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mpv/loader/ldt_keeper.c

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C
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/**
* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
* 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 */
/*
* Modified for use with MPlayer, detailed CVS changelog at
* http://www.mplayerhq.hu/cgi-bin/cvsweb.cgi/main/
* $Id$
*/
#include "ldt_keeper.h"
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <stdio.h>
#include <unistd.h>
#ifdef __linux__
#include <asm/unistd.h>
#include <asm/ldt.h>
// 2.5.xx+ calls this user_desc:
#include <linux/version.h>
#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
/// declare modify_ldt with the _syscall3 macro for older glibcs
#if defined(__GLIBC__) && (__GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ == 0))
_syscall3( int, modify_ldt, int, func, void *, ptr, unsigned long, bytecount );
#else
int modify_ldt(int func, void *ptr, unsigned long bytecount);
#endif
#ifdef __cplusplus
}
#endif
#else
#if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__)
#include <machine/segments.h>
#include <machine/sysarch.h>
#endif
#ifdef __svr4__
#include <sys/segment.h>
#include <sys/sysi86.h>
/* solaris x86: add missing prototype for sysi86() */
#ifdef HAVE_SYSI86
#ifdef __cplusplus
extern "C" {
#endif
int sysi86(int, void*);
#ifdef __cplusplus
}
#endif
#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 */
#if defined(__FreeBSD__) && defined(LDT_AUTO_ALLOC)
#define TEB_SEL_IDX LDT_AUTO_ALLOC
#endif
#ifndef TEB_SEL_IDX
#define TEB_SEL_IDX 17
#endif
static unsigned int fs_ldt = 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)
{
unsigned int ldt_desc = LDT_SEL(fs_ldt);
__asm__ __volatile__(
"movl %0,%%eax; movw %%ax, %%fs" : : "r" (ldt_desc)
:"eax"
);
}
/* 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__) || defined(__DragonFly__)
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;
memset(&array, 0, sizeof(array));
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__) || defined(__DragonFly__)
{
unsigned long d[2];
LDT_EntryToBytes( d, &array );
#if defined(__FreeBSD__) && defined(LDT_AUTO_ALLOC)
ret = i386_set_ldt(LDT_AUTO_ALLOC, (union descriptor *)d, 1);
array.entry_number = ret;
fs_ldt = ret;
#else
ret = i386_set_ldt(array.entry_number, (union descriptor *)d, 1);
#endif
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");
#ifdef __OpenBSD__
printf("On newer OpenBSD systems did you set machdep.userldt to 1?\n");
#endif
}
}
#endif /* __NetBSD__ || __FreeBSD__ || __OpenBSD__ || __DragonFly__ */
#if defined(__svr4__)
{
struct ssd ssd;
ssd.sel = LDT_SEL(TEB_SEL_IDX);
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);
}
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