loader/ldt_keeper.c

   1 /**
   2  * !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
   3  * This file MUST be in main library because LDT must
   4  * be modified before program creates first thread
   5  * - avifile includes this file from C++ code
   6  * and initializes it at the start of player!
   7  * it might sound like a hack and it really is - but
   8  * as aviplay is deconding video with more than just one
   9  * thread currently it's necessary to do it this way
  10  * this might change in the future
  11  */
  12
  13 /* applied some modification to make make our xine friend more happy */
  14
  15 /*
  16  * Modified for use with MPlayer, detailed changelog at
  17  * http://svn.mplayerhq.hu/mplayer/trunk/
  18  */
  19
  20 #include "config.h"
  21 #include "ldt_keeper.h"
  22
  23 #include <string.h>
  24 #include <stdlib.h>
  25 #include <errno.h>
  26 #include <fcntl.h>
  27 #ifdef HAVE_SYS_MMAN_H
  28 #include <sys/mman.h>
  29 #else
  30 #include "osdep/mmap.h"
  31 #endif
  32 #include <sys/types.h>
  33 #include <stdio.h>
  34 #include <unistd.h>
  35 #include "osdep/mmap_anon.h"
  36 #include "mp_msg.h"
  37 #include "help_mp.h"
  38 #ifdef __linux__
  39 #include <asm/unistd.h>
  40 #include <asm/ldt.h>
  41 // 2.5.xx+ calls this user_desc:
  42 #include <linux/version.h>
  43 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,5,47)
  44 #define modify_ldt_ldt_s user_desc
  45 #endif
  46 /* prototype it here, so we won't depend on kernel headers */
  47 #ifdef  __cplusplus
  48 extern "C" {
  49 #endif
  50 /// declare modify_ldt with the _syscall3 macro for older glibcs
  51 #if defined(__GLIBC__) &&  (__GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ == 0))
  52 _syscall3( int, modify_ldt, int, func, void *, ptr, unsigned long, bytecount );
  53 #else
  54 int modify_ldt(int func, void *ptr, unsigned long bytecount);
  55 #endif
  56 #ifdef  __cplusplus
  57 }
  58 #endif
  59 #else
  60 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__)
  61 #include <machine/segments.h>
  62 #include <machine/sysarch.h>
  63 #endif
  64
  65 #if defined(__APPLE__)
  66 #include <architecture/i386/table.h>
  67 #include <i386/user_ldt.h>
  68 #endif
  69
  70 #ifdef __svr4__
  71 #include <sys/segment.h>
  72 #include <sys/sysi86.h>
  73
  74 /* solaris x86: add missing prototype for sysi86(), but only when sysi86(int, void*) is known to be valid */
  75 #ifdef HAVE_SYSI86_iv
  76 #ifdef  __cplusplus
  77 extern "C" {
  78 #endif
  79 int sysi86(int, void*);
  80 #ifdef  __cplusplus
  81 }
  82 #endif
  83 #endif
  84
  85 #ifndef NUMSYSLDTS             /* SunOS 2.5.1 does not define NUMSYSLDTS */
  86 #define NUMSYSLDTS     6       /* Let's hope the SunOS 5.8 value is OK */
  87 #endif
  88
  89 #define       TEB_SEL_IDX     NUMSYSLDTS
  90 #endif
  91
  92 #define LDT_ENTRIES     8192
  93 #define LDT_ENTRY_SIZE  8
  94 #pragma pack(4)
  95 struct modify_ldt_ldt_s {
  96         unsigned int  entry_number;
  97         unsigned long base_addr;
  98         unsigned int  limit;
  99         unsigned int  seg_32bit:1;
 100         unsigned int  contents:2;
 101         unsigned int  read_exec_only:1;
 102         unsigned int  limit_in_pages:1;
 103         unsigned int  seg_not_present:1;
 104         unsigned int  useable:1;
 105 };
 106
 107 #define MODIFY_LDT_CONTENTS_DATA        0
 108 #define MODIFY_LDT_CONTENTS_STACK       1
 109 #define MODIFY_LDT_CONTENTS_CODE        2
 110 #endif
 111
 112
 113 /* user level (privilege level: 3) ldt (1<<2) segment selector */
 114 #define       LDT_SEL(idx) ((idx) << 3 | 1 << 2 | 3)
 115
 116 /* i got this value from wine sources, it's the first free LDT entry */
 117 #if (defined(__APPLE__) || defined(__FreeBSD__)) && defined(LDT_AUTO_ALLOC)
 118 #define       TEB_SEL_IDX     LDT_AUTO_ALLOC
 119 #define       USE_LDT_AA
 120 #endif
 121
 122 #ifndef       TEB_SEL_IDX
 123 #define       TEB_SEL_IDX     17
 124 #endif
 125
 126 static unsigned int fs_ldt = TEB_SEL_IDX;
 127
 128
 129 /**
 130  * here is a small logical problem with Restore for multithreaded programs -
 131  * in C++ we use static class for this...
