• Pedro Alves's avatar
    gdb+gdbserver/Linux: avoid reading registers while going through shell · a9deee17
    Pedro Alves authored
    For every stop, Linux GDB and GDBserver save the stopped thread's PC,
    in lwp->stop_pc.  This is done in save_stop_reason, in both
    gdb/linux-nat.c and gdbserver/linux-low.cc.  However, while we're
    going through the shell after "run", in startup_inferior, we shouldn't
    be reading registers, as we haven't yet determined the target's
    architecture -- the shell's architecture may not even be the same as
    the final inferior's.
    
    In gdb/linux-nat.c, lwp->stop_pc is only needed when the thread has
    stopped for a breakpoint, and since when going through the shell, no
    breakpoint is going to hit, we could simply teach save_stop_reason to
    only record the stop pc when the thread stopped for a breakpoint.
    
    However, in gdbserver/linux-low.cc, lwp->stop_pc is used in more cases
    than breakpoint hits (e.g., it's used in tracepoints & the
    "while-stepping" feature).
    
    So to avoid GDB vs GDBserver divergence, we apply the same approach to
    both implementations.
    
    We set a flag in the inferior (process in GDBserver) whenever it is
    being nursed through the shell, and when that flag is set,
    save_stop_reason bails out early.  While going through the shell,
    we'll only ever get process exits (normal or signalled), random
    signals, and exec events, so nothing is lost.
    
    Change-Id: If0f01831514d3a74d17efd102875de7d2c6401ad
    a9deee17