From 3204a7fb98a3bccd0004ea0f2769fbeadc2c2dba Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sun, 28 Feb 2021 15:10:26 +0900 Subject: kbuild: prefix $(srctree)/ to some included Makefiles VPATH is used in Kbuild to make pattern rules search for prerequisites in both $(objtree) and $(srctree). Some of *.c, *.S files are not real sources, but generated by tools such as flex, bison, perl. In contrast, I doubt the benefit of --include-dir=$(abs_srctree) because it is always clear which Makefiles are real sources, and which are not. So, my hope is to add $(srctree)/ prefix to all check-in Makefiles, then remove --include-dir=$(abs_srctree) flag in the future. I am touching only some Kbuild core parts for now. Treewide fixes will be needed to achieve this goal. Signed-off-by: Masahiro Yamada --- scripts/Makefile.modpost | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'scripts/Makefile.modpost') diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index 066beffca09a..df57e259fac3 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -41,10 +41,10 @@ PHONY := __modpost __modpost: include include/config/auto.conf -include scripts/Kbuild.include +include $(srctree)/scripts/Kbuild.include # for ld_flags -include scripts/Makefile.lib +include $(srctree)/scripts/Makefile.lib MODPOST = scripts/mod/modpost \ $(if $(CONFIG_MODVERSIONS),-m) \ -- cgit v1.2.3 From 69bc8d386aebbd91a6bb44b6d33f77c8dfa9ed8c Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Fri, 26 Mar 2021 03:54:09 +0900 Subject: kbuild: generate Module.symvers only when vmlinux exists The external module build shows the following warning if Module.symvers is missing in the kernel tree. WARNING: Symbol version dump "Module.symvers" is missing. Modules may not have dependencies or modversions. I think this is an important heads-up because the resulting modules may not work as expected. This happens when you did not build the entire kernel tree, for example, you might have prepared the minimal setups for external modules by 'make defconfig && make modules_preapre'. A problem is that 'make modules' creates Module.symvers even without vmlinux. In this case, that warning is suppressed since Module.symvers already exists in spite of its incomplete content. The incomplete (i.e. invalid) Module.symvers should not be created. This commit changes the second pass of modpost to dump symbols into modules-only.symvers. The final Module.symvers is created by concatenating vmlinux.symvers and modules-only.symvers if both exist. Module.symvers is supposed to collect symbols from both vmlinux and modules. It might be a bit confusing, and I am not quite sure if it is an official interface, but presumably it is difficult to rename it because some tools (e.g. kmod) parse it. Signed-off-by: Masahiro Yamada --- scripts/Makefile.modpost | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) (limited to 'scripts/Makefile.modpost') diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index df57e259fac3..3f5b09a09aef 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -68,7 +68,20 @@ else ifeq ($(KBUILD_EXTMOD),) input-symdump := vmlinux.symvers -output-symdump := Module.symvers +output-symdump := modules-only.symvers + +quiet_cmd_cat = GEN $@ + cmd_cat = cat $(real-prereqs) > $@ + +ifneq ($(wildcard vmlinux.symvers),) + +__modpost: Module.symvers +Module.symvers: vmlinux.symvers modules-only.symvers FORCE + $(call if_changed,cat) + +targets += Module.symvers + +endif else -- cgit v1.2.3 From 5ab70ff4286f74732c082b65366bad39146d2b10 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Fri, 26 Mar 2021 03:54:10 +0900 Subject: kbuild: do not set -w for vmlinux.o modpost The -w option is meaningless for the first pass of modpost (vmlinux.o). We know there are unresolved symbols in vmlinux.o, hence we skip check_exports() and other checks when mod->is_vmlinux is set. See the following part in the for-loop. if (mod->is_vmlinux || mod->from_dump) continue; Signed-off-by: Masahiro Yamada --- scripts/Makefile.modpost | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'scripts/Makefile.modpost') diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index 3f5b09a09aef..b3e08fb1fd56 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -32,8 +32,6 @@ # Step 