Re: [PATCH 0/2] linux-user/s390x: Fix single-stepping SVC

[Thomas Huth]

On 11/05/2023 01.02, Ilya Leoshkevich wrote:
> Hi,
>
> I noticed that single-stepping SVC runs two instructions instead of
> one. The reason is that EXCP_SVC masks EXCP_DEBUG.
> Patch 1 fixes this problem, patch 2 adds a test.
>
> Btw, there is at least one more problem in that area, namely
> single-stepping instructions that cause e.g. SIGILL. Using the
> existing signals-s390x test as an example:
>
>      (gdb) x/i $pc
>      => 0x1001740 <illegal_op>:      .long   0x000007fe
>
>      (gdb) si
>      Program received signal SIGILL, Illegal instruction.
>      (gdb) x/i $pc
>      => 0x1001742 <after_illegal_op>:        br      %r14
>      # So far so good.
>
>      (gdb) si
>      (gdb) x/i $pc
>      => 0x10017b6 <handle_signal+6>: lay     %r15,-344(%r15)
>      # Missed the first signal handler instruction!
>
> I'm not sure what to do about it - the trivial fix to add
> gdb_handlesig(cpu, 0) to the end of handle_pending_signal() caused GDB
> to hang, and I haven't looked further yet.
>
> Best regards,
> Ilya
>
> Ilya Leoshkevich (2):
>    linux-user/s390x: Fix single-stepping SVC
>    tests/tcg/s390x: Test single-stepping SVC

If there are no disagreements, I can take this through my s390x tree. Queued 
it for my next pull request now.

 Thomas