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: Sam Ravnborg <sam@ravnborg.org>
diff --git a/Makefile b/Makefile
index 6847464..8533f25 100644
--- a/Makefile
+++ b/Makefile
@@ -520,6 +520,11 @@
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)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 14fb355..748e72b 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -79,6 +79,36 @@
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
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index db38ef4..67fb453 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -103,6 +103,10 @@
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 @@
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=-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)