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 #ifdef __linux__
  38 #include <asm/unistd.h>
  39 #include <asm/ldt.h>
  40 // 2.5.xx+ calls this user_desc:
  41 #include <linux/version.h>
  42 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,5,47)
  43 #define modify_ldt_ldt_s user_desc
  44 #endif
  45 /// declare modify_ldt with the _syscall3 macro for older glibcs
  46 #if defined(__GLIBC__) &&  (__GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ == 0))
  47 _syscall3( int, modify_ldt, int, func, void *, ptr, unsigned long, bytecount );
  48 #else
  49 int modify_ldt(int func, void *ptr, unsigned long bytecount);
  50 #endif
  51 #else
  52 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__)
  53 #include <machine/segments.h>
  54 #include <machine/sysarch.h>
  55 #elif defined(__APPLE__)
  56 #include <architecture/i386/table.h>
  57 #include <i386/user_ldt.h>
  58 #elif defined(__svr4__)
  59 #include <sys/segment.h>
  60 #include <sys/sysi86.h>
  61
  62 /* solaris x86: add missing prototype for sysi86(), but only when sysi86(int, void*) is known to be valid */
  63 #ifdef HAVE_SYSI86_iv
  64 int sysi86(int, void*);
  65 #endif
  66
  67 #ifndef NUMSYSLDTS             /* SunOS 2.5.1 does not define NUMSYSLDTS */
  68 #define NUMSYSLDTS     6       /* Let's hope the SunOS 5.8 value is OK */
  69 #endif
  70
  71 #define       TEB_SEL_IDX     NUMSYSLDTS
  72 #endif
  73
  74 #define LDT_ENTRIES     8192
  75 #define LDT_ENTRY_SIZE  8
  76 #pragma pack(4)
  77 struct modify_ldt_ldt_s {
  78         unsigned int  entry_number;
  79         unsigned long base_addr;
  80         unsigned int  limit;
  81         unsigned int  seg_32bit:1;
  82         unsigned int  contents:2;
  83         unsigned int  read_exec_only:1;
  84         unsigned int  limit_in_pages:1;
  85         unsigned int  seg_not_present:1;
  86         unsigned int  useable:1;
  87 };
  88
  89 #define MODIFY_LDT_CONTENTS_DATA        0
  90 #define MODIFY_LDT_CONTENTS_STACK       1
  91 #define MODIFY_LDT_CONTENTS_CODE        2
  92 #endif
  93
  94
  95 /* user level (privilege level: 3) ldt (1<<2) segment selector */
  96 #define       LDT_SEL(idx) ((idx) << 3 | 1 << 2 | 3)
  97
  98 /* i got this value from wine sources, it's the first free LDT entry */
  99 #if (defined(__APPLE__) || defined(__FreeBSD__)) && defined(LDT_AUTO_ALLOC)
 100 #define       TEB_SEL_IDX     LDT_AUTO_ALLOC
 101 #define       USE_LDT_AA
 102 #endif
 103
 104 #ifndef       TEB_SEL_IDX
 105 #define       TEB_SEL_IDX     17
 106 #endif
 107
 108 static unsigned int fs_ldt = TEB_SEL_IDX;
 109
 110
 111 /**
 112  * here is a small logical problem with Restore for multithreaded programs -
 113  * in C++ we use static class for this...
 114  */
 115
 116 void Setup_FS_Segment(void)
 117 {
 118     unsigned int ldt_desc = LDT_SEL(fs_ldt);
 119
 120     __asm__ volatile(
 121         "movl %0,%%eax; movw %%ax, %%fs" : : "r" (ldt_desc)
 122         :"eax"
 123     );
 124 }
 125
 126 /* we don't need this - use modify_ldt instead */
 127 #if 0
 128 #ifdef __linux__
 129 /* XXX: why is this routine from libc redefined here? */
 130 /* NOTE: the redefined version ignores the count param, count is hardcoded as 16 */
 131 static int LDT_Modify( int func, struct modify_ldt_ldt_s *ptr,
 132                        unsigned long count )
 133 {
 134     int res;
 135 #ifdef __PIC__
 136     __asm__ volatile( "pushl %%ebx\n\t"
 137                           "movl %2,%%ebx\n\t"
 138                           "int $0x80\n\t"
 139                           "popl %%ebx"
 140                           : "=a" (res)
 141                           : "0" (__NR_modify_ldt),
 142                           "r" (func),
 143                           "c" (ptr),
 144                           "d"(16)//sizeof(*ptr) from kernel point of view
 145                           :"esi"     );
 146 #else
 147     __asm__ volatile("int $0x80"
 148                          : "=a" (res)
 149                          : "0" (__NR_modify_ldt),
 150                          "b" (func),
 151                          "c" (ptr),
 152                          "d"(16)
 153                          :"esi");
 154 #endif  /* __PIC__ */
 155     if (res >= 0) return res;
