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