On Tue, Feb 2, 2021 at 6:13 AM Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote: > > On Fri, Jan 29, 2021 at 08:17:51AM +0900, Masahiro Yamada wrote: > > [3] > > Peterz already pointed out asm-goto as an example of ABI mismatch. > > > > I remember a trouble reported in the past due > > to the mismatch of -mstack-protector-guard-offset. > > > > https://bugzilla.kernel.org/show_bug.cgi?id=201891 > > > > This has already been fixed, > > and it will no longer happen though. > > This is kind of concerning though. It would be nice to somehow store > KCLAGS in the config and warn if it changes unexpectedly. > > This can be a problem not only for OOT modules, but for regular kernel > builds which have a .config copied from somewhere. > > Because of the toolchain-dependent kconfig options, features can > silently disappear if the toolchain doesn't support them, due to a > different compiler version, or even a missing library. > > > [2] > > > > As for this patch, it is wrong to do this check in the Makefile > > parse stage. > > > > "make M=... clean" > > "make M=... help" > > > > etc. will fail. > > Such targets do not require the compiler in the first place. > > > > This check must be done before starting building something, > > > > Also, this patch is not applicable. > > gcc-version.sh and clang-version.sh do not exist. > > See linux-next. > > Something like so? No, I do not think so. > > diff --git a/Makefile b/Makefile > index 95ab9856f357..10ca621369fb 100644 > --- a/Makefile > +++ b/Makefile > @@ -1721,12 +1721,25 @@ KBUILD_MODULES := 1 > > build-dirs := $(KBUILD_EXTMOD) > PHONY += modules > -modules: $(MODORDER) > +modules: ext_compiler_check $(MODORDER) For the single thread build, yes GNU Make will run the targets from left to right, so ext_compiler_check is run before compiling any build artifact. If -j <N> option is given, there is no guarantee that ext_compiler_check finishes first. > $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost > > $(MODORDER): descend > @: > > +orig_name := $(if $(CONFIG_CC_IS_GCC),GCC,CLANG) > +orig_minor := $(shell expr $(if $(CONFIG_CC_IS_GCC),$(CONFIG_GCC_VERSION),$(CONFIG_CLANG_VERSION)) / 100) > +cur_namever := $(shell $(srctree)/scripts/cc-version.sh $(CC)) > +cur_name := $(word 1,$(cur_namever)) > +cur_minor := $(shell expr $(word 2,$(cur_namever)) / 100) These are still calculated by 'make M=... clean' or 'make M=... help'. Using '=' assignment solves it, but the code is still ugly. I attached my alternative implementation. > +PHONY += ext_compiler_check > +ext_compiler_check: > + @if [ $(orig_name) != $(cur_name) ] || [ $(orig_minor) != $(cur_minor) ]; then \ > + echo >&2 "warning: The compiler differs from the version which was used to build the kernel."; \ > + echo >&2 "warning: Some kernel features are compiler-dependent."; \ > + echo >&2 "warning: It's recommended that you change your compiler to match the version in the .config file."; \ > + fi > + > PHONY += modules_install > modules_install: _emodinst_ _emodinst_post > > -- Best Regards Masahiro Yamada
From 8152c47d19cab5af361d097fcb939a4e8ecefa28 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada <masahiroy@kernel.org> Date: Fri, 5 Mar 2021 14:10:26 +0900 Subject: [PATCH] kbuild: show notice if a different compiler is used for external module build This commit shows a notice unless the compiler is exactly the same. notice: the compiler differs from the one used to build the kernel The kernel was built by: gcc (GCC) 10.0.1 20200328 (Red Hat 10.0.1-0.11) You are using: gcc (GCC) 10.2.1 20201125 (Red Hat 10.2.1-9) Check the difference, and determine if you are OK with that. If you believe mixing two compilers is OK, please proceed at your risk. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> --- Makefile | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/Makefile b/Makefile index a3336d9b4a22..e592456673a3 100644 --- a/Makefile +++ b/Makefile @@ -1779,6 +1779,16 @@ clean-dirs := $(KBUILD_EXTMOD) clean: rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps \ $(KBUILD_EXTMOD)/compile_commands.json $(KBUILD_EXTMOD)/.thinlto-cache +PHONY += prepare +# now expand this into a simple variable to reduce the cost of shell evaluations +prepare: CC_VERSION_TEXT := $(CC_VERSION_TEXT) +prepare: + @if [ "$(CC_VERSION_TEXT)" != $(CONFIG_CC_VERSION_TEXT) ]; then \ + echo "notice: the compiler differs from the one used to build the kernel"; \ + echo " The kernel was built by: "$(CONFIG_CC_VERSION_TEXT); \ + echo " You are using: $(CC_VERSION_TEXT)"; \ + fi + PHONY += help help: @echo ' Building external modules.' @@ -1790,7 +1800,7 @@ help: @echo '' # no-op for external module builds -PHONY += prepare modules_prepare +PHONY += modules_prepare endif # KBUILD_EXTMOD -- 2.27.0
