summaryrefslogtreecommitdiffstats
path: root/tests/runcom.c
blob: cbbaf313babe5f982494479add17d31152882012 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
/*
 * Simple example of use of vm86: launch a basic .com DOS executable
 */
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <inttypes.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <signal.h>

#include <linux/unistd.h>
#include <asm/vm86.h>

//#define SIGTEST

#undef __syscall_return
#define __syscall_return(type, res) \
do { \
	return (type) (res); \
} while (0)

_syscall2(int, vm86, int, func, struct vm86plus_struct *, v86)

#define COM_BASE_ADDR    0x10100

void usage(void)
{
    printf("runcom version 0.1 (c) 2003 Fabrice Bellard\n"
           "usage: runcom file.com\n"
           "VM86 Run simple .com DOS executables (linux vm86 test mode)\n");
    exit(1);
}

static inline void set_bit(uint8_t *a, unsigned int bit)
{
    a[bit / 8] |= (1 << (bit % 8));
}

static inline uint8_t *seg_to_linear(unsigned int seg, unsigned int reg)
{
    return (uint8_t *)((seg << 4) + (reg & 0xffff));
}

static inline void pushw(struct vm86_regs *r, int val)
{
    r->esp = (r->esp & ~0xffff) | ((r->esp - 2) & 0xffff);
    *(uint16_t *)seg_to_linear(r->ss, r->esp) = val;
}

void dump_regs(struct vm86_regs *r)
{
    fprintf(stderr,
            "EAX=%08lx EBX=%08lx ECX=%08lx EDX=%08lx\n"
            "ESI=%08lx EDI=%08lx EBP=%08lx ESP=%08lx\n"
            "EIP=%08lx EFL=%08lx\n"
            "CS=%04x DS=%04x ES=%04x SS=%04x FS=%04x GS=%04x\n",
            r->eax, r->ebx, r->ecx, r->edx, r->esi, r->edi, r->ebp, r->esp,
            r->eip, r->eflags,
            r->cs, r->ds, r->es, r->ss, r->fs, r->gs);
}

#ifdef SIGTEST
void alarm_handler(int sig)
{
    fprintf(stderr, "alarm signal=%d\n", sig);
    alarm(1);
}
#endif

int main(int argc, char **argv)
{
    uint8_t *vm86_mem;
    const char *filename;
    int fd, ret, seg;
    struct vm86plus_struct ctx;
    struct vm86_regs *r;

    if (argc != 2)
        usage();
    filename = argv[1];

    vm86_mem = mmap((void *)0x00000000, 0x110000,
                    PROT_WRITE | PROT_READ | PROT_EXEC,
                    MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 0);
    if (vm86_mem == MAP_FAILED) {
        perror("mmap");
        exit(1);
    }
#ifdef SIGTEST
    {
        struct sigaction act;

        act.sa_handler = alarm_handler;
        sigemptyset(&act.sa_mask);
        act.sa_flags = 0;
        sigaction(SIGALRM, &act, NULL);
        alarm(1);
    }
#endif

    /* load the MSDOS .com executable */
    fd = open(filename, O_RDONLY);
    if (fd < 0) {
        perror(filename);
        exit(1);
    }
    ret = read(fd, vm86_mem + COM_BASE_ADDR, 65536 - 256);
    if (ret < 0) {
        perror("read");
        exit(1);
    }
    close(fd);

    memset(&ctx, 0, sizeof(ctx));
    /* init basic registers */
    r = &ctx.regs;
    r->eip = 0x100;
    r->esp = 0xfffe;
    seg = (COM_BASE_ADDR - 0x100) >> 4;
    r->cs = seg;
    r->ss = seg;
    r->ds = seg;
    r->es = seg;
    r->fs = seg;
    r->gs = seg;
    r->eflags = VIF_MASK;

    /* put return code */
    set_bit((uint8_t *)&ctx.int_revectored, 0x21);
    *seg_to_linear(r->cs, 0) = 0xb4; /* mov ah, $0 */
    *seg_to_linear(r->cs, 1) = 0x00;
    *seg_to_linear(r->cs, 2) = 0xcd; /* int $0x21 */
    *seg_to_linear(r->cs, 3) = 0x21;
    pushw(&ctx.regs, 0x0000);

    /* the value of these registers seem to be assumed by pi_10.com */
    r->esi = 0x100;
    r->ecx = 0xff;
    r->ebp = 0x0900;
    r->edi = 0xfffe;

    for(;;) {
        ret = vm86(VM86_ENTER, &ctx);
        switch(VM86_TYPE(ret)) {
        case VM86_INTx:
            {
                int int_num, ah;

                int_num = VM86_ARG(ret);
                if (int_num != 0x21)
                    goto unknown_int;
                ah = (r->eax >> 8) & 0xff;
                switch(ah) {
                case 0x00: /* exit */
                    exit(0);
                case 0x02: /* write char */
                    {
                        uint8_t c = r->edx;
                        write(1, &c, 1);
                    }
                    break;
                case 0x09: /* write string */
                    {
                        uint8_t c;
                        for(;;) {
                            c = *seg_to_linear(r->ds, r->edx);
                            if (c == '$')
                                break;
                            write(1, &c, 1);
                        }
                        r->eax = (r->eax & ~0xff) | '$';
                    }
                    break;
                default:
                unknown_int:
                    fprintf(stderr, "unsupported int 0x%02x\n", int_num);
                    dump_regs(&ctx.regs);
                    //                    exit(1);
                }
            }
            break;
        case VM86_SIGNAL:
            /* a signal came, we just ignore that */
            break;
        case VM86_STI:
            break;
        default:
            fprintf(stderr, "unhandled vm86 return code (0x%x)\n", ret);
            dump_regs(&ctx.regs);
            exit(1);
        }
    }
}
OpenPOWER on IntegriCloud