On Fri, Aug 12, 2016 at 07:23:03AM +0200, Borislav Petkov wrote: > On Fri, Aug 12, 2016 at 05:51:29AM +0200, Luis R. Rodriguez wrote: > > OK I've added CONFIG_BUILD_AVOID_BITROT. > > What does that do? Enabling it allows the forced compilation chosen by maintainers. Otherwise forced compilations with the new special targets are ignored. I've gone with table-obj-y and table-lib-y as we have to support both lib-y and obj-y respective targets. diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 33e2966dd741..7893e3b8da82 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1895,6 +1895,30 @@ config PROVIDE_OHCI1394_DMA_INIT See Documentation/debugging-via-ohci1394.txt for more information. +config BUILD_AVOID_BITROT + bool "Always force building specially annotated" + default y + help + If enabled then the the special table-* Makefile targets will always + be forced to be compiled even if their respective CONFIG_ option has + been disabled, but its objects will only be linked in if the same + respective CONFIG_ option has been enabled. This helps avoid code + bit rot issues, use for these targets should be carefully considred + by maintainers. You can safely enable this option at the expense of + increasing compile time slightly. Enabling this option helps avoid + code bit rot by taking advantage of the facilities provided and + enabled by using linker tables documented under: + + include/linux/tables.h + + The special targets supported are: + + o table-obj-y + o table-lib-y + + Say Y unless you are a grumpy maintainer and don't trust other + maintainer's judgements on what code should always get compiled. + config BUILD_DOCSRC bool "Build targets in Documentation/ tree" depends on HEADERS_CHECK diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 002857fe8d0d..17ced5ac44b2 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -91,7 +91,8 @@ modorder-target := $(obj)/modules.order # We keep a list of all modules in $(MODVERDIR) -__build: $(if $(KBUILD_BUILTIN),$(builtin-target) $(lib-target) $(extra-y) $(table-y)) \ +__build: $(if $(KBUILD_BUILTIN),$(builtin-target) $(lib-target) $(extra-y) \ + $(table-obj-y)) \ $(if $(KBUILD_MODULES),$(obj-m) $(modorder-target)) \ $(subdir-ym) $(always) @: @@ -325,8 +326,8 @@ cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $< $(obj)/%.o: $(src)/%.S $(objtool_obj) FORCE $(call if_changed_rule,as_o_S) -targets += $(real-objs-y) $(real-objs-m) $(lib-y) -targets += $(extra-y) $(table-y) $(MAKECMDGOALS) $(always) +targets += $(real-objs-y) $(real-objs-m) $(lib-y) $(table-lib-y) +targets += $(extra-y) $(table-obj-y) $(MAKECMDGOALS) $(always) # Linker scripts preprocessor (.lds.S -> .lds) # --------------------------------------------------------------------------- diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 494f215ebaa4..58db6b503aca 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -12,15 +12,14 @@ export KBUILD_SUBDIR_CCFLAGS := $(KBUILD_SUBDIR_CCFLAGS) $(subdir-ccflags-y) # Figure out what we need to build from the various variables # =========================================================================== -# Linker tables objects always wish to be built to avoid bit-rot in -# code, but only linked in *iff* they were enabled. We accomplish this -# using pegging linker table objects into extra-y, which forces -# compilation and then using the respective table-y and table-m as -# as hints for things we do want enabled. Objects which we want to -# avoid linking in will be in table-, not table-y and table-m. -extra-y += $(table-) -obj-m += $(table-m) -obj-y += $(table-y) +ifeq ($(CONFIG_BUILD_AVOID_BITROT),y) +extra-y += $(table-obj-) $(table-lib-) +endif + +obj-m += $(table-obj-m) +obj-y += $(table-obj-y) +lib-m += $(table-lib-m) +lib-y += $(table-lib-y) # When an object is listed to be built compiled-in and modular, # only build the compiled-in version @@ -82,8 +81,8 @@ real-objs-m := $(foreach m, $(obj-m), $(if $(strip $($(m:.o=-objs)) $($(m:.o=-y) # Add subdir path extra-y := $(addprefix $(obj)/,$(extra-y)) -table-y := $(addprefix $(obj)/,$(table-y)) -table-m := $(addprefix $(obj)/,$(table-m)) +table-obj-y := $(addprefix $(obj)/,$(table-obj-y)) +table-obj-m := $(addprefix $(obj)/,$(table-obj-m)) always := $(addprefix $(obj)/,$(always)) targets := $(addprefix $(obj)/,$(targets)) modorder := $(addprefix $(obj)/,$(modorder)) -- 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
