| Message ID | 1521166725-24157-8-git-send-email-yamada.masahiro@socionext.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | kbuild: various fix, clean-up, improvements of CONFIG_TRIM_UNUSED_KSYMS | expand |
On Fri, 16 Mar 2018, Masahiro Yamada wrote: > +# Recurse until adjust_autoksyms.sh is satisfied > +PHONY += autoksyms_recursive > +autoksyms_recursive: $(vmlinux-deps) > + $(Q)$(CONFIG_SHELL) $(srctree)/scripts/adjust_autoksyms.sh \ > "$(MAKE) -f $(srctree)/Makefile vmlinux" > -endif > > # For the kernel to actually contain only the needed exported symbols, > # we have to build modules as well to determine what those symbols are. > @@ -1034,7 +1024,13 @@ cmd_link-vmlinux = \ > $(CONFIG_SHELL) $< $(LD) $(LDFLAGS) $(LDFLAGS_vmlinux) ; \ > $(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true) > > -vmlinux: scripts/link-vmlinux.sh vmlinux_prereq $(vmlinux-deps) FORCE > +vmlinux: scripts/link-vmlinux.sh autoksyms_recursive $(vmlinux-deps) FORCE Don't you have to make the autoksyms_recursive dependency conditional on CONFIG_TRIM_UNUSED_KSYMS? Nicolas
2018-03-16 11:32 GMT+09:00 Nicolas Pitre <nicolas.pitre@linaro.org>: > On Fri, 16 Mar 2018, Masahiro Yamada wrote: > >> +# Recurse until adjust_autoksyms.sh is satisfied >> +PHONY += autoksyms_recursive >> +autoksyms_recursive: $(vmlinux-deps) >> + $(Q)$(CONFIG_SHELL) $(srctree)/scripts/adjust_autoksyms.sh \ >> "$(MAKE) -f $(srctree)/Makefile vmlinux" >> -endif >> >> # For the kernel to actually contain only the needed exported symbols, >> # we have to build modules as well to determine what those symbols are. >> @@ -1034,7 +1024,13 @@ cmd_link-vmlinux = \ >> $(CONFIG_SHELL) $< $(LD) $(LDFLAGS) $(LDFLAGS_vmlinux) ; \ >> $(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true) >> >> -vmlinux: scripts/link-vmlinux.sh vmlinux_prereq $(vmlinux-deps) FORCE >> +vmlinux: scripts/link-vmlinux.sh autoksyms_recursive $(vmlinux-deps) FORCE > > Don't you have to make the autoksyms_recursive dependency conditional on > CONFIG_TRIM_UNUSED_KSYMS? > Oops, I accidentally removed that conditional. I will fix it shortly. Thanks! -- Best Regards Masahiro Yamada
diff --git a/Makefile b/Makefile index 5fee703..3e871d2 100644 --- a/Makefile +++ b/Makefile @@ -998,21 +998,11 @@ export KBUILD_ALLDIRS := $(sort $(filter-out arch/%,$(vmlinux-alldirs)) arch Doc vmlinux-deps := $(KBUILD_LDS) $(KBUILD_VMLINUX_INIT) $(KBUILD_VMLINUX_MAIN) $(KBUILD_VMLINUX_LIBS) -# Include targets which we want to execute sequentially if the rest of the -# kernel build went well. If CONFIG_TRIM_UNUSED_KSYMS is set, this might be -# evaluated more than once. -PHONY += vmlinux_prereq -vmlinux_prereq: $(vmlinux-deps) FORCE -ifdef CONFIG_HEADERS_CHECK - $(Q)$(MAKE) -f $(srctree)/Makefile headers_check -endif -ifdef CONFIG_GDB_SCRIPTS - $(Q)ln -fsn $(abspath $(srctree)/scripts/gdb/vmlinux-gdb.py) -endif -ifdef CONFIG_TRIM_UNUSED_KSYMS - $(Q)$(CONFIG_SHELL) $(srctree)/scripts/adjust_autoksyms.sh \ +# Recurse until adjust_autoksyms.sh is satisfied +PHONY += autoksyms_recursive +autoksyms_recursive: $(vmlinux-deps) + $(Q)$(CONFIG_SHELL) $(srctree)/scripts/adjust_autoksyms.sh \ "$(MAKE) -f $(srctree)/Makefile vmlinux" -endif # For the kernel to actually contain only the needed exported symbols, # we have to build modules as well to determine what those symbols are. @@ -1034,7 +1024,13 @@ cmd_link-vmlinux = \ $(CONFIG_SHELL) $< $(LD) $(LDFLAGS) $(LDFLAGS_vmlinux) ; \ $(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true) -vmlinux: scripts/link-vmlinux.sh vmlinux_prereq $(vmlinux-deps) FORCE +vmlinux: scripts/link-vmlinux.sh autoksyms_recursive $(vmlinux-deps) FORCE +ifdef CONFIG_HEADERS_CHECK + $(Q)$(MAKE) -f $(srctree)/Makefile headers_check +endif +ifdef CONFIG_GDB_SCRIPTS + $(Q)ln -fsn $(abspath $(srctree)/scripts/gdb/vmlinux-gdb.py) +endif +$(call if_changed,link-vmlinux) # Build samples along the rest of the kernel
If CONFIG_TRIM_UNUSED_KSYMS is enabled and the kernel is built from a pristine state, the vmlinux is linked twice. [1] A user runs "make" [2] First build with empty autoksyms.h [3] adjust_autoksyms.sh updates autoksyms.h and recurses "make vmlinux" --------(begin sub-make)-------- [4] Second build with new autoksyms.h [5] link-vmlinux.sh is invoked because "vmlinux" is missing ---------(end sub-make)--------- [6] link-vmlinux.sh is invoked again despite "vmlinux" is up-to-date. The reason of [6] is probably because Make already decided to update "vmlinux" at the time of [2] because "vmlinux" was missing when Make built up the dependency graph. Because 'if_changed' is implemented based on '$?', this issue can be narrowed down to how Make handles '$?'. You can test it with the following simple code: [Test Makefile] A: B cp B A @echo newer prerequisite: $? B: C cp C B touch A [Result] $ rm -f A B $ touch C $ make cp C B touch A cp B A newer prerequisite: B Here, 'A' has been touched in the recipe of 'B'. So, the dependency 'A: B' has already been met before the recipe of 'A' is executed. However, Make does not notice the fact that the recipe of 'B' also updates 'A' as a side-effect. The situation is similar in this case; 'vmlinux' has actually been updated in the 'vmlinux_prereq' target. Make cannot predict this, so judges 'vmlinux' is old. link-vmlinus.sh is costly, so it is better to not run it when unneeded. Split CONFIG_TRIM_UNUSED_KSYMS recursion to a dedicated target. The reason of commit 2441e78b1919 ("kbuild: better abstract vmlinux sequential prerequisites") was to cater to CONFIG_BUILD_DOCSRC, but it was later removed by commit 184892925118 ("samples: move blackfin gptimers-example from Documentation"). Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> --- Changes in v2: - Discard my wrong change to adjust_autoksyms.sh - Add more commit log to explain how Make is working Makefile | 26 +++++++++++--------------- 1 file changed, 11 insertions(+), 15 deletions(-) -- 2.7.4