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

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
......@@ -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)
......
......@@ -79,6 +79,36 @@ config HEADERS_CHECK
exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
your build tree), to make sure they're suitable.
config DEBUG_SECTION_MISMATCH
bool "Enable full Section mismatch analysis"
default n
help
The section mismatch analysis checks if there are illegal
references from one section to another section.
Linux will during link or during runtime drop some sections
and any use of code/data previously in these sections will
most likely result in an oops.
In the code functions and variables are annotated with
__init, __devinit etc. (see full list in include/linux/init.h)
which result in the code/data being placed in specific sections.
The section mismatch anaylsis are always done after a full
kernel build but enabling this options will in addition
do the following:
- Add the option -fno-inline-functions-called-once to gcc
When inlining a function annotated __init in a non-init
function we would loose the section information and thus
the analysis would not catch the illegal reference.
This options tell gcc to inline less but will also
result in a larger kernel.
- Run the section mismatch analysis for each module/built-in.o
When we run the section mismatch analysis on vmlinux.o we
looses valueable information about where the mismatch was
introduced.
Running the analysis for each module/built-in.o file
will tell where the mismatch happens much closer to the
source. The drawback is that we will report the same
mismatch at least twice.
config DEBUG_KERNEL
bool "Kernel debugging"
help
......
......@@ -103,6 +103,10 @@ ifneq ($(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)
......
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