src/getty-generator/getty-generator.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <fcntl.h>
   5 #include <unistd.h>
   6
   7 #include "alloc-util.h"
   8 #include "errno-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 "strv.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 = NULL;
  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_or_else(EIO);
  98
  99         return 0;
 100 }
 101
 102 static int run_container(void) {
 103         _cleanup_free_ char *container_ttys = NULL;
 104         int r;
 105
 106         log_debug("Automatically adding console shell.");
 107
 108         r = add_symlink("console-getty.service", "console-getty.service");
 109         if (r < 0)
 110                 return r;
 111
 112         /* When $container_ttys is set for PID 1, spawn gettys on all ptys named therein.
 113          * Note that despite the variable name we only support ptys here. */
 114
 115         (void) getenv_for_pid(1, "container_ttys", &container_ttys);
 116
 117         for (const char *p = container_ttys;;) {
 118                _cleanup_free_ char *word = NULL;
 119
 120                 r = extract_first_word(&p, &word, NULL, 0);
 121                 if (r < 0)
 122                         return log_error_errno(r, "Failed to parse $container_ttys: %m");
 123                 if (r == 0)
 124                         return 0;
 125
 126                 const char *tty = word;
 127
 128                 /* First strip off /dev/ if it is specified */
 129                 tty = path_startswith(tty, "/dev/") ?: tty;
 130
 131                 /* Then, make sure it's actually a pty */
 132                 tty = path_startswith(tty, "pts/");
 133                 if (!tty)
 134                         continue;
 135
 136                 r = add_container_getty(tty);
 137                 if (r < 0)
 138                         return r;
 139         }
 140 }
 141
 142 static int run(const char *dest, const char *dest_early, const char *dest_late) {
 143         int r;
 144
 145         assert_se(arg_dest = dest);
 146
 147         if (detect_container() > 0)
 148                 /* Add console shell and look at $container_ttys, but don't do add any
 149                  * further magic if we are in a container. */
 150                 return run_container();
 151
 152         /* Automatically add in a serial getty on all active kernel consoles */
 153         _cleanup_free_ char *active = NULL;
 154         (void) read_one_line_file("/sys/class/tty/console/active", &active);
 155         for (const char *p = active;;) {
 156                _cleanup_free_ char *tty = NULL;
 157
 158                 r = extract_first_word(&p, &tty, NULL, 0);
 159                 if (r < 0)
 160                         return log_error_errno(r, "Failed to parse /sys/class/tty/console/active: %m");
 161                 if (r == 0)
 162                         break;
 163
 164                 /* We assume that gettys on virtual terminals are started via manual configuration and do
 165                  * this magic only for non-VC terminals. */
 166
 167                 if (isempty(tty) || tty_is_vc(tty))
 168                         continue;
 169
 170                 if (verify_tty(tty) < 0)
 171                         continue;
 172
 173                 r = add_serial_getty(tty);
 174                 if (r < 0)
 175                         return r;
 176         }
 177
 178         /* Automatically add in a serial getty on the first
 179          * virtualizer console */
 180         const char *j;
 181         FOREACH_STRING(j,
 182                        "hvc0",
 183                        "xvc0",
 184                        "hvsi0",
 185                        "sclp_line0",
 186                        "ttysclp0",
 187                        "3270!tty1") {
 188                 _cleanup_free_ char *p = NULL;
 189
 190                 p = path_join("/sys/class/tty", j);
 191                 if (!p)
 192                         return -ENOMEM;
 193                 if (access(p, F_OK) < 0)
 194                         continue;
 195
 196                 r = add_serial_getty(j);
 197                 if (r < 0)
 198                         return r;
 199         }
 200
 201         return 0;
 202 }
 203
 204 DEFINE_MAIN_GENERATOR_FUNCTION(run);