Re: [PATCH] linux-user/host/s390: Treat EX and EXRL as writes

[Thomas Huth <thuth@redhat.com>]

On 04/05/2022 13.48, Ilya Leoshkevich wrote:
> clang-built s390x branch-relative-long test fails on clang-built s390x
> QEMU due to the following sequence of events:
> 
> - The test zeroes out a code page, clang generates exrl+xc for this.
> 
> - do_helper_xc() is called. Clang generates exrl+xc there as well.
> 
> - Since there already exists a TB for the code in question, its page is
>    read-only and SIGSEGV is raised.
> 
> - host_signal_handler() calls host_signal_write() and the latter does
>    not recognize exrl as a write. Therefore page_unprotect() is not
>    called and the signal is forwarded to the test.
> 
> Fix by treating EXRL (and EX, just in case) as writes. There may be
> false positives, but they will lead only to an extra page_unprotect()
> call.
> 
> Reported-by: Thomas Huth <thuth@redhat.com>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> ---
>   linux-user/include/host/s390/host-signal.h | 7 +++++++
>   1 file changed, 7 insertions(+)

Great, this fixes the crash for me, indeed! Thank you!

Tested-by: Thomas Huth <thuth@redhat.com>