Re: [Qemu-devel] [PATCH 0/6] linux-user: Handle SEGV on signal entry/exit correctly

[Riku Voipio]

On Thu, Jul 28, 2016 at 04:44:44PM +0100, Peter Maydell wrote:
> This patchset fixes bugs in our handling of failure to read
> or write guest memory on entry and exit from a signal handler.
> This is supposed to cause a SIGSEGV, but the guest is permitted
> a chance to handle the SIGSEGV (assuming it wasn't generated
> in the course of trying to enter a SIGSEGV handler in the first
> place). Our current implementation makes the SIGSEGV always
> fatal, regardless of whether the guest had a signal handler
> set up for it.
> 
> The main cause of this bug is that our implementation of
> force_sig() had drifted away from the semantics of the kernel
> function of that name, so the series renames that to
> dump_core_and_abort(), and provides a force_sig() that just
> queues a synchronous signal to be taken in the usual way.
> 
> The patchset sits on top of my various other pending linux-user
> fixes. There are getting to be quite a lot of those now, so
> you can find them and this patchset at:
> 
> https://git.linaro.org/people/peter.maydell/qemu-arm.git linux-fixes
> 
> The test program I used is at
> http://people.linaro.org/~peter.maydell/sigaltstack.c
> (NB: contains a magic constant that will need tweaking for
> non-x86 guests); it arranges to take a SIGSEGV while trying to
> take a SIGUSR1.
> 
> Although this is a bugfix, it's for a fairly obscure corner
> case, so we might want to defer this to 2.8.

Applied to linux-user que, thanks!
 
> thanks
> -- PMM
> 
> Peter Maydell (6):
>   linux-user: Recheck for pending synchronous signals too
>   linux-user: Pass si_type information to queue_signal() explicitly
>   linux-user: SIGSEGV on signal entry need not be fatal
>   linux-user: ARM: Give SIGSEGV if signal frame setup fails
>   linux-user: SIGSEGV from sigreturn need not be fatal
>   linux-user: Implement force_sigsegv() via force_sig()
> 
>  linux-user/main.c    | 124 ++++++++++++++++-----------------
>  linux-user/qemu.h    |   3 +-
>  linux-user/signal.c  | 189 
> ++++++++++++++++++++++++++++++---------------------
>  linux-user/syscall.c |   6 +-
>  4 files changed, 180 insertions(+), 142 deletions(-)
> 
> -- 
> 1.9.1
>