src/getty-generator/getty-generator.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <fcntl.h>
   5 #include <string.h>
   6 #include <unistd.h>
   7
   8 #include "alloc-util.h"
   9 #include "fd-util.h"
  10 #include "fileio.h"
  11 #include "generator.h"
  12 #include "log.h"
  13 #include "mkdir.h"
  14 #include "path-util.h"
  15 #include "process-util.h"
  16 #include "string-util.h"
  17 #include "terminal-util.h"
  18 #include "unit-name.h"
  19 #include "util.h"
  20 #include "virt.h"
  21
  22 static const char *arg_dest = "/tmp";
  23
  24 static int add_symlink(const char *fservice, const char *tservice) {
  25         char *from, *to;
  26         int r;
  27
  28         assert(fservice);
  29         assert(tservice);
  30
  31         from = strjoina(SYSTEM_DATA_UNIT_PATH "/", fservice);
  32         to = strjoina(arg_dest, "/getty.target.wants/", tservice);
  33
  34         mkdir_parents_label(to, 0755);
  35
  36         r = symlink(from, to);
  37         if (r < 0) {
  38                 /* In case console=hvc0 is passed this will very likely result in EEXIST */
  39                 if (errno == EEXIST)
  40                         return 0;
  41
  42                 return log_error_errno(errno, "Failed to create symlink %s: %m", to);
  43         }
  44
  45         return 0;
  46 }
  47
  48 static int add_serial_getty(const char *tty) {
  49         _cleanup_free_ char *n = NULL;
  50         int r;
  51
  52         assert(tty);
  53
  54         log_debug("Automatically adding serial getty for /dev/%s.", tty);
  55
  56         r = unit_name_from_path_instance("serial-getty", tty, ".service", &n);
  57         if (r < 0)
  58                 return log_error_errno(r, "Failed to generate service name: %m");
  59
  60         return add_symlink("serial-getty@.service", n);
  61 }
  62
  63 static int add_container_getty(const char *tty) {
  64         _cleanup_free_ char *n = NULL;
  65         int r;
  66
  67         assert(tty);
  68
  69         log_debug("Automatically adding container getty for /dev/pts/%s.", tty);
  70
  71         r = unit_name_from_path_instance("container-getty", tty, ".service", &n);
  72         if (r < 0)
  73                 return log_error_errno(r, "Failed to generate service name: %m");
  74
  75         return add_symlink("container-getty@.service", n);
  76 }
  77
  78 static int verify_tty(const char *name) {
  79         _cleanup_close_ int fd = -1;
  80         const char *p;
  81
  82         /* Some TTYs are weird and have been enumerated but don't work
  83          * when you try to use them, such as classic ttyS0 and
  84          * friends. Let's check that and open the device and run
  85          * isatty() on it. */
  86
  87         p = strjoina("/dev/", name);
  88
  89         /* O_NONBLOCK is essential here, to make sure we don't wait
  90          * for DCD */
  91         fd = open(p, O_RDWR|O_NONBLOCK|O_NOCTTY|O_CLOEXEC|O_NOFOLLOW);
  92         if (fd < 0)
  93                 return -errno;
  94
  95         errno = 0;
  96         if (isatty(fd) <= 0)
  97                 return errno > 0 ? -errno : -EIO;
  98
  99         return 0;
 100 }
 101
 102 int main(int argc, char *argv[]) {
 103
 104         static const char virtualization_consoles[] =
 105                 "hvc0\0"
 106                 "xvc0\0"
 107                 "hvsi0\0"
 108                 "sclp_line0\0"
 109                 "ttysclp0\0"
 110                 "3270!tty1\0";
 111
 112         _cleanup_free_ char *active = NULL;
 113         const char *j;
 114         int r;
 115
 116         if (argc > 1 && argc != 4) {
 117                 log_error("This program takes three or no arguments.");
 118                 return EXIT_FAILURE;
 119         }
 120
 121         if (argc > 1)
 122                 arg_dest = argv[1];
 123
 124         log_setup_generator();
 125
 126         if (detect_container() > 0) {
 127                 _cleanup_free_ char *container_ttys = NULL;
 128
 129                 log_debug("Automatically adding console shell.");
 130
 131                 if (add_symlink("console-getty.service", "console-getty.service") < 0)
 132                         return EXIT_FAILURE;
 133
 134                 /* When $container_ttys is set for PID 1, spawn
 135                  * gettys on all ptys named therein. Note that despite
 136                  * the variable name we only support ptys here. */
 137
 138                 r = getenv_for_pid(1, "container_ttys", &container_ttys);
 139                 if (r > 0) {
 140                         const char *word, *state;
 141                         size_t l;
 142
 143                         FOREACH_WORD(word, l, container_ttys, state) {
 144                                 const char *t;
 145                                 char tty[l + 1];
 146
 147                                 memcpy(tty, word, l);
 148                                 tty[l] = 0;
 149
 150                                 /* First strip off /dev/ if it is specified */
 151                                 t = path_startswith(tty, "/dev/");
 152                                 if (!t)
 153                                         t = tty;
 154
 155                                 /* Then, make sure it's actually a pty */
 156                                 t = path_startswith(t, "pts/");
 157                                 if (!t)
 158                                         continue;
 159
 160                                 if (add_container_getty(t) < 0)
 161                                         return EXIT_FAILURE;
 162                         }
 163                 }
 164
 165                 /* Don't add any further magic if we are in a container */
 166                 return EXIT_SUCCESS;
 167         }
 168
 169         if (read_one_line_file("/sys/class/tty/console/active", &active) >= 0) {
 170                 const char *word, *state;
 171                 size_t l;
 172
 173                 /* Automatically add in a serial getty on all active
 174                  * kernel consoles */
 175                 FOREACH_WORD(word, l, active, state) {
 176                         _cleanup_free_ char *tty = NULL;
 177
 178                         tty = strndup(word, l);
 179                         if (!tty) {
 180                                 log_oom();
 181                                 return EXIT_FAILURE;
 182                         }
 183
 184                         /* We assume that gettys on virtual terminals are
 185                          * started via manual configuration and do this magic
 186                          * only for non-VC terminals. */
 187
 188                         if (isempty(tty) || tty_is_vc(tty))
 189                                 continue;
 190
 191                         if (verify_tty(tty) < 0)
 192                                 continue;
 193
 194                         if (add_serial_getty(tty) < 0)
 195                                 return EXIT_FAILURE;
 196                 }
 197         }
 198
 199         /* Automatically add in a serial getty on the first
 200          * virtualizer console */
 201         NULSTR_FOREACH(j, virtualization_consoles) {
 202                 char *p;
 203
 204                 p = strjoina("/sys/class/tty/", j);
 205                 if (access(p, F_OK) < 0)
 206                         continue;
 207
 208                 if (add_serial_getty(j) < 0)
 209                         return EXIT_FAILURE;
 210         }
 211
 212         return EXIT_SUCCESS;
 213 }