (at your option) any later version.
  11
  12   systemd is distributed in the hope that it will be useful, but
  13   WITHOUT ANY WARRANTY; without even the implied warranty of
  14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15   Lesser General Public License for more details.
  16
  17   You should have received a copy of the GNU Lesser General Public License
  18   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  19 ***/
  20
  21 #include <errno.h>
  22 #include <fcntl.h>
  23 #include <sys/stat.h>
  24 #include <unistd.h>
  25 #if HAVE_LINUX_MEMFD_H
  26 #include <linux/memfd.h>
  27 #endif
  28 #include <stdio.h>
  29 #include <sys/mman.h>
  30 #include <sys/prctl.h>
  31
  32 #include "alloc-util.h"
  33 #include "fd-util.h"
  34 #include "macro.h"
  35 #include "memfd-util.h"
  36 #include "missing.h"
  37 #include "string-util.h"
  38 #include "utf8.h"
  39
  40 int memfd_new(const char *name) {
  41         _cleanup_free_ char *g = NULL;
  42         int fd;
  43
  44         if (!name) {
  45                 char pr[17] = {};
  46
  47                 /* If no name is specified we generate one. We include
  48                  * a hint indicating our library implementation, and
  49                  * add the thread name to it */
  50
  51                 assert_se(prctl(PR_GET_NAME, (unsigned long) pr) >= 0);
  52
  53                 if (isempty(pr))
  54                         name = "sd";
  55                 else {
  56                         _cleanup_free_ char *e = NULL;
  57
  58                         e = utf8_escape_invalid(pr);
  59                         if (!e)
  60                                 return -ENOMEM;
  61
  62                         g = strappend("sd-", e);
  63                         if (!g)
  64                                 return -ENOMEM;
  65
  66                         name = g;
  67                 }
  68         }
  69
  70         fd = memfd_create(name, MFD_ALLOW_SEALING | MFD_CLOEXEC);
  71         if (fd < 0)
  72                 return -errno;
  73
  74         return fd;
  75 }
  76
  77 int memfd_map(int fd, uint64_t offset, size_t size, void **p) {
  78         void *q;
  79         int sealed;
  80
  81         assert(fd >= 0);
  82         assert(size > 0);
  83         assert(p);
  84
  85         sealed = memfd_get_sealed(fd);
  86         if (sealed < 0)
  87                 return sealed;
  88
  89         if (sealed)
  90                 q = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, offset);
  91         else
  92                 q = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, offset);
  93
  94         if (q == MAP_FAILED)
  95                 return -errno;
  96
  97         *p = q;
  98         return 0;
  99 }
 100
 101 int memfd_set_sealed(int fd) {
 102         int r;
 103
 104         assert(fd >= 0);
 105
 106         r = fcntl(fd, F_ADD_SEALS, F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE | F_SEAL_SEAL);
 107         if (r < 0)
 108                 return -errno;
 109
 110         return 0;
 111 }
 112
 113 int memfd_get_sealed(int fd) {
 114         int r;
 115
 116         assert(fd >= 0);
 117
 118         r = fcntl(fd, F_GET_SEALS);
 119         if (r < 0)
 120                 return -errno;
 121
 122         return r == (F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE | F_SEAL_SEAL);
 123 }
 124
 125 int memfd_get_size(int fd, uint64_t *sz) {
 126         struct stat stat;
 127         int r;
 128
 129         assert(fd >= 0);
 130         assert(sz);
 131
 132         r = fstat(fd, &stat);
 133         if (r < 0)
 134                 return -errno;
 135
 136         *sz = stat.st_size;
 137         return 0;
 138 }
 139
 140 int memfd_set_size(int fd, uint64_t sz) {
 141         int r;
 142
 143         assert(fd >= 0);
 144
 145         r = ftruncate(fd, sz);
 146         if (r < 0)
 147                 return -errno;
 148
 149         return 0;
 150 }
 151
 152 int memfd_new_and_map(const char *name, size_t sz, void **p) {
 153         _cleanup_close_ int fd = -1;
 154         int r;
 155
 156         assert(sz > 0);
 157         assert(p);
 158
 159         fd = memfd_new(name);
 160         if (fd < 0)
 161                 return fd;
 162
 163         r = memfd_set_size(fd, sz);
 164         if (r < 0)
 165                 return r;
 166
 167         r = memfd_map(fd, 0, sz, p);
 168         if (r < 0)
 169                 return r;
 170
 171         r = fd;
 172         fd = -1;
 173
 174         return r;
 175 }