src/basic/memfd-util.c

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