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 "fd-util.h"
  31 #include "memfd-util.h"
  32 #include "missing.h"
  33 #include "string-util.h"
  34 #include "utf8.h"
  35 #include "util.h"
  36
  37 int memfd_new(const char *name) {
  38         _cleanup_free_ char *g = NULL;
  39         int fd;
  40
  41         if (!name) {
  42                 char pr[17] = {};
  43
  44                 /* If no name is specified we generate one. We include
  45                  * a hint indicating our library implementation, and
  46                  * add the thread name to it */
  47
  48                 assert_se(prctl(PR_GET_NAME, (unsigned long) pr) >= 0);
  49
  50                 if (isempty(pr))
  51                         name = "sd";
  52                 else {
  53                         _cleanup_free_ char *e = NULL;
  54
  55                         e = utf8_escape_invalid(pr);
  56                         if (!e)
  57                                 return -ENOMEM;
  58
  59                         g = strappend("sd-", e);
  60                         if (!g)
  61                                 return -ENOMEM;
  62
  63                         name = g;
  64                 }
  65         }
  66
  67         fd = memfd_create(name, MFD_ALLOW_SEALING | MFD_CLOEXEC);
  68         if (fd < 0)
  69                 return -errno;
  70
  71         return fd;
  72 }
  73
  74 int memfd_map(int fd, uint64_t offset, size_t size, void **p) {
  75         void *q;
  76         int sealed;
  77
  78         assert(fd >= 0);
  79         assert(size > 0);
  80         assert(p);
  81
  82         sealed = memfd_get_sealed(fd);
  83         if (sealed < 0)
  84                 return sealed;
  85
  86         if (sealed)
  87                 q = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, offset);
  88         else
  89                 q = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, offset);
  90
  91         if (q == MAP_FAILED)
  92                 return -errno;
  93
  94         *p = q;
  95         return 0;
  96 }
  97
  98 int memfd_set_sealed(int fd) {
  99         int r;
 100
 101         assert(fd >= 0);
 102
 103         r = fcntl(fd, F_ADD_SEALS, F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE | F_SEAL_SEAL);
 104         if (r < 0)
 105                 return -errno;
 106
 107         return 0;
 108 }
 109
 110 int memfd_get_sealed(int fd) {
 111         int r;
 112
 113         assert(fd >= 0);
 114
 115         r = fcntl(fd, F_GET_SEALS);
 116         if (r < 0)
 117                 return -errno;
 118
 119         return r == (F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE | F_SEAL_SEAL);
 120 }
 121
 122 int memfd_get_size(int fd, uint64_t *sz) {
 123         struct stat stat;
 124         int r;
 125
 126         assert(fd >= 0);
 127         assert(sz);
 128
 129         r = fstat(fd, &stat);
 130         if (r < 0)
 131                 return -errno;
 132
 133         *sz = stat.st_size;
 134         return 0;
 135 }
 136
 137 int memfd_set_size(int fd, uint64_t sz) {
 138         int r;
 139
 140         assert(fd >= 0);
 141
 142         r = ftruncate(fd, sz);
 143         if (r < 0)
 144                 return -errno;
 145
 146         return 0;
 147 }
 148
 149 int memfd_new_and_map(const char *name, size_t sz, void **p) {
 150         _cleanup_close_ int fd = -1;
 151         int r;
 152
 153         assert(sz > 0);
 154         assert(p);
 155
 156         fd = memfd_new(name);
 157         if (fd < 0)
 158                 return fd;
 159
 160         r = memfd_set_size(fd, sz);
 161         if (r < 0)
 162                 return r;
 163
 164         r = memfd_map(fd, 0, sz, p);
 165         if (r < 0)
 166                 return r;
 167
 168         r = fd;
 169         fd = -1;
 170
 171         return r;
 172 }