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                 fd = -errno;
 125                 if(fd != -ENOENT){
 126                         printk("not_dead_yet : couldn't open pid file '%s', "
 127                                "err = %d\n", file, -fd);
 128                 }
 129                 goto out;
 130         }
 131
 132         err = 0;
 133         n = read(fd, pid, sizeof(pid));
 134         if(n < 0){
 135                 printk("not_dead_yet : couldn't read pid file '%s', "
 136                        "err = %d\n", file, errno);
 137                 goto out_close;
 138         } else if(n == 0){
 139                 printk("not_dead_yet : couldn't read pid file '%s', "
 140                        "0-byte read\n", file);
 141                 goto out_close;
 142         }
 143
 144         p = strtoul(pid, &end, 0);
 145         if(end == pid){
 146                 printk("not_dead_yet : couldn't parse pid file '%s', "
 147                        "errno = %d\n", file, errno);
 148                 goto out_close;
 149         }
 150
 151         if((kill(p, 0) == 0) || (errno != ESRCH)){
 152                 printk("umid \"%s\" is already in use by pid %d\n", umid, p);
 153                 return 1;
 154         }
 155
 156         err = actually_do_remove(dir);
 157         if(err)
 158                 printk("not_dead_yet - actually_do_remove failed with "
 159                        "err = %d\n", err);
 160
 161         return err;
 162
 163 out_close:
 164         close(fd);
 165 out:
 166         return 0;
 167 }
 168
 169 static void __init create_pid_file(void)
 170 {
 171         char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")];
 172         char pid[sizeof("nnnnn\0")];
 173         int fd, n;
 174
 175         if(umid_file_name("pid", file, sizeof(file)))
 176                 return;
 177
 178         fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0644);
 179         if(fd < 0){
 180                 printk("Open of machine pid file \"%s\" failed: %s\n",
 181                        file, strerror(errno));
 182                 return;
 183         }
 184
 185         snprintf(pid, sizeof(pid), "%d\n", getpid());
 186         n = write(fd, pid, strlen(pid));
 187         if(n != strlen(pid))
 188                 printk("Write of pid file failed - err = %d\n", errno);
 189
 190         close(fd);
 191 }
 192
 193 int __init set_umid(char *name)
 194 {
 195         if(strlen(name) > UMID_LEN - 1)
 196                 return -E2BIG;
 197
 198         strlcpy(umid, name, sizeof(umid));
 199
 200         return 0;
 201 }
 202
 203 static int umid_setup = 0;
 204
 205 int __init make_umid(void)
 206 {
 207         int fd, err;
 208         char tmp[256];
 209
 210         if(umid_setup)
 211                 return 0;
 212
 213         make_uml_dir();
 214
 215         if(*umid == '\0'){
 216                 strlcpy(tmp, uml_dir, sizeof(tmp));
 217                 strlcat(tmp, "XXXXXX", sizeof(tmp));
 218                 fd = mkstemp(tmp);
 219                 if(fd < 0){
 220                         printk("make_umid - mkstemp(%s) failed: %s\n",
 221                                tmp, strerror(errno));
 222                         err = -errno;
 223                         goto err;
 224                 }
 225
 226                 close(fd);
 227
 228                 set_umid(&tmp[strlen(uml_dir)]);
 229
 230                 /* There's a nice tiny little race between this unlink and
 231                  * the mkdir below.  It'd be nice if there were a mkstemp
 232                  * for directories.
 233                  */
 234                 if(unlink(tmp)){
 235                         err = -errno;
 236                         goto err;
 237                 }
 238         }
 239
 240         snprintf(tmp, sizeof(tmp), "%s%s", uml_dir, umid);
 241         err = mkdir(tmp, 0777);
 242         if(err < 0){
 243                 err = -errno;
 244                 if(err != -EEXIST)
 245                         goto err;
 246
 247                 /* 1   -> this umid is already in use
 248                  * < 0 -> we couldn't remove the umid directory
 249                  * In either case, we can't use this umid, so return -EEXIST.
 250                  */
 251                 if(not_dead_yet(tmp) != 0)
 252                         goto err;
 253
 254                 err = mkdir(tmp, 0777);
 255         }
 256         if(err){
 257                 err = -errno;
 258                 printk("Failed to create '%s' - err = %d\n", umid, -errno);
 259                 goto err;
 260         }
 261
 262         umid_setup = 1;
 263
 264         create_pid_file();
 265
 266         err = 0;
 267  err:
 268         return err;
 269 }
 270
 271 static int __init make_umid_init(void)
 272 {
 273         if(!make_umid())
 274                 return 0;
 275
 276         /* If initializing with the given umid failed, then try again with
 277          * a random one.
 278          */
 279         printk("Failed to initialize umid \"%s\", trying with a random umid\n",
 280                umid);
 281         *umid = '\0';
 282         make_umid();
 283
 284         return 0;
 285 }
 286
 287 __initcall(make_umid_init);
 288
 289 int __init umid_file_name(char *name, char *buf, int len)
 290 {
 291         int n, err;
 292
 293         err = make_umid();
 294         if(err)
 295                 return err;
 296
 297         n = snprintf(buf, len, "%s%s/%s", uml_dir, umid, name);
 298         if(n >= len){
 299                 printk("umid_file_name : buffer too short\n");
 300                 return -E2BIG;
 301         }
 302
 303         return 0;
 304 }
 305
 306 char *get_umid(void)
 307 {
 308         return umid;
 309 }
 310
 311 static int __init set_uml_dir(char *name, int *add)
 312 {
 313         if(*name == '\0'){
 314                 printf("uml_dir can't be an empty string\n");
 315                 return 0;
 316         }
 317
 318         if(name[strlen(name) - 1] == '/'){
 319                 uml_dir = name;
 320                 return 0;
 321         }
 322
 323         uml_dir = malloc(strlen(name) + 2);
 324         if(uml_dir == NULL){
 325                 printf("Failed to malloc uml_dir - error = %d\n", errno);
 326
 327                 /* Return 0 here because do_initcalls doesn't look at
 328                  * the return value.
 329                  */
 330                 return 0;
 331         }
 332         sprintf(uml_dir, "%s/", name);
 333
 334         return 0;
 335 }
 336
 337 __uml_setup("uml_dir=", set_uml_dir,
 338 "uml_dir=<directory>\n"
 339 "    The location to place the pid and umid files.\n\n"
 340 );
 341
 342 static void remove_umid_dir(void)
 343 {
 344         char dir[strlen(uml_dir) + UMID_LEN + 1], err;
 345
 346         sprintf(dir, "%s%s", uml_dir, umid);
 347         err = actually_do_remove(dir);
 348         if(err)
 349                 printf("remove_umid_dir - actually_do_remove failed with "
 350                        "err = %d\n", err);
 351 }
 352
 353 __uml_exitcall(remove_umid_dir);