On 10/22, Ananth N Mavinakayanahalli wrote: > > On Wed, Oct 19, 2011 at 11:53:44PM +0200, Oleg Nesterov wrote: > > Finally, add UTASK_SSTEP_TRAPPED state/code to handle the case when > > xol insn itself triggers the signal. > > > > In this case we should restart the original insn even if the task is > > already SIGKILL'ed (say, the coredump should report the correct ip). > > This is even more important if the task has a handler for SIGSEGV/etc, > > The _same_ instruction should be repeated again after return from the > > signal handler, and SSTEP can never finish in this case. > > Oleg, > > Not sure I understand this completely... I hope you do not think I do ;) > When you say 'correct ip' you mean the original vaddr where we now have > a uprobe breakpoint and not the xol copy, right? Yes, > Coredump needs to report the correct ip, but should it also not report > correctly the instruction that caused the signal? Ergo, shouldn't we > put the original instruction back at the uprobed vaddr? OK, now I see what you mean. I was confused by the "restore the original instruction before _restart_" suggestion. Agreed! it would be nice to "hide" these int3's if we dump the core, but I think this is a bit off-topic. It makes sense to do this in any case, even if the core-dumping was triggered by another thread/insn. It makes sense to remove all int3's, not only at regs->ip location. But how can we do this? This is nontrivial. And. Even worse. Suppose that you do "gdb probed_application". Now you see int3's in the disassemble output. What can we do? I think we can do nothing, at least currently. This just reflects the fact that uprobe connects to inode, not to process/mm/etc. What do you think? Oleg. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>