On Fri, May 09, 2025 at 08:13:18AM +0900, Masahiro Yamada wrote: > On Fri, May 9, 2025 at 1:56 AM Kees Cook <k...@kernel.org> wrote: > > > > On Fri, May 09, 2025 at 01:44:09AM +0900, Masahiro Yamada wrote: > > > On Sun, May 4, 2025 at 2:37 AM Kees Cook <k...@kernel.org> wrote: > > > > > > > > On Sat, May 03, 2025 at 06:39:28PM +0900, Masahiro Yamada wrote: > > > > > On Sat, May 3, 2025 at 7:54 AM Kees Cook <k...@kernel.org> wrote: > > > > > > > > > > > > v2: > > > > > > - switch from -include to -I with a -D gated include > > > > > > compiler-version.h > > > > > > v1: > > > > > > https://lore.kernel.org/lkml/20250501193839.work.525-k...@kernel.org/ > > > > > > > > > > > > > > > What do you think of my patch as a prerequisite? > > > > > https://lore.kernel.org/linux-kbuild/20250503084145.1994176-1-masahi...@kernel.org/T/#u > > > > > Perhaps, can you implement this series more simply? > > > > > > > > > > My idea is to touch a single include/generated/global-rebuild.h > > > > > rather than multiple files such as gcc-plugins-deps.h, > > > > > integer-wrap.h, etc. > > > > > > > > > > When the file is touched, the entire kernel source tree will be > > > > > rebuilt. > > > > > This may rebuild more than needed (e.g. vdso) but I do not think > > > > > it is a big deal. > > > > > > > > This is roughly where I started when trying to implement this, but I > > > > didn't like the ergonomics of needing to scatter "touch" calls all over, > > > > which was especially difficult for targets that shared a build rule but > > > > may not all need to trigger a global rebuild. But what ultimately pushed > > > > me away from it was when I needed to notice if a non-built source file > > > > changed (the Clang .scl file), and I saw that I need to be dependency > > > > driven rather than target driven. (Though perhaps there is a way to > > > > address this with your global-rebuild.h?) > > > > > > > > As far as doing a full rebuild, if it had been available last week, I > > > > probably would have used it, but now given the work that Nicolas, you, > > > > and I have put into this, we have a viable way (I think) to make this > > > > more specific. It does end up being a waste of time/resources to rebuild > > > > stuff that doesn't need to be (efi-stub, vdso, boot code, etc), and that > > > > does add up when I'm iterating on something that keeps triggering a full > > > > rebuild. We already have to do the argument filtering for targets that > > > > don't want randstruct, etc, so why not capitalize on that and make the > > > > rebuild avoid those files too? > > > > > > > > > efi-stub, vdso are very small. > > > > > > Unless this turns out to be painful, I prefer > > > a simpler implementation. > > > > > > You will see how .scl file is handled. > > > > > > See the below code: > > > > > > > > > diff --git a/Kbuild b/Kbuild > > > index f327ca86990c..85747239314c 100644 > > > --- a/Kbuild > > > +++ b/Kbuild > > > @@ -67,10 +67,20 @@ targets += $(atomic-checks) > > > $(atomic-checks): $(obj)/.checked-%: include/linux/atomic/% FORCE > > > $(call if_changed,check_sha1) > > > > > > +rebuild-$(CONFIG_GCC_PLUGINS) += $(addprefix > > > scripts/gcc-plugins/, $(GCC_PLUGIN)) > > > +rebuild-$(CONFIG_RANDSTRUCT) += > > > include/generated/randstruct_hash.h > > > > These are in $(objtree) > > Yes. > > > > +rebuild-$(CONFIG_UBSAN_INTEGER_WRAP) += scripts/integer-wrap-ignore.scl > > > > This is in $(srctree) > > Yes. > > > > + > > > +quiet_cmd_touch = TOUCH $@ > > > + cmd_touch = touch $@ > > > + > > > +include/generated/global-rebuild.h: $(rebuild-y) > > > + $(call cmd,touch) > > > > Is this rule going to find the right versions of the dependencies? > > I think so, but please test it.
The patch was white-space damaged and wrapped, but I rebuilt it manually and it mostly works. There still seems to be some ordering issues, as some stuff gets rebuilt on a record build: # Clean the tree and pick an "everything" build $ make O=gcc-test clean allmodconfig -s # Make a target normally $ make O=gcc-test kernel/seccomp.o -s # Touch a gcc plugin that was in .config $ touch scripts/gcc-plugins/stackleak_plugin.c # Build and a full rebuild is triggered (good) $ make O=gcc-test kernel/seccomp.o make[1]: Entering directory '/srv/code/gcc-test' GEN Makefile DESCEND objtool HOSTCXX scripts/gcc-plugins/stackleak_plugin.so INSTALL libsubcmd_headers TOUCH include/generated/global-rebuild.h CC kernel/bounds.s CC arch/x86/kernel/asm-offsets.s CALL ../scripts/checksyscalls.sh CC kernel/seccomp.o make[1]: Leaving directory '/srv/code/gcc-test' # Build again, but more stuff gets built $ make O=gcc-test kernel/seccomp.o make[1]: Entering directory '/srv/code/gcc-test' GEN Makefile DESCEND objtool CC scripts/mod/empty.o CC scripts/mod/devicetable-offsets.s INSTALL libsubcmd_headers MKELF scripts/mod/elfconfig.h HOSTCC scripts/mod/modpost.o HOSTCC scripts/mod/sumversion.o HOSTCC scripts/mod/symsearch.o HOSTCC scripts/mod/file2alias.o HOSTLD scripts/mod/modpost CALL ../scripts/checksyscalls.sh make[1]: Leaving directory '/srv/code/gcc-test' # Third time finally everything is stable $ hmake O=gcc-test kernel/seccomp.o make[1]: Entering directory '/srv/code/gcc-test' GEN Makefile DESCEND objtool CALL ../scripts/checksyscalls.sh INSTALL libsubcmd_headers make[1]: Leaving directory '/srv/code/gcc-test' Note that scripts/mod/* gets rebuilt on the second rebuild. -- Kees Cook
