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
13 /* applied some modification to make make our xine friend more happy */
16 * Modified for use with MPlayer, detailed CVS changelog at
17 * http://www.mplayerhq.hu/cgi-bin/cvsweb.cgi/main/
21 #include "ldt_keeper.h"
28 #include <sys/types.h>
32 #include <asm/unistd.h>
34 // 2.5.xx+ calls this user_desc:
35 #include <linux/version.h>
36 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,5,47)
37 #define modify_ldt_ldt_s user_desc
39 /* prototype it here, so we won't depend on kernel headers */
43 /// declare modify_ldt with the _syscall3 macro for older glibcs
44 #if defined(__GLIBC__) && (__GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ == 0))
45 _syscall3( int, modify_ldt, int, func, void *, ptr, unsigned long, bytecount );
47 int modify_ldt(int func, void *ptr, unsigned long bytecount);
53 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__)
54 #include <machine/segments.h>
55 #include <machine/sysarch.h>
59 #include <sys/segment.h>
60 #include <sys/sysi86.h>
62 /* solaris x86: add missing prototype for sysi86() */
66 int sysi86(int, void*);
71 #ifndef NUMSYSLDTS /* SunOS 2.5.1 does not define NUMSYSLDTS */
72 #define NUMSYSLDTS 6 /* Let's hope the SunOS 5.8 value is OK */
75 #define TEB_SEL_IDX NUMSYSLDTS
78 #define LDT_ENTRIES 8192
79 #define LDT_ENTRY_SIZE 8
81 struct modify_ldt_ldt_s {
82 unsigned int entry_number;
83 unsigned long base_addr;
85 unsigned int seg_32bit:1;
86 unsigned int contents:2;
87 unsigned int read_exec_only:1;
88 unsigned int limit_in_pages:1;
89 unsigned int seg_not_present:1;
90 unsigned int useable:1;
93 #define MODIFY_LDT_CONTENTS_DATA 0
94 #define MODIFY_LDT_CONTENTS_STACK 1
95 #define MODIFY_LDT_CONTENTS_CODE 2
99 /* user level (privilege level: 3) ldt (1<<2) segment selector */
100 #define LDT_SEL(idx) ((idx) << 3 | 1 << 2 | 3)
102 /* i got this value from wine sources, it's the first free LDT entry */
103 #if defined(__FreeBSD__) && defined(LDT_AUTO_ALLOC)
104 #define TEB_SEL_IDX LDT_AUTO_ALLOC
108 #define TEB_SEL_IDX 17
111 static unsigned int fs_ldt = TEB_SEL_IDX;
115 * here is a small logical problem with Restore for multithreaded programs -
116 * in C++ we use static class for this...
122 void Setup_FS_Segment(void)
124 unsigned int ldt_desc = LDT_SEL(fs_ldt);
126 __asm__ __volatile__(
127 "movl %0,%%eax; movw %%ax, %%fs" : : "r" (ldt_desc)
132 /* we don't need this - use modify_ldt instead */
135 /* XXX: why is this routine from libc redefined here? */
136 /* NOTE: the redefined version ignores the count param, count is hardcoded as 16 */
137 static int LDT_Modify( int func, struct modify_ldt_ldt_s *ptr,
138 unsigned long count )
142 __asm__ __volatile__( "pushl %%ebx\n\t"
147 : "0" (__NR_modify_ldt),
150 "d"(16)//sizeof(*ptr) from kernel point of view
153 __asm__ __volatile__("int $0x80"
155 : "0" (__NR_modify_ldt),
161 if (res >= 0) return res;
168 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__)
169 static void LDT_EntryToBytes( unsigned long *buffer, const struct modify_ldt_ldt_s *content )
171 *buffer++ = ((content->base_addr & 0x0000ffff) << 16) |
172 (content->limit & 0x0ffff);
173 *buffer = (content->base_addr & 0xff000000) |
174 ((content->base_addr & 0x00ff0000)>>16) |
175 (content->limit & 0xf0000) |
176 (content->contents << 10) |
177 ((content->read_exec_only == 0) << 9) |
178 ((content->seg_32bit != 0) << 22) |
179 ((content->limit_in_pages != 0) << 23) |
186 ldt_fs_t* Setup_LDT_Keeper(void)
188 struct modify_ldt_ldt_s array;
190 ldt_fs_t* ldt_fs = (ldt_fs_t*) malloc(sizeof(ldt_fs_t));
195 ldt_fs->fd = open("/dev/zero", O_RDWR);
197 perror( "Cannot open /dev/zero for READ+WRITE. Check permissions! error: ");
201 ldt_fs->fs_seg = mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE, MAP_PRIVATE,
203 if (ldt_fs->fs_seg == (void*)-1)
205 perror("ERROR: Couldn't allocate memory for fs segment");
210 *(void**)((char*)ldt_fs->fs_seg+0x18) = ldt_fs->fs_seg;
211 memset(&array, 0, sizeof(array));
212 array.base_addr=(int)ldt_fs->fs_seg;
213 array.entry_number=TEB_SEL_IDX;
214 array.limit=array.base_addr+getpagesize()-1;
216 array.read_exec_only=0;
217 array.seg_not_present=0;
218 array.contents=MODIFY_LDT_CONTENTS_DATA;
219 array.limit_in_pages=0;
221 //ret=LDT_Modify(0x1, &array, sizeof(struct modify_ldt_ldt_s));
222 ret=modify_ldt(0x1, &array, sizeof(struct modify_ldt_ldt_s));
225 perror("install_fs");
226 printf("Couldn't install fs segment, expect segfault\n");
230 #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__)
234 LDT_EntryToBytes( d, &array );
235 #if defined(__FreeBSD__) && defined(LDT_AUTO_ALLOC)
236 ret = i386_set_ldt(LDT_AUTO_ALLOC, (union descriptor *)d, 1);
237 array.entry_number = ret;
240 ret = i386_set_ldt(array.entry_number, (union descriptor *)d, 1);
244 perror("install_fs");
245 printf("Couldn't install fs segment, expect segfault\n");
246 printf("Did you reconfigure the kernel with \"options USER_LDT\"?\n");
249 #endif /* __NetBSD__ || __FreeBSD__ || __OpenBSD__ || __DragonFly__ */
251 #if defined(__svr4__)
254 ssd.sel = LDT_SEL(TEB_SEL_IDX);
255 ssd.bo = array.base_addr;
256 ssd.ls = array.limit - array.base_addr;
257 ssd.acc1 = ((array.read_exec_only == 0) << 1) |
258 (array.contents << 2) |
259 0xf0; /* P(resent) | DPL3 | S */
260 ssd.acc2 = 0x4; /* byte limit, 32-bit segment */
261 if (sysi86(SI86DSCR, &ssd) < 0) {
262 perror("sysi86(SI86DSCR)");
263 printf("Couldn't install fs segment, expect segfault\n");
270 ldt_fs->prev_struct = (char*)malloc(sizeof(char) * 8);
271 *(void**)array.base_addr = ldt_fs->prev_struct;
276 void Restore_LDT_Keeper(ldt_fs_t* ldt_fs)
278 if (ldt_fs == NULL || ldt_fs->fs_seg == 0)
280 if (ldt_fs->prev_struct)
281 free(ldt_fs->prev_struct);
282 munmap((char*)ldt_fs->fs_seg, getpagesize());