Archipelago » qemu

/*

 * Example of use of user mode libqemu: 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 <malloc.h>

#include "cpu.h"

//#define SIGTEST

int cpu_get_pic_interrupt(CPUState *env)

{

    return -1;

}

uint64_t cpu_get_tsc(CPUState *env)

{

    return 0;

}

static void set_gate(void *ptr, unsigned int type, unsigned int dpl,

                     unsigned long addr, unsigned int sel)

{

    unsigned int e1, e2;

    e1 = (addr & 0xffff) | (sel << 16);

    e2 = (addr & 0xffff0000) | 0x8000 | (dpl << 13) | (type << 8);

    stl((uint8_t *)ptr, e1);

    stl((uint8_t *)ptr + 4, e2);

}

uint64_t idt_table[256];

/* only dpl matters as we do only user space emulation */

static void set_idt(int n, unsigned int dpl)

{

    set_gate(idt_table + n, 0, dpl, 0, 0);

}

void qemu_free(void *ptr)

{

    free(ptr);

}

void *qemu_malloc(size_t size)

{

    return malloc(size);

}

void *qemu_mallocz(size_t size)

{

    void *ptr;

    ptr = qemu_malloc(size);

    if (!ptr)

        return NULL;

    memset(ptr, 0, size);

    return ptr;

}

void *qemu_vmalloc(size_t size)

{

    return memalign(4096, size);

}

void qemu_vfree(void *ptr)

{

    free(ptr);

}

void qemu_printf(const char *fmt, ...)

{

    va_list ap;

    va_start(ap, fmt);

    vprintf(fmt, ap);

    va_end(ap);

}

/* XXX: this is a bug in helper2.c */

int errno;

/**********************************************/

#define COM_BASE_ADDR    0x10100

void usage(void)

{

    printf("qruncom version 0.1 (c) 2003 Fabrice Bellard\n"

           "usage: qruncom file.com\n"

           "user mode libqemu demo: run simple .com DOS executables\n");

    exit(1);

}

static inline uint8_t *seg_to_linear(unsigned int seg, unsigned int reg)

{

    return (uint8_t *)((seg << 4) + (reg & 0xffff));

}

static inline void pushw(CPUState *env, int val)

{

    env->regs[R_ESP] = (env->regs[R_ESP] & ~0xffff) | ((env->regs[R_ESP] - 2) & 0xffff);

    *(uint16_t *)seg_to_linear(env->segs[R_SS].selector, env->regs[R_ESP]) = val;

}

static void host_segv_handler(int host_signum, siginfo_t *info,

                              void *puc)

{

    if (cpu_signal_handler(host_signum, info, puc)) {

        return;

    }

    abort();

}

int main(int argc, char **argv)

{

    uint8_t *vm86_mem;

    const char *filename;

    int fd, ret, seg;

    CPUState *env;

    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);

    }

    /* 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);

    /* install exception handler for CPU emulator */

    {

        struct sigaction act;

        sigfillset(&act.sa_mask);

        act.sa_flags = SA_SIGINFO;

        //        act.sa_flags |= SA_ONSTACK;

        act.sa_sigaction = host_segv_handler;

        sigaction(SIGSEGV, &act, NULL);

        sigaction(SIGBUS, &act, NULL);

    }

    //    cpu_set_log(CPU_LOG_TB_IN_ASM | CPU_LOG_TB_OUT_ASM | CPU_LOG_EXEC);

    env = cpu_init("qemu32");

    cpu_x86_set_cpl(env, 3);

    env->cr[0] = CR0_PG_MASK | CR0_WP_MASK | CR0_PE_MASK;

    /* NOTE: hflags duplicates some of the virtual CPU state */

    env->hflags |= HF_PE_MASK | VM_MASK;

    /* flags setup : we activate the IRQs by default as in user

       mode. We also activate the VM86 flag to run DOS code */

    env->eflags |= IF_MASK | VM_MASK;

