Hi. 2018年9月27日(木) 2:57 Nadav Amit <namit@xxxxxxxxxx>: > > at 1:58 AM, Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx> wrote: > > > On 2018-09-18 23:28, Nadav Amit wrote: > > > >> diff --git a/arch/x86/Makefile b/arch/x86/Makefile > >> index 8f6e7eb8ae9f..944fa3bc9376 100644 > >> --- a/arch/x86/Makefile > >> +++ b/arch/x86/Makefile > >> @@ -214,8 +214,8 @@ ifdef CONFIG_X86_64 > >> KBUILD_LDFLAGS += $(call ld-option, -z max-page-size=0x200000) > >> endif > >> > >> -# Speed up the build > >> -KBUILD_CFLAGS += -pipe > >> +# We cannot use -pipe flag since we give an additional .s file to the compiler > >> +#KBUILD_CFLAGS += -pipe > > > > Is this really necessary? The gas manual says that one can use -- to > > name stdin, though that's probably a typo and should just be - . Doing > > > > gcc -pipe -Wa,foo.s -Wa,- > > Good idea. I didn’t think of it. Yes, this can do the trick. I’ll do it in > v9. > > > does seem to work as expected (and would also make it possible to append > > some .s file should that ever be required). > >> +archmacros: > >> + $(Q)$(MAKE) $(build)=arch/x86/kernel arch/x86/kernel/macros.s > >> + > >> +ASM_MACRO_FLAGS = -Wa,arch/x86/kernel/macros.s > >> +export ASM_MACRO_FLAGS > >> +KBUILD_CFLAGS += $(ASM_MACRO_FLAGS) > > How does this affect what gets rebuilt when one of the asm/foo.h files > > going into macros.s changes? Does that cause a global rebuild because > > everything depends on macros.s, or do we still only rebuild the files > > that actually include asm/foo.h? > > There will not be a global rebuild. Any source file that uses the header > files that are included in macros.S will be rebuilt. > > But your question actually raises two issues: > > 1. If macros.S changes, there *should* be a global rebuild, Looking at this series, I can see this rule: "macros and inline functions that calls them are placed in the same header". For example, REFCOUNT_CHECK_LE_ZERO is defined in <asm/refcount.h>, and REFCOUNT_CHECK_LE_ZERO is invoked via refcount_sub_and_test() etc. in the same header. Therefore, all users of REFCOUNT_CHECK_LE_ZERO must have included <asm/refcount.h> This means all C files using REFCOUNT_CHECK_LE_ZERO will be appropriately recompiled as long as the rule above is observed. > and currently > there wouldn’t be one. Do you happen to know what would be the appropriate > way to trigger one? > > 2. Someone might mistakenly use the macros through inline assembly without > including the header file. Right, it is possible to use REFCOUNT_CHECK_LE_ZERO directly. If this happens, my assumption breaks. It would be unlikely to happen, though... > It would be better to detect such cases and fail > the build. I may be able to create another asm macro in the C part of the > header that would cause the build to fail. But let me know if you any > better idea. > > Regards, > Nadav > -- Best Regards Masahiro Yamada
