drivers/char/vc_screen.c

   1 /*
   2  * linux/drivers/char/vc_screen.c
   3  *
   4  * Provide access to virtual console memory.
   5  * /dev/vcs0: the screen as it is being viewed right now (possibly scrolled)
   6  * /dev/vcsN: the screen of /dev/ttyN (1 <= N <= 63)
   7  *            [minor: N]
   8  *
   9  * /dev/vcsaN: idem, but including attributes, and prefixed with
  10  *      the 4 bytes lines,columns,x,y (as screendump used to give).
  11  *      Attribute/character pair is in native endianity.
  12  *            [minor: N+128]
  13  *
  14  * This replaces screendump and part of selection, so that the system
  15  * administrator can control access using file system permissions.
  16  *
  17  * aeb@cwi.nl - efter Friedas begravelse - 950211
  18  *
  19  * machek@k332.feld.cvut.cz - modified not to send characters to wrong console
  20  *       - fixed some fatal off-by-one bugs (0-- no longer == -1 -> looping and looping and looping...)
  21  *       - making it shorter - scr_readw are macros which expand in PRETTY long code
  22  */
  23
  24 #include <linux/kernel.h>
  25 #include <linux/major.h>
  26 #include <linux/errno.h>
  27 #include <linux/tty.h>
  28 #include <linux/sched.h>
  29 #include <linux/interrupt.h>
  30 #include <linux/mm.h>
  31 #include <linux/init.h>
  32 #include <linux/vt_kern.h>
  33 #include <linux/console_struct.h>
  34 #include <linux/selection.h>
  35 #include <asm/uaccess.h>
  36 #include <asm/byteorder.h>
  37
  38 #undef attr
  39 #undef org
  40 #undef addr
  41 #define HEADER_SIZE     4
  42
  43 static int
  44 vcs_size(struct inode *inode)
  45 {
  46         int size;
  47         int currcons = MINOR(inode->i_rdev) & 127;
  48         if (currcons == 0)
  49                 currcons = fg_console;
  50         else
  51                 currcons--;
  52         if (!vc_cons_allocated(currcons))
  53                 return -ENXIO;
  54
  55         size = video_num_lines * video_num_columns;
  56
  57         if (MINOR(inode->i_rdev) & 128)
  58                 size = 2*size + HEADER_SIZE;
  59         return size;
  60 }
  61
  62 static long long vcs_lseek(struct file *file, long long offset, int orig)
  63 {
  64         int size = vcs_size(file->f_dentry->d_inode);
  65
  66         switch (orig) {
  67                 default:
  68                         return -EINVAL;
  69                 case 2:
  70                         offset += size;
  71                         break;
  72                 case 1:
  73                         offset += file->f_pos;
  74                 case 0:
  75                         break;
  76         }
  77         if (offset < 0 || offset > size)
  78                 return -EINVAL;
  79         file->f_pos = offset;
  80         return file->f_pos;
  81 }
  82
  83 #define RETURN(x) { enable_bh(CONSOLE_BH); return x; }
  84 static ssize_t
  85 vcs_read(struct file *file, char *buf, size_t count, loff_t *ppos)
  86 {
  87         struct inode *inode = file->f_dentry->d_inode;
  88         unsigned int currcons = MINOR(inode->i_rdev);
  89         long p = *ppos;
  90         long viewed, attr, size, read;
  91         char *buf0;
  92         unsigned short *org = NULL;
  93
  94         attr = (currcons & 128);
  95         currcons = (currcons & 127);
  96         disable_bh(CONSOLE_BH);
  97         if (currcons == 0) {
  98                 currcons = fg_console;
  99                 viewed = 1;
 100         } else {
 101                 currcons--;
 102                 viewed = 0;
 103         }
 104         if (!vc_cons_allocated(currcons))
 105                 RETURN( -ENXIO );
 106
 107         size = vcs_size(inode);
 108         if (p < 0 || p > size)
 109                 RETURN( -EINVAL );
 110         if (count > size - p)
 111                 count = size - p;
 112
 113         buf0 = buf;
 114         if (!attr) {
 115                 org = screen_pos(currcons, p, viewed);
 116                 while (count-- > 0)
 117                         put_user(vcs_scr_readw(currcons, org++) & 0xff, buf++);
 118         } else {
 119                 if (p < HEADER_SIZE) {
 120                         char header[HEADER_SIZE];
 121                         header[0] = (char) video_num_lines;
 122                         header[1] = (char) video_num_columns;
 123                         getconsxy(currcons, header+2);
 124                         while (p < HEADER_SIZE && count > 0)
 125                             { count--; put_user(header[p++], buf++); }
 126                 }
 127                 if (count > 0) {
 128                     p -= HEADER_SIZE;
 129                     org = screen_pos(currcons, p/2, viewed);
 130                     if ((p & 1) && count > 0)
 131 #ifdef __BIG_ENDIAN
 132                             { count--; put_user(vcs_scr_readw(currcons, org++) & 0xff, buf++); }
 133 #else
 134                             { count--; put_user(vcs_scr_readw(currcons, org++) >> 8, buf++); }
 135 #endif
 136                 }
 137                 while (count > 1) {
 138                         put_user(vcs_scr_readw(currcons, org++), (unsigned short *) buf);
 139                         buf += 2;
 140                         count -= 2;
