tests/runcom.c

   1 /*
   2  * Simple example of use of vm86: launch a basic .com DOS executable
   3  */
   4 #include <stdlib.h>
   5 #include <stdio.h>
   6 #include <string.h>
   7 #include <inttypes.h>
   8 #include <unistd.h>
   9 #include <fcntl.h>
  10 #include <sys/mman.h>
  11 #include <signal.h>
  12
  13 #include <linux/unistd.h>
  14 #include <asm/vm86.h>
  15
  16 //#define SIGTEST
  17
  18 #undef __syscall_return
  19 #define __syscall_return(type, res) \
  20 do { \
  21         return (type) (res); \
  22 } while (0)
  23
  24 _syscall2(int, vm86, int, func, struct vm86plus_struct *, v86)
  25
  26 #define COM_BASE_ADDR    0x10100
  27
  28 void usage(void)
  29 {
  30     printf("runcom version 0.1 (c) 2003 Fabrice Bellard\n"
  31            "usage: runcom file.com\n"
  32            "VM86 Run simple .com DOS executables (linux vm86 test mode)\n");
  33     exit(1);
  34 }
  35
  36 static inline void set_bit(uint8_t *a, unsigned int bit)
  37 {
  38     a[bit / 8] |= (1 << (bit % 8));
  39 }
  40
  41 static inline uint8_t *seg_to_linear(unsigned int seg, unsigned int reg)
  42 {
  43     return (uint8_t *)((seg << 4) + (reg & 0xffff));
  44 }
  45
  46 static inline void pushw(struct vm86_regs *r, int val)
  47 {
  48     r->esp = (r->esp & ~0xffff) | ((r->esp - 2) & 0xffff);
  49     *(uint16_t *)seg_to_linear(r->ss, r->esp) = val;
  50 }
  51
  52 void dump_regs(struct vm86_regs *r)
  53 {
  54     fprintf(stderr,
  55             "EAX=%08lx EBX=%08lx ECX=%08lx EDX=%08lx\n"
  56             "ESI=%08lx EDI=%08lx EBP=%08lx ESP=%08lx\n"
  57             "EIP=%08lx EFL=%08lx\n"
  58             "CS=%04x DS=%04x ES=%04x SS=%04x FS=%04x GS=%04x\n",
  59             r->eax, r->ebx, r->ecx, r->edx, r->esi, r->edi, r->ebp, r->esp,
  60             r->eip, r->eflags,
  61             r->cs, r->ds, r->es, r->ss, r->fs, r->gs);
  62 }
  63
  64 #ifdef SIGTEST
  65 void alarm_handler(int sig)
  66 {
  67     fprintf(stderr, "alarm signal=%d\n", sig);
  68     alarm(1);
  69 }
  70 #endif
  71
  72 int main(int argc, char **argv)
  73 {
  74     uint8_t *vm86_mem;
  75     const char *filename;
  76     int fd, ret, seg;
  77     struct vm86plus_struct ctx;
  78     struct vm86_regs *r;
  79
  80     if (argc != 2)
  81         usage();
  82     filename = argv[1];
  83
  84     vm86_mem = mmap((void *)0x00000000, 0x110000,
  85                     PROT_WRITE | PROT_READ | PROT_EXEC,
  86                     MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 0);
  87     if (vm86_mem == MAP_FAILED) {
  88         perror("mmap");
  89         exit(1);
  90     }
  91 #ifdef SIGTEST
  92     {
  93         struct sigaction act;
  94
  95         act.sa_handler = alarm_handler;
  96         sigemptyset(&act.sa_mask);
  97         act.sa_flags = 0;
  98         sigaction(SIGALRM, &act, NULL);
  99         alarm(1);
 100     }
 101 #endif
 102
 103     /* load the MSDOS .com executable */
 104     fd = open(filename, O_RDONLY);
 105     if (fd < 0) {
 106         perror(filename);
 107         exit(1);
 108     }
 109     ret = read(fd, vm86_mem + COM_BASE_ADDR, 65536 - 256);
 110     if (ret < 0) {
 111         perror("read");
 112         exit(1);
 113     }
 114     close(fd);
 115
 116     memset(&ctx, 0, sizeof(ctx));
 117     /* init basic registers */
 118     r = &ctx.regs;
 119     r->eip = 0x100;
 120     r->esp = 0xfffe;
 121     seg = (COM_BASE_ADDR - 0x100) >> 4;
 122     r->cs = seg;
 123     r->ss = seg;
 124     r->ds = seg;
 125     r->es = seg;
 126     r->fs = seg;
 127     r->gs = seg;
 128     r->eflags = VIF_MASK;
 129
 130     /* put return code */
 131     set_bit((uint8_t *)&ctx.int_revectored, 0x21);
 132     *seg_to_linear(r->cs, 0) = 0xb4; /* mov ah, $0 */
 133     *seg_to_linear(r->cs, 1) = 0x00;
 134     *seg_to_linear(r->cs, 2) = 0xcd; /* int $0x21 */
 135     *seg_to_linear(r->cs, 3) = 0x21;
 136     pushw(&ctx.regs, 0x0000);
 137
 138     /* the value of these registers seem to be assumed by pi_10.com */
 139     r->esi = 0x100;
 140     r->ecx = 0xff;
 141     r->ebp = 0x0900;
 142     r->edi = 0xfffe;
 143
 144     for(;;) {
 145         ret = vm86(VM86_ENTER, &ctx);
 146         switch(VM86_TYPE(ret)) {
 147         case VM86_INTx:
 148             {
 149                 int int_num, ah;
 150
 151                 int_num = VM86_ARG(ret);
 152                 if (int_num != 0x21)
 153                     goto unknown_int;
 154                 ah = (r->eax >> 8) & 0xff;
 155                 switch(ah) {
 156                 case 0x00: /* exit */
 157                     exit(0);
 158                 case 0x02: /* write char */
 159                     {
 160                         uint8_t c = r->edx;
 161                         write(1, &c, 1);
 162                     }
 163                     break;
 164                 case 0x09: /* write string */
 165                     {
 166                         uint8_t c;
 167                         for(;;) {
 168                             c = *seg_to_linear(r->ds, r->edx);
 169                             if (c == '$')
 170                                 break;
 171                             write(1, &c, 1);
 172                         }
 173                         r->eax = (r->eax & ~0xff) | '$';
 174                     }
 175                     break;
 176                 default:
 177                 unknown_int:
 178                     fprintf(stderr, "unsupported int 0x%02x\n", int_num);
 179                     dump_regs(&ctx.regs);
 180                     //                    exit(1);
 181                 }
 182             }
 183             break;
 184         case VM86_SIGNAL:
 185             /* a signal came, we just ignore that */
 186             break;
 187         case VM86_STI:
 188             break;
 189         default:
 190             fprintf(stderr, "unhandled vm86 return code (0x%x)\n", ret);
 191             dump_regs(&ctx.regs);
 192             exit(1);
 193         }
 194     }
 195 }