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ecab4115c4
`rustc` (like Cargo) may take advantage of the jobserver at any time (e.g. for backend parallelism, or eventually frontend too). In the kernel, we call `rustc` with `-Ccodegen-units=1` (and `-Zthreads` is 1 so far), so we do not expect parallelism. However, in the upcoming Rust 1.76.0, a warning is emitted by `rustc` [1] when it cannot connect to the jobserver it was passed (in many cases, but not all: compiling and `--print sysroot` do, but `--version` does not). And given GNU Make always passes the jobserver in the environment variable (even when a line is deemed non-recursive), `rustc` will end up complaining about it (in particular in Make 4.3 where there is only the simple pipe jobserver style). One solution is to remove the jobserver from `MAKEFLAGS`. However, we can mark the lines with calls to `rustc` (and Cargo) as recursive, which looks simpler. This is being documented as a recommendation in `rustc` [2] and allows us to be ready for the time we may use parallelism inside `rustc` (potentially now, if a user passes `-Zthreads`). Thus do so. Similarly, do the same for `rustdoc` and `cargo` calls. Finally, there is one case that the solution does not cover, which is the `$(shell ...)` call we have. Thus, for that one, set an empty `MAKEFLAGS` environment variable. Link: https://github.com/rust-lang/rust/issues/120515 [1] Acked-by: Masahiro Yamada <masahiroy@kernel.org> Link: https://github.com/rust-lang/rust/pull/121564 [2] Link: https://lore.kernel.org/r/20240217002638.57373-1-ojeda@kernel.org [ Reworded to add link to PR documenting the recommendation. ] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
163 lines
5.9 KiB
Makefile
163 lines
5.9 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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# LEX
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# ---------------------------------------------------------------------------
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quiet_cmd_flex = LEX $@
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cmd_flex = $(LEX) -o$@ -L $<
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$(obj)/%.lex.c: $(src)/%.l FORCE
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$(call if_changed,flex)
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# YACC
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# ---------------------------------------------------------------------------
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quiet_cmd_bison = YACC $(basename $@).[ch]
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cmd_bison = $(YACC) -o $(basename $@).c --defines=$(basename $@).h -t -l $<
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$(obj)/%.tab.c $(obj)/%.tab.h: $(src)/%.y FORCE
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$(call if_changed,bison)
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# ==========================================================================
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# Building binaries on the host system
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# Binaries are used during the compilation of the kernel, for example
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# to preprocess a data file.
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#
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# Both C and C++ are supported, but preferred language is C for such utilities.
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# Rust is also supported, but it may only be used in scenarios where a Rust
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# toolchain is required to be available (e.g. when `CONFIG_RUST` is enabled).
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#
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# Sample syntax (see Documentation/kbuild/makefiles.rst for reference)
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# hostprogs := bin2hex
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# Will compile bin2hex.c and create an executable named bin2hex
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#
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# hostprogs := lxdialog
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# lxdialog-objs := checklist.o lxdialog.o
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# Will compile lxdialog.c and checklist.c, and then link the executable
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# lxdialog, based on checklist.o and lxdialog.o
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#
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# hostprogs := qconf
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# qconf-cxxobjs := qconf.o
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# qconf-objs := menu.o
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# Will compile qconf as a C++ program, and menu as a C program.
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# They are linked as C++ code to the executable qconf
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#
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# hostprogs := target
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# target-rust := y
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# Will compile `target` as a Rust program, using `target.rs` as the crate root.
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# The crate may consist of several source files.
