hedrick@athos.rutgers.edu (Charles Hedrick) (04/05/88)
The following is only for the adventuresome:
Here's my proposed fix for the DST problem in SV/AT. This is only
intended for SV/AT. It presumably will not work on the 386 version.
(Judging by the Uport bbs system, the 386 version does have the
problem, but it's very unlikely that ctime.o will use the exact code
sequence that this program is looking for.) This consists of a
program that will patch executables to change the start date of DST to
the first Sunday in April. Unfortunately, it has to be called on
every executable on the system that uses the routine ctime, and there
are a lot of them. So I also supply a shell script that will apply it
to a whole directory (actually any wildcard spec). Typically I do
something like
cd /bin
fixdstdir *
It needs to be done on /bin, /usr/bin, /usr/lib, /usr/lib/uucp, /etc,
/lib/large, /lib/small, /lib/libp/large, and /lib/libp/small. This is
on a system that has the base Unix and the development system. I
haven't loaded the word-processing software, so I don't know what
additional things might need to be fixed up there.
Some caveats:
- the C program searches for specific executable code sequences.
It appears to work for 2.3.0-L, but could fail for other
releases if ctime.o happens to compile differently.
- in theory the program could trigger falsely, if some other
piece of code happened to generate the right code sequence.
I sort of doubt it. The test is for loading 119 and
then 303 into two specific registers (these are the day
numbers for the start and end of DST), but you never know.
So back up your system software being doing this.
- when I was using this, the system crashed once with a general
protection failure. I presume there was just too much
disk I/O going on. So I suggest doing this when nobody is
logged in who will get upset with a crash.
- it will fail on any files that are currently in use (another
argument for doing it single-user)
- for some reason I got a wierd error message in /etc. I
ended up doing
fixdstdir [a-g]*
fixdstdir [h-z]*
which worked fine.
- this program will change the last-write dates on any files
that are updated. This appears to be reasonable, but note
that if you do incremental backups, your next backup will
have lots of files in it. (I count about 70 files that
get changed.)
- if you have directories with your own software, e.g.
/usr/local/bin, you'll want to do them as well.
- the C program is quite inefficient. It's the way it is because
it was easy to design that way. Debugging printout is
still present. Since it's only going to be run once, none
of this matters.
#! /bin/sh
# This is a shell archive, meaning:
# 1. Remove everything above the #! /bin/sh line.
# 2. Save the resulting text in a file.
# 3. Execute the file with /bin/sh (not csh) to create the files:
# fixdst.c
# fixdstdir
# This archive created: Tue Apr 5 06:06:08 1988
export PATH; PATH=/bin:$PATH
if test -f 'fixdst.c'
then
echo shar: will not over-write existing file "'fixdst.c'"
else
cat << \SHAR_EOF > 'fixdst.c'
#include <stdio.h>
int buffer[16];
main (argc,argv)
int argc;
char **argv;
{
register int *pt;
register int i;
FILE *f;
int target;
long pos;
f = fopen(argv[1],"r");
if (f == NULL) {
printf("can't open file\n");
exit(2);
}
while (! feof(f)) {
for (pt = buffer, i = 0; i < 15; pt++, i++)
*pt = *(pt+1);
buffer[15] = getw(f);
if (buffer[0] == 0x46c7 && buffer[1] == 0x77fc &&
buffer[2] == 0xc700 && buffer[3] == 0xfa46 &&
buffer[4] == 0x012f) {
for (i = 0; i < 16; i++)
printf("%d ", buffer[i]);
printf("\n");
pos = ftell(f);
f = fopen(argv[1],"r+");
if (f == NULL) {
printf("can't reopen file for update\n");
exit(2);
}
fseek(f, pos-30, 0);
putw(0x60fc, f);
fclose(f);
exit(0);
}
else if (buffer[0] == 0xfc46 && buffer[1] == 0x0077 &&
buffer[2] == 0x46c7 && buffer[3] == 0x2ffa) {
for (i = 0; i < 16; i++)
printf("%d ", buffer[i]);
printf("\n");
printf("\n");
pos = ftell(f);
f = fopen(argv[1],"r+");
if (f == NULL) {
printf("can't reopen file for update\n");
exit(2);
}
fseek(f, pos-30, 0);
putw(0x0060, f);
fclose(f);
exit(0);
}
}
exit(1);
}
SHAR_EOF
chmod +x 'fixdst.c'
fi # end of overwriting check
if test -f 'fixdstdir'
then
echo shar: will not over-write existing file "'fixdstdir'"
else
cat << \SHAR_EOF > 'fixdstdir'
#!/bin/csh
foreach i ($*)
fixdst $i
if ($status == 0) then
echo $i
endif
end
SHAR_EOF
chmod +x 'fixdstdir'
fi # end of overwriting check
# End of shell archive
exit 0