arch/um/os-Linux/mem.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <stddef.h>
   4 #include <stdarg.h>
   5 #include <unistd.h>
   6 #include <errno.h>
   7 #include <string.h>
   8 #include <fcntl.h>
   9 #include <sys/types.h>
  10 #include <sys/mman.h>
  11 #include <sys/statfs.h>
  12 #include "user.h"
  13 #include "mem_user.h"
  14 #include "init.h"
  15 #include "os.h"
  16 #include "tempfile.h"
  17 #include "kern_constants.h"
  18
  19 #include <sys/param.h>
  20
  21 /* Modified by which_tmpdir, which is called during early boot */
  22 static char *default_tmpdir = "/tmp";
  23
  24 /*
  25  *  Modified when creating the physical memory file and when checking
  26  * the tmp filesystem for usability, both happening during early boot.
  27  */
  28 static char *tempdir = NULL;
  29
  30 static void __init find_tempdir(void)
  31 {
  32         const char *dirs[] = { "TMP", "TEMP", "TMPDIR", NULL };
  33         int i;
  34         char *dir = NULL;
  35
  36         if(tempdir != NULL) /* We've already been called */
  37                 return;
  38         for(i = 0; dirs[i]; i++){
  39                 dir = getenv(dirs[i]);
  40                 if((dir != NULL) && (*dir != '\0'))
  41                         break;
  42         }
  43         if((dir == NULL) || (*dir == '\0'))
  44                 dir = default_tmpdir;
  45
  46         tempdir = malloc(strlen(dir) + 2);
  47         if(tempdir == NULL){
  48                 fprintf(stderr, "Failed to malloc tempdir, "
  49                         "errno = %d\n", errno);
  50                 return;
  51         }
  52         strcpy(tempdir, dir);
  53         strcat(tempdir, "/");
  54 }
  55
  56 /* This will return 1, with the first character in buf being the
  57  * character following the next instance of c in the file.  This will
  58  * read the file as needed.  If there's an error, -errno is returned;
  59  * if the end of the file is reached, 0 is returned.
  60  */
  61 static int next(int fd, char *buf, size_t size, char c)
  62 {
  63         ssize_t n;
  64         size_t len;
  65         char *ptr;
  66
  67         while((ptr = strchr(buf, c)) == NULL){
  68                 n = read(fd, buf, size - 1);
  69                 if(n == 0)
  70                         return 0;
  71                 else if(n < 0)
  72                         return -errno;
  73
  74                 buf[n] = '\0';
  75         }
  76
  77         ptr++;
  78         len = strlen(ptr);
  79         memmove(buf, ptr, len + 1);
  80
  81         /* Refill the buffer so that if there's a partial string that we care
  82          * about, it will be completed, and we can recognize it.
  83          */
  84         n = read(fd, &buf[len], size - len - 1);
  85         if(n < 0)
  86                 return -errno;
  87
  88         buf[len + n] = '\0';
  89         return 1;
  90 }
  91
  92 /* which_tmpdir is called only during early boot */
  93 static int checked_tmpdir = 0;
  94
  95 /* Look for a tmpfs mounted at /dev/shm.  I couldn't find a cleaner
  96  * way to do this than to parse /proc/mounts.  statfs will return the
  97  * same filesystem magic number and fs id for both /dev and /dev/shm
  98  * when they are both tmpfs, so you can't tell if they are different
  99  * filesystems.  Also, there seems to be no other way of finding the
 100  * mount point of a filesystem from within it.
 101  *
 102  * If a /dev/shm tmpfs entry is found, then we switch to using it.
 103  * Otherwise, we stay with the default /tmp.
