init.c

简单的虚拟机

#include <stdio.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <stdbool.h>
#include "dbgdata.h"
#include "init.h"

bool initcpu(struct CmdLine cl)
{
	int fileSize;
	FILE* fptr;
	struct HeaderRec hr;
	struct RelocRec* rptr=NULL;

	int bytecodeStart;
	int bytecodeEnd;
	int exec_bytes;
	int total_bytes;

	/*1) open executable and read header */
	fileSize = getFileSize(cl.binFile);
	if(fileSize==0)
	{
		printf("initcpu(): executable has zero size!\n");
		return false;
	}
	if(!(fptr=fopen(cl.binFile,"rb")))
	{
		printf("initcpu(): cannot open %s!\n",cl.binFile);
		return false;
	}

	if(readDebugData(&hr,rptr,fptr)==false)
		return false;

	/*2) validate header data */
	if(hr.magic!=SIGNATURE)
	{
		printf("initcpu(): file not DOS executable!\n");
		if(rptr)
			free(rptr);
		fclose(fptr);
		return false;
	}

	/*3) user header data to allocate RAM and init cpu registers */
	bytecodeStart = hr.hdsize * 16;
	bytecodeEnd = fileSize - 1;
	exec_bytes = bytecodeEnd - bytecodeStart + 1;

	if(hr.minparas * 16 > AVAILMEM)
	{
		printf("initcpu(): not enough memory to init runtime\n");
		if(rptr)
			free(rptr);
		fclose(fptr);
		return false;
	}
	total_bytes = (hr.maxparas*16)>AVAILMEM?AVAILMEM:(hr.maxparas*16);
	if(exec_bytes>total_bytes)
	{
		printf("initcpu(): error exe file, ram alloc mismatch!\n");
		if(rptr)
			free(rptr);
		fclose(fptr);
		return false;
	}	
	printf("initcpu(): allocating %d bytes\n",total_bytes);
	cpu.ram = (byte*)malloc(total_bytes); 

	cpu.greg.ax=0;
	cpu.greg.cx=0;
	cpu.greg.dx=0;
	cpu.greg.bx=0;
	cpu.greg.sp=hr.sp;
	cpu.greg.bp=0;
	cpu.greg.si=0;
	cpu.greg.di=0;
	cpu.sreg.es=0;
	cpu.sreg.cs=hr.cs;
	cpu.sreg.ss=hr.ss;
	cpu.sreg.ds=0;
	cpu.sreg.fs=0;
	cpu.sreg.gs=0;
	cpu.ip=hr.ip;
	cpu.flags=0;
	cpu.status=true;

	if(cpu.sreg.ss!=0)
	{
		cpu.sreg.ds=cpu.sreg.ss+(cpu.greg.sp>>4)+1;
		cpu.ram[(cpu.sreg.ds<<4)]=0xCD;
		cpu.ram[(cpu.sreg.ds<<4)+1]=0x20;
	}


	/*4) load bytecode into ram */
	fseek(fptr,bytecodeStart,SEEK_SET);
	fread(cpu.ram, 1, exec_bytes, fptr);
		if(feof(fptr)||ferror(fptr))
		{
			printf("initcpu(): error exe file, exec bytes mismatch!\n");
				if(rptr)
					free(rptr);
			fclose(fptr);
			return false;
		}

	/*relocating*/

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

	if(rptr)
		free(rptr);
	fclose(fptr);
		return true;
}

int getFileSize(char *name)
{
	char ret;
	struct stat buffer;
	ret = lstat(name,&buffer);
	if(ret==0)
	{
		return (int)buffer.st_size;
	}
	else
	{
		return 0;
	}

}