• Stephen Warren's avatar
    test/py: support running sandbox under gdbserver · 89ab8410
    Stephen Warren authored
    Implement command--line option --gdbserver COMM, which does two things:
    
    a) Run the sandbox process under gdbserver, using COMM as gdbserver's
       communication channel.
    
    b) Disables all timeouts, so that if U-Boot is halted under the debugger,
       tests don't fail. If the user gives up in the middle of a debugging
       session, they can simply CTRL-C the test script to abort it.
    
    This allows easy debugging of test failures without having to manually
    re-create the failure conditions. Usage is:
    
    Window 1:
    ./test/py/test.py --bd sandbox --gdbserver localhost:1234
    
    Window 2:
    gdb ./build-sandbox/u-boot -ex 'target remote localhost:1234'
    
    When using this option, it likely makes sense to use pytest's -k option
    to limit the set of tests that are executed.
    
    Simply running U-Boot directly under gdb (rather than gdbserver) was
    also considered. However, this was rejected because:
    
    a) gdb's output would then be processed by the test script, and likely
       confuse it causing false failures.
    
    b) pytest by default hides stdout from tests, which would prevent the
       user from interacting with gdb.
    
       While gdb can be told to redirect the debugee's stdio to a separate
       PTY, this would appear to leave gdb's stdio directed at the test
       scripts and the debugee's stdio directed elsewhere, which is the
       opposite of the desired effect. Perhaps some complicated PTY muxing
       and process hierarchy could invert this. However, the current scheme
       is simple to implement and use, so it doesn't seem worth complicating
       matters.
    
    c) Using gdbserver allows arbitrary debuggers to be used, even those with
       a GUI. If the test scripts invoked the debugger themselves, they'd have
       to know how to execute arbitary applications. While the user could hide
       this all in a wrapper script, this feels like extra complication.
    
    An interesting future idea might be a --gdb-screen option, which could
    spawn both U-Boot and gdb separately, and spawn the screen into a newly
    created window under screen. Similar options could be envisaged for
    creating a new xterm/... too.
    
    --gdbserver  currently only supports sandbox, and not real hardware.
    That's primarily because the test hooks are responsible for all aspects of
    hardware control, so there's nothing for the test scripts themselves can
    do to enable gdbserver on real hardware. We might consider introducing a
    separate --disable-timeouts option to support use of debuggers on real
    hardware, and having --gdbserver imply that option.
    Signed-off-by: default avatarStephen Warren <swarren@nvidia.com>
    89ab8410
conftest.py 13.6 KB