 132  */
 133
 134 #ifdef __cplusplus
 135 extern "C"
 136 #endif
 137 void Setup_FS_Segment(void)
 138 {
 139     unsigned int ldt_desc = LDT_SEL(fs_ldt);
 140
 141     __asm__ volatile(
 142         "movl %0,%%eax; movw %%ax, %%fs" : : "r" (ldt_desc)
 143         :"eax"
 144     );
 145 }
 146
 147 /* we don't need this - use modify_ldt instead */
 148 #if 0
 149 #ifdef __linux__
 150 /* XXX: why is this routine from libc redefined here? */
 151 /* NOTE: the redefined version ignores the count param, count is hardcoded as 16 */
 152 static int LDT_Modify( int func, struct modify_ldt_ldt_s *ptr,
 153                        unsigned long count )
 154 {
 155     int res;
 156 #ifdef __PIC__
 157     __asm__ volatile( "pushl %%ebx\n\t"
 158                           "movl %2,%%ebx\n\t"
 159                           "int $0x80\n\t"
 160                           "popl %%ebx"
 161                           : "=a" (res)
 162                           : "0" (__NR_modify_ldt),
 163                           "r" (func),
 164                           "c" (ptr),
 165                           "d"(16)//sizeof(*ptr) from kernel point of view
 166                           :"esi"     );
 167 #else
 168     __asm__ volatile("int $0x80"
 169                          : "=a" (res)
 170                          : "0" (__NR_modify_ldt),
 171                          "b" (func),
 172                          "c" (ptr),
 173                          "d"(16)
 174                          :"esi");
 175 #endif  /* __PIC__ */
 176     if (res >= 0) return res;
 177     errno = -res;
 178     return -1;
 179 }
 180 #endif
 181 #endif
 182
 183 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__) || defined(__APPLE__)
 184 static void LDT_EntryToBytes( unsigned long *buffer, const struct modify_ldt_ldt_s *content )
 185 {
 186     *buffer++ = ((content->base_addr & 0x0000ffff) << 16) |
 187         (content->limit & 0x0ffff);
 188     *buffer = (content->base_addr & 0xff000000) |
 189         ((content->base_addr & 0x00ff0000)>>16) |
 190         (content->limit & 0xf0000) |
 191         (content->contents << 10) |
 192         ((content->read_exec_only == 0) << 9) |
 193         ((content->seg_32bit != 0) << 22) |
 194         ((content->limit_in_pages != 0) << 23) |
 195         0xf000;
 196 }
 197 #endif
 198
 199 void* fs_seg=0;
 200
 201 ldt_fs_t* Setup_LDT_Keeper(void)
 202 {
 203     struct modify_ldt_ldt_s array;
 204     int ret;
 205     ldt_fs_t* ldt_fs = (ldt_fs_t*) malloc(sizeof(ldt_fs_t));
 206
 207     if (!ldt_fs)
 208         return NULL;
 209
 210 #ifdef __APPLE__
 211     if (getenv("DYLD_BIND_AT_LAUNCH") == NULL)
 212         mp_msg(MSGT_LOADER, MSGL_WARN, MSGTR_LOADER_DYLD_Warning);
 213 #endif /* __APPLE__ */
 214
 215     fs_seg=
 216     ldt_fs->fs_seg = mmap_anon(NULL, getpagesize(), PROT_READ | PROT_WRITE, MAP_PRIVATE, 0);
 217     if (ldt_fs->fs_seg == (void*)-1)
 218     {
