Re: [Qemu-devel] [PATCH] linux-user: SIGSEGV protection on host/guest signal masks

[Alex Barcelo <abarcelo@ac.upc.edu>]

>> +
>> +/*
>> + * Use SETSIGNAL and GETSIGNAL macros for SIGSEGV protection.
>> + *
>> + * This should protect SIGSEGV unconscious manipulations from guest apps
>> + * (but we still do not let the emulated software play the signal game)
>> + */
>> +#define SETSIGNAL(set) sigdelset( (set), SIGSEGV)
>> +#define GETSIGNAL(get) sigaddset( (get), SIGSEGV)
>> +
>
> I think we could probably structure this in a cleaner way. I think
> it would be better to define and use a wrapper for sigprocmask() which
> was a "do/emulate sigprocmask in way that is safe for guest" (call it
> do_sigprocmask, put it in signal.c). Then we could start with a really
> simple version that just prevents the guest trying to fiddle with
> SIGSEGV, and extend it later to better emulation if necessary (eg
> storing the actual guest signal mask in TaskState so we can emulate
> delivery or otherwise in process_pending_signals(), and so we can
> report the correct thing if the guest later tries to read back the
> signal mask).

Ok, I couldn't find a good way to do this. A sigprocmask wrapper seems
a good idea.


> Note that another place the guest can set the signal mask is via
> sigreturn.

Noted, will check it and add wrapping.