memory/ldt.c

   1 /*
   2  * LDT manipulation functions
   3  *
   4  * Copyright 1993 Robert J. Amstadt
   5  * Copyright 1995 Alexandre Julliard
   6  */
   7
   8 #include <stdlib.h>
   9 #include <string.h>
  10 #include <errno.h>
  11 #include "ldt.h"
  12 #include "debug.h"
  13
  14 #ifdef __i386__
  15
  16 #ifdef linux
  17 #include <sys/syscall.h>
  18
  19 struct modify_ldt_s
  20 {
  21     unsigned int  entry_number;
  22     unsigned long base_addr;
  23     unsigned int  limit;
  24     unsigned int  seg_32bit : 1;
  25     unsigned int  contents : 2;
  26     unsigned int  read_exec_only : 1;
  27     unsigned int  limit_in_pages : 1;
  28     unsigned int  seg_not_present : 1;
  29 };
  30
  31 static __inline__ int modify_ldt( int func, struct modify_ldt_s *ptr,
  32                                   unsigned long count )
  33 {
  34     int res;
  35 #ifdef __PIC__
  36     __asm__ __volatile__( "pushl %%ebx\n\t"
  37                           "movl %2,%%ebx\n\t"
  38                           "int $0x80\n\t"
  39                           "popl %%ebx"
  40                           : "=a" (res)
  41                           : "0" (SYS_modify_ldt),
  42                             "g" (func),
  43                             "c" (ptr),
  44                             "d" (count) );
  45 #else
  46     __asm__ __volatile__("int $0x80"
  47                          : "=a" (res)
  48                          : "0" (SYS_modify_ldt),
  49                            "b" (func),
  50                            "c" (ptr),
  51                            "d" (count) );
  52 #endif  /* __PIC__ */
  53     if (res >= 0) return res;
  54     errno = -res;
  55     return -1;
  56 }
  57
  58 #endif  /* linux */
  59
  60 #if defined(__svr4__) || defined(_SCO_DS)
  61 #include <sys/sysi86.h>
  62 #ifndef __sun__
  63 #include <sys/seg.h>
  64 #endif
  65 #endif
  66
  67 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__)
  68 #include <machine/segments.h>
  69
  70 extern int i386_get_ldt(int, union descriptor *, int);
  71 extern int i386_set_ldt(int, union descriptor *, int);
  72 #endif  /* __NetBSD__ || __FreeBSD__ || __OpenBSD__ */
  73
  74 #endif  /* __i386__ */
  75
  76
  77 ldt_copy_entry ldt_copy[LDT_SIZE];
  78 unsigned char ldt_flags_copy[LDT_SIZE];
  79
  80
  81 /***********************************************************************
  82  *           LDT_BytesToEntry
  83  *
  84  * Convert the raw bytes of the descriptor to an ldt_entry structure.
  85  */
  86 void LDT_BytesToEntry( const unsigned long *buffer, ldt_entry *content )
  87 {
  88     content->base  = (*buffer >> 16) & 0x0000ffff;
  89     content->limit = *buffer & 0x0000ffff;
  90     buffer++;
  91     content->base  |= (*buffer & 0xff000000) | ((*buffer << 16) & 0x00ff0000);
  92     content->limit |= (*buffer & 0x000f0000);
  93     content->type           = (*buffer >> 10) & 3;
  94     content->seg_32bit      = (*buffer & 0x00400000) != 0;
  95     content->read_only      = (*buffer & 0x00000200) == 0;
  96     content->limit_in_pages = (*buffer & 0x00800000) != 0;
  97 }
  98
  99
 100 /***********************************************************************
 101  *           LDT_EntryToBytes
 102  *
 103  * Convert an ldt_entry structure to the raw bytes of the descriptor.
