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 /// 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 #else
  53 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__)
  54 #include <machine/segments.h>
  55 #include <machine/sysarch.h>
  56 #elif defined(__APPLE__)
  57 #include <architecture/i386/table.h>
  58 #include <i386/user_ldt.h>
  59 #elif defined(__svr4__)
  60 #include <sys/segment.h>
  61 #include <sys/sysi86.h>
  62
  63 /* solaris x86: add missing prototype for sysi86(), but only when sysi86(int, void*) is known to be valid */
  64 #ifdef HAVE_SYSI86_iv
  65 int sysi86(int, void*);
  66 #endif
  67
  68 #ifndef NUMSYSLDTS             /* SunOS 2.5.1 does not define NUMSYSLDTS */
  69 #define NUMSYSLDTS     6       /* Let's hope the SunOS 5.8 value is OK */
  70 #endif
  71
  72 #define       TEB_SEL_IDX     NUMSYSLDTS
  73 #endif
  74
  75 #define LDT_ENTRIES     8192
  76 #define LDT_ENTRY_SIZE  8
  77 #pragma pack(4)
  78 struct modify_ldt_ldt_s {
  79         unsigned int  entry_number;
  80         unsigned long base_addr;
  81         unsigned int  limit;
  82         unsigned int  seg_32bit:1;
  83         unsigned int  contents:2;
  84         unsigned int  read_exec_only:1;
  85         unsigned int  limit_in_pages:1;
  86         unsigned int  seg_not_present:1;
  87         unsigned int  useable:1;
  88 };
  89
  90 #define MODIFY_LDT_CONTENTS_DATA        0
  91 #define MODIFY_LDT_CONTENTS_STACK       1
  92 #define MODIFY_LDT_CONTENTS_CODE        2
  93 #endif
  94
  95
  96 /* user level (privilege level: 3) ldt (1<<2) segment selector */
  97 #define       LDT_SEL(idx) ((idx) << 3 | 1 << 2 | 3)
  98
  99 /* i got this value from wine sources, it's the first free LDT entry */
 100 #if (defined(__APPLE__) || defined(__FreeBSD__)) && defined(LDT_AUTO_ALLOC)
 101 #define       TEB_SEL_IDX     LDT_AUTO_ALLOC
 102 #define       USE_LDT_AA
 103 #endif
 104
 105 #ifndef       TEB_SEL_IDX
 106 #define       TEB_SEL_IDX     17
 107 #endif
 108
 109 static unsigned int fs_ldt = TEB_SEL_IDX;
 110
 111
 112 /**
 113  * here is a small logical problem with Restore for multithreaded programs -
 114  * in C++ we use static class for this...
 115  */
 116
 117 void Setup_FS_Segment(void)
 118 {
 119     unsigned int ldt_desc = LDT_SEL(fs_ldt);
 120
 121     __asm__ volatile(
 122         "movl %0,%%eax; movw %%ax, %%fs" : : "r" (ldt_desc)
 123         :"eax"
 124     );
 125 }
 126
 127 /* we don't need this - use modify_ldt instead */
 128 #if 0
 129 #ifdef __linux__
 130 /* XXX: why is this routine from libc redefined here? */
 131 /* NOTE: the redefined version ignores the count param, count is hardcoded as 16 */
 132 static int LDT_Modify( int func, struct modify_ldt_ldt_s *ptr,
 133                        unsigned long count )
 134 {
 135     int res;
 136 #ifdef __PIC__
 137     __asm__ volatile( "pushl %%ebx\n\t"
 138                           "movl %2,%%ebx\n\t"
 139                           "int $0x80\n\t"
 140                           "popl %%ebx"
 141                           : "=a" (res)
 142                           : "0" (__NR_modify_ldt),
 143                           "r" (func),
 144                           "c" (ptr),
 145                           "d"(16)//sizeof(*ptr) from kernel point of view
 146                           :"esi"     );
 147 #else
 148     __asm__ volatile("int $0x80"
 149                          : "=a" (res)
 150                          : "0" (__NR_modify_ldt),
 151                          "b" (func),
 152                          "c" (ptr),
 153                          "d"(16)
 154                          :"esi");
 155 #endif  /* __PIC__ */
 156     if (res >= 0) return res;
 157     errno = -res;
 158     return -1;
 159 }
 160 #endif
 161 #endif
 162
 163 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__) || defined(__APPLE__)
 164 static void LDT_EntryToBytes( unsigned long *buffer, const struct modify_ldt_ldt_s *content )
 165 {
 166     *buffer++ = ((content->base_addr & 0x0000ffff) << 16) |
