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 <errno.h>
  23 #include <fcntl.h>
  24 #include <sys/stat.h>
  25 #include <unistd.h>
  26 #ifdef HAVE_LINUX_MEMFD_H
  27 #include <linux/memfd.h>
  28 #endif
  29 #include <stdio.h>
  30 #include <sys/mman.h>
  31 #include <sys/prctl.h>
  32
  33 #include "alloc-util.h"
  34 #include "fd-util.h"
  35 #include "memfd-util.h"
  36 #include "missing.h"
  37 #include "macro.h"
  38 #include "string-util.h"
  39 #include "utf8.h"
  40
  41 int memfd_new(const char *name) {
  42         _cleanup_free_ char *g = NULL;
  43         int fd;
  44
  45         if (!name) {
  46                 char pr[17] = {};
  47
  48                 /* If no name is specified we generate one. We include
  49                  * a hint indicating our library implementation, and
  50                  * add the thread name to it */
  51
  52                 assert_se(prctl(PR_GET_NAME, (unsigned long) pr) >= 0);
  53
  54                 if (isempty(pr))
  55                         name = "sd";
  56                 else {
  57                         _cleanup_free_ char *e = NULL;
  58
  59                         e = utf8_escape_invalid(pr);
  60                         if (!e)
  61                                 return -ENOMEM;
  62
  63                         g = strappend("sd-", e);
  64                         if (!g)
  65                                 return -ENOMEM;
  66
  67                         name = g;
  68                 }
  69         }
  70
  71         fd = memfd_create(name, MFD_ALLOW_SEALING | MFD_CLOEXEC);
  72         if (fd < 0)
  73                 return -errno;
  74
  75         return fd;
  76 }
  77
  78 int memfd_map(int fd, uint64_t offset, size_t size, void **p) {
  79         void *q;
  80         int sealed;
  81
  82         assert(fd >= 0);
  83         assert(size > 0);
  84         assert(p);
  85
  86         sealed = memfd_get_sealed(fd);
  87         if (sealed < 0)
  88                 return sealed;
  89
  90         if (sealed)
  91                 q = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, offset);
  92         else
  93                 q = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, offset);
  94
  95         if (q == MAP_FAILED)
  96                 return -errno;
  97
  98         *p = q;
  99         return 0;
 100 }
 101
 102 int memfd_set_sealed(int fd) {
 103         int r;
 104
 105         assert(fd >= 0);
 106
 107         r = fcntl(fd, F_ADD_SEALS, F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE | F_SEAL_SEAL);
 108         if (r < 0)
 109                 return -errno;
 110
 111         return 0;
 112 }
 113
 114 int memfd_get_sealed(int fd) {
 115         int r;
 116
 117         assert(fd >= 0);
 118
 119         r = fcntl(fd, F_GET_SEALS);
 120         if (r < 0)
 121                 return -errno;
 122
 123         return r == (F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE | F_SEAL_SEAL);
 124 }
 125
 126 int memfd_get_size(int fd, uint64_t *sz) {
 127         struct stat stat;
 128         int r;
 129
 130         assert(fd >= 0);
 131         assert(sz);
 132
 133         r = fstat(fd, &stat);
 134         if (r < 0)
 135                 return -errno;
 136
 137         *sz = stat.st_size;
 138         return 0;
 139 }
 140
 141 int memfd_set_size(int fd, uint64_t sz) {
 142         int r;
 143
 144         assert(fd >= 0);
 145
 146         r = ftruncate(fd, sz);
 147         if (r < 0)
 148                 return -errno;
 149
 150         return 0;
 151 }
 152
 153 int memfd_new_and_map(const char *name, size_t sz, void **p) {
 154         _cleanup_close_ int fd = -1;
 155         int r;
 156
 157         assert(sz > 0);
 158         assert(p);
 159
 160         fd = memfd_new(name);
 161         if (fd < 0)
 162                 return fd;
 163
 164         r = memfd_set_size(fd, sz);
 165         if (r < 0)
 166                 return r;
 167
 168         r = memfd_map(fd, 0, sz, p);
 169         if (r < 0)
 170                 return r;
 171
 172         r = fd;
 173         fd = -1;
 174
 175         return r;
 176 }