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#include <sys/types.h>
#include <sys/io.h>
#include <sys/stat.h>
#include <sys/vm86.h>
#include <sys/syscall.h>
#include <sys/mman.h>
#include <ctype.h>
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <netinet/in.h>
#include "bioscall.h"
#ident "$Id$"
#define DFLAG 0x0400
#define IFLAG 0x0200
#define TFLAG 0x0100
#define SFLAG 0x0080
#define ZFLAG 0x0040
#define AFLAG 0x0010
#define PFLAG 0x0004
#define CFLAG 0x0001
/* Dump some of the interesting parts of a register struct to stdout. */
void dump_regs(struct vm86_regs *regs)
{
printf("ax = 0x%04lx\n", regs->eax & 0xffff);
printf("bx = 0x%04lx\n", regs->ebx & 0xffff);
printf("cx = 0x%04lx\n", regs->ecx & 0xffff);
printf("dx = 0x%04lx\n", regs->edx & 0xffff);
printf("cs = 0x%04x\n", regs->cs & 0xffff);
printf("ip = 0x%08lx\n", regs->eip & 0xffffffff);
printf("ss = 0x%04x\n", regs->ss & 0xffff);
printf("sp = 0x%08lx\n", regs->esp & 0xffffffff);
printf("%04x:%08lx = (%ld)\n",
regs->cs & 0xffff, regs->eip,
regs->cs * 16 + regs->eip);
}
/* Call vm86, but do I/O that gets trapped. We could skip vm86() altogether,
but then I'm not trying to emulate an entire CPU here. Luckily, none of
the I/O instructions (or push/pop) affect the flags, so we can leave them
alone and just deal with performing the I/O operation that caused a return
to 32-bit mode. */
void do_vm86(struct vm86_struct *vm, char *memory, unsigned stop_eip) {
int ret;
unsigned start_cs, start_eip;
unsigned char *ip = NULL;
/* Save the starting instruction address. */
start_cs = vm->regs.cs;
start_eip = vm->regs.eip;
/* We'll need to pass I/O through. PCI devices have higher addresses
than we can get access to with ioperm(). */
if(iopl(3) != 0) {
return;
}
/* Do it. */
ret = syscall(SYS_vm86old, vm);
while((vm->regs.cs * 16 + vm->regs.eip) != (start_cs * 16 + stop_eip)) {
ip = &memory[vm->regs.cs * 16 + vm->regs.eip];
#ifdef DEBUG2
printf("Unexpected return:\n");
dump_regs(&vm->regs);
printf("Offending instructions: %02x %02x %02x %02x\n",
ip[0], ip[1], ip[2], ip[3]);
#endif
switch(ip[0]) {
case 0xe4: { /* in al, literal */
vm->regs.eax &= 0xffffff00;
vm->regs.eax |= inb(ip[1]);
vm->regs.eip += 2;
break;
}
case 0xe6: { /* out al, literal */
outb(vm->regs.eax & 0xff, ip[1]);
vm->regs.eip += 2;
break;
}
case 0xec: { /* in al, dx */
vm->regs.eax &= 0xffffff00;
vm->regs.eax |= inb(vm->regs.edx & 0xffff);
vm->regs.eip++;
break;
}
case 0xed: { /* in ax, dx */
vm->regs.eax &= 0xffff0000;
vm->regs.eax |= inw(vm->regs.edx & 0xffff);
vm->regs.eip++;
break;
}
case 0xee: { /* out al, dx */
outb(vm->regs.eax & 0xff,
vm->regs.edx & 0xffff);
vm->regs.eip++;
break;
}
case 0xef: { /* out ax, dx */
outw(vm->regs.eax & 0xffff,
vm->regs.edx & 0xffff);
vm->regs.eip++;
break;
}
case 0x6c: { /* insb */
unsigned char *result = (unsigned char*)
&memory[vm->regs.es*16 + vm->regs.edi];
*result = inb(vm->regs.edx & 0xffff);
if(vm->regs.eflags & DFLAG) {
vm->regs.edi -= 1;
} else {
vm->regs.edi += 1;
}
if(ip[-1] == 0xf3) { /* rep'ped */
vm->regs.ecx--;
vm->regs.eip--;
} else {
vm->regs.eip++;
}
break;
}
case 0x6d: { /* insw */
u_int16_t *result = (u_int16_t*)
&memory[vm->regs.es*16 + vm->regs.edi];
*result = inw(vm->regs.edx & 0xffff);
if(vm->regs.eflags & DFLAG) {
vm->regs.edi -= 2;
} else {
vm->regs.edi += 2;
}
if(ip[-1] == 0xf3) { /* rep'ped */
vm->regs.ecx--;
vm->regs.eip--;
} else {
vm->regs.eip++;
}
break;
}
case 0x6e: { /* outsb */
unsigned char *result = (unsigned char*)
&memory[vm->regs.es*16 + vm->regs.edi];
outb(*result,
vm->regs.edx & 0xffff);
if(vm->regs.eflags & DFLAG) {
vm->regs.edi -= 1;
} else {
vm->regs.edi += 1;
}
if(ip[-1] == 0xf3) { /* rep'ped */
vm->regs.ecx--;
vm->regs.eip--;
} else {
vm->regs.eip++;
}
break;
}
case 0x6f: { /* outsw */
u_int16_t *result = (u_int16_t*)
&memory[vm->regs.es*16 + vm->regs.edi];
outw(*result,
vm->regs.edx & 0xffff);
if(vm->regs.eflags & DFLAG) {
vm->regs.edi -= 2;
} else {
