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

[Peter Maydell <peter.maydell@linaro.org>]

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.

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