Re: kern/50430: syscall_disestablish() can remove active syscalls

[christos%zoulas.com@localhost (Christos Zoulas)]

The following reply was made to PR kern/50430; it has been noted by GNATS.

From: christos%zoulas.com@localhost (Christos Zoulas)
To: Masao Uebayashi <uebayasi%gmail.com@localhost>
Cc: gnats-bugs%netbsd.org@localhost, kern-bug-people%netbsd.org@localhost, 
	gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost, 
	Paul Goyette <paul%whooppee.com@localhost>
Subject: Re: kern/50430: syscall_disestablish() can remove active syscalls
Date: Mon, 16 Nov 2015 08:10:01 -0500

 On Nov 16,  5:08pm, uebayasi%gmail.com@localhost (Masao Uebayashi) wrote:
 -- Subject: Re: kern/50430: syscall_disestablish() can remove active syscalls
 
 | On Mon, Nov 16, 2015 at 6:45 AM, Christos Zoulas <christos%zoulas.com@localhost> wrote:
 | > On Nov 15,  8:25pm, mrg%eterna.com.au@localhost (matthew green) wrote:
 | > -- Subject: re: kern/50430: syscall_disestablish() can remove active syscalls
 | >
 | > |  until bug is fixed, can we disable the autounload?
 | >
 | > Sure, that sounds prudent. It is difficult to fix properly. One way to do
 | > this would be to mark all lwps that have used compat syscalls with a bit
 | > depending on the module they have used, and refuse to unload the module
 | > until the lwp is gone.
 | >
 | > - when load a module that has compat syscalls, assign to it a bit.
 | > - mark a flags field of all syscalls that were loaded with that module
 | >   with that bit.
 | > - or the lwp flags with the syscall flags on each syscall.
 | > - when it is time to unload check that no lwp has that bit in the flags set.
 | > - instead of keeping l_sysent, keep l_sysmodflags or something.
 | 
 | What happens if signal handler does longjmp(3) and interrupted syscall
 | never returns?
 
 It does not matter. The flag is never cleared (even when that does not
 happen). Once an lwp executes a syscall from a compat module, that module
 cannot be unloaded until the lwp exits.
 
 christos