On Wed, Feb 15, 2017 at 01:18:40PM +0100, Miroslav Benes wrote: > On Mon, 13 Feb 2017, Josh Poimboeuf wrote: > > > For live patching and possibly other use cases, a stack trace is only > > useful if it can be assured that it's completely reliable. Add a new > > save_stack_trace_tsk_reliable() function to achieve that. > > > > Note that if the target task isn't the current task, and the target task > > is allowed to run, then it could be writing the stack while the unwinder > > is reading it, resulting in possible corruption. So the caller of > > save_stack_trace_tsk_reliable() must ensure that the task is either > > 'current' or inactive. > > > > save_stack_trace_tsk_reliable() relies on the x86 unwinder's detection > > of pt_regs on the stack. If the pt_regs are not user-mode registers > > from a syscall, then they indicate an in-kernel interrupt or exception > > (e.g. preemption or a page fault), in which case the stack is considered > > unreliable due to the nature of frame pointers. > > > > It also relies on the x86 unwinder's detection of other issues, such as: > > > > - corrupted stack data > > - stack grows the wrong way > > - stack walk doesn't reach the bottom > > - user didn't provide a large enough entries array > > > > Such issues are reported by checking unwind_error() and !unwind_done(). > > > > Also add CONFIG_HAVE_RELIABLE_STACKTRACE so arch-independent code can > > determine at build time whether the function is implemented. > > > > Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> > > I do not see any difference from 4.1 version, so my > > Reviewed-by: Miroslav Benes <mbenes@xxxxxxx> Sorry, forgot to add your Reviewed-by from last time. The patch is indeed the same. Thanks! -- Josh -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
