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1.1 root 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:
1.1.1.3 ! root 28: static void usage(void)
1.1 root 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: {
1.1.1.2 root 54: fprintf(stderr,
1.1 root 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];
1.1.1.2 root 83:
84: vm86_mem = mmap((void *)0x00000000, 0x110000,
85: PROT_WRITE | PROT_READ | PROT_EXEC,
1.1 root 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 $0x21 */
135: *seg_to_linear(r->cs, 3) = 0x21;
136: pushw(&ctx.regs, 0x0000);
137:
138: /* the value of these registers seem to be assumed by pi_10.com */
139: r->esi = 0x100;
140: r->ecx = 0xff;
141: r->ebp = 0x0900;
142: r->edi = 0xfffe;
143:
144: for(;;) {
145: ret = vm86(VM86_ENTER, &ctx);
146: switch(VM86_TYPE(ret)) {
147: case VM86_INTx:
148: {
149: int int_num, ah;
1.1.1.2 root 150:
1.1 root 151: int_num = VM86_ARG(ret);
152: if (int_num != 0x21)
153: goto unknown_int;
154: ah = (r->eax >> 8) & 0xff;
155: switch(ah) {
156: case 0x00: /* exit */
157: exit(0);
158: case 0x02: /* write char */
159: {
160: uint8_t c = r->edx;
161: write(1, &c, 1);
162: }
163: break;
164: case 0x09: /* write string */
165: {
166: uint8_t c;
167: for(;;) {
168: c = *seg_to_linear(r->ds, r->edx);
169: if (c == '$')
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: }
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