 141                 }
 142                 if (count > 0)
 143 #ifdef __BIG_ENDIAN
 144                         put_user(vcs_scr_readw(currcons, org) >> 8, buf++);
 145 #else
 146                         put_user(vcs_scr_readw(currcons, org) & 0xff, buf++);
 147 #endif
 148         }
 149         read = buf - buf0;
 150         *ppos += read;
 151         RETURN( read );
 152 }
 153
 154 static ssize_t
 155 vcs_write(struct file *file, const char *buf, size_t count, loff_t *ppos)
 156 {
 157         struct inode *inode = file->f_dentry->d_inode;
 158         unsigned int currcons = MINOR(inode->i_rdev);
 159         long p = *ppos;
 160         long viewed, attr, size, written;
 161         const char *buf0;
 162         u16 *org0 = NULL, *org = NULL;
 163
 164         attr = (currcons & 128);
 165         currcons = (currcons & 127);
 166         disable_bh(CONSOLE_BH);
 167         if (currcons == 0) {
 168                 currcons = fg_console;
 169                 viewed = 1;
 170         } else {
 171                 currcons--;
 172                 viewed = 0;
 173         }
 174         if (!vc_cons_allocated(currcons))
 175                 RETURN( -ENXIO );
 176
 177         size = vcs_size(inode);
 178         if (p < 0 || p > size)
 179                 RETURN( -EINVAL );
 180         if (count > size - p)
 181                 count = size - p;
 182
 183         buf0 = buf;
 184         if (!attr) {
 185                 org0 = org = screen_pos(currcons, p, viewed);
 186                 while (count > 0) {
 187                         unsigned char c;
 188                         count--;
 189                         get_user(c, (const unsigned char*)buf++);
 190                         vcs_scr_writew(currcons, (vcs_scr_readw(currcons, org) & 0xff00) | c, org);
 191                         org++;
 192                 }
 193         } else {
 194                 if (p < HEADER_SIZE) {
 195                         char header[HEADER_SIZE];
 196                         getconsxy(currcons, header+2);
 197                         while (p < HEADER_SIZE && count > 0)
 198                                 { count--; get_user(header[p++], buf++); }
 199                         if (!viewed)
 200                                 putconsxy(currcons, header+2);
 201                 }
 202                 if (count > 0) {
 203                         p -= HEADER_SIZE;
 204                         org0 = org = screen_pos(currcons, p/2, viewed);
 205                         if ((p & 1) && count > 0) {
 206                             char c;
 207                                 count--;
 208                                 get_user(c,buf++);
 209 #ifdef __BIG_ENDIAN
 210                                 vcs_scr_writew(currcons, c |
 211                                      (vcs_scr_readw(currcons, org) & 0xff00), org);
 212 #else
 213                                 vcs_scr_writew(currcons, (c << 8) |
 214                                      (vcs_scr_readw(currcons, org) & 0xff), org);
 215 #endif
 216                                 org++;
 217                         }
 218                 }
 219                 while (count > 1) {
 220                         unsigned short w;
 221                         get_user(w, (const unsigned short *) buf);
 222                         vcs_scr_writew(currcons, w, org++);
 223                         buf += 2;
 224                         count -= 2;
 225                 }
 226                 if (count > 0) {
 227                         unsigned char c;
 228                         get_user(c, (const unsigned char*)buf++);
 229 #ifdef __BIG_ENDIAN
 230                         vcs_scr_writew(currcons, (vcs_scr_readw(currcons, org) & 0xff) | (c << 8), org);
 231 #else
 232                         vcs_scr_writew(currcons, (vcs_scr_readw(currcons, org) & 0xff00) | c, org);
 233 #endif
 234                 }
 235         }
 236         if (org0)
 237                 update_region(currcons, (unsigned long)(org0), org-org0);
 238         written = buf - buf0;
 239         *ppos += written;
 240         RETURN( written );
 241 }
 242
 243 static int
 244 vcs_open(struct inode *inode, struct file *filp)
 245 {
 246         unsigned int currcons = (MINOR(inode->i_rdev) & 127);
 247         if(currcons && !vc_cons_allocated(currcons-1))
 248                 return -ENXIO;
 249         return 0;
 250 }
 251
 252 static struct file_operations vcs_fops = {
 253         vcs_lseek,      /* lseek */
 254         vcs_read,       /* read */
 255         vcs_write,      /* write */
 256         NULL,           /* readdir */
 257         NULL,           /* poll */
 258         NULL,           /* ioctl */
 259         NULL,           /* mmap */
 260         vcs_open,       /* open */
 261         NULL,           /* flush */
 262         NULL,           /* release */
 263         NULL            /* fsync */
 264 };
 265
 266 __initfunc(int vcs_init(void))
 267 {
 268         int error;
 269
 270         error = register_chrdev(VCS_MAJOR, "vcs", &vcs_fops);
 271         if (error)
 272                 printk("unable to get major %d for vcs device", VCS_MAJOR);
 273         return error;
 274 }