On Fri, 2012-04-27 at 14:11 -0700, H. Peter Anvin wrote: > On 04/27/2012 01:57 PM, Steven Rostedt wrote: > >> > >> Except it is the wrong thing. This is not the only user of frame > >> pointer. What I think you mean is remove the dependency in Kconfig, but > >> force the frame pointer enabled if -mfentry is not supported. > > > > You mean option 3? > > > > 3) Add frame pointers silently if gcc fails to build with gcc -pg. > > > > Yes, your option 3. > Actually, I just noticed this in the Makefile: ifdef CONFIG_FRAME_POINTER KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls else # Some targets (ARM with Thumb2, for example), can't be built with frame # pointers. For those, we don't have FUNCTION_TRACER automatically # select FRAME_POINTER. However, FUNCTION_TRACER adds -pg, and this is # incompatible with -fomit-frame-pointer with current GCC, so we don't use # -fomit-frame-pointer with FUNCTION_TRACER. ifndef CONFIG_FUNCTION_TRACER KBUILD_CFLAGS += -fomit-frame-pointer endif endif Because of ARM thumb2, -fomit-frame-pointer is not added if CONFIG_FRAME_POINTER is not set and FUNCTION_TRACER is. As it is fine to just use '-pg', which gcc will add frame pointers if needed, and it is only a problem if both -pg and -fomit-frame-pointer is set. We only need to remove the select without doing anything else. If -mfentry is added with -pg, and -fno-omit-frame-pointer is not set, gcc will not add frame pointers by default. So it seems that gcc took care of this problem for me :-) I'll go and make a patch that simply removes the select. Sorry for the noise ;-) -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