    /* init basic registers */

    env->eip = 0x100;

    env->regs[R_ESP] = 0xfffe;

    seg = (COM_BASE_ADDR - 0x100) >> 4;

    cpu_x86_load_seg_cache(env, R_CS, seg,

                           (seg << 4), 0xffff, 0);

    cpu_x86_load_seg_cache(env, R_SS, seg,

                           (seg << 4), 0xffff, 0);

    cpu_x86_load_seg_cache(env, R_DS, seg,

                           (seg << 4), 0xffff, 0);

    cpu_x86_load_seg_cache(env, R_ES, seg,

                           (seg << 4), 0xffff, 0);

    cpu_x86_load_seg_cache(env, R_FS, seg,

                           (seg << 4), 0xffff, 0);

    cpu_x86_load_seg_cache(env, R_GS, seg,

                           (seg << 4), 0xffff, 0);

    /* exception support */

    env->idt.base = (unsigned long)idt_table;

    env->idt.limit = sizeof(idt_table) - 1;

    set_idt(0, 0);

    set_idt(1, 0);

    set_idt(2, 0);

    set_idt(3, 3);

    set_idt(4, 3);

    set_idt(5, 3);

    set_idt(6, 0);

    set_idt(7, 0);

    set_idt(8, 0);

    set_idt(9, 0);

    set_idt(10, 0);

    set_idt(11, 0);

    set_idt(12, 0);

    set_idt(13, 0);

    set_idt(14, 0);

    set_idt(15, 0);

    set_idt(16, 0);

    set_idt(17, 0);

    set_idt(18, 0);

    set_idt(19, 0);

    /* put return code */

    *seg_to_linear(env->segs[R_CS].selector, 0) = 0xb4; /* mov ah, $0 */

    *seg_to_linear(env->segs[R_CS].selector, 1) = 0x00;

    *seg_to_linear(env->segs[R_CS].selector, 2) = 0xcd; /* int $0x21 */

    *seg_to_linear(env->segs[R_CS].selector, 3) = 0x21;

    pushw(env, 0x0000);

    /* the value of these registers seem to be assumed by pi_10.com */

    env->regs[R_ESI] = 0x100;

    env->regs[R_ECX] = 0xff;

    env->regs[R_EBP] = 0x0900;

    env->regs[R_EDI] = 0xfffe;

    /* inform the emulator of the mmaped memory */

    page_set_flags(0x00000000, 0x110000,

                   PAGE_WRITE | PAGE_READ | PAGE_EXEC | PAGE_VALID);

    for(;;) {

        ret = cpu_x86_exec(env);

        switch(ret) {

        case EXCP0D_GPF:

            {

                int int_num, ah;

                int_num = *(uint8_t *)(env->segs[R_CS].base + env->eip + 1);

                if (int_num != 0x21)

                    goto unknown_int;

                ah = (env->regs[R_EAX] >> 8) & 0xff;

                switch(ah) {

                case 0x00: /* exit */

                    exit(0);

                case 0x02: /* write char */

                    {

                        uint8_t c = env->regs[R_EDX];

                        write(1, &c, 1);

                    }

                    break;

                case 0x09: /* write string */

                    {

                        uint8_t c;

                        for(;;) {

                            c = *seg_to_linear(env->segs[R_DS].selector, env->regs[R_EAX]);

                            if (c == '$')

                                break;

                            write(1, &c, 1);

                        }

                        env->regs[R_EAX] = (env->regs[R_EAX] & ~0xff) | '$';

                    }

                    break;

                default:

                unknown_int:

                    fprintf(stderr, "unsupported int 0x%02x\n", int_num);

                    cpu_dump_state(env, stderr, fprintf, 0);

                    //                    exit(1);

                }

                env->eip += 2;

            }

            break;

        default:

            fprintf(stderr, "unhandled cpu_exec return code (0x%x)\n", ret);

            cpu_dump_state(env, stderr, fprintf, 0);

            exit(1);

        }

    }

}