Let me show the simplified piece.
obj-m += test.o
KBUILD_CFLAGS := $(subst -pg,,$(KBUILD_CFLAGS))
all:
@echo $(KBUILD_CFLAGS)
$(MAKE) -C /lib/modules/`uname`/build M=$(PWD) modules
So if it's not a kbuild makefile, why the -pg flag can be successful removed through KBUILD_CFLAGS.
I objdump my test.o, there is not mcount inside. Opposite, with -pg every function inside test.o will be insert
a ftrace point.
Best regards,
Raphael
> On 2015-08-20 12:45, RaphaelWu@xxxxxxxxxxxxxx wrote:
> > Hi,
> >
> > I have seen this VAR used in some kernel module which also forbid ftrace.
> > but I was curious about whenever I echo $(KBUILD_CFLAGS), it's always
> empty.
> >
> > all:
> > @echo $(KBUILD_CFLAGS)
> > $(MAKE) -C /path-of-kernel/ M=$(PWD) modules
>
> This does not look like a kbuild makefile, so it does not see any
> KBUILD_* variables.
>
> Michal
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