Re: [PATCH] x86/dumpstack/64: Add guard pages to stack_info

On Thu, Sep 16, 2021 at 10:00:15AM +0200, Peter Zijlstra wrote:

On Thu, Sep 16, 2021 at 11:47:49AM +0800, 王贇 wrote:

quoted

I did some debug and found the issue, we are missing:

@@ -122,7 +137,10 @@ static __always_inline bool in_exception_stack(unsigned long *stack, struct stac
        info->type      = ep->type;
        info->begin     = (unsigned long *)begin;
        info->end       = (unsigned long *)end;
-       info->next_sp   = (unsigned long *)regs->sp;
+
+       if (!(ep->type & STACK_TYPE_GUARD))
+               info->next_sp   = (unsigned long *)regs->sp;
+
        return true;
 }

as the guard page are not working as real stack I guess?

Correct, but I thought I put if (type & GUARD) terminators in all paths
that ended up caring about ->next_sp. Clearly I seem to have missed one
:/

Let me try and figure out where that happens.

Oh, I'm an idiot... yes it tries to read regs the stack, but clearly
that won't work for the guard page.