 104  */
 105 static void which_tmpdir(void)
 106 {
 107         int fd, found;
 108         char buf[128] = { '\0' };
 109
 110         if(checked_tmpdir)
 111                 return;
 112
 113         checked_tmpdir = 1;
 114
 115         printf("Checking for tmpfs mount on /dev/shm...");
 116
 117         fd = open("/proc/mounts", O_RDONLY);
 118         if(fd < 0){
 119                 printf("failed to open /proc/mounts, errno = %d\n", errno);
 120                 return;
 121         }
 122
 123         while(1){
 124                 found = next(fd, buf, ARRAY_SIZE(buf), ' ');
 125                 if(found != 1)
 126                         break;
 127
 128                 if(!strncmp(buf, "/dev/shm", strlen("/dev/shm")))
 129                         goto found;
 130
 131                 found = next(fd, buf, ARRAY_SIZE(buf), '\n');
 132                 if(found != 1)
 133                         break;
 134         }
 135
 136 err:
 137         if(found == 0)
 138                 printf("nothing mounted on /dev/shm\n");
 139         else if(found < 0)
 140                 printf("read returned errno %d\n", -found);
 141
 142 out:
 143         close(fd);
 144
 145         return;
 146
 147 found:
 148         found = next(fd, buf, ARRAY_SIZE(buf), ' ');
 149         if(found != 1)
 150                 goto err;
 151
 152         if(strncmp(buf, "tmpfs", strlen("tmpfs"))){
 153                 printf("not tmpfs\n");
 154                 goto out;
 155         }
 156
 157         printf("OK\n");
 158         default_tmpdir = "/dev/shm";
 159         goto out;
 160 }
 161
 162 /*
 163  * This proc still used in tt-mode
 164  * (file: kernel/tt/ptproxy/proxy.c, proc: start_debugger).
 165  * So it isn't 'static' yet.
 166  */
 167 int __init make_tempfile(const char *template, char **out_tempname,
 168                          int do_unlink)
 169 {
 170         char *tempname;
 171         int fd;
 172
 173         which_tmpdir();
 174         tempname = malloc(MAXPATHLEN);
 175         if (!tempname)
 176                 goto out;
 177
 178         find_tempdir();
 179         if (template[0] != '/')
 180                 strcpy(tempname, tempdir);
 181         else
 182                 tempname[0] = '\0';
 183         strncat(tempname, template, MAXPATHLEN-1-strlen(tempname));
 184         fd = mkstemp(tempname);
 185         if(fd < 0){
 186                 fprintf(stderr, "open - cannot create %s: %s\n", tempname,
 187                         strerror(errno));
 188                 goto out;
 189         }
 190         if(do_unlink && (unlink(tempname) < 0)){
 191                 perror("unlink");
 192                 goto out;
 193         }
 194         if(out_tempname){
 195                 *out_tempname = tempname;
 196         } else {
 197                 free(tempname);
 198         }
 199         return fd;
 200 out:
 201         free(tempname);
 202         return -1;
 203 }
 204
 205 #define TEMPNAME_TEMPLATE "vm_file-XXXXXX"
 206
 207 /*
 208  * This proc is used in start_up.c
 209  * So it isn't 'static'.
 210  */
 211 int __init create_tmp_file(unsigned long long len)
 212 {
 213         int fd, err;
 214         char zero;
 215
 216         fd = make_tempfile(TEMPNAME_TEMPLATE, NULL, 1);
 217         if(fd < 0) {
 218                 exit(1);
 219         }
 220
 221         err = fchmod(fd, 0777);
 222         if(err < 0){
 223                 perror("fchmod");
 224                 exit(1);
 225         }
 226
 227         /* Seek to len - 1 because writing a character there will
 228          * increase the file size by one byte, to the desired length.
 229          */
 230         if (lseek64(fd, len - 1, SEEK_SET) < 0) {
 231                 perror("lseek64");
 232                 exit(1);
 233         }
 234
 235         zero = 0;
 236
 237         err = write(fd, &zero, 1);
 238         if(err != 1){
 239                 perror("write");
 240                 exit(1);
 241         }
 242
 243         return fd;
 244 }
 245
 246 int __init create_mem_file(unsigned long long len)
 247 {
 248         int err, fd;
 249
 250         fd = create_tmp_file(len);
 251
 252         err = os_set_exec_close(fd);
 253         if(err < 0){
 254                 errno = -err;
 255                 perror("exec_close");
 256         }
 257         return fd;
 258 }
 259
 260
 261 void __init check_tmpexec(void)
 262 {
 263         void *addr;
 264         int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
 265
 266         addr = mmap(NULL, UM_KERN_PAGE_SIZE,
 267                     PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
 268         printf("Checking PROT_EXEC mmap in %s...",tempdir);
 269         fflush(stdout);
 270         if(addr == MAP_FAILED){
 271                 err = errno;
 272                 perror("failed");
 273                 close(fd);
 274                 if(err == EPERM)
 275                         printf("%s must be not mounted noexec\n",tempdir);
 276                 exit(1);
 277         }
 278         printf("OK\n");
 279         munmap(addr, UM_KERN_PAGE_SIZE);
 280
 281         close(fd);
 282 }