On Mon, Nov 20, 2017 at 12:42 PM, Josh Poimboeuf <jpoim...@redhat.com> wrote: > On Mon, Nov 20, 2017 at 09:07:33AM -0800, Andy Lutomirski wrote: >> +bool in_SYSENTER_stack(unsigned long *stack, struct stack_info *info) > > Can you make it lowercase for consistency with the other in_*_stack() > functions? For example, in_irq_stack() is all lowercase even though > "IRQ" is normally written in uppercase. > > But also, I'm wondering whether this get_stack_info() support is even > really needed. > > As currently written, the trampoline code doesn't have any ORC data > associated with it. So the unwinder would never have the need to > actually read the SYSENTER stack. > > You _could_ add an UNWIND_HINT_IRET_REGS annotation after the simulated > iret frame is written, which would allow the unwinder to dump those regs > when unwinding from an NMI.
There's some ORC data in the non-trampoline SYSENTER path but, more importantly, the OOPS unwinder will just bail without this patch. With the patch, we get a valid unwind, except that everything has a ? in front. > > But there's only a tiny window where that would be possible: only a few > instructions. I'm not sure that would be worth the effort, unless we > got to the point where we expect to have 100% unwinder coverage. But > that's currently unrealistic anyway because of generated code and > runtime patching. I tripped it myself several times when debugging this code. > > -- > Josh
