Messages in this thread | | | Date | Wed, 20 May 2015 18:52:23 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v4 0/3] Compile-time stack frame pointer validation |
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On Wed, May 20, 2015 at 11:25:37AM -0500, Josh Poimboeuf wrote: > > I've never quite understood what the '?' means. > > It basically means "here's a function address we found on the stack, > which may or may not have been called." It's needed because stack > walking isn't currently 100% reliable.
Yeah, that was not that trivial to figure out at the time:
unsigned long print_context_stack(struct thread_info *tinfo, ...
if (__kernel_text_address(addr)) { if ((unsigned long) stack == bp + sizeof(long)) { ops->address(data, addr, 1); frame = frame->next_frame; bp = (unsigned long) frame; } else { ops->address(data, addr, 0); }
and that ops->address is
print_trace_address() |-> printk_stack_address()
So if I'm understanding this correctly, if rBP+8 is equal to rSP, i.e. return address is on the stack, then this frame got called.
Otherwise -> "?".
I might be missing something though...
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
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