Re: [PATCH v4 0/3] Compile-time stack frame pointer validation

Josh Poimboeuf
2015-05-22T22:22:56Z

On Fri, May 22, 2015 at 11:18:57PM +0200, Jiri Kosina wrote:
> On Fri, 22 May 2015, Josh Poimboeuf wrote:
>
> > Hm, alternatives do complicate things a bit. It *is* a false positive,
> > but not necessarily because its part of an alternative instruction
> > block.
> >
> > The above code would be patched into memmove(), which is a leaf function
> > because it doesn't call any other functions. Leaf functions don't need
> > frame pointer logic, so we can ignore them.
> >
> > If instead the above code were patched into a non-leaf function, we'd
> > have to change it to restore the frame pointer before returning.
>
> Is this really only a problem of alternatives? How about
> dynamically-enabled tracepoints?

I think tracepoints are only in C code, right? stackvalidate only
analyzes asm code, so it's not a concern for this patch set.

And I think tracepoints rely on normal call instructions, so they
shouldn't cause any problems with frame pointers as far as I can tell.

--
Josh