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# C code
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# Executables compiled from a single .c file
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host-csingle := $(foreach m,$(hostprogs), \
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$(if $($(m)-objs)$($(m)-cxxobjs)$($(m)-rust),,$(m)))
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# C executables linked based on several .o files
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host-cmulti := $(foreach m,$(hostprogs),\
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$(if $($(m)-cxxobjs)$($(m)-rust),,$(if $($(m)-objs),$(m))))
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# Object (.o) files compiled from .c files
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host-cobjs := $(sort $(foreach m,$(hostprogs),$($(m)-objs)))
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# C++ code
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# C++ executables compiled from at least one .cc file
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# and zero or more .c files
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host-cxxmulti := $(foreach m,$(hostprogs),$(if $($(m)-cxxobjs),$(m)))
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# C++ Object (.o) files compiled from .cc files
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host-cxxobjs := $(sort $(foreach m,$(host-cxxmulti),$($(m)-cxxobjs)))
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# Rust code
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# Executables compiled from a single Rust crate (which may consist of
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# one or more .rs files)
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host-rust := $(foreach m,$(hostprogs),$(if $($(m)-rust),$(m)))
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host-csingle := $(addprefix $(obj)/,$(host-csingle))
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host-cmulti := $(addprefix $(obj)/,$(host-cmulti))
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host-cobjs := $(addprefix $(obj)/,$(host-cobjs))
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host-cxxmulti := $(addprefix $(obj)/,$(host-cxxmulti))
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host-cxxobjs := $(addprefix $(obj)/,$(host-cxxobjs))
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host-rust := $(addprefix $(obj)/,$(host-rust))
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#####
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# Handle options to gcc. Support building with separate output directory
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hostc_flags = -Wp,-MMD,$(depfile) \
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$(KBUILD_HOSTCFLAGS) $(HOST_EXTRACFLAGS) \
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$(HOSTCFLAGS_$(target-stem).o)
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hostcxx_flags = -Wp,-MMD,$(depfile) \
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$(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
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$(HOSTCXXFLAGS_$(target-stem).o)
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# `--out-dir` is required to avoid temporaries being created by `rustc` in the
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# current working directory, which may be not accessible in the out-of-tree
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# modules case.
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hostrust_flags = --out-dir $(dir $@) --emit=dep-info=$(depfile) \
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-Clinker-flavor=gcc -Clinker=$(HOSTCC) \
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-Clink-args='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
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$(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
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$(HOSTRUSTFLAGS_$(target-stem))
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# $(objtree)/$(obj) for including generated headers from checkin source files
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ifeq ($(KBUILD_EXTMOD),)
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ifdef building_out_of_srctree
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hostc_flags += -I $(objtree)/$(obj)
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hostcxx_flags += -I $(objtree)/$(obj)
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endif
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endif
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#####
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# Compile programs on the host
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# Create executable from a single .c file
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# host-csingle -> Executable
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quiet_cmd_host-csingle = HOSTCC $@
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cmd_host-csingle = $(HOSTCC) $(hostc_flags) $(KBUILD_HOSTLDFLAGS) -o $@ $< \
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$(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem))
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$(host-csingle): $(obj)/%: $(src)/%.c FORCE
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$(call if_changed_dep,host-csingle)
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# Link an executable based on list of .o files, all plain c
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# host-cmulti -> executable
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quiet_cmd_host-cmulti = HOSTLD $@
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cmd_host-cmulti = $(HOSTCC) $(KBUILD_HOSTLDFLAGS) -o $@ \
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$(addprefix $(obj)/, $($(target-stem)-objs)) \
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$(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem))
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$(host-cmulti): FORCE
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$(call if_changed,host-cmulti)
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$(call multi_depend, $(host-cmulti), , -objs)
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# Create .o file from a single .c file
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# host-cobjs -> .o
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quiet_cmd_host-cobjs = HOSTCC $@
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cmd_host-cobjs = $(HOSTCC) $(hostc_flags) -c -o $@ $<
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$(host-cobjs): $(obj)/%.o: $(src)/%.c FORCE
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$(call if_changed_dep,host-cobjs)
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# Link an executable based on list of .o files, a mixture of .c and .cc
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# host-cxxmulti -> executable
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quiet_cmd_host-cxxmulti = HOSTLD $@
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cmd_host-cxxmulti = $(HOSTCXX) $(KBUILD_HOSTLDFLAGS) -o $@ \
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$(foreach o,objs cxxobjs,\
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$(addprefix $(obj)/, $($(target-stem)-$(o)))) \
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$(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem))
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$(host-cxxmulti): FORCE
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$(call if_changed,host-cxxmulti)
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$(call multi_depend, $(host-cxxmulti), , -objs -cxxobjs)
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# Create .o file from a single .cc (C++) file
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quiet_cmd_host-cxxobjs = HOSTCXX $@
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cmd_host-cxxobjs = $(HOSTCXX) $(hostcxx_flags) -c -o $@ $<
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$(host-cxxobjs): $(obj)/%.o: $(src)/%.cc FORCE
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$(call if_changed_dep,host-cxxobjs)
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# Create executable from a single Rust crate (which may consist of
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# one or more `.rs` files)
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# host-rust -> Executable
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quiet_cmd_host-rust = HOSTRUSTC $@
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cmd_host-rust = \
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$(HOSTRUSTC) $(hostrust_flags) --emit=link=$@ $<
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$(host-rust): $(obj)/%: $(src)/%.rs FORCE
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+$(call if_changed_dep,host-rust)
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targets += $(host-csingle) $(host-cmulti) $(host-cobjs) \
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$(host-cxxmulti) $(host-cxxobjs) $(host-rust)
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