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;
  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         memmove(buf, ptr, strlen(ptr) + 1);
  73         return 1;
  74 }
  75
  76 static int checked_tmpdir = 0;
  77
  78 /* Look for a tmpfs mounted at /dev/shm.  I couldn't find a cleaner
  79  * way to do this than to parse /proc/mounts.  statfs will return the
  80  * same filesystem magic number and fs id for both /dev and /dev/shm
  81  * when they are both tmpfs, so you can't tell if they are different
  82  * filesystems.  Also, there seems to be no other way of finding the
  83  * mount point of a filesystem from within it.
  84  *
  85  * If a /dev/shm tmpfs entry is found, then we switch to using it.
  86  * Otherwise, we stay with the default /tmp.
  87  */
  88 static void which_tmpdir(void)
  89 {
  90         int fd, found;
  91         char buf[128] = { '\0' };
  92
  93         if(checked_tmpdir)
  94                 return;
  95
  96         checked_tmpdir = 1;
  97
  98         printf("Checking for tmpfs mount on /dev/shm...");
  99
 100         fd = open("/proc/mounts", O_RDONLY);
 101         if(fd < 0){
 102                 printf("failed to open /proc/mounts, errno = %d\n", errno);
 103                 return;
 104         }
 105
 106         while(1){
 107                 found = next(fd, buf, sizeof(buf) / sizeof(buf[0]), ' ');
 108                 if(found != 1)
 109                         break;
 110
 111                 if(!strncmp(buf, "/dev/shm", strlen("/dev/shm")))
 112                         goto found;
 113
 114                 found = next(fd, buf, sizeof(buf) / sizeof(buf[0]), '\n');
 115                 if(found != 1)
 116                         break;
 117         }
 118
 119 err:
 120         if(found == 0)
 121                 printf("nothing mounted on /dev/shm\n");
 122         else if(found < 0)
 123                 printf("read returned errno %d\n", -found);
 124
 125         return;
 126
 127 found:
 128         found = next(fd, buf, sizeof(buf) / sizeof(buf[0]), ' ');
 129         if(found != 1)
 130                 goto err;
 131
 132         if(strncmp(buf, "tmpfs", strlen("tmpfs"))){
 133                 printf("not tmpfs\n");
 134                 return;
 135         }
 136
 137         printf("OK\n");
 138         default_tmpdir = "/dev/shm";
 139 }
 140
 141 /*
 142  * This proc still used in tt-mode
 143  * (file: kernel/tt/ptproxy/proxy.c, proc: start_debugger).
 144  * So it isn't 'static' yet.
 145  */
 146 int make_tempfile(const char *template, char **out_tempname, int do_unlink)
 147 {
 148         char *tempname;
 149         int fd;
 150
 151         which_tmpdir();
 152         tempname = malloc(MAXPATHLEN);
 153
 154         find_tempdir();
 155         if (template[0] != '/')
 156                 strcpy(tempname, tempdir);
 157         else
 158                 tempname[0] = '\0';
 159         strcat(tempname, template);
 160         fd = mkstemp(tempname);
 161         if(fd < 0){
 162                 fprintf(stderr, "open - cannot create %s: %s\n", tempname,
 163                         strerror(errno));
 164                 goto out;
 165         }
 166         if(do_unlink && (unlink(tempname) < 0)){
 167                 perror("unlink");
 168                 goto out;
 169         }
 170         if(out_tempname){
 171                 *out_tempname = tempname;
 172         } else {
 173                 free(tempname);
 174         }
 175         return(fd);
 176 out:
 177         free(tempname);
 178         return -1;
 179 }
 180
 181 #define TEMPNAME_TEMPLATE "vm_file-XXXXXX"
 182
 183 /*
 184  * This proc is used in start_up.c
 185  * So it isn't 'static'.
 186  */
 187 int create_tmp_file(unsigned long long len)
 188 {
 189         int fd, err;
 190         char zero;
 191
 192         fd = make_tempfile(TEMPNAME_TEMPLATE, NULL, 1);
 193         if(fd < 0) {
 194                 exit(1);
 195         }
 196
 197         err = fchmod(fd, 0777);
 198         if(err < 0){
 199                 perror("os_mode_fd");
 200                 exit(1);
 201         }
 202
 203         if (lseek64(fd, len, SEEK_SET) < 0) {
 204                 perror("os_seek_file");
 205                 exit(1);
 206         }
 207
 208         zero = 0;
 209
 210         err = os_write_file(fd, &zero, 1);
 211         if(err != 1){
 212                 errno = -err;
 213                 perror("os_write_file");
 214                 exit(1);
 215         }
 216
 217         return(fd);
 218 }
 219
 220 int create_mem_file(unsigned long long len)
 221 {
 222         int err, fd;
 223
 224         fd = create_tmp_file(len);
 225
 226         err = os_set_exec_close(fd, 1);
 227         if(err < 0){
 228                 errno = -err;
 229                 perror("exec_close");
 230         }
 231         return(fd);
 232 }
 233
 234
 235 void check_tmpexec(void)
 236 {
 237         void *addr;
 238         int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
 239
 240         addr = mmap(NULL, UM_KERN_PAGE_SIZE,
 241                     PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
 242         printf("Checking PROT_EXEC mmap in %s...",tempdir);
 243         fflush(stdout);
 244         if(addr == MAP_FAILED){
 245                 err = errno;
 246                 perror("failed");
 247                 if(err == EPERM)
 248                         printf("%s must be not mounted noexec\n",tempdir);
 249                 exit(1);
 250         }
 251         printf("OK\n");
 252         munmap(addr, UM_KERN_PAGE_SIZE);
 253
 254         close(fd);
 255 }