arch/um/os-Linux/umid.c

   1 #include <stdio.h>
   2 #include <unistd.h>
   3 #include <stdlib.h>
   4 #include <string.h>
   5 #include <errno.h>
   6 #include <signal.h>
   7 #include <dirent.h>
   8 #include <sys/fcntl.h>
   9 #include <sys/stat.h>
  10 #include <sys/param.h>
  11 #include "init.h"
  12 #include "os.h"
  13 #include "user.h"
  14 #include "mode.h"
  15
  16 #define UML_DIR "~/.uml/"
  17
  18 #define UMID_LEN 64
  19
  20 /* Changed by set_umid, which is run early in boot */
  21 char umid[UMID_LEN] = { 0 };
  22
  23 /* Changed by set_uml_dir and make_uml_dir, which are run early in boot */
  24 static char *uml_dir = UML_DIR;
  25
  26 static int __init make_uml_dir(void)
  27 {
  28         char dir[512] = { '\0' };
  29         int len, err;
  30
  31         if(*uml_dir == '~'){
  32                 char *home = getenv("HOME");
  33
  34                 err = -ENOENT;
  35                 if(home == NULL){
  36                         printk("make_uml_dir : no value in environment for "
  37                                "$HOME\n");
  38                         goto err;
  39                 }
  40                 strlcpy(dir, home, sizeof(dir));
  41                 uml_dir++;
  42         }
  43         strlcat(dir, uml_dir, sizeof(dir));
  44         len = strlen(dir);
  45         if (len > 0 && dir[len - 1] != '/')
  46                 strlcat(dir, "/", sizeof(dir));
  47
  48         err = -ENOMEM;
  49         uml_dir = malloc(strlen(dir) + 1);
  50         if (uml_dir == NULL) {
  51                 printf("make_uml_dir : malloc failed, errno = %d\n", errno);
  52                 goto err;
  53         }
  54         strcpy(uml_dir, dir);
  55
  56         if((mkdir(uml_dir, 0777) < 0) && (errno != EEXIST)){
  57                 printf("Failed to mkdir '%s': %s\n", uml_dir, strerror(errno));
  58                 err = -errno;
  59                 goto err_free;
  60         }
  61         return 0;
  62
  63 err_free:
  64         free(uml_dir);
  65 err:
  66         uml_dir = NULL;
  67         return err;
  68 }
  69
  70 static int actually_do_remove(char *dir)
  71 {
  72         DIR *directory;
  73         struct dirent *ent;
  74         int len;
  75         char file[256];
  76
  77         directory = opendir(dir);
  78         if(directory == NULL)
  79                 return -errno;
  80
  81         while((ent = readdir(directory)) != NULL){
  82                 if(!strcmp(ent->d_name, ".") || !strcmp(ent->d_name, ".."))
  83                         continue;
  84                 len = strlen(dir) + sizeof("/") + strlen(ent->d_name) + 1;
  85                 if(len > sizeof(file))
  86                         return -E2BIG;
  87
  88                 sprintf(file, "%s/%s", dir, ent->d_name);
  89                 if(unlink(file) < 0)
  90                         return -errno;
  91         }
  92         if(rmdir(dir) < 0)
  93                 return -errno;
  94
  95         return 0;
  96 }
  97
  98 /* This says that there isn't already a user of the specified directory even if
  99  * there are errors during the checking.  This is because if these errors
 100  * happen, the directory is unusable by the pre-existing UML, so we might as
 101  * well take it over.  This could happen either by
 102  *      the existing UML somehow corrupting its umid directory
 103  *      something other than UML sticking stuff in the directory
 104  *      this boot racing with a shutdown of the other UML
 105  * In any of these cases, the directory isn't useful for anything else.
