Re: [Qemu-devel] [PATCH 0/5] linux-user: Support signal passing for targets having more signals than host

[Peter Maydell]

On Wed, 22 May 2019 at 19:57, Aleksandar Markovic
<address@hidden> wrote:
>
> From: Aleksandar Markovic <address@hidden>
>
> Most of the targets (including Intel) define 64 signals. This
> creates difficulties for targets that define, for example, 128
> signals. This series adds support for signal passing even if
> the host defines less signals than the target.

Could you elaborate a bit on how much functionality
is provided for signal numbers which the target has
but the host does not? For instance, it seems likely
that attempts by the guest to kill(other_pid, sig) will
fail if sig is not in the supported-by-the-target range.
But is it possible for the guest process to deliver
one of these signals to itself ?

This patchset is interesting because in fact pretty much
every target supports more signals than our host code
can provide, because the host libc steals several
signals for its own purposes and QEMU can't use them.
Being able to multiplex several guest signals onto
one host signal might let us run some guest binaries
we currently can't handle correctly.

thanks
-- PMM