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//convert.c by Steve Rhoads 4/26/01

//set $gp and zero .sbss and .bss

#include <stdio.h>

#include <stdlib.h>

#define BUF_SIZE (1024*1024)

/*Assumes running on PC little endian*/

#define ntohl(A) ((A>>24)|((A&0x00ff0000)>>8)|((A&0xff00)<<8)|(A<<24))

#define CODE_START 0x60

#define SECTION_START 0x4c

#define SECTION_END 0x160

#define SECTION_SIZE 0x28

#define SECTION_OFFSET 0xc

#define SECTION_LENGTH 0x10

struct header_t {

   unsigned long text_offset,text_length;

   unsigned long rdata_offset,rdata_length;

   unsigned long data_offset,data_length;

   unsigned long sdata_offset,sdata_length;

   unsigned long sbss_offset,sbss_length;

   unsigned long bss_offset,bss_length;

} header;

unsigned long load(char *ptr,unsigned long address)

{

   unsigned long value;

   value=*(unsigned long*)(ptr+address);

   value=ntohl(value);

   return value;

}

void set_low(char *ptr,unsigned long address,unsigned long value)

{

   unsigned long opcode;

   opcode=*(unsigned long*)(ptr+address);

   opcode=ntohl(opcode);

   opcode=(opcode&0xffff0000)|(value&0xffff);

   opcode=ntohl(opcode);

   *(unsigned long*)(ptr+address)=opcode;

}

int main(int argc,char *argv[])

{

   FILE *infile,*outfile,*txtfile;

   unsigned char *buf,*code;

   long size,stack_pointer;

   unsigned long code_offset,index,name,offset,length,d,i,gp_ptr;

   printf("test.exe -> code.txt & test2.exe\n");

   infile=fopen("test.exe","rb");

   if(infile==NULL) {

      printf("Can't open test.exe");

      return 0;

   }

   buf=(unsigned char*)malloc(BUF_SIZE);

   size=fread(buf,1,BUF_SIZE,infile);

   fclose(infile);

   code_offset=load(buf,CODE_START);

   printf("code_offset=0x%x ",code_offset);

   code=buf+code_offset;

   /*load all of the segment offsets and lengths*/

   for(index=SECTION_START;index<code_offset-0x20;index+=SECTION_SIZE) {

      name=load(buf,index);

      offset=load(buf,index+SECTION_OFFSET);

      length=load(buf,index+SECTION_LENGTH);

      switch(name) {

      case 0x2e746578: /*.text*/

         header.text_offset=offset;

         header.text_length=length;

         offset+=length;

         length=0;

         header.rdata_offset=offset;

         header.rdata_length=length;

         header.data_offset=offset;

         header.data_length=length;

         header.sdata_offset=offset;

         header.sdata_length=length;

         header.sbss_offset=offset;

         header.sbss_length=length;

         header.bss_offset=offset;

         header.bss_length=length;

         break;

      case 0x2e726461: /*.rdata*/

         header.rdata_offset=offset;

         header.rdata_length=length;

         offset+=length;

         length=0;

         header.data_offset=offset;

         header.data_length=length;

         header.sdata_offset=offset;

         header.sdata_length=length;

         header.sbss_offset=offset;

         header.sbss_length=length;

         header.bss_offset=offset;

         header.bss_length=length;

         break;

      case 0x2e646174: /*.data*/

         header.data_offset=offset;

         header.data_length=length;

         offset+=length;

         length=0;

         header.sdata_offset=offset;

         header.sdata_length=length;

         header.sbss_offset=offset;

         header.sbss_length=length;

         header.bss_offset=offset;

         header.bss_length=length;

         break;

      case 0x2e736461: /*.sdata*/

         header.sdata_offset=offset;

         header.sdata_length=length;

         offset+=length;

         length=0;

         header.sbss_offset=offset;

         header.sbss_length=length;

         header.bss_offset=offset;

         header.bss_length=length;

         break;

      case 0x2e736273: /*.sbss*/

         header.sbss_offset=offset;

         header.sbss_length=length;

         offset+=length;

         length=0;

         header.bss_offset=offset;

         header.bss_length=length;

         break;

      case 0x2e627373:  /*.bss*/

         header.bss_offset=offset;

         header.bss_length=length;

         break;

      default: printf("unknown 0x%x\n",name);

      }

   }

   /*Initialize the $gp register for sdata and sbss*/

   gp_ptr=header.sdata_offset+0x8000;

   printf("gp_ptr=0x%x ",gp_ptr);

   /*modify the first opcodes in boot.asm*/

   /*modify the lui opcode*/

   set_low(code,0,gp_ptr>>16);

   /*modify the ori opcode*/

   set_low(code,4,gp_ptr&0xffff);

   /*Clear .sbss and .bss*/

   printf(".sbss=0x%x .bss_end=0x%x\n",

      header.sbss_offset,header.bss_offset+header.bss_length);

   set_low(code,8,header.sbss_offset);

   set_low(code,12,header.bss_offset+header.bss_length);

   /*Set stack pointer*/

   stack_pointer=header.bss_offset+header.bss_length+512;

   printf("Stack pointer=0x%x\n",stack_pointer);

   set_low(code,16,stack_pointer);

   /*write out code.txt*/

   outfile=fopen("test2.exe","wb");

   txtfile=fopen("code.txt","w");

   for(i=0;i<=header.sdata_offset+header.sdata_length;i+=4) {

      d=load(code,i);

      fprintf(txtfile,"%8.8x\n",d);

      fwrite(code+i,4,1,outfile);

   }

   fclose(outfile);

   fclose(txtfile);

   free(buf);

   return 0;

}