Re: [uml-devel] [REVIEW][PATCH 19/22] signal/um: Use force_sig_fault in relay_signal.

From: Eric W. Biederman
Date: Tue Apr 24 2018 - 12:01:23 EST

Sigh I should have Cc'd Martin Partel as well as this bit is his
original code.

Anton Ivanov <anton.ivanov@xxxxxxxxxxxxxxxxx> writes:

> Hi Richard,
> There was a post to uml-devel during the days when the sourceforge mailing list
> was working in random drop mode which claimed that "this fixes the arm build".
> I have not kept it locally and I do not see it the archive (I do not see a few
> other posts there either - including some of mine).
> The joys of having a broken list :(
> Whoever posted it, if you are reading it, please re-post again so we can have a
> look.
> In the meantime we are as you said - x86 only.

The only case I can see my changed relay_signal affecting on arm is the
nasty hach where errno is set in conjunction with trap_trace.

Having a second look I really don't understand what relay_signal is
trying to do.

The function relay_signal does not pass siginfo through unchanged.
The function relay_signal does not handle cases where si_code is
not SI_USER or SI_KERNEL, or any of the other signal independent

In my change I believe I have preserved the character of relay_signal of
just passing through the fault.

Still even after reading the commit that upgraded relay_signal to
preserve si_code and si_addr I really don't understand the intended

Am I missing something subtle or have the subtle details of siginfo just
always been ignored?

commit d3c1cfcdb43e023ab1b1c7a555cd9e929026500a
Author: Martin PÃrtel <martin.partel@xxxxxxxxx>
Date: Thu Aug 2 00:49:17 2012 +0200

um: pass siginfo to guest process

UML guest processes now get correct siginfo_t for SIGTRAP, SIGFPE,
SIGILL and SIGBUS. Specifically, si_addr and si_code are now correct
where previously they were si_addr = NULL and si_code = 128.

Signed-off-by: Martin PÃrtel <martin.partel@xxxxxxxxx>
Signed-off-by: Richard Weinberger <richard@xxxxxx>