October 1993/Debugging Embedded Systems/Listing 1
/*
* fakeRom : This program supports
* debugging of ROM
* images in RAM.
*/
/* System includes */
#include <stdio.h>
#include <alloc.h>
#include <string.h>
#include <mem.h>
/* Useful defines and type defs */
define FAKE_ROM_SIZE 65536L
/* Other useful types */
typedef unsigned long ULONG;
typedef unsigned short USHORT;
/* Pointer to void far function */
typedef void (far *FUNCPTR) ();
/* -- procedures -- */
/*
* getAddrPart : Return the segment
* or offset of a
* pointer
*/
USHORT getAddrPart
(void *tptr, char part) {
/* Overlay for pointer */
USHORT components[2];
/*
* Overlay far pointer on
* two 16-bit words.
*/
memcpy ( (void *)components,
(void *)&tptr,
(long) 4 );
/*
* Return segment or offset
* as requested by user.
*/
if ( part == 's' )
return components[1];
else
return components[0];
}
/*
* physAddr : Make a physical
* address from
* segment, offset
*/
ULONG physAddr (void *tptr) {
ULONG addr; /* return value */
/* Get segment */
addr = getAddrPart(tptr,'s');
addr = addr << 4;
/* Get offset */
addr = addr|getAddrPart(tptr,'o');
/* Return whole thing */
return addr;
}
/*
* loadImage : load a file
* into a physical
* address.
*/
long loadImage ( FILE *fptr,
char buffer[],
ULONG size)
{
/* Local variables */
long leftToRead;
int thisRead;
long actual;
int block;
/* Initialize */
actual = 0;
block = 0;
leftToRead = size;
/* Assume 512 blocks */
while( 1 ) {
/* Calculate amount to read */
if ( leftToRead > 512L )
thisRead = 512L;
else
thisRead = leftToRead;
/* Perform the read */
block=fread
(&buffer[actual],
1,
thisRead,
fptr);
/* End-of-file test */
if ( block == 0 )
return (actual);
/* Update counters */
actual += (long)block;
leftToRead -= (long)thisRead;
}
} /* END loadImage */
/*
* main : main routine of ramrom.c
*/
void main () {
/* Local variables */
ULONG phys;
FILE *ifl;
char *fake_rom_p;
static char imageName[128];
long int actSize;
static char answer[4];
ULONG huge *tptr;
ULONG i;
/*
* Allocate enough memory
* for the ROM image
*/
fake_rom_p=
farmalloc(FAKE_ROM_SIZE);
phys = physAddr ( fake_rom_p );
/*
* Force all the locations that
* will not be filled during load
* to have OxFF in them. This
* mimics the actions of an
* EPROM programming device.
*/
tptr=(ULONG * huge) fake_rom_p;
for(i=0;i<(FAKE_ROM_SIZE/4);i++){
*tptr = 0xFFFFFFFF;
tptr++;
}
/* Show address to user and tell
user what to do with it */
printf("\n\nFake rom address:");
printf(" 0x%08lx\n",phys);
printf("\nINSTRUCTIONS FOR ");
printf("COMPLETING EMULATION\n");
printf("1. Go to development ");
printf("system or window.\n");
printf("2. Perform the final ");
printf("absolute link of the \n");
printf(" code specifying ");
printf("0x%08lx\n",phys);
printf(" as absolute address,");
printf(" instead of\n");
printf(" usual EPROM address.\n");
printf("3. Move final image to");
printf(" where it can be \n");
printf(" loaded by this ");
printf(" debug program.\n");
printf("4. Enter image name.\n");
printf("5. Enter YES when you are");
printf(" ready to run.\n");
printf("\n=====================\n");
ifl = NULL;
/* Load EPROM IMAGE */
while (ifl==NULL) {
printf("\nEnter image name: ");
(void) gets(imageName);
ifl=fopen(imageName,"rb");
if (ifl==NULL) {
perror(imageName);
continue;
}
actSize=
loadImage(ifl,
fake_rom_p,
FAKE_ROM_SIZE);
if ( actSize < 1 ) {
ifl = NULL;
fclose(ifl);
continue;
}
fclose(ifl);
} /* while ifl==NULL */
printf("%lu bytes loaded",actSize);
printf(" from %s\n", imageName);
/* Run EPROM IMAGE */
/*
* Note: If you set a breakpoint
* right here, you can examine
* your loaded EPROM IMAGE in
* memory.
*/
printf("Run it? YES/NO: ");
(void) gets( answer );
if (strcmp(answer,"YES")==0) {
(void)(*((FUNCPTR)fake_rom_p)) ();
}
} /* END main() */
/* End of File */