 106  */
 107
 108 static int not_dead_yet(char *dir)
 109 {
 110         char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")];
 111         char pid[sizeof("nnnnn\0")], *end;
 112         int dead, fd, p, n, err;
 113
 114         n = snprintf(file, sizeof(file), "%s/pid", dir);
 115         if(n >= sizeof(file)){
 116                 printk("not_dead_yet - pid filename too long\n");
 117                 err = -E2BIG;
 118                 goto out;
 119         }
 120
 121         dead = 0;
 122         fd = open(file, O_RDONLY);
 123         if(fd < 0){
 124                 if(fd != -ENOENT){
 125                         printk("not_dead_yet : couldn't open pid file '%s', "
 126                                "err = %d\n", file, -fd);
 127                 }
 128                 goto out;
 129         }
 130
 131         err = 0;
 132         n = read(fd, pid, sizeof(pid));
 133         if(n <= 0){
 134                 printk("not_dead_yet : couldn't read pid file '%s', "
 135                        "err = %d\n", file, -n);
 136                 goto out_close;
 137         }
 138
 139         p = strtoul(pid, &end, 0);
 140         if(end == pid){
 141                 printk("not_dead_yet : couldn't parse pid file '%s', "
 142                        "errno = %d\n", file, errno);
 143                 goto out_close;
 144         }
 145
 146         if((kill(p, 0) == 0) || (errno != ESRCH))
 147                 return 1;
 148
 149         err = actually_do_remove(dir);
 150         if(err)
 151                 printk("not_dead_yet - actually_do_remove failed with "
 152                        "err = %d\n", err);
 153
 154         return err;
 155
 156  out_close:
 157         close(fd);
 158  out:
 159         return 0;
 160 }
 161
 162 static void __init create_pid_file(void)
 163 {
 164         char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")];
 165         char pid[sizeof("nnnnn\0")];
 166         int fd, n;
 167
 168         if(umid_file_name("pid", file, sizeof(file)))
 169                 return;
 170
 171         fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0644);
 172         if(fd < 0){
 173                 printk("Open of machine pid file \"%s\" failed: %s\n",
 174                        file, strerror(-fd));
 175                 return;
 176         }
 177
 178         snprintf(pid, sizeof(pid), "%d\n", getpid());
 179         n = write(fd, pid, strlen(pid));
 180         if(n != strlen(pid))
 181                 printk("Write of pid file failed - err = %d\n", -n);
 182
 183         close(fd);
 184 }
 185
 186 int __init set_umid(char *name)
 187 {
 188         if(strlen(name) > UMID_LEN - 1)
 189                 return -E2BIG;
 190
 191         strlcpy(umid, name, sizeof(umid));
 192
 193         return 0;
 194 }
 195
 196 static int umid_setup = 0;
 197
 198 int __init make_umid(void)
 199 {
 200         int fd, err;
 201         char tmp[256];
 202
 203         if(umid_setup)
 204                 return 0;
 205
 206         make_uml_dir();
 207
 208         if(*umid == '\0'){
 209                 strlcpy(tmp, uml_dir, sizeof(tmp));
 210                 strlcat(tmp, "XXXXXX", sizeof(tmp));
 211                 fd = mkstemp(tmp);
 212                 if(fd < 0){
 213                         printk("make_umid - mkstemp(%s) failed: %s\n",
 214                                tmp, strerror(errno));
 215                         err = -errno;
 216                         goto err;
 217                 }
 218
 219                 close(fd);
 220
 221                 set_umid(&tmp[strlen(uml_dir)]);
 222
 223                 /* There's a nice tiny little race between this unlink and
 224                  * the mkdir below.  It'd be nice if there were a mkstemp
 225                  * for directories.
 226                  */
 227                 if(unlink(tmp)){
 228                         err = -errno;
 229                         goto err;
 230                 }
 231         }
 232
 233         snprintf(tmp, sizeof(tmp), "%s%s", uml_dir, umid);
 234         err = mkdir(tmp, 0777);
 235         if(err < 0){
 236                 err = -errno;
 237                 if(errno != EEXIST)
 238                         goto err;
 239
 240                 if(not_dead_yet(tmp) < 0)
 241                         goto err;
 242
 243                 err = mkdir(tmp, 0777);
 244         }
 245         if(err < 0){
 246                 printk("Failed to create '%s' - err = %d\n", umid, err);
 247                 goto err_rmdir;
 248         }
 249
 250         umid_setup = 1;
 251
 252         create_pid_file();
 253
 254         return 0;
 255
 256  err_rmdir:
 257         rmdir(tmp);
 258  err:
 259         return err;
 260 }
 261
 262 static int __init make_umid_init(void)
 263 {
 264         make_umid();
 265
 266         return 0;
 267 }
 268
 269 __initcall(make_umid_init);
 270
 271 int __init umid_file_name(char *name, char *buf, int len)
 272 {
 273         int n, err;
 274
 275         err = make_umid();
 276         if(err)
 277                 return err;
 278
 279         n = snprintf(buf, len, "%s%s/%s", uml_dir, umid, name);
 280         if(n >= len){
 281                 printk("umid_file_name : buffer too short\n");
 282                 return -E2BIG;
 283         }
 284
 285         return 0;
 286 }
 287
 288 char *get_umid(void)
 289 {
 290         return umid;
 291 }
 292
 293 static int __init set_uml_dir(char *name, int *add)
 294 {
 295         if(*name == '\0'){
 296                 printf("uml_dir can't be an empty string\n");
 297                 return 0;
 298         }
 299
 300         if(name[strlen(name) - 1] == '/'){
 301                 uml_dir = name;
 302                 return 0;
 303         }
 304
 305         uml_dir = malloc(strlen(name) + 2);
 306         if(uml_dir == NULL){
 307                 printf("Failed to malloc uml_dir - error = %d\n", errno);
 308
 309                 /* Return 0 here because do_initcalls doesn't look at
 310                  * the return value.
 311                  */
 312                 return 0;
 313         }
 314         sprintf(uml_dir, "%s/", name);
 315
 316         return 0;
 317 }
 318
 319 __uml_setup("uml_dir=", set_uml_dir,
 320 "uml_dir=<directory>\n"
 321 "    The location to place the pid and umid files.\n\n"
 322 );
 323
 324 static void remove_umid_dir(void)
 325 {
 326         char dir[strlen(uml_dir) + UMID_LEN + 1], err;
 327
 328         sprintf(dir, "%s%s", uml_dir, umid);
 329         err = actually_do_remove(dir);
 330         if(err)
 331                 printf("remove_umid_dir - actually_do_remove failed with "
 332                        "err = %d\n", err);
 333 }
 334
 335 __uml_exitcall(remove_umid_dir);