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  * $Id$
  19  */
  20
  21 #include "ldt_keeper.h"
  22
  23 #include <string.h>
  24 #include <stdlib.h>
  25 #include <errno.h>
  26 #include <fcntl.h>
  27 #include <sys/mman.h>
  28 #include <sys/types.h>
  29 #include <stdio.h>
  30 #include <unistd.h>
  31 #include "osdep/mmap_anon.h"
  32 #include "mp_msg.h"
  33 #include "help_mp.h"
  34 #ifdef __linux__
  35 #include <asm/unistd.h>
  36 #include <asm/ldt.h>
  37 // 2.5.xx+ calls this user_desc:
  38 #include <linux/version.h>
  39 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,5,47)
  40 #define modify_ldt_ldt_s user_desc
  41 #endif
  42 /* prototype it here, so we won't depend on kernel headers */
  43 #ifdef  __cplusplus
  44 extern "C" {
  45 #endif
  46 /// declare modify_ldt with the _syscall3 macro for older glibcs
  47 #if defined(__GLIBC__) &&  (__GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ == 0))
  48 _syscall3( int, modify_ldt, int, func, void *, ptr, unsigned long, bytecount );
  49 #else
  50 int modify_ldt(int func, void *ptr, unsigned long bytecount);
  51 #endif
  52 #ifdef  __cplusplus
  53 }
  54 #endif
  55 #else
  56 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__)
  57 #include <machine/segments.h>
  58 #include <machine/sysarch.h>
  59 #endif
  60
  61 #ifdef __svr4__
  62 #include <sys/segment.h>
  63 #include <sys/sysi86.h>
  64
  65 /* solaris x86: add missing prototype for sysi86() */
  66 #ifdef HAVE_SYSI86
  67 #ifdef  __cplusplus
  68 extern "C" {
  69 #endif
  70 int sysi86(int, void*);
  71 #ifdef  __cplusplus
  72 }
  73 #endif
  74 #endif
  75
  76 #ifndef NUMSYSLDTS             /* SunOS 2.5.1 does not define NUMSYSLDTS */
  77 #define NUMSYSLDTS     6       /* Let's hope the SunOS 5.8 value is OK */
  78 #endif
  79
  80 #define       TEB_SEL_IDX     NUMSYSLDTS
  81 #endif
  82
  83 #define LDT_ENTRIES     8192
  84 #define LDT_ENTRY_SIZE  8
  85 #pragma pack(4)
  86 struct modify_ldt_ldt_s {
  87         unsigned int  entry_number;
  88         unsigned long base_addr;
  89         unsigned int  limit;
  90         unsigned int  seg_32bit:1;
  91         unsigned int  contents:2;
  92         unsigned int  read_exec_only:1;
  93         unsigned int  limit_in_pages:1;
  94         unsigned int  seg_not_present:1;
  95         unsigned int  useable:1;
  96 };
  97
  98 #define MODIFY_LDT_CONTENTS_DATA        0
  99 #define MODIFY_LDT_CONTENTS_STACK       1
 100 #define MODIFY_LDT_CONTENTS_CODE        2
 101 #endif
 102
 103
 104 /* user level (privilege level: 3) ldt (1<<2) segment selector */
 105 #define       LDT_SEL(idx) ((idx) << 3 | 1 << 2 | 3)
 106
 107 /* i got this value from wine sources, it's the first free LDT entry */
 108 #if (defined(__APPLE__) || defined(__FreeBSD__)) && defined(LDT_AUTO_ALLOC)
 109 #define       TEB_SEL_IDX     LDT_AUTO_ALLOC
 110 #define       USE_LDT_AA
 111 #endif
 112
 113 #ifndef       TEB_SEL_IDX
 114 #define       TEB_SEL_IDX     17
 115 #endif
 116
 117 static unsigned int fs_ldt = TEB_SEL_IDX;
 118
 119
 120 /**
 121  * here is a small logical problem with Restore for multithreaded programs -
 122  * in C++ we use static class for this...
