arch/um/os-Linux/mem.c

   1 /*
   2  * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <stdio.h>
   7 #include <stddef.h>
   8 #include <stdlib.h>
   9 #include <unistd.h>
  10 #include <errno.h>
  11 #include <fcntl.h>
  12 #include <string.h>
  13 #include <sys/stat.h>
  14 #include <sys/mman.h>
  15 #include <sys/param.h>
  16 #include "init.h"
  17 #include "kern_constants.h"
  18 #include "os.h"
  19 #include "user.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)
  37                 /* We've already been called */
  38                 return;
  39         for (i = 0; dirs[i]; i++) {
  40                 dir = getenv(dirs[i]);
  41                 if ((dir != NULL) && (*dir != '\0'))
  42                         break;
  43         }
  44         if ((dir == NULL) || (*dir == '\0'))
  45                 dir = default_tmpdir;
  46
  47         tempdir = malloc(strlen(dir) + 2);
  48         if (tempdir == NULL) {
  49                 fprintf(stderr, "Failed to malloc tempdir, "
  50                         "errno = %d\n", errno);
  51                 return;
  52         }
  53         strcpy(tempdir, dir);
  54         strcat(tempdir, "/");
  55 }
  56
  57 /*
  58  * This will return 1, with the first character in buf being the
  59  * character following the next instance of c in the file.  This will
  60  * read the file as needed.  If there's an error, -errno is returned;
  61  * if the end of the file is reached, 0 is returned.
  62  */
  63 static int next(int fd, char *buf, size_t size, char c)
  64 {
  65         ssize_t n;
  66         size_t len;
  67         char *ptr;
  68
  69         while ((ptr = strchr(buf, c)) == NULL) {
  70                 n = read(fd, buf, size - 1);
  71                 if (n == 0)
  72                         return 0;
  73                 else if (n < 0)
  74                         return -errno;
  75
  76                 buf[n] = '\0';
  77         }
  78
  79         ptr++;
  80         len = strlen(ptr);
  81         memmove(buf, ptr, len + 1);
  82
  83         /*
  84          * Refill the buffer so that if there's a partial string that we care
  85          * about, it will be completed, and we can recognize it.
  86          */
  87         n = read(fd, &buf[len], size - len - 1);
  88         if (n < 0)
  89                 return -errno;
  90
  91         buf[len + n] = '\0';
  92         return 1;
  93 }
  94
  95 /* which_tmpdir is called only during early boot */
  96 static int checked_tmpdir = 0;
  97
  98 /*
  99  * Look for a tmpfs mounted at /dev/shm.  I couldn't find a cleaner
 100  * way to do this than to parse /proc/mounts.  statfs will return the
 101  * same filesystem magic number and fs id for both /dev and /dev/shm
 102  * when they are both tmpfs, so you can't tell if they are different
 103  * filesystems.  Also, there seems to be no other way of finding the
 104  * mount point of a filesystem from within it.
 105  *
 106  * If a /dev/shm tmpfs entry is found, then we switch to using it.
 107  * Otherwise, we stay with the default /tmp.