 156     errno = -res;
 157     return -1;
 158 }
 159 #endif
 160 #endif
 161
 162 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__) || defined(__APPLE__)
 163 static void LDT_EntryToBytes( unsigned long *buffer, const struct modify_ldt_ldt_s *content )
 164 {
 165     *buffer++ = ((content->base_addr & 0x0000ffff) << 16) |
 166         (content->limit & 0x0ffff);
 167     *buffer = (content->base_addr & 0xff000000) |
 168         ((content->base_addr & 0x00ff0000)>>16) |
 169         (content->limit & 0xf0000) |
 170         (content->contents << 10) |
 171         ((content->read_exec_only == 0) << 9) |
 172         ((content->seg_32bit != 0) << 22) |
 173         ((content->limit_in_pages != 0) << 23) |
 174         0xf000;
 175 }
 176 #endif
 177
 178 void* fs_seg=0;
 179
 180 ldt_fs_t* Setup_LDT_Keeper(void)
 181 {
 182     struct modify_ldt_ldt_s array;
 183     int ret;
 184     ldt_fs_t* ldt_fs = malloc(sizeof(ldt_fs_t));
 185
 186     if (!ldt_fs)
 187         return NULL;
 188
 189 #ifdef __APPLE__
 190     if (getenv("DYLD_BIND_AT_LAUNCH") == NULL)
 191         mp_tmsg(MSGT_LOADER, MSGL_WARN, "WARNING: Attempting to use DLL codecs but environment variable\n         DYLD_BIND_AT_LAUNCH not set. This will likely crash.\n");
 192 #endif /* __APPLE__ */
 193
 194     fs_seg=
 195     ldt_fs->fs_seg = mmap_anon(NULL, getpagesize(), PROT_READ | PROT_WRITE, MAP_PRIVATE, 0);
 196     if (ldt_fs->fs_seg == (void*)-1)
 197     {
 198         perror("ERROR: Couldn't allocate memory for fs segment");
 199         free(ldt_fs);
 200         return NULL;
 201     }
 202     *(void**)((char*)ldt_fs->fs_seg+0x18) = ldt_fs->fs_seg;
 203     memset(&array, 0, sizeof(array));
 204     array.base_addr=(int)ldt_fs->fs_seg;
 205     array.entry_number=TEB_SEL_IDX;
 206     array.limit=array.base_addr+getpagesize()-1;
 207     array.seg_32bit=1;
 208     array.read_exec_only=0;
 209     array.seg_not_present=0;
 210     array.contents=MODIFY_LDT_CONTENTS_DATA;
 211     array.limit_in_pages=0;
 212 #ifdef __linux__
 213     //ret=LDT_Modify(0x1, &array, sizeof(struct modify_ldt_ldt_s));
 214     ret=modify_ldt(0x1, &array, sizeof(struct modify_ldt_ldt_s));
 215     if(ret<0)
 216     {
 217         perror("install_fs");
 218         printf("Couldn't install fs segment, expect segfault\n");
 219     }
 220 #elif defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__) || defined(__APPLE__)
 221     {
 222         unsigned long d[2];
 223
 224         LDT_EntryToBytes( d, &array );
 225 #ifdef USE_LDT_AA
 226         ret = i386_set_ldt(LDT_AUTO_ALLOC, (union descriptor *)d, 1);
 227         array.entry_number = ret;
 228         fs_ldt = ret;
 229 #else
 230         ret = i386_set_ldt(array.entry_number, (union descriptor *)d, 1);
 231 #endif
 232         if (ret < 0)
 233         {
 234             perror("install_fs");
 235             printf("Couldn't install fs segment, expect segfault\n");
 236             printf("Did you reconfigure the kernel with \"options USER_LDT\"?\n");
 237 #ifdef __OpenBSD__
 238             printf("On newer OpenBSD systems did you set machdep.userldt to 1?\n");
 239 #endif
 240         }
 241     }
 242 #elif defined(__svr4__)
 243     {
 244         struct ssd ssd;
 245         ssd.sel = LDT_SEL(TEB_SEL_IDX);
 246         ssd.bo = array.base_addr;
 247         ssd.ls = array.limit - array.base_addr;
 248         ssd.acc1 = ((array.read_exec_only == 0) << 1) |
 249             (array.contents << 2) |
 250             0xf0;   /* P(resent) | DPL3 | S */
 251         ssd.acc2 = 0x4;   /* byte limit, 32-bit segment */
 252         if (sysi86(SI86DSCR, &ssd) < 0) {
 253             perror("sysi86(SI86DSCR)");
 254             printf("Couldn't install fs segment, expect segfault\n");
 255         }
 256     }
 257 #endif
 258
 259     Setup_FS_Segment();
 260
 261     ldt_fs->prev_struct = malloc(8);
 262     *(void**)array.base_addr = ldt_fs->prev_struct;
 263
 264     return ldt_fs;
 265 }
 266
 267 void Restore_LDT_Keeper(ldt_fs_t* ldt_fs)
 268 {
 269     if (ldt_fs == NULL || ldt_fs->fs_seg == 0)
 270         return;
 271     free(ldt_fs->prev_struct);
 272     munmap((char*)ldt_fs->fs_seg, getpagesize());
 273     ldt_fs->fs_seg = 0;
 274     free(ldt_fs);
 275 }