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Date: Mon, 20 Jun 2016 14:00:42 +0200 (CEST)
From: Igmar Palsenberg <igmar@...senberg.com>
To: musl@...ts.openwall.com
Subject: Re: abort() fails to terminate PID 1 process
> > First, processes kan install handlers, which might
> > instruct the kernel to ignore the signal. SIGABORT can be ignored. I don't
>
> abort() should terminate the process even if SIGABRT is ignored.
That rule doesn't apply to pid 1 by default. Pid 1 should be a proper init
system, not a full blows application that makes the system blow up on
every error.
> > expect my process to be SIGILL'ed next because of this (which, can also be
> > ignored).
> > Libc should NOT mess with these kind of things, that's up to the
> > application.
>
> the glibc fallbacks are
>
> change signal mask and set default handling for SIGABRT
> raise(SIGABRT);
> "abort instruction" (segfault, sigtrap or sigill depending on target)
> _exit(127);
> infinite loop
Pid 1 is an exception to all of this.
> http://sourceware.org/git/?p=glibc.git;a=blob;f=stdlib/abort.c;h=155d70b0647e848f1d40fc0e3b15a2914d7145c0;hb=HEAD
>
> on x86 glibc, pid 1 would terminate with SIGSEGV
> (unless there is a segfault handler).
>
> the musl logic is explained in
>
> http://git.musl-libc.org/cgit/musl/commit/?id=2557d0ba47286ed3e868f8ddc9dbed0942fe99dc
>
> neither of them is correct because it is not possible to
> exit with the right status in general.
>
> SIGKILL can only be ignored by pid 1 whose exit status is
> not supposed to be observable so musl may want to have a
> fallback after it since the pid namespace thing is nowadays
> widely abused on linux.
Well, normally abort() does some signal magic, and then raises again.
Which is what POSIX mandates I think.
If you're pid 1 however, you should behave like one.
Igmar
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