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 DEFAULT_DEBUG_CHANNEL(ldt)
  15
  16 #ifdef __i386__
  17
  18 #ifdef linux
  19 #include <sys/syscall.h>
  20
  21 struct modify_ldt_s
  22 {
  23     unsigned int  entry_number;
  24     unsigned long base_addr;
  25     unsigned int  limit;
  26     unsigned int  seg_32bit : 1;
  27     unsigned int  contents : 2;
  28     unsigned int  read_exec_only : 1;
  29     unsigned int  limit_in_pages : 1;
  30     unsigned int  seg_not_present : 1;
  31 };
  32
  33 static __inline__ int modify_ldt( int func, struct modify_ldt_s *ptr,
  34                                   unsigned long count )
  35 {
  36     int res;
  37 #ifdef __PIC__
  38     __asm__ __volatile__( "pushl %%ebx\n\t"
  39                           "movl %2,%%ebx\n\t"
  40                           "int $0x80\n\t"
  41                           "popl %%ebx"
  42                           : "=a" (res)
  43                           : "0" (SYS_modify_ldt),
  44                             "r" (func),
  45                             "c" (ptr),
  46                             "d" (count) );
  47 #else
  48     __asm__ __volatile__("int $0x80"
  49                          : "=a" (res)
  50                          : "0" (SYS_modify_ldt),
  51                            "b" (func),
  52                            "c" (ptr),
  53                            "d" (count) );
  54 #endif  /* __PIC__ */
  55     if (res >= 0) return res;
  56     errno = -res;
  57     return -1;
  58 }
  59
  60 #endif  /* linux */
  61
  62 #if defined(__svr4__) || defined(_SCO_DS)
  63 #include <sys/sysi86.h>
  64 #ifndef __sun__
  65 #include <sys/seg.h>
  66 #endif
  67 #endif
  68
  69 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__)
  70 #include <machine/segments.h>
  71
  72 extern int i386_get_ldt(int, union descriptor *, int);
  73 extern int i386_set_ldt(int, union descriptor *, int);
  74 #endif  /* __NetBSD__ || __FreeBSD__ || __OpenBSD__ */
  75
  76 #endif  /* __i386__ */
  77
  78
  79 ldt_copy_entry ldt_copy[LDT_SIZE];
  80 unsigned char ldt_flags_copy[LDT_SIZE];
  81
  82
  83 /***********************************************************************
  84  *           LDT_BytesToEntry
  85  *
  86  * Convert the raw bytes of the descriptor to an ldt_entry structure.
  87  */
  88 void LDT_BytesToEntry( const unsigned long *buffer, ldt_entry *content )
  89 {
  90     content->base  = (*buffer >> 16) & 0x0000ffff;
  91     content->limit = *buffer & 0x0000ffff;
  92     buffer++;
  93     content->base  |= (*buffer & 0xff000000) | ((*buffer << 16) & 0x00ff0000);
  94     content->limit |= (*buffer & 0x000f0000);
  95     content->type           = (*buffer >> 10) & 3;
  96     content->seg_32bit      = (*buffer & 0x00400000) != 0;
  97     content->read_only      = (*buffer & 0x00000200) == 0;
  98     content->limit_in_pages = (*buffer & 0x00800000) != 0;
  99 }
 100
 101
 102 /***********************************************************************
 103  *           LDT_EntryToBytes
 104  *
 105  * Convert an ldt_entry structure to the raw bytes of the descriptor.
 106  */
 107 void LDT_EntryToBytes( unsigned long *buffer, const ldt_entry *content )
 108 {
 109     *buffer++ = ((content->base & 0x0000ffff) << 16) |
 110                  (content->limit & 0x0ffff);
 111     *buffer = (content->base & 0xff000000) |
 112               ((content->base & 0x00ff0000)>>16) |
 113               (content->limit & 0xf0000) |
 114               (content->type << 10) |
 115               ((content->read_only == 0) << 9) |
 116               ((content->seg_32bit != 0) << 22) |
 117               ((content->limit_in_pages != 0) << 23) |
 118               0xf000;
 119 }
 120
 121
 122 /***********************************************************************
 123  *           LDT_GetEntry
 124  *
 125  * Retrieve an LDT entry.