 123  */
 124
 125 #ifdef __cplusplus
 126 extern "C"
 127 #endif
 128 void Setup_FS_Segment(void)
 129 {
 130     unsigned int ldt_desc = LDT_SEL(fs_ldt);
 131
 132     __asm__ __volatile__(
 133         "movl %0,%%eax; movw %%ax, %%fs" : : "r" (ldt_desc)
 134         :"eax"
 135     );
 136 }
 137
 138 /* we don't need this - use modify_ldt instead */
 139 #if 0
 140 #ifdef __linux__
 141 /* XXX: why is this routine from libc redefined here? */
 142 /* NOTE: the redefined version ignores the count param, count is hardcoded as 16 */
 143 static int LDT_Modify( int func, struct modify_ldt_ldt_s *ptr,
 144                        unsigned long count )
 145 {
 146     int res;
 147 #ifdef __PIC__
 148     __asm__ __volatile__( "pushl %%ebx\n\t"
 149                           "movl %2,%%ebx\n\t"
 150                           "int $0x80\n\t"
 151                           "popl %%ebx"
 152                           : "=a" (res)
 153                           : "0" (__NR_modify_ldt),
 154                           "r" (func),
 155                           "c" (ptr),
 156                           "d"(16)//sizeof(*ptr) from kernel point of view
 157                           :"esi"     );
 158 #else
 159     __asm__ __volatile__("int $0x80"
 160                          : "=a" (res)
 161                          : "0" (__NR_modify_ldt),
 162                          "b" (func),
 163                          "c" (ptr),
 164                          "d"(16)
 165                          :"esi");
 166 #endif  /* __PIC__ */
 167     if (res >= 0) return res;
 168     errno = -res;
 169     return -1;
 170 }
 171 #endif
 172 #endif
 173
 174 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__) || defined(__APPLE__)
 175 static void LDT_EntryToBytes( unsigned long *buffer, const struct modify_ldt_ldt_s *content )
 176 {
 177     *buffer++ = ((content->base_addr & 0x0000ffff) << 16) |
 178         (content->limit & 0x0ffff);
 179     *buffer = (content->base_addr & 0xff000000) |
 180         ((content->base_addr & 0x00ff0000)>>16) |
 181         (content->limit & 0xf0000) |
 182         (content->contents << 10) |
 183         ((content->read_exec_only == 0) << 9) |
 184         ((content->seg_32bit != 0) << 22) |
 185         ((content->limit_in_pages != 0) << 23) |
 186         0xf000;
 187 }
 188 #endif
 189
 190 void* fs_seg=0;
 191
 192 ldt_fs_t* Setup_LDT_Keeper(void)
 193 {
 194     struct modify_ldt_ldt_s array;
 195     int ret;
 196     ldt_fs_t* ldt_fs = (ldt_fs_t*) malloc(sizeof(ldt_fs_t));
 197
 198     if (!ldt_fs)
 199         return NULL;
 200
 201 #ifdef __APPLE__
 202     if (getenv("DYLD_BIND_AT_LAUNCH") == NULL)
 203         mp_msg(MSGT_LOADER, MSGL_WARN, MSGTR_LOADER_DYLD_Warning);
 204 #endif /* __APPLE__ */
 205
 206     fs_seg=
 207     ldt_fs->fs_seg = mmap_anon(NULL, getpagesize(), PROT_READ | PROT_WRITE, MAP_PRIVATE, 0);
 208     if (ldt_fs->fs_seg == (void*)-1)
 209     {
 210         perror("ERROR: Couldn't allocate memory for fs segment");
 211         free(ldt_fs);
 212         return NULL;
 213     }
 214     *(void**)((char*)ldt_fs->fs_seg+0x18) = ldt_fs->fs_seg;
 215     memset(&array, 0, sizeof(array));
 216     array.base_addr=(int)ldt_fs->fs_seg;
 217     array.entry_number=TEB_SEL_IDX;
 218     array.limit=array.base_addr+getpagesize()-1;
 219     array.seg_32bit=1;
 220     array.read_exec_only=0;
 221     array.seg_not_present=0;
 222     array.contents=MODIFY_LDT_CONTENTS_DATA;
 223     array.limit_in_pages=0;
 224 #ifdef __linux__
 225     //ret=LDT_Modify(0x1, &array, sizeof(struct modify_ldt_ldt_s));
 226     ret=modify_ldt(0x1, &array, sizeof(struct modify_ldt_ldt_s));
 227     if(ret<0)
 228     {
 229         perror("install_fs");
 230         printf("Couldn't install fs segment, expect segfault\n");
 231     }
 232 #endif /*linux*/
 233
 234 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__) || defined(__APPLE__)
 235     {
 236         unsigned long d[2];
 237
 238         LDT_EntryToBytes( d, &array );
 239 #ifdef USE_LDT_AA
 240         ret = i386_set_ldt(LDT_AUTO_ALLOC, (union descriptor *)d, 1);
 241         array.entry_number = ret;
 242         fs_ldt = ret;
 243 #else
 244         ret = i386_set_ldt(array.entry_number, (union descriptor *)d, 1);
 245 #endif
 246         if (ret < 0)
 247         {
 248             perror("install_fs");
 249             printf("Couldn't install fs segment, expect segfault\n");
 250             printf("Did you reconfigure the kernel with \"options USER_LDT\"?\n");
 251 #ifdef __OpenBSD__
 252             printf("On newer OpenBSD systems did you set machdep.userldt to 1?\n");
 253 #endif
 254         }
 255     }
 256 #endif  /* __NetBSD__ || __FreeBSD__ || __OpenBSD__ || __DragonFly__ || __APPLE__ */
 257
 258 #if defined(__svr4__)
 259     {
 260         struct ssd ssd;
 261         ssd.sel = LDT_SEL(TEB_SEL_IDX);
 262         ssd.bo = array.base_addr;
 263         ssd.ls = array.limit - array.base_addr;
 264         ssd.acc1 = ((array.read_exec_only == 0) << 1) |
 265             (array.contents << 2) |
 266             0xf0;   /* P(resent) | DPL3 | S */
 267         ssd.acc2 = 0x4;   /* byte limit, 32-bit segment */
 268         if (sysi86(SI86DSCR, &ssd) < 0) {
 269             perror("sysi86(SI86DSCR)");
 270             printf("Couldn't install fs segment, expect segfault\n");
 271         }
 272     }
 273 #endif
 274
 275     Setup_FS_Segment();
 276
 277     ldt_fs->prev_struct = malloc(8);
 278     *(void**)array.base_addr = ldt_fs->prev_struct;
 279
 280     return ldt_fs;
 281 }
 282
 283 void Restore_LDT_Keeper(ldt_fs_t* ldt_fs)
 284 {
 285     if (ldt_fs == NULL || ldt_fs->fs_seg == 0)
 286         return;
 287     if (ldt_fs->prev_struct)
 288         free(ldt_fs->prev_struct);
 289     munmap((char*)ldt_fs->fs_seg, getpagesize());
 290     ldt_fs->fs_seg = 0;
 291     free(ldt_fs);
 292 }