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