 126  */
 127 int LDT_GetEntry( int entry, ldt_entry *content )
 128 {
 129     int ret = 0;
 130
 131     content->base           = ldt_copy[entry].base;
 132     content->limit          = ldt_copy[entry].limit;
 133     content->type           = (ldt_flags_copy[entry] & LDT_FLAGS_TYPE);
 134     content->seg_32bit      = (ldt_flags_copy[entry] & LDT_FLAGS_32BIT) != 0;
 135     content->read_only      = (ldt_flags_copy[entry] & LDT_FLAGS_READONLY) !=0;
 136     content->limit_in_pages = (ldt_flags_copy[entry] & LDT_FLAGS_BIG) !=0;
 137     if (content->limit_in_pages) content->limit >>= 12;
 138     return ret;
 139 }
 140
 141
 142 /***********************************************************************
 143  *           LDT_SetEntry
 144  *
 145  * Set an LDT entry.
 146  */
 147 int LDT_SetEntry( int entry, const ldt_entry *content )
 148 {
 149     int ret = 0;
 150
 151     TRACE(ldt, "entry=%04x base=%08lx limit=%05lx %s %d-bit "
 152                  "flags=%c%c%c\n", entry, content->base, content->limit,
 153                  content->limit_in_pages ? "pages" : "bytes",
 154                  content->seg_32bit ? 32 : 16,
 155                  content->read_only && (content->type & SEGMENT_CODE) ? '-' : 'r',
 156                  content->read_only || (content->type & SEGMENT_CODE) ? '-' : 'w',
 157                  (content->type & SEGMENT_CODE) ? 'x' : '-' );
 158
 159     /* Entry 0 must not be modified; its base and limit are always 0 */
 160     if (!entry) return 0;
 161
 162 #ifdef __i386__
 163
 164 #ifdef linux
 165     {
 166         struct modify_ldt_s ldt_info;
 167
 168         ldt_info.entry_number    = entry;
 169         ldt_info.base_addr       = content->base;
 170         ldt_info.limit           = content->limit;
 171         ldt_info.seg_32bit       = content->seg_32bit != 0;
 172         ldt_info.contents        = content->type;
 173         ldt_info.read_exec_only  = content->read_only != 0;
 174         ldt_info.limit_in_pages  = content->limit_in_pages != 0;
 175         ldt_info.seg_not_present = 0;
 176         /* Make sure the info will be accepted by the kernel */
 177         /* This is ugly, but what can I do? */
 178         if (content->type == SEGMENT_STACK)
 179         {
 180             /* FIXME */
 181         }
 182         else
 183         {
 184             if (ldt_info.base_addr >= 0xc0000000)
 185             {
 186                 WARN(ldt, "Invalid base addr %08lx\n",
 187                          ldt_info.base_addr );
 188                 return -1;
 189             }
 190             if (content->limit_in_pages)
 191             {
 192                 if ((ldt_info.limit << 12) + 0xfff >
 193                                                0xc0000000 - ldt_info.base_addr)
 194                     ldt_info.limit = (0xc0000000 - 0xfff - ldt_info.base_addr) >> 12;
 195             }
 196             else
 197             {
 198                 if (ldt_info.limit > 0xc0000000 - ldt_info.base_addr)
 199                     ldt_info.limit = 0xc0000000 - ldt_info.base_addr;
 200             }
 201         }
 202         if ((ret = modify_ldt(1, &ldt_info, sizeof(ldt_info))) < 0)
 203             perror( "modify_ldt" );
 204     }
 205 #endif  /* linux */
 206
