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