scc%computer-lab.cambridge.ac.uk@ucl-cs.arpa (Stephen Crawley) (08/11/85)
While writing a program which uses various bits of information from
the proc table, I found the following oddity.
The <sys/proc.h> header file contains the following line :-
#define SLOGIN 0x0800000 /* a login process (legit child of init) */
However, ps -axl indicates that this bit is not set for any processes.
Indeed, grepping /sys/sys confirmed that SLOGIN isn't referenced anywhere.
While making sure that the flag gets set would seem to be straight forward,
I'm not convinced that it would be stunningly useful. [ What would be
more useful would be if the login shell pid were recorded in /etc/utmp! ]
I was wondering what this all means. Is this something that the 4.2
implementors dropped as being a bad idea? Or something that didn't get
finished in time? Are all login processes under 4.2 illegitimate?? :-) :-)
Stephen C. Crawley
ARPA: scc%cl.cam.ac.uk@ucl-cs.ARPA SMail: Cambridge Univ. Computer Lab.,
JANET: scc@uk.ac.cam.cl Corn Exchange Street,
UUCP: {ukc,kcl-cs}!cl-jenny!scc Cambridge CB2 3QG,
PHONE: +44 223 352 435 England.
p.s. No prizes for guessing what the program is supposed to do.jjg@security.UUCP (Jeff Glass) (08/13/85)
In article <607@brl-tgr.ARPA> scc%computer-lab.cambridge.ac.uk@ucl-cs.arpa (Stephen Crawley) writes: > The <sys/proc.h> header file contains the following line :- > > #define SLOGIN 0x0800000 /* a login process (legit child of init) */ > > However, ps -axl indicates that this bit is not set for any processes. > Indeed, grepping /sys/sys confirmed that SLOGIN isn't referenced anywhere. > While making sure that the flag gets set would seem to be straight forward, > I'm not convinced that it would be stunningly useful. [ What would be > more useful would be if the login shell pid were recorded in /etc/utmp! ] I think this method would be superior to the way that {c,}sh now find that they are login shells (checking if argv[0][0] == '-'). at least one security hole takes advantage of this. I also think Stephen's suggestion (putting the pid in utmp) is pretty neat. /jeff -- security!jjg@mitre-bedford.ARPA (MIL) {allegra,ihnp4,utzoo,philabs,uw-beaver}!linus!security!jjg (UUCP)
kre@ucbvax.ARPA (Robert Elz) (08/14/85)
In article <607@brl-tgr.ARPA>, scc%computer-lab.cambridge.ac.uk@ucl-cs.arpa (Stephen Crawley) writes: > The <sys/proc.h> header file contains the following line :- > > #define SLOGIN 0x0800000 /* a login process (legit child of init) */ > > However, ps -axl indicates that this bit is not set for any processes. Well, I hope its not set (on your, or any 4.2bsd or 4.3bsd system) but I assure you that it is set on my system (Melbourne Australia). > While making sure that the flag gets set would seem to be straight forward, > I'm not convinced that it would be stunningly useful. Well, it has its uses on my system - its related to the scheduling stuff that we have that requires the kernel to be able to detect when a user logs out (so it can send data to a daemon process waiting to record information about scheduling, so when he logs in again, minutes/hours/days/months later, things can be restored to their previous values (this is a gross simplification)). The flag is retained in proc.h so that no-one else will "accidentally" re-use the bit (or the name). Someday, perhaps, in the distant future, the Melbourne stuff might become a config option in 4.x bsd, just like the disc quota stuff is at the minute. Robert Elz kre@munnari.oz (Australia) seismo!munnari!kre (uucp) kre%munnari.oz@seimso.css.gov (arpa) (temporarily) ucvbax!kre or kre@ucbvax.berkeley.edu ps: I believe that I said much of this before, not very long ago...