From: Steve Lionel [Steve.Lionel@compaq.com]
Sent: Wednesday, March 08, 2000 12:45 PM
To: Info-VAX@Mvb.Saic.Com
Subject: Re: how to patch image linked /debug to run without invoking
the debugger when image is run as foreign command.

On Wed, 08 Mar 2000 16:47:24 GMT, snead_george_w@my-deja.com wrote:


>Years back, there was a short patch procedure
>applied against a field in the image's header
>which disabled the debugger from starting up when
>the image was run.  Does anyone remember this
>patch.  Or, is there a better way?


On VAX, the following will do it:

$ patch/absolute/nonew_version/journal=nl: 'p1'
examine/byte 20; deposit/byte 20 = \ and 0fe; update; exit

On Alpha, there's no PATCH (and the offsets are different) - the
following C program will do it:

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

main (int argc, char *argv[])
{
    FILE    *inf;
    fpos_t  pos;
    unsigned char   buffer[512];
    int     offset = 0x50;
    int     turn_off = 1;

    if (argc < 3) {
        fprintf(stderr, "Syntax: {off | on} image_file\n");
        exit(EXIT_FAILURE);
    }

    if (strcmp(argv[1], "off") == 0)
        turn_off = 1;
    else if (strcmp(argv[1], "on") == 0)
        turn_off = 0;
    else {
        fprintf(stderr, "Specify OFF or ON as the first parameter\n");
        exit(EXIT_FAILURE);
    }

    if (argc == 4) {
        if (strcmp(argv[3], "vax") == 0)
            offset = 0x20;
        else if (strcmp(argv[3], "alpha") == 0)
            offset = 0x50;
        else {
            fprintf(stderr, "Unknown system type: %s\n", argv[3]);
            exit(EXIT_FAILURE);
        }
    }

    if ((inf = fopen(argv[2], "r+b")) == NULL) {
        fprintf(stderr, "Unable to open %s\n", argv[2]);
        exit(EXIT_FAILURE);
    }

    fgetpos(inf, &pos);
    if (fread(buffer, sizeof(buffer), 1, inf) != 1) {
        fprintf(stderr, "Error reading %s\n", argv[2]);
        exit(EXIT_FAILURE);
    }

    printf("Old value: %x\n", buffer[offset]);
    if (turn_off)
        buffer[offset] &= 0xFE;
    else
        buffer[offset] |= 0x1;
    printf("New value: %x\n", buffer[offset]);

    fsetpos(inf, &pos);
    if (fwrite(buffer, sizeof(buffer), 1, inf) != 1) {
        fprintf(stderr, "Error writing %s\n", argv[2]);
        exit(EXIT_FAILURE);
    }

    fclose(inf);
}


Steve Lionel (mailto:Steve.Lionel@compaq.com)
Fortran Engineering
Compaq Computer Corporation, Nashua NH

Compaq Fortran web site: http://www.compaq.com/fortran