On Mon, Dec 06, 2021 at 11:02:05PM +0100, Salvatore Bonaccorso wrote: > Hi, > > On Mon, Dec 06, 2021 at 11:53:41AM -0800, Kees Cook wrote: > > On Sun, Dec 05, 2021 at 02:54:05AM +0900, Masahiro Yamada wrote: > > > On Sun, Dec 5, 2021 at 1:53 AM Linus Torvalds > > > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > On Sat, Dec 4, 2021 at 5:13 AM Salvatore Bonaccorso <carnil@xxxxxxxxxx> wrote: > > > > > > > > > > Andreas suggested to replace the > > > > > > > > > > KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH) > > > > > > > > > > with > > > > > > > > > > KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(patsubst "%",%,$(CONFIG_CC_IMPLICIT_FALLTHROUGH)) > > > > > > > > Ugh. I think the external build environment is a bit broken, but > > > > whatever. The above is ugly but I guess it works. > > > > > > > > Another alternative would be to make the Kconfig strings simply not > > > > have '"' as part of them. > > > > > > > > When you do > > > > > > > > a = "hello" > > > > print $a > > > > > > > > in any normal language, you generally wouldn't expect it to print the > > > > quotes, it should just print the bare word. > > > > > > > > But that's what the Kconfig string language basically does in this > > > > case. And I guess several users expect and take advantage of that ;( > > > > > > > > Masahiro? Comments? > > > > > > Yes, you get to the point. > > > > > > In fact, this is in my TODO list for a while > > > (and this is the reason I was doing prerequisite Kconfig refactoring > > > in the previous development cycle). > > > I will try to find some spare time to complete this work. > > > > > > > > > > > > Kconfig generates two similar files, > > > > > > - .config > > > - include/config/auto.conf > > > > > > Changing the format of the .config is presumably problematic > > > since it is the saved user configuration as well. > > > > > > It is possible (and more reasonable) to change include/config/auto.conf > > > so strings are not quoted. > > > > > > In Makefiles, quotations are just normal characters; they have no > > > special functionality. > > > > > > So, in Makefile context, it is more handy to do > > > > > > CONFIG_X=foo bar > > > > > > instead of > > > > > > CONFIG_X="foo bar" > > > > > > > > > > > > One problem is include/config/auto.conf is included not only by Makefiles > > > but also by shell scripts. > > > > > > > > > In shell context, the right hand side must be quoted > > > in case the value contains spaces. > > > > > > CONFIG_X="foo bar" > > > > > > > > > > > > My plan is to fix > > > scripts/link-vmlinux.sh > > > scripts/gen_autoksyms.sh > > > etc. to not directly include the auto.conf. > > > Later, change Kconfig to generate the auto.conf without "". > > > > > > > > > > > > In the meantime, > > > > > > KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(patsubst > > > "%",%,$(CONFIG_CC_IMPLICIT_FALLTHROUGH)) > > > > > > or if you prefer slightly shorter form, > > > > > > KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH:"%"=%) > > > > > > will be a workaround. > > > > It'll be nice to get this fixed. There are a few places where there is > > a test for a compiler flag in Kconfig, and then the option is repeated > > in the Makefile, due to the above quoting issues. For example: > > > > arch/arm64/Kconfig: > > config CC_HAS_BRANCH_PROT_PAC_RET > > # GCC 9 or later, clang 8 or later > > def_bool $(cc-option,-mbranch-protection=pac-ret+leaf) > > > > arch/arm64/Makefile: > > branch-prot-flags-$(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET) := -mbranch-protection=pac-ret+leaf > > > > > > I like the $(CONFIG_CC_IMPLICIT_FALLTHROUGH:"%"=%) solution: it's short. > > Does the following look correct, as well from formal style/commit > description? I have not yet done many contributions directly. Looks good to me; thanks! > > Regards, > Salvatore > > From c2d01ea3ee1c7cc539468bba5b25522245d513de Mon Sep 17 00:00:00 2001 > From: Salvatore Bonaccorso <carnil@xxxxxxxxxx> > Date: Mon, 6 Dec 2021 21:42:01 +0100 > Subject: [PATCH] Makefile: Do not quote value for > CONFIG_CC_IMPLICIT_FALLTHROUGH > > Andreas reported that a specific build environment for an external > module, being a bit broken, does pass CC_IMPLICIT_FALLTHROUGH quoted as > argument to gcc, causing an error > > gcc-11: error: "-Wimplicit-fallthrough=5": linker input file not found: No such file or directory > > Until this is more generally fixed as outlined in [1], by fixing > scripts/link-vmlinux.sh, scripts/gen_autoksyms.sh, etc to not directly > include the include/config/auto.conf, and in a second step, change > Kconfig to generate the auto.conf without "", workaround the issue by > explicitly unquoting CC_IMPLICIT_FALLTHROUGH. > > [1] https://lore.kernel.org/linux-kbuild/CAK7LNAR-VXwHFEJqCcrFDZj+_4+Xd6oynbj_0eS8N504_ydmyw@xxxxxxxxxxxxxx/ > > Reported-by: Andreas Beckmann <anbe@xxxxxxxxxx> > Link: https://bugs.debian.org/1001083 > Signed-off-by: Salvatore Bonaccorso <carnil@xxxxxxxxxx> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Does anyone have a preference as to who should take this? Gustavo, Marahiro, me, or Linus directly? -- Kees Cook
