loader/dos/dosmod.c

   1 /*
   2  * DOS Virtual Machine
   3  *
   4  * Copyright 1998 Ove Kåven
   5  */
   6
   7 #ifdef linux
   8
   9 /* apparently ELF images are usually loaded high anyway */
  10 #ifndef __ELF__
  11 /* if not, force dosmod at high addresses */
  12 asm(".org 0x110000");
  13 #endif __ELF__
  14
  15 #include <stdio.h>
  16 #include <stdlib.h>
  17 #include <string.h>
  18 #include <errno.h>
  19 #include <unistd.h>
  20 #include <fcntl.h>
  21 #include <signal.h>
  22 #include <sys/stat.h>
  23 #include <sys/mman.h>
  24 #include <sys/vm86.h>
  25 #include <sys/types.h>
  26 #include <sys/ptrace.h>
  27 #include <sys/wait.h>
  28
  29  /* FIXME: hack because libc vm86 may be the old syscall version */
  30
  31 #define SYS_vm86   166
  32
  33 static __inline__ int vm86plus( int func, struct vm86plus_struct *ptr )
  34 {
  35     int res;
  36 #ifdef __PIC__
  37     __asm__ __volatile__( "pushl %%ebx\n\t"
  38                           "movl %2,%%ebx\n\t"
  39                           "int $0x80\n\t"
  40                           "popl %%ebx"
  41                           : "=a" (res)
  42                           : "0" (SYS_vm86),
  43                             "g" (func),
  44                             "c" (ptr) );
  45 #else
  46     __asm__ __volatile__("int $0x80"
  47                          : "=a" (res)
  48                          : "0" (SYS_vm86),
  49                            "b" (func),
  50                            "c" (ptr) );
  51 #endif  /* __PIC__ */
  52     if (res >= 0) return res;
  53     errno = -res;
  54     return -1;
  55 }
  56
  57 int main(int argc,char**argv)
  58 {
  59  int mfd=open(argv[0],O_RDWR);
  60  void*img;
  61  struct vm86plus_struct VM86;
  62  int func,ret;
  63  off_t fofs=0;
  64  pid_t ppid=getppid();
  65
  66 /* fprintf(stderr,"main is at %08lx, file is %s, fd=%d\n",(unsigned long)&main,argv[0],mfd); */
  67  if (mfd<0) return 1;
  68 /* Map in our DOS image at the start of the process address space */
  69  if (argv[1]) {
  70   /* Ulrich Weigand suggested mapping in the DOS image directly from the Wine
  71      address space */
  72   fofs=atol(argv[1]);
  73   /* linux currently only allows mapping a process memory if it's being ptraced */
  74   /* Linus doesn't like it, so this probably won't work in the future */
  75   /* it doesn't even work for me right now */
  76   ptrace(PTRACE_ATTACH,ppid,0,0);
  77   kill(ppid,SIGSTOP);
  78   waitpid(ppid,NULL,0);
  79  }
  80  img=mmap(NULL,0x110000,PROT_EXEC|PROT_READ|PROT_WRITE,MAP_FIXED|MAP_SHARED,mfd,fofs);
  81  if (argv[1]) {
  82   ptrace(PTRACE_DETACH,ppid,0,0);
  83   kill(ppid,SIGCONT);
  84  }
  85  if (img==(void*)-1) {
  86   fprintf(stderr,"DOS memory map failed, error=%s\n",strerror(errno));
  87   fprintf(stderr,"in attempt to map %s, offset %08lX, length 110000, to offset 0\n",argv[0],fofs);
  88   return 1;
  89  }
  90 /* fprintf(stderr,"Successfully mapped DOS memory, entering vm86 loop\n"); */
  91 /* report back to the main program that we're ready */
  92  ret=0;
  93  write(1,&ret,sizeof(ret));
  94 /* context exchange loop */
  95  do {
  96   if (read(0,&func,sizeof(func))!=sizeof(func)) return 1;
  97   if (read(0,&VM86,sizeof(VM86))!=sizeof(VM86)) return 1;
  98   if (func<0) break;
  99   ret=vm86plus(func,&VM86);
 100   if (write(1,&ret,sizeof(ret))!=sizeof(ret)) return 1;
 101   if (write(1,&VM86,sizeof(VM86))!=sizeof(VM86)) return 1;
 102  } while (1);
 103  return 0;
 104 }
 105
 106 #else /* !linux */
 107 int main(void) {return 1;}
 108 #endif