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Commit 91341d4b authored by Sam Ravnborg's avatar Sam Ravnborg
Browse files

kbuild: introduce new option to enhance section mismatch analysis 



Setting the option DEBUG_SECTION_MISMATCH will
report additional section mismatch'es but this
should in the end makes it possible to get rid of
all of them.

See help text in lib/Kconfig.debug for details.

Signed-off-by: default avatarSam Ravnborg <sam@ravnborg.org>
parent eb8f6890

Makefile

+5 −0
Original line number Diff line number Diff line
@@ -520,6 +520,11 @@ KBUILD_CFLAGS += -g 
KBUILD_AFLAGS	+= -gdwarf-2

endif



# We trigger additional mismatches with less inlining

ifdef CONFIG_DEBUG_SECTION_MISMATCH

KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)

endif



# Force gcc to behave correct even for buggy distributions

KBUILD_CFLAGS         += $(call cc-option, -fno-stack-protector)

lib/Kconfig.debug

+30 −0
Original line number Diff line number Diff line
@@ -79,6 +79,36 @@ config HEADERS_CHECK 
	  exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in

	  your build tree), to make sure they're suitable.



config DEBUG_SECTION_MISMATCH

	bool "Enable full Section mismatch analysis"

	default n

	help

	  The section mismatch analysis checks if there are illegal

	  references from one section to another section.

	  Linux will during link or during runtime drop some sections

	  and any use of code/data previously in these sections will

	  most likely result in an oops.

	  In the code functions and variables are annotated with

	  __init, __devinit etc. (see full list in include/linux/init.h)

	  which result in the code/data being placed in specific sections.

	  The section mismatch anaylsis are always done after a full

	  kernel build but enabling this options will in addition

	  do the following:

	  - Add the option -fno-inline-functions-called-once to gcc

	    When inlining a function annotated __init in a non-init

	    function we would loose the section information and thus

	    the analysis would not catch the illegal reference.

	    This options tell gcc to inline less but will also

	    result in a larger kernel.

	  - Run the section mismatch analysis for each module/built-in.o

	    When we run the section mismatch analysis on vmlinux.o we

	    looses valueable information about where the mismatch was

	    introduced.

	    Running the analysis for each module/built-in.o file

	    will tell where the mismatch happens much closer to the

	    source. The drawback is that we will report the same

	    mismatch at least twice.



config DEBUG_KERNEL

	bool "Kernel debugging"

	help

scripts/Makefile.build

+7 −2
Original line number Diff line number Diff line
@@ -103,6 +103,10 @@ ifneq ($(KBUILD_CHECKSRC),0) 
  endif

endif



# Do section mismatch analysis for each module/built-in.o

ifdef CONFIG_DEBUG_SECTION_MISMATCH

  cmd_secanalysis = ; scripts/mod/modpost $@

endif



# Compile C sources (.c)

# ---------------------------------------------------------------------------
@@ -268,7 +272,8 @@ ifdef builtin-target 
quiet_cmd_link_o_target = LD      $@

# If the list of objects to link is empty, just create an empty built-in.o

cmd_link_o_target = $(if $(strip $(obj-y)),\

		      $(LD) $(ld_flags) -r -o $@ $(filter $(obj-y), $^),\

		      $(LD) $(ld_flags) -r -o $@ $(filter $(obj-y), $^) \

		      $(cmd_secanalysis),\

		      rm -f $@; $(AR) rcs $@)



$(builtin-target): $(obj-y) FORCE
@@ -316,7 +321,7 @@ $($(subst $(obj)/,,$(@:.o=-objs))) \ 
$($(subst $(obj)/,,$(@:.o=-y)))), $^)

 

quiet_cmd_link_multi-y = LD      $@

cmd_link_multi-y = $(LD) $(ld_flags) -r -o $@ $(link_multi_deps)

cmd_link_multi-y = $(LD) $(ld_flags) -r -o $@ $(link_multi_deps) $(cmd_secanalysis)



quiet_cmd_link_multi-m = LD [M]  $@

cmd_link_multi-m = $(cmd_link_multi-y)