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

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

Ping!

thanks
-- PMM

On 17 May 2016 at 15:18, Peter Maydell <peter.maydell@linaro.org> wrote:
> 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