Re: hardcoded SIGSEGV in __die() ?

[Joakim Tjernlund <Joakim.Tjernlund@infinera.com>]

On Mon, 2020-03-23 at 16:31 +0100, Christophe Leroy wrote:
> 
> Le 23/03/2020 à 16:08, Joakim Tjernlund a écrit :
> > On Mon, 2020-03-23 at 15:45 +0100, Christophe Leroy wrote:
> > > CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
> > > 
> > > 
> > > Le 23/03/2020 à 15:43, Christophe Leroy a écrit :
> > > > Le 23/03/2020 à 15:17, Joakim Tjernlund a écrit :
> > > > > In __die(), see below, there is this call to notify_send() with
> > > > > SIGSEGV hardcoded, this seems odd
> > > > > to me as the variable "err" holds the true signal(in my case SIGBUS)
> > > > > Should not SIGSEGV be replaced with the true signal no.?
> > > > 
> > > > As far as I can see, comes from
> > > > https://nam03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcommit%2F%3Fid%3D66fcb1059&data=02%7C01%7CJoakim.Tjernlund%40infinera.com%7Cefe6d37a85e1494658ec08d7cf3f513f%7C285643de5f5b4b03a1530ae2dc8aaf77%7C1%7C0%7C637205743206770599&sdata=k8%2Bs7ifiCyuNzXuOhykjXUEtWzD62q3HGIIiavqE6%2FA%3D&reserved=0
> > > > 
> > > 
> > > And
> > > https://nam03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcommit%2F%3Fid%3Dae87221d3ce49d9de1e43756da834fd0bf05a2ad&data=02%7C01%7CJoakim.Tjernlund%40infinera.com%7Cefe6d37a85e1494658ec08d7cf3f513f%7C285643de5f5b4b03a1530ae2dc8aaf77%7C1%7C0%7C637205743206770599&sdata=oCU%2FMelrWDOCjmGOfVuNp2tM%2BwQ%2BRD25jzRWoGbHAew%3D&reserved=0
> > > shows it is (was?) similar on x86.
> > > 
> > 
> > I tried to follow that chain thinking it would end up sending a signal to user space but I cannot see
> > that happens. Seems to be related to debugging.
> > 
> > In short, I cannot see any signal being delivered to user space. If so that would explain why
> > our user space process never dies.
> > Is there a signal hidden in machine_check handler for SIGBUS I cannot see?
> > 
> 
> Isn't it done in do_exit(), called from oops_end() ?

hmm, so it seems. The odd thing though is that do_exit takes an exit code, not signal number.
Also, feels a bit odd to force an exit(that we haven't seen happening) rather than just a signal.

     Jocke