On Tue, Apr 28, 2015 at 09:04:54AM -0500, Josh Poimboeuf wrote: > On Tue, Apr 28, 2015 at 02:16:06PM +0200, Peter Zijlstra wrote: > > On Mon, Apr 27, 2015 at 08:56:27AM -0500, Josh Poimboeuf wrote: > > > Frame pointer based stack traces aren't always reliable. One big reason > > > is that most asm functions don't set up the frame pointer. > > > > > > Fix that by enforcing that all asm functions honor CONFIG_FRAME_POINTER. > > > This is done with a new stackvalidate host tool which is automatically > > > run for every compiled .S file and which validates that every asm > > > function does the proper frame pointer setup. > > > > Would it make sense (maybe as an additional CONFIG_*_DEBUG thing) to > > also process the output of GCC with this tool? To both double check GCC > > and to give the tool more input? > > I tried that, but I discovered that gcc's usage of frame pointers would > be a lot harder to validate. It only sets up the frame pointer in code > paths which have call instructions. There are a lot of functions which > have conditional jumps at the beginning which can jump straight to a > return instruction without first doing the frame pointer setup. Hmm, would not such code break your patching? -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