 108  */
 109 static void which_tmpdir(void)
 110 {
 111         int fd, found;
 112         char buf[128] = { '\0' };
 113
 114         if (checked_tmpdir)
 115                 return;
 116
 117         checked_tmpdir = 1;
 118
 119         printf("Checking for tmpfs mount on /dev/shm...");
 120
 121         fd = open("/proc/mounts", O_RDONLY);
 122         if (fd < 0) {
 123                 printf("failed to open /proc/mounts, errno = %d\n", errno);
 124                 return;
 125         }
 126
 127         while (1) {
 128                 found = next(fd, buf, ARRAY_SIZE(buf), ' ');
 129                 if (found != 1)
 130                         break;
 131
 132                 if (!strncmp(buf, "/dev/shm", strlen("/dev/shm")))
 133                         goto found;
 134
 135                 found = next(fd, buf, ARRAY_SIZE(buf), '\n');
 136                 if (found != 1)
 137                         break;
 138         }
 139
 140 err:
 141         if (found == 0)
 142                 printf("nothing mounted on /dev/shm\n");
 143         else if (found < 0)
 144                 printf("read returned errno %d\n", -found);
 145
 146 out:
 147         close(fd);
 148
 149         return;
 150
 151 found:
 152         found = next(fd, buf, ARRAY_SIZE(buf), ' ');
 153         if (found != 1)
 154                 goto err;
 155
 156         if (strncmp(buf, "tmpfs", strlen("tmpfs"))) {
 157                 printf("not tmpfs\n");
 158                 goto out;
 159         }
 160
 161         printf("OK\n");
 162         default_tmpdir = "/dev/shm";
 163         goto out;
 164 }
 165
 166 static int __init make_tempfile(const char *template, char **out_tempname,
 167                                 int do_unlink)
 168 {
 169         char *tempname;
 170         int fd;
 171
 172         which_tmpdir();
 173         tempname = malloc(MAXPATHLEN);
 174         if (tempname == NULL)
 175                 return -1;
 176
 177         find_tempdir();
 178         if ((tempdir == NULL) || (strlen(tempdir) >= MAXPATHLEN))
 179                 goto out;
 180
 181         if (template[0] != '/')
 182                 strcpy(tempname, tempdir);
 183         else
 184                 tempname[0] = '\0';
 185         strncat(tempname, template, MAXPATHLEN-1-strlen(tempname));
 186         fd = mkstemp(tempname);
 187         if (fd < 0) {
 188                 fprintf(stderr, "open - cannot create %s: %s\n", tempname,
 189                         strerror(errno));
 190                 goto out;
 191         }
 192         if (do_unlink && (unlink(tempname) < 0)) {
 193                 perror("unlink");
 194                 goto close;
 195         }
 196         if (out_tempname) {
 197                 *out_tempname = tempname;
 198         } else
 199                 free(tempname);
 200         return fd;
 201 close:
 202         close(fd);
 203 out:
 204         free(tempname);
 205         return -1;
 206 }
 207
 208 #define TEMPNAME_TEMPLATE "vm_file-XXXXXX"
 209
 210 static int __init create_tmp_file(unsigned long long len)
 211 {
 212         int fd, err;
 213         char zero;
 214
 215         fd = make_tempfile(TEMPNAME_TEMPLATE, NULL, 1);
 216         if (fd < 0)
 217                 exit(1);
 218
 219         err = fchmod(fd, 0777);
 220         if (err < 0) {
 221                 perror("fchmod");
 222                 exit(1);
 223         }
 224
 225         /*
 226          * Seek to len - 1 because writing a character there will
 227          * increase the file size by one byte, to the desired length.
 228          */
 229         if (lseek64(fd, len - 1, SEEK_SET) < 0) {
 230                 perror("lseek64");
 231                 exit(1);
 232         }
 233
 234         zero = 0;
 235
 236         err = write(fd, &zero, 1);
 237         if (err != 1) {
 238                 perror("write");
 239                 exit(1);
 240         }
 241
 242         return fd;
 243 }
 244
 245 int __init create_mem_file(unsigned long long len)
 246 {
 247         int err, fd;
 248
 249         fd = create_tmp_file(len);
 250
 251         err = os_set_exec_close(fd);
 252         if (err < 0) {
 253                 errno = -err;
 254                 perror("exec_close");
 255         }
 256         return fd;
 257 }
 258
 259
 260 void __init check_tmpexec(void)
 261 {
 262         void *addr;
 263         int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
 264
 265         addr = mmap(NULL, UM_KERN_PAGE_SIZE,
 266                     PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
 267         printf("Checking PROT_EXEC mmap in %s...",tempdir);
 268         fflush(stdout);
 269         if (addr == MAP_FAILED) {
 270                 err = errno;
 271                 perror("failed");
 272                 close(fd);
 273                 if (err == EPERM)
 274                         printf("%s must be not mounted noexec\n",tempdir);
 275                 exit(1);
 276         }
 277         printf("OK\n");
 278         munmap(addr, UM_KERN_PAGE_SIZE);
 279
 280         close(fd);
 281 }