[Qemu-devel] [PATCH v2 0/6] user-exec: cpu_resume_from_signal() cleanups

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

I was trying to reason about user-mode's handling of signal masks,
and I found our current code a bit confusing, so I cleaned it up.

At the moment for user-only mode cpu_resume_from_signal() takes a
usercontext pointer; if this is non-NULL then it has some awkward
OS and CPU specific code to set the signal mask from something
inside the usercontext before doing the same kind of siglongjmp()
that the softmmu cpu_resume_from_signal() does.

In fact the two use cases are completely separate:
 * almost all calls to cpu_resume_from_signal() pass a NULL puc
   argument (and most of those are softmmu-only anyway)
 * only the code path handle_cpu_signal -> page_unprotect ->
   tb_invalidate_phys_page -> cpu_resume_from_signal will pass
   a non-NULL puc.

The cleanups are:
 * pull the call to cpu_resume_from_signal() up through the
   callstack so we do the signal mask manipulation in
   handle_cpu_signal()
 * drop the OS/CPU spceific code to get a signal mask out of
   a usercontext, because in the specific case of handle_cpu_signal()
   we already have the signal mask value and can just use it
 * rename cpu_resume_from_signal() to cpu_loop_exit_noexc(),
   since all the remaining callsites are not in fact signal handlers
   or even called from signal handlers
 * get rid of an ugly TARGET_I386 ifdef in user-exec.c by moving
   the i386-specific code into its handle_mmu_fault hook.

Changes v1->v2:
 * patches 1-4 are the same and already reviewed
 * patch 5 is new, and just adds a clarifying comment to
   do_interrupt_user()
 * patch 6 is the old patch 5, and now sets env->exception_next_eip
   to -1 as a clear indication that the value is not going to be used
   (as noted in the comment in the new patch 5)

thanks
-- PMM


Peter Maydell (6):
  translate-all.c: Don't pass puc, locked to tb_invalidate_phys_page()
  user-exec: Push resume-from-signal code out to handle_cpu_signal()
  cpu-exec: Rename cpu_resume_from_signal() to cpu_loop_exit_noexc()
  user-exec: Don't reextract sigmask from usercontext pointer
  target-i386: Add comment about do_interrupt_user() next_eip argument
  target-i386: Move user-mode exception actions out of user-exec.c

 cpu-exec-common.c        |  8 ++---
 exec.c                   |  2 +-
 hw/i386/kvmvapic.c       |  2 +-
 include/exec/exec-all.h  |  2 +-
 target-i386/bpt_helper.c |  2 +-
 target-i386/helper.c     |  2 ++
 target-i386/seg_helper.c |  6 +++-
 target-lm32/helper.c     |  2 +-
 target-s390x/helper.c    |  2 +-
 target-xtensa/helper.c   |  2 +-
 translate-all.c          | 40 ++++++++++++---------
 translate-all.h          |  2 +-
 user-exec.c              | 93 +++++++++++++++++++++---------------------------
 13 files changed, 82 insertions(+), 83 deletions(-)

-- 
1.9.1