 104  */
 105 void LDT_EntryToBytes( unsigned long *buffer, const ldt_entry *content )
 106 {
 107     *buffer++ = ((content->base & 0x0000ffff) << 16) |
 108                  (content->limit & 0x0ffff);
 109     *buffer = (content->base & 0xff000000) |
 110               ((content->base & 0x00ff0000)>>16) |
 111               (content->limit & 0xf0000) |
 112               (content->type << 10) |
 113               ((content->read_only == 0) << 9) |
 114               ((content->seg_32bit != 0) << 22) |
 115               ((content->limit_in_pages != 0) << 23) |
 116               0xf000;
 117 }
 118
 119
 120 /***********************************************************************
 121  *           LDT_GetEntry
 122  *
 123  * Retrieve an LDT entry.
 124  */
 125 int LDT_GetEntry( int entry, ldt_entry *content )
 126 {
 127     int ret = 0;
 128
 129     content->base           = ldt_copy[entry].base;
 130     content->limit          = ldt_copy[entry].limit;
 131     content->type           = (ldt_flags_copy[entry] & LDT_FLAGS_TYPE);
 132     content->seg_32bit      = (ldt_flags_copy[entry] & LDT_FLAGS_32BIT) != 0;
 133     content->read_only      = (ldt_flags_copy[entry] & LDT_FLAGS_READONLY) !=0;
 134     content->limit_in_pages = (ldt_flags_copy[entry] & LDT_FLAGS_BIG) !=0;
 135     if (content->limit_in_pages) content->limit >>= 12;
 136     return ret;
 137 }
 138
 139
 140 /***********************************************************************
 141  *           LDT_SetEntry
 142  *
 143  * Set an LDT entry.
 144  */
 145 int LDT_SetEntry( int entry, const ldt_entry *content )
 146 {
 147     int ret = 0;
 148
 149     TRACE(ldt, "entry=%04x base=%08lx limit=%05lx %s %d-bit "
 150                  "flags=%c%c%c\n", entry, content->base, content->limit,
 151                  content->limit_in_pages ? "pages" : "bytes",
 152                  content->seg_32bit ? 32 : 16,
 153                  content->read_only && (content->type & SEGMENT_CODE) ? '-' : 'r',
 154                  content->read_only || (content->type & SEGMENT_CODE) ? '-' : 'w',
 155                  (content->type & SEGMENT_CODE) ? 'x' : '-' );
 156
 157     /* Entry 0 must not be modified; its base and limit are always 0 */
 158     if (!entry) return 0;
 159
 160 #ifdef __i386__
 161
 162 #ifdef linux
 163     {
 164         struct modify_ldt_s ldt_info;
 165
 166         ldt_info.entry_number    = entry;
 167         ldt_info.base_addr       = content->base;
 168         ldt_info.limit           = content->limit;
 169         ldt_info.seg_32bit       = content->seg_32bit != 0;
 170         ldt_info.contents        = content->type;
 171         ldt_info.read_exec_only  = content->read_only != 0;
 172         ldt_info.limit_in_pages  = content->limit_in_pages != 0;
 173         ldt_info.seg_not_present = 0;
 174         /* Make sure the info will be accepted by the kernel */
 175         /* This is ugly, but what can I do? */
 176         if (content->type == SEGMENT_STACK)
 177         {
 178             /* FIXME */
 179         }
 180         else
 181         {
 182             if (ldt_info.base_addr >= 0xc0000000)
 183             {
 184                 WARN(ldt, "Invalid base addr %08lx\n",
 185                          ldt_info.base_addr );
 186                 return -1;
 187             }
 188             if (content->limit_in_pages)
 189             {
 190                 if ((ldt_info.limit << 12) + 0xfff >
 191                                                0xc0000000 - ldt_info.base_addr)
 192                     ldt_info.limit = (0xc0000000 - 0xfff - ldt_info.base_addr) >> 12;
 193             }
 194             else