4 is solely used to allow module versioning in external modules, # where the CRC of each module is retrieved from the Module.symvers file. -# KBUILD_MODPOST_WARN can be set to avoid error out in case of undefined -# symbols in the final module linking stage # KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules. # This is solely useful to speed up test compiles @@ -50,7 +48,6 @@ MODPOST = scripts/mod/modpost \ $(if $(CONFIG_MODVERSIONS),-m) \ $(if $(CONFIG_MODULE_SRCVERSION_ALL),-a) \ $(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E) \ - $(if $(KBUILD_MODPOST_WARN),-w) \ -o $@ ifdef MODPOST_VMLINUX @@ -136,6 +133,11 @@ endif modules := $(sort $(shell cat $(MODORDER))) +# KBUILD_MODPOST_WARN can be set to avoid error out in case of undefined symbols +ifneq ($(KBUILD_MODPOST_WARN),) +MODPOST += -w +endif + # Read out modules.order to pass in modpost. # Otherwise, allmodconfig would fail with "Argument list too long". quiet_cmd_modpost = MODPOST $@ -- cgit v1.2.3 From 4475dff55c54d855ef0179a055b3ce20a9c1ab3e Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Fri, 26 Mar 2021 03:54:11 +0900 Subject: kbuild: fix false-positive modpost warning when all symbols are trimmed Nathan reports that the mips defconfig emits the following warning: WARNING: modpost: Symbol info of vmlinux is missing. Unresolved symbol check will be entirely skipped. This false-positive happens when CONFIG_TRIM_UNUSED_KSYMS is enabled, but no CONFIG option is set to 'm'. Commit a0590473c5e6 ("nfs: fix PNFS_FLEXFILE_LAYOUT Kconfig default") turned the last 'm' into 'y' for the mips defconfig, and uncovered this issue. In this case, the module feature itself is enabled, but we have no module to build. As a result, CONFIG_TRIM_UNUSED_KSYMS drops all the instances of EXPORT_SYMBOL. Then, modpost wrongly assumes vmlinux is missing because vmlinux.symvers is empty. (As another false-positive case, you can create a module that does not use any symbol of vmlinux). The current behavior is to entirely suppress the unresolved symbol warnings when vmlinux is missing just because there are too many. I found the origin of this code in the historical git tree. [1] If this is a matter of noisiness, I think modpost can display the first 10 warnings, and the number of suppressed warnings at the end. You will get a bit noisier logs when you run 'make modules' without vmlinux, but such warnings are better to show because you never know the resulting modules are actually loadable or not. This commit changes the following: - If any of input *.symver files is missing, pass -w option to let the module build keep going with warnings instead of errors. - If there are too many (10+) unresolved symbol warnings, show only the first 10, and also the number of suppressed warnings. [1]: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=1cc0e0529569bf6a94f6d49770aa6d4b599d2c46 Reported-by: Nathan Chancellor Signed-off-by: Masahiro Yamada --- scripts/Makefile.modpost | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'scripts/Makefile.modpost') diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index b3e08fb1fd56..c383ba33d837 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -98,9 +98,11 @@ output-symdump := $(KBUILD_EXTMOD)/Module.symvers endif +existing-input-symdump := $(wildcard $(input-symdump)) + # modpost options for modules (both in-kernel and external) MODPOST += \ - $(addprefix -i ,$(wildcard $(input-symdump))) \ + $(addprefix -i ,$(existing-input-symdump)) \ $(if $(KBUILD_NSDEPS),-d $(MODULES_NSDEPS)) \ $(if $(CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS)$(KBUILD_NSDEPS),-N) @@ -114,6 +116,7 @@ VPATH := $(input-symdump): @echo >&2 'WARNING: Symbol version dump "$@" is missing.' @echo >&2 ' Modules may not have dependencies or modversions.' + @echo >&2 ' You may get many unresolved symbol warnings.' ifdef CONFIG_LTO_CLANG # With CONFIG_LTO_CLANG, .o files might be LLVM bitcode, so we need to run @@ -134,7 +137,7 @@ endif modules := $(sort $(shell cat $(MODORDER))) # KBUILD_MODPOST_WARN can be set to avoid error out in case of undefined symbols -ifneq ($(KBUILD_MODPOST_WARN),) +ifneq ($(KBUILD_MODPOST_WARN)$(filter-out $(existing-input-symdump), $(input-symdump)),) MODPOST += -w endif -- cgit v1.2.3