This allows debugged real-time processes to execute crucial operations right before and after being stopped by a debugger. Such operations can include pausing physical devices and resuming them in an ordered manner so that no harm is caused to the outer world while debugging takes place and the real-time process can resume normally after the debugging session. It may also involve informing cooperating processes about the ongoing debug session.
The model chosen for this is dedicating a real-time thread to this task. This has the advantage of isolating the thread a bit from the debugged contexts and also avoids having to introduce any kind of asynchronous signaling mechanism. The helper thread will register itself with the core and then run a loop, waiting for the next stop or resume event. At the point the helper receives such an event, all other real-time threads in the process have been stopped or not yet resumed so that the helper cannot interact with them nor should wait for resources they may have locked. The helper thread may also migrate to secondary mode before releasing control, usually only after/before all time-sensitive operations are executed. These patches have a very long (likely too long) internal history at Siemens, thus have shown to be useful at least for one of our use cases. Jan Jan Kiszka (3): cobalt/kernel: Introduce XNDBGCTRL to block SIGINT/SIGSTOP cobalt: Add ptrace debugging helper interface testsuite/smokey/gdb: Add test cases for ptrace-based debugging helper include/cobalt/Makefile.am | 1 + include/cobalt/ptrace.h | 37 +++++++++++ include/cobalt/uapi/Makefile.am | 1 + include/cobalt/uapi/kernel/thread.h | 1 + include/cobalt/uapi/ptrace.h | 24 +++++++ include/cobalt/uapi/syscall.h | 2 + kernel/cobalt/posix/process.c | 34 +++++++++- kernel/cobalt/posix/process.h | 5 ++ kernel/cobalt/posix/syscall.c | 98 ++++++++++++++++++++++++++++- lib/cobalt/Makefile.am | 1 + lib/cobalt/ptrace.c | 91 +++++++++++++++++++++++++++ testsuite/smokey/gdb/gdb.c | 84 ++++++++++++++++++++++++- 12 files changed, 374 insertions(+), 5 deletions(-) create mode 100644 include/cobalt/ptrace.h create mode 100644 include/cobalt/uapi/ptrace.h create mode 100644 lib/cobalt/ptrace.c -- 2.26.2
