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

[Laurent Vivier]

Le 04/05/2022 à 13:48, Ilya Leoshkevich a écrit :
> 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(+)
>
> diff --git a/linux-user/include/host/s390/host-signal.h 
> b/linux-user/include/host/s390/host-signal.h
> index 6f191e64d7..25fefa00bd 100644
> --- a/linux-user/include/host/s390/host-signal.h
> +++ b/linux-user/include/host/s390/host-signal.h
> @@ -50,6 +50,7 @@ static inline bool host_signal_write(siginfo_t *info, 
> host_sigcontext *uc)
>       case 0x50: /* ST */
>       case 0x42: /* STC */
>       case 0x40: /* STH */
> +    case 0x44: /* EX */
>       case 0xba: /* CS */
>       case 0xbb: /* CDS */
>           return true;
> @@ -61,6 +62,12 @@ static inline bool host_signal_write(siginfo_t *info, 
> host_sigcontext *uc)
>               return true;
>           }
>           break;
> +    case 0xc6: /* RIL-b format insns */
> +        switch (pinsn[0] & 0xf) {
> +        case 0x0: /* EXRL */
> +            return true;
> +        }
> +        break;
>       case 0xc8: /* SSF format insns */
>           switch (pinsn[0] & 0xf) {
>           case 0x2: /* CSST */

Applied to my linux-user-for-7.1 branch.

Thanks,
Laurent