/** * !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! * This file MUST be in main library because LDT must * be modified before program creates first thread * - avifile includes this file from C++ code * and initializes it at the start of player! * it might sound like a hack and it really is - but * as aviplay is deconding video with more than just one * thread currently it's necessary to do it this way * this might change in the future */ /* applied some modification to make make our xine friend more happy */ #include "ldt_keeper.h" #include #include #include #include #include #include #include #include #ifdef __linux__ #include #include // 2.5.xx+ calls this user_desc: #include #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,5,47) #define modify_ldt_ldt_s user_desc #endif /* prototype it here, so we won't depend on kernel headers */ #ifdef __cplusplus extern "C" { #endif int modify_ldt(int func, void *ptr, unsigned long bytecount); #ifdef __cplusplus } #endif #else #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) #include #include #endif #ifdef __svr4__ #include #include /* solaris x86: add missing prototype for sysi86() */ #ifdef __cplusplus extern "C" { #endif int sysi86(int, void*); #ifdef __cplusplus } #endif #ifndef NUMSYSLDTS /* SunOS 2.5.1 does not define NUMSYSLDTS */ #define NUMSYSLDTS 6 /* Let's hope the SunOS 5.8 value is OK */ #endif #define TEB_SEL_IDX NUMSYSLDTS #endif #define LDT_ENTRIES 8192 #define LDT_ENTRY_SIZE 8 #pragma pack(4) struct modify_ldt_ldt_s { unsigned int entry_number; unsigned long base_addr; unsigned int limit; unsigned int seg_32bit:1; unsigned int contents:2; unsigned int read_exec_only:1; unsigned int limit_in_pages:1; unsigned int seg_not_present:1; unsigned int useable:1; }; #define MODIFY_LDT_CONTENTS_DATA 0 #define MODIFY_LDT_CONTENTS_STACK 1 #define MODIFY_LDT_CONTENTS_CODE 2 #endif /* user level (privilege level: 3) ldt (1<<2) segment selector */ #define LDT_SEL(idx) ((idx) << 3 | 1 << 2 | 3) /* i got this value from wine sources, it's the first free LDT entry */ #ifndef TEB_SEL_IDX #define TEB_SEL_IDX 17 #endif #define TEB_SEL LDT_SEL(TEB_SEL_IDX) /** * here is a small logical problem with Restore for multithreaded programs - * in C++ we use static class for this... */ #ifdef __cplusplus extern "C" #endif void Setup_FS_Segment(void) { __asm__ __volatile__( "movl %0,%%eax; movw %%ax, %%fs" : : "i" (TEB_SEL) ); } /* we don't need this - use modify_ldt instead */ #if 0 #ifdef __linux__ /* XXX: why is this routine from libc redefined here? */ /* NOTE: the redefined version ignores the count param, count is hardcoded as 16 */ static int LDT_Modify( int func, struct modify_ldt_ldt_s *ptr, unsigned long count ) { int res; #ifdef __PIC__ __asm__ __volatile__( "pushl %%ebx\n\t" "movl %2,%%ebx\n\t" "int $0x80\n\t" "popl %%ebx" : "=a" (res) : "0" (__NR_modify_ldt), "r" (func), "c" (ptr), "d"(16)//sizeof(*ptr) from kernel point of view :"esi" ); #else __asm__ __volatile__("int $0x80" : "=a" (res) : "0" (__NR_modify_ldt), "b" (func), "c" (ptr), "d"(16) :"esi"); #endif /* __PIC__ */ if (res >= 0) return res; errno = -res; return -1; } #endif #endif #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) static void LDT_EntryToBytes( unsigned long *buffer, const struct modify_ldt_ldt_s *content ) { *buffer++ = ((content->base_addr & 0x0000ffff) << 16) | (content->limit & 0x0ffff); *buffer = (content->base_addr & 0xff000000) | ((content->base_addr & 0x00ff0000)>>16) | (content->limit & 0xf0000) | (content->contents << 10) | ((content->read_exec_only == 0) << 9) | ((content->seg_32bit != 0) << 22) | ((content->limit_in_pages != 0) << 23) | 0xf000; } #endif void* fs_seg=0; ldt_fs_t* Setup_LDT_Keeper(void) { struct modify_ldt_ldt_s array; int ret; ldt_fs_t* ldt_fs = (ldt_fs_t*) malloc(sizeof(ldt_fs_t)); if (!ldt_fs) return NULL; ldt_fs->fd = open("/dev/zero", O_RDWR); if(ldt_fs->fd<0){ perror( "Cannot open /dev/zero for READ+WRITE. Check permissions! error: "); return NULL; } fs_seg= ldt_fs->fs_seg = mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE, MAP_PRIVATE, ldt_fs->fd, 0); if (ldt_fs->fs_seg == (void*)-1) { perror("ERROR: Couldn't allocate memory for fs segment"); close(ldt_fs->fd); free(ldt_fs); return NULL; } *(void**)((char*)ldt_fs->fs_seg+0x18) = ldt_fs->fs_seg; array.base_addr=(int)ldt_fs->fs_seg; array.entry_number=TEB_SEL_IDX; array.limit=array.base_addr+getpagesize()-1; array.seg_32bit=1; array.read_exec_only=0; array.seg_not_present=0; array.contents=MODIFY_LDT_CONTENTS_DATA; array.limit_in_pages=0; #ifdef __linux__ //ret=LDT_Modify(0x1, &array, sizeof(struct modify_ldt_ldt_s)); ret=modify_ldt(0x1, &array, sizeof(struct modify_ldt_ldt_s)); if(ret<0) { perror("install_fs"); printf("Couldn't install fs segment, expect segfault\n"); } #endif /*linux*/ #if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) { unsigned long d[2]; LDT_EntryToBytes( d, &array ); ret = i386_set_ldt(array.entry_number, (union descriptor *)d, 1); if (ret < 0) { perror("install_fs"); printf("Couldn't install fs segment, expect segfault\n"); printf("Did you reconfigure the kernel with \"options USER_LDT\"?\n"); } } #endif /* __NetBSD__ || __FreeBSD__ || __OpenBSD__ */ #if defined(__svr4__) { struct ssd ssd; ssd.sel = TEB_SEL; ssd.bo = array.base_addr; ssd.ls = array.limit - array.base_addr; ssd.acc1 = ((array.read_exec_only == 0) << 1) | (array.contents << 2) | 0xf0; /* P(resent) | DPL3 | S */ ssd.acc2 = 0x4; /* byte limit, 32-bit segment */ if (sysi86(SI86DSCR, &ssd) < 0) { perror("sysi86(SI86DSCR)"); printf("Couldn't install fs segment, expect segfault\n"); } } #endif Setup_FS_Segment(); ldt_fs->prev_struct = (char*)malloc(sizeof(char) * 8); *(void**)array.base_addr = ldt_fs->prev_struct; return ldt_fs; } void Restore_LDT_Keeper(ldt_fs_t* ldt_fs) { if (ldt_fs == NULL || ldt_fs->fs_seg == 0) return; if (ldt_fs->prev_struct) free(ldt_fs->prev_struct); munmap((char*)ldt_fs->fs_seg, getpagesize()); ldt_fs->fs_seg = 0; close(ldt_fs->fd); free(ldt_fs); }