 207 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__)
 208     {
 209         long d[2];
 210
 211         LDT_EntryToBytes( d, content );
 212         ret = i386_set_ldt(entry, (union descriptor *)d, 1);
 213         if (ret < 0)
 214         {
 215             perror("i386_set_ldt");
 216             MSG("Did you reconfigure the kernel with \"options USER_LDT\"?\n");
 217             exit(1);
 218         }
 219     }
 220 #endif  /* __NetBSD__ || __FreeBSD__ || __OpenBSD__ */
 221
 222 #if defined(__svr4__) || defined(_SCO_DS)
 223     {
 224         struct ssd ldt_mod;
 225         int i;
 226         ldt_mod.sel = ENTRY_TO_SELECTOR(entry) | 4;
 227         ldt_mod.bo = content->base;
 228         ldt_mod.ls = content->limit;
 229         i = ((content->limit & 0xf0000) |
 230              (content->type << 10) |
 231              (((content->read_only != 0) ^ 1) << 9) |
 232              ((content->seg_32bit != 0) << 22) |
 233              ((content->limit_in_pages != 0)<< 23) |
 234              (1<<15) |
 235              0x7000);
 236
 237         ldt_mod.acc1 = (i & 0xff00) >> 8;
 238         ldt_mod.acc2 = (i & 0xf00000) >> 20;
 239
 240         if (content->base == 0)
 241         {
 242             ldt_mod.acc1 =  0;
 243             ldt_mod.acc2 = 0;
 244         }
 245         if ((ret = sysi86(SI86DSCR, &ldt_mod)) == -1) perror("sysi86");
 246     }
 247 #endif
 248
 249 #endif  /* __i386__ */
 250
 251     if (ret < 0) return ret;
 252     ldt_copy[entry].base = content->base;
 253     if (!content->limit_in_pages) ldt_copy[entry].limit = content->limit;
 254     else ldt_copy[entry].limit = (content->limit << 12) | 0x0fff;
 255     ldt_flags_copy[entry] = (content->type & LDT_FLAGS_TYPE) |
 256                             (content->read_only ? LDT_FLAGS_READONLY : 0) |
 257                             (content->seg_32bit ? LDT_FLAGS_32BIT : 0) |
 258                             (content->limit_in_pages ? LDT_FLAGS_BIG : 0) |
 259                             (ldt_flags_copy[entry] & LDT_FLAGS_ALLOCATED);
 260     return ret;
 261 }
 262
 263
 264 /***********************************************************************
 265  *           LDT_Print
 266  *
 267  * Print the content of the LDT on stdout.
 268  */
 269 void LDT_Print( int start, int length )
 270 {
 271     int i;
 272     char flags[3];
 273
 274     if (length == -1) length = LDT_SIZE - start;
 275     for (i = start; i < start + length; i++)
 276     {
 277         if (!ldt_copy[i].base && !ldt_copy[i].limit) continue; /* Free entry */
 278         if ((ldt_flags_copy[i] & LDT_FLAGS_TYPE) == SEGMENT_CODE)
 279         {
 280             flags[0] = (ldt_flags_copy[i] & LDT_FLAGS_EXECONLY) ? '-' : 'r';
 281             flags[1] = '-';
 282             flags[2] = 'x';
 283         }
 284         else
 285         {
 286             flags[0] = 'r';
 287             flags[1] = (ldt_flags_copy[i] & LDT_FLAGS_READONLY) ? '-' : 'w';
 288             flags[2] = '-';
 289         }
 290         MSG("%04x: sel=%04x base=%08lx limit=%08lx %d-bit %c%c%c\n",
 291             i, ENTRY_TO_SELECTOR(i), ldt_copy[i].base, ldt_copy[i].limit,
 292             ldt_flags_copy[i] & LDT_FLAGS_32BIT ? 32 : 16,
 293             flags[0], flags[1], flags[2] );
 294     }
 295 }