Messages in this thread Patch in this message | | | Date | Wed, 25 Jan 2023 17:49:42 -0800 | From | Josh Poimboeuf <> | Subject | Re: [PATCH v3 3/3] objtool: Alter how HOSTCC is forced |
| |
On Thu, Jan 05, 2023 at 01:01:55AM -0800, Ian Rogers wrote: > HOSTCC is always wanted when building objtool. Setting CC to HOSTCC > happens after tools/scripts/Makefile.include is included, meaning > flags are set assuming say CC is gcc, but then it can be later set to > HOSTCC which may be clang. tools/scripts/Makefile.include is needed > for host set up and common macros in objtool's Makefile. Rather than > override CC to HOSTCC, just pass CC as HOSTCC to Makefile.build, the > libsubcmd builds and the linkage step. This means the Makefiles don't > see things like CC changing and tool flag determination, and similar, > work properly.
I'm having trouble parsing this last sentence, can you rephrase or restructure it?
> To avoid mixing CFLAGS from different compilers just > the objtool CFLAGS are determined with the exception of > EXTRA_WARNINGS.
I'm not really sure what this one means either.
> HOSTCFLAGS is added to these so that command line > flags can add to the CFLAGS.
Overall this patch description is a big wall of dense text which I found hard to decipher. Please split it up into paragraphs and make it more legible and logical.
For example, un-jumble the ordering, with the background first, then the problem(s), then the fix(es). (At least three paragraphs)
If possible, the subject should describe the end result for the user, something like
objtool: Fix HOSTCFLAGS cmdline support
... unless I'm misunderstanding the point of the patch.
HOSTCFLAGS from the cmdline *used* to work, a git bisect shows it stopped working with
96f14fe738b6 ("kbuild: Rename HOSTCFLAGS to KBUILD_HOSTCFLAGS")
... so please add a "Fixes" tag for that commit.
> +MAKE = make -S
Why?
> LIBSUBCMD_DIR = $(srctree)/tools/lib/subcmd/ > ifneq ($(OUTPUT),) > LIBSUBCMD_OUTPUT = $(abspath $(OUTPUT))/libsubcmd > @@ -37,12 +33,19 @@ INCLUDES := -I$(srctree)/tools/include \ > -I$(srctree)/tools/objtool/arch/$(SRCARCH)/include \ > -I$(LIBSUBCMD_OUTPUT)/include > WARNINGS := $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -Wno-packed -Wno-nested-externs > -CFLAGS := -Werror $(WARNINGS) $(KBUILD_HOSTCFLAGS) -g $(INCLUDES) $(LIBELF_FLAGS) > -LDFLAGS += $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS) > +OBJTOOL_CFLAGS := -Werror $(WARNINGS) -g $(INCLUDES) $(LIBELF_FLAGS) $(HOSTCFLAGS)
I *think* I understand the reason for the switch from KBUILD_HOSTCFLAGS to HOSTCFLAGS -- because KBUILD_HOSTCFLAGS is defined in the top-level kernel Makefile which isn't included here so it's undefined? -- but regardless that should be called out more explicitly as a problem being fixed in the commit log.
This issue really has me scratching my head, as I could have sworn objtool was being built with -O2.
> +OBJTOOL_LDFLAGS := $(LIBELF_LIBS) $(LIBSUBCMD)
Is there a reason to not include $(HOSTLDFLAGS) here?
> # Allow old libelf to be used: > elfshdr := $(shell echo '$(pound)include <libelf.h>' | $(CC) $(CFLAGS) -x c -E - | grep elf_getshdr) > -CFLAGS += $(if $(elfshdr),,-DLIBELF_USE_DEPRECATED) > +OBJTOOL_CFLAGS += $(if $(elfshdr),,-DLIBELF_USE_DEPRECATED) > + > +# Always want host compilation. > +HOST_OVERRIDES := CC="$(HOSTCC)" EXTRA_CFLAGS="$(OBJTOOL_CFLAGS)" \ > + LD="$(HOSTLD)" AR="$(HOSTAR)" > +BUILD_HOST_OVERRIDES := CC="$(HOSTCC)" CFLAGS="$(OBJTOOL_CFLAGS)" \ > + LD="$(HOSTLD)" LDFLAGS="$(OBJTOOL_LDFLAGS)" \ > + AR="$(HOSTAR)"
Maybe it depends on your perspective, but I'm thinking that some of these aren't really overrides, but rather normal expected flags. And the distinction between these two variables is muddy: it's not only Build vs non-Build, but also objtool vs libsubcmd.
How about just
HOST_OVERRIDES := CC="$(HOSTCC) "LD="$(HOSTLD)" AR="$(HOSTAR)"
And then specifying the {EXTRA_}CFLAGS and LDFLAGS below where needed.
> AWK = awk > MKDIR = mkdir > @@ -65,10 +68,11 @@ include $(srctree)/tools/build/Makefile.include > > $(OBJTOOL_IN): fixdep FORCE > $(Q)$(CONFIG_SHELL) ./sync-check.sh > - $(Q)$(MAKE) $(build)=objtool > + $(Q)$(MAKE) $(build)=objtool $(BUILD_HOST_OVERRIDES) > + > > $(OBJTOOL): $(LIBSUBCMD) $(OBJTOOL_IN) > - $(QUIET_LINK)$(CC) $(OBJTOOL_IN) $(LDFLAGS) -o $@ > + $(QUIET_LINK)$(HOSTCC) $(OBJTOOL_IN) $(KBUILD_HOSTLDFLAGS) $(OBJTOOL_LDFLAGS) -o $@
Does KBUILD_HOSTLDFLAGS even work here?
-- Josh
| |