 167         (content->limit & 0x0ffff);
 168     *buffer = (content->base_addr & 0xff000000) |
 169         ((content->base_addr & 0x00ff0000)>>16) |
 170         (content->limit & 0xf0000) |
 171         (content->contents << 10) |
 172         ((content->read_exec_only == 0) << 9) |
 173         ((content->seg_32bit != 0) << 22) |
 174         ((content->limit_in_pages != 0) << 23) |
 175         0xf000;
 176 }
 177 #endif
 178
 179 void* fs_seg=0;
 180
 181 ldt_fs_t* Setup_LDT_Keeper(void)
 182 {
 183     struct modify_ldt_ldt_s array;
 184     int ret;
 185     ldt_fs_t* ldt_fs = malloc(sizeof(ldt_fs_t));
 186
 187     if (!ldt_fs)
 188         return NULL;
 189
 190 #ifdef __APPLE__
 191     if (getenv("DYLD_BIND_AT_LAUNCH") == NULL)
 192         mp_msg(MSGT_LOADER, MSGL_WARN, MSGTR_LOADER_DYLD_Warning);
 193 #endif /* __APPLE__ */
 194
 195     fs_seg=
 196     ldt_fs->fs_seg = mmap_anon(NULL, getpagesize(), PROT_READ | PROT_WRITE, MAP_PRIVATE, 0);
 197     if (ldt_fs->fs_seg == (void*)-1)
 198     {
 199         perror("ERROR: Couldn't allocate memory for fs segment");
 200         free(ldt_fs);
 201         return NULL;
 202     }
 203     *(void**)((char*)ldt_fs->fs_seg+0x18) = ldt_fs->fs_seg;
 204     memset(&array, 0, sizeof(array));
 205     array.base_addr=(int)ldt_fs->fs_seg;
 206     array.entry_number=TEB_SEL_IDX;
 207     array.limit=array.base_addr+getpagesize()-1;
 208     array.seg_32bit=1;
 209     array.read_exec_only=0;
 210     array.seg_not_present=0;
 211     array.contents=MODIFY_LDT_CONTENTS_DATA;
 212     array.limit_in_pages=0;
 213 #ifdef __linux__
 214     //ret=LDT_Modify(0x1, &array, sizeof(struct modify_ldt_ldt_s));
 215     ret=modify_ldt(0x1, &array, sizeof(struct modify_ldt_ldt_s));
 216     if(ret<0)
 217     {
 218         perror("install_fs");
 219         printf("Couldn't install fs segment, expect segfault\n");
 220     }
 221 #elif defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__) || defined(__APPLE__)
 222     {
 223         unsigned long d[2];
 224
 225         LDT_EntryToBytes( d, &array );
 226 #ifdef USE_LDT_AA
 227         ret = i386_set_ldt(LDT_AUTO_ALLOC, (union descriptor *)d, 1);
 228         array.entry_number = ret;
 229         fs_ldt = ret;
 230 #else
 231         ret = i386_set_ldt(array.entry_number, (union descriptor *)d, 1);
 232 #endif
 233         if (ret < 0)
 234         {
 235             perror("install_fs");
 236             printf("Couldn't install fs segment, expect segfault\n");
 237             printf("Did you reconfigure the kernel with \"options USER_LDT\"?\n");
 238 #ifdef __OpenBSD__
 239             printf("On newer OpenBSD systems did you set machdep.userldt to 1?\n");
 240 #endif
 241         }
 242     }
 243 #elif defined(__svr4__)
 244     {
 245         struct ssd ssd;
 246         ssd.sel = LDT_SEL(TEB_SEL_IDX);
 247         ssd.bo = array.base_addr;
 248         ssd.ls = array.limit - array.base_addr;
 249         ssd.acc1 = ((array.read_exec_only == 0) << 1) |
 250             (array.contents << 2) |
 251             0xf0;   /* P(resent) | DPL3 | S */
 252         ssd.acc2 = 0x4;   /* byte limit, 32-bit segment */
 253         if (sysi86(SI86DSCR, &ssd) < 0) {
 254             perror("sysi86(SI86DSCR)");
 255             printf("Couldn't install fs segment, expect segfault\n");
 256         }
 257     }
 258 #elif defined(__OS2__)
 259     /* convert flat addr to sel idx for LDT_SEL() */
 260     fs_ldt = (uintptr_t)fs_seg >> 16;
 261 #endif
 262
 263     Setup_FS_Segment();
 264
 265     ldt_fs->prev_struct = malloc(8);
 266     *(void**)array.base_addr = ldt_fs->prev_struct;
 267
 268     return ldt_fs;
 269 }
 270
 271 void Restore_LDT_Keeper(ldt_fs_t* ldt_fs)
 272 {
 273     if (ldt_fs == NULL || ldt_fs->fs_seg == 0)
 274         return;
 275     if (ldt_fs->prev_struct)
 276         free(ldt_fs->prev_struct);
 277     munmap((char*)ldt_fs->fs_seg, getpagesize());
 278     ldt_fs->fs_seg = 0;
 279     free(ldt_fs);
 280 }