On 04/29, Al Viro wrote: > > On Sun, Apr 29, 2012 at 06:41:55PM +0200, Oleg Nesterov wrote: > > > > Besides, at least on x86 tracehook_signal_handler's logic is not exactly > > right and should be fixed. > > Details, please... See http://marc.info/?t=127550678000005 and https://bugzilla.kernel.org/show_bug.cgi?id=16061 - the tracee reports a signal SIG - the tracer does ptrace(SINGLESTEP, SIG), this approves the signal and also sets TF - the tracee dequeues the signal, changes its IP to sig_handler(). then it notices TIF_SINGLESTEP and notifies the tracer without return to user-space _and_ without clearing TF or TIF_SINGLESTEP - the tracer does ptrace(SINGLESTEP) again, but now enable_single_step() looses TIF_FORCED_TF. - the tracer does ptrace(CONT), but user_disable_single_step() doesn't clear TF since TIF_FORCED_TF is not set - the tracee returns to user-space with X86_EFLAGS_TF in eflags Somehow we forgot about this bug... Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