vm->regs.edi += 2;
}
if(ip[-1] == 0xf3) { /* rep'ped */
vm->regs.ecx--;
vm->regs.eip--;
} else {
vm->regs.eip++;
}
break;
}
case 0xfa: { /* cli */
vm->regs.eflags &= ~(IFLAG);
vm->regs.eip++;
break;
}
case 0xfb: { /* sti */
vm->regs.eflags |= ~(IFLAG);
vm->regs.eip++;
break;
}
case 0x9c: { /* pushf */
vm->regs.esp -= 2;
*(u_int16_t*) &memory[vm->regs.ss * 16 +
vm->regs.esp]
= vm->regs.eflags & 0xffff;
vm->regs.eip++;
break;
}
case 0x9d: { /* popf */
vm->regs.esp += 2;
vm->regs.eflags &= 0xffff0000;
vm->regs.eflags |=
*(u_int16_t*) &memory[vm->regs.ss * 16 +
vm->regs.esp];
vm->regs.eip++;
break;
}
case 0xf0: { /* lock prefix */
/* ignore it */
vm->regs.eip++;
break;
}
case 0x66: {
/* 32-bit extension prefix. Valid, even in
v86 mode. Weird. */
vm->regs.eip++;
ip++;
switch(ip[0]) {
case 0xed: { /* in eax, dx */
vm->regs.eax =
inl(vm->regs.edx & 0xffff);
vm->regs.eip++;
break;
}
case 0xef: { /* out eax, dx */
outl(vm->regs.eax,
vm->regs.edx & 0xffff);
vm->regs.eip++;
break;
}
default: {
fprintf(stderr, "unhandled "
"32-bit opcode\n");
exit(1);
}
}
break;
}
case 0x55: { /* push bp */
vm->regs.esp -= 2;
*(u_int16_t*) &memory[vm->regs.ss * 16 +
vm->regs.esp]
= vm->regs.ebp & 0xffff;
vm->regs.eip++;
break;
}
case 0x5d: { /* pop bp */
vm->regs.ebp &= 0xffff0000;
vm->regs.ebp |= *(u_int16_t*)
&memory[vm->regs.ss*16 + vm->regs.esp];
vm->regs.esp += 2;
vm->regs.eip++;
break;
}
case 0x59: { /* pop cx -- Banshee */
vm->regs.ecx &= 0xffff0000;
vm->regs.ecx |= *(u_int16_t*)
&memory[vm->regs.ss*16 + vm->regs.esp];
vm->regs.esp += 2;
vm->regs.eip++;
}
case 0xc3: { /* ret near, just pop ip */
vm->regs.eip &= 0xffff0000;
vm->regs.eip |= *(u_int16_t*)
&memory[vm->regs.ss*16 + vm->regs.esp];
vm->regs.esp += 2;
break;
}
case 0xcb: { /* ret far, pop both ip and cs */
vm->regs.eip &= 0xffff0000;
vm->regs.eip |= *(u_int16_t*)
&memory[vm->regs.ss*16 + vm->regs.esp];
vm->regs.esp += 2;
vm->regs.cs = *(u_int16_t*)
&memory[vm->regs.ss*16 + vm->regs.esp];
vm->regs.esp += 2;
break;
}
default: {
fprintf(stderr, "Unexpected stop!\n");
dump_regs(&vm->regs);
printf("Offending instructions: %02x %02x %02x %02x\n",
ip[0], ip[1], ip[2], ip[3]);
exit(1);
}
}
ip = &memory[vm->regs.cs * 16 + vm->regs.eip];
#ifdef DEBUG
printf("Resuming execution:\n");
dump_regs(&vm->regs);
printf("Offending instructions: %02x %02x %02x %02x\n",
ip[0], ip[1], ip[2], ip[3]);
#endif
ret = syscall(SYS_vm86old, vm);
}
#ifdef DEBUG
printf("Reached stopping point, returning.\n");
#endif
return;
}
/* Get a snapshot of the first megabyte of memory for use with vm86. */
unsigned char *vm86_ram_alloc()
{
unsigned char *memory;
int fd;
/* Grab address 0 for this process. mmap() 1 megabyte + 64k HMA */
memory = mmap(0, 0x110000, PROT_READ | PROT_EXEC | PROT_WRITE,
MAP_PRIVATE | MAP_FIXED | MAP_ANON, -1, 0x00000);
if(memory == MAP_FAILED) {
perror("error mmap()ing memory for the BIOS");
return MAP_FAILED;
}
/* Copy the low megabyte to our mmap()'ed buffer. */
fd = open("/dev/mem", O_RDONLY);
if(fd == -1) {
perror("reading kernel memory");
return MAP_FAILED;
}
// read(fd, memory, 0x110000);
lseek(fd, 0, SEEK_SET);
read(fd, &memory[0], 0x10000);
lseek(fd, 0xa0000, SEEK_SET);
read(fd, &memory[0xa0000], 0x50000);
close(fd);
return memory;
}
void vm86_ram_free(unsigned char *ram)
{
munmap(ram, 0x110000);
}
void bioscall(unsigned char int_no, struct vm86_regs *regs, unsigned char *mem)
{
unsigned char call[] = {0xcd, int_no, 0xcd, 0x09};
struct vm86_struct vm;
memset(&vm, 0, sizeof(vm));
memcpy(&vm.regs, regs, sizeof(vm.regs));
vm.regs.cs = BIOSCALL_START_SEG;
vm.regs.eip = BIOSCALL_START_OFS;
vm.regs.ss = BIOSCALL_START_SEG;
vm.regs.esp = 0xfff0 - BIOSCALL_START_OFS;
vm.regs.eflags = VM_MASK | IOPL_MASK;
memcpy(&mem[BIOSCALL_START_SEG * 16 + BIOSCALL_START_OFS], call,
sizeof(call));
do_vm86(&vm, mem, BIOSCALL_START_OFS + sizeof(call));
memcpy(regs, &vm.regs, sizeof(vm.regs));
}
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