 195             {
 196                 if (ldt_info.limit > 0xc0000000 - ldt_info.base_addr)
 197                     ldt_info.limit = 0xc0000000 - ldt_info.base_addr;
 198             }
 199         }
 200         if ((ret = modify_ldt(1, &ldt_info, sizeof(ldt_info))) < 0)
 201             perror( "modify_ldt" );
 202     }
 203 #endif  /* linux */
 204
 205 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__)
 206     {
 207         long d[2];
 208
 209         LDT_EntryToBytes( d, content );
 210         ret = i386_set_ldt(entry, (union descriptor *)d, 1);
 211         if (ret < 0)
 212         {
 213             perror("i386_set_ldt");
 214             MSG("Did you reconfigure the kernel with \"options USER_LDT\"?\n");
 215             exit(1);
 216         }
 217     }
 218 #endif  /* __NetBSD__ || __FreeBSD__ || __OpenBSD__ */
 219
 220 #if defined(__svr4__) || defined(_SCO_DS)
 221     {
 222         struct ssd ldt_mod;
 223         int i;
 224         ldt_mod.sel = ENTRY_TO_SELECTOR(entry) | 4;
 225         ldt_mod.bo = content->base;
 226         ldt_mod.ls = content->limit;
 227         i = ((content->limit & 0xf0000) |
 228              (content->type << 10) |
 229              (((content->read_only != 0) ^ 1) << 9) |
 230              ((content->seg_32bit != 0) << 22) |
 231              ((content->limit_in_pages != 0)<< 23) |
 232              (1<<15) |
 233              0x7000);
 234
 235         ldt_mod.acc1 = (i & 0xff00) >> 8;
 236         ldt_mod.acc2 = (i & 0xf00000) >> 20;
 237
 238         if (content->base == 0)
 239         {
 240             ldt_mod.acc1 =  0;
 241             ldt_mod.acc2 = 0;
 242         }
 243         if ((ret = sysi86(SI86DSCR, &ldt_mod)) == -1) perror("sysi86");
 244     }
 245 #endif
 246
 247 #endif  /* __i386__ */
 248
 249     if (ret < 0) return ret;
 250     ldt_copy[entry].base = content->base;
 251     if (!content->limit_in_pages) ldt_copy[entry].limit = content->limit;
 252     else ldt_copy[entry].limit = (content->limit << 12) | 0x0fff;
 253     ldt_flags_copy[entry] = (content->type & LDT_FLAGS_TYPE) |
 254                             (content->read_only ? LDT_FLAGS_READONLY : 0) |
 255                             (content->seg_32bit ? LDT_FLAGS_32BIT : 0) |
 256                             (content->limit_in_pages ? LDT_FLAGS_BIG : 0) |
 257                             (ldt_flags_copy[entry] & LDT_FLAGS_ALLOCATED);
 258     return ret;
 259 }
 260
 261
 262 /***********************************************************************
 263  *           LDT_Print
 264  *
 265  * Print the content of the LDT on stdout.
 266  */
 267 void LDT_Print( int start, int length )
 268 {
 269     int i;
 270     char flags[3];
 271
 272     if (length == -1) length = LDT_SIZE - start;
 273     for (i = start; i < start + length; i++)
 274     {
 275         if (!ldt_copy[i].base && !ldt_copy[i].limit) continue; /* Free entry */
 276         if ((ldt_flags_copy[i] & LDT_FLAGS_TYPE) == SEGMENT_CODE)
 277         {
 278             flags[0] = (ldt_flags_copy[i] & LDT_FLAGS_EXECONLY) ? '-' : 'r';
 279             flags[1] = '-';
 280             flags[2] = 'x';
 281         }
 282         else
 283         {
 284             flags[0] = 'r';
 285             flags[1] = (ldt_flags_copy[i] & LDT_FLAGS_READONLY) ? '-' : 'w';
 286             flags[2] = '-';
 287         }
 288         MSG("%04x: sel=%04x base=%08lx limit=%08lx %d-bit %c%c%c\n",
 289             i, ENTRY_TO_SELECTOR(i), ldt_copy[i].base, ldt_copy[i].limit,
 290             ldt_flags_copy[i] & LDT_FLAGS_32BIT ? 32 : 16,
 291             flags[0], flags[1], flags[2] );
 292     }
 293 }