 219         perror("ERROR: Couldn't allocate memory for fs segment");
 220         free(ldt_fs);
 221         return NULL;
 222     }
 223     *(void**)((char*)ldt_fs->fs_seg+0x18) = ldt_fs->fs_seg;
 224     memset(&array, 0, sizeof(array));
 225     array.base_addr=(int)ldt_fs->fs_seg;
 226     array.entry_number=TEB_SEL_IDX;
 227     array.limit=array.base_addr+getpagesize()-1;
 228     array.seg_32bit=1;
 229     array.read_exec_only=0;
 230     array.seg_not_present=0;
 231     array.contents=MODIFY_LDT_CONTENTS_DATA;
 232     array.limit_in_pages=0;
 233 #ifdef __linux__
 234     //ret=LDT_Modify(0x1, &array, sizeof(struct modify_ldt_ldt_s));
 235     ret=modify_ldt(0x1, &array, sizeof(struct modify_ldt_ldt_s));
 236     if(ret<0)
 237     {
 238         perror("install_fs");
 239         printf("Couldn't install fs segment, expect segfault\n");
 240     }
 241 #endif /*linux*/
 242
 243 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__) || defined(__APPLE__)
 244     {
 245         unsigned long d[2];
 246
 247         LDT_EntryToBytes( d, &array );
 248 #ifdef USE_LDT_AA
 249         ret = i386_set_ldt(LDT_AUTO_ALLOC, (union descriptor *)d, 1);
 250         array.entry_number = ret;
 251         fs_ldt = ret;
 252 #else
 253         ret = i386_set_ldt(array.entry_number, (union descriptor *)d, 1);
 254 #endif
 255         if (ret < 0)
 256         {
 257             perror("install_fs");
 258             printf("Couldn't install fs segment, expect segfault\n");
 259             printf("Did you reconfigure the kernel with \"options USER_LDT\"?\n");
 260 #ifdef __OpenBSD__
 261             printf("On newer OpenBSD systems did you set machdep.userldt to 1?\n");
 262 #endif
 263         }
 264     }
 265 #endif  /* __NetBSD__ || __FreeBSD__ || __OpenBSD__ || __DragonFly__ || __APPLE__ */
 266
 267 #if defined(__svr4__)
 268     {
 269         struct ssd ssd;
 270         ssd.sel = LDT_SEL(TEB_SEL_IDX);
 271         ssd.bo = array.base_addr;
 272         ssd.ls = array.limit - array.base_addr;
 273         ssd.acc1 = ((array.read_exec_only == 0) << 1) |
 274             (array.contents << 2) |
 275             0xf0;   /* P(resent) | DPL3 | S */
 276         ssd.acc2 = 0x4;   /* byte limit, 32-bit segment */
 277         if (sysi86(SI86DSCR, &ssd) < 0) {
 278             perror("sysi86(SI86DSCR)");
 279             printf("Couldn't install fs segment, expect segfault\n");
 280         }
 281     }
 282 #endif
 283
 284     Setup_FS_Segment();
 285
 286     ldt_fs->prev_struct = malloc(8);
 287     *(void**)array.base_addr = ldt_fs->prev_struct;
 288
 289     return ldt_fs;
 290 }
 291
 292 void Restore_LDT_Keeper(ldt_fs_t* ldt_fs)
 293 {
 294     if (ldt_fs == NULL || ldt_fs->fs_seg == 0)
 295         return;
 296     if (ldt_fs->prev_struct)
 297         free(ldt_fs->prev_struct);
 298     munmap((char*)ldt_fs->fs_seg, getpagesize());
 299     ldt_fs->fs_seg = 0;
 300     free(ldt_fs);
 301 }