On Thu, 16 Jul 2020 at 11:08, Luc Michel <luc.mic...@greensocs.com> wrote: > > When single-stepping with a debugger attached to QEMU, and when an > exception is raised, the debugger misses the first instruction after the > exception:
This is a long-standing bug; thanks for looking at it. (https://bugs.launchpad.net/qemu/+bug/757702) > diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c > index d95c4848a4..e85fab5d40 100644 > --- a/accel/tcg/cpu-exec.c > +++ b/accel/tcg/cpu-exec.c > @@ -502,10 +502,21 @@ static inline bool cpu_handle_exception(CPUState *cpu, > int *ret) > CPUClass *cc = CPU_GET_CLASS(cpu); > qemu_mutex_lock_iothread(); > cc->do_interrupt(cpu); > qemu_mutex_unlock_iothread(); > cpu->exception_index = -1; > + > + if (unlikely(cpu->singlestep_enabled)) { > + /* > + * After processing the exception, ensure an EXCP_DEBUG is > + * raised when single-stepping so that GDB doesn't miss the > + * next instruction. > + */ > + cpu->exception_index = EXCP_DEBUG; > + return cpu_handle_exception(cpu, ret); > + } I like the idea of being able to do this generically in the main loop. How about interrupts? If we are single-stepping and we take an interrupt I guess we want to stop before the first insn of the interrupt handler rather than after it, which would imply a similar change to cpu_handle_interrupt(). thanks -- PMM
