Re: [Qemu-devel] [PATCH 0/2] linux-user: Don't call gdb_handlesig unnecessarily

[Peter Maydell]

Ping? This got reviewed but hasn't made it to master...

thanks
-- PMM

On 19 October 2018 at 18:49, Peter Maydell <address@hidden> wrote:
> This patchset fixes a minor bug in our handling of SIGTRAP
> in linux-user.
>
> The CPU main-loop routines for linux-user generally call
> gdb_handlesig() when they're about to queue a SIGTRAP signal.  This
> is wrong, because queue_signal() will cause us to pend a signal, and
> process_pending_signals() will then call gdb_handlesig() itself.  So
> the effect is that we notify gdb of the SIGTRAP, and then if gdb says
> "OK, continue with signal X" we will incorrectly notify gdb of the
> signal X as well.  We don't do this double-notify for anything else,
> only SIGTRAP.
>
> This bug only manifests if the user responds to the reported SIGTRAP
> using "signal SIGFOO" rather than "continue"; since the latter is the
> overwhelmingly common thing to do after a breakpoint most people
> won't have hit this.
>
> Patch 1 fixes this bug for every target except nios2, by
> deleting the incorrect code.
>
> Patch 2 fixes nios2 separately, because it was doing some odd
> things with gdb_handlesig(). This also fixes in passing a Coverity
> issue.
>
> Tested with "make check-tcg", and with some by-hand stepping
> around with an attached gdb. NB that the nios2 patch is only
> compile tested as I don't have a nios2 linux-user environment
> and check-tcg doesn't cover it.
>
> thanks
> -- PMM
>
> Peter Maydell (2):
>   linux-user: Don't call gdb_handlesig() before queue_signal()
>   linux-user: Clean up nios2 main loop signal handling
>
>  linux-user/aarch64/cpu_loop.c    | 13 +++++--------
>  linux-user/alpha/cpu_loop.c      | 12 ++++--------
>  linux-user/arm/cpu_loop.c        | 16 ++++------------
>  linux-user/cris/cpu_loop.c       | 16 ++++------------
>  linux-user/hppa/cpu_loop.c       | 11 ++++-------
>  linux-user/i386/cpu_loop.c       | 16 ++++------------
>  linux-user/m68k/cpu_loop.c       | 16 ++++------------
>  linux-user/microblaze/cpu_loop.c | 16 ++++------------
>  linux-user/mips/cpu_loop.c       | 16 ++++------------
>  linux-user/nios2/cpu_loop.c      | 14 +++++---------
>  linux-user/openrisc/cpu_loop.c   | 11 ++++-------
>  linux-user/ppc/cpu_loop.c        | 15 +++++----------
>  linux-user/riscv/cpu_loop.c      |  2 +-
>  linux-user/s390x/cpu_loop.c      |  9 +++------
>  linux-user/sh4/cpu_loop.c        | 17 ++++-------------
>  linux-user/sparc/cpu_loop.c      | 16 ++++------------
>  linux-user/xtensa/cpu_loop.c     | 11 ++++-------
>  17 files changed, 67 insertions(+), 160 deletions(-)