On Thu, Oct 3, 2024 at 1:44 PM Yonghong Song <yonghong.song@xxxxxxxxx> wrote: > > > Looks like the idea needs more thought. > > > > in_task_stack() won't recognize the private stack, > > so it will look like stack overflow and double fault. > > > > do you have CONFIG_VMAP_STACK ? > > Yes, my above test runs fine withCONFIG_VMAP_STACK. Let me guard private stack support with > CONFIG_VMAP_STACK for now. Not sure whether distributions enable > CONFIG_VMAP_STACK or not. Good! but I'm surprised it makes a difference. Please still root cause the crash without VMAP_STACK. We need to do a lot more homework here before proceeding. Look at arch/x86/kernel/dumpstack_64.c At least we need new stack_type for priv stack. stack_type_unknown doesn't inspire confidence. Need to make sure stack trace is still reliable with priv stack. Though it may look appealing from performance pov. We may need to go back to r9 approach with push/pop around calls, since that is surely keeping unwinder happy while this approach will have to teach unwinder.
