There has been a long-standing request to support building external
modules in a separate build directory.
This commit introduces a new environment variable, KBUILD_EXTMOD_OUTPUT,
and its shorthand Make variable, MO.
A simple usage:
$ make -C <kernel-dir> M=<module-src-dir> MO=<module-build-dir>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Flex and Bison are used only for host programs. Move their intermediate
target processing from scripts/Makefile.build to scripts/Makefile.host.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Use $(obj)/ instead of $(src)/ prefix when building C++ modules for
host, as explained in commit b1992c3772 ("kbuild: use $(src) instead
of $(srctree)/$(src) for source directory"). This fixes build failures
of 'xconfig':
$ make O=build/ xconfig
make[1]: Entering directory '/data/linux/kbuild-review/build'
GEN Makefile
make[3]: *** No rule to make target '../scripts/kconfig/qconf-moc.cc', needed by 'scripts/kconfig/qconf-moc.o'. Stop.
Fixes: b1992c3772 ("kbuild: use $(src) instead of $(srctree)/$(src) for source directory")
Reported-by: Rolf Eike Beer <eb@emlix.com>
Signed-off-by: Nicolas Schier <n.schier@avm.de>
Tested-by: Rolf Eike Beer <eb@emlix.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Kbuild conventionally uses $(obj)/ for generated files, and $(src)/ for
checked-in source files. It is merely a convention without any functional
difference. In fact, $(obj) and $(src) are exactly the same, as defined
in scripts/Makefile.build:
src := $(obj)
Before changing the semantics of $(src) in the next commit, this commit
replaces $(obj)/ with $(src)/ in pattern rules where the prerequisite
might be a generated file.
C, assembly, Rust, and DTS files are sometimes generated by tools, so
they could be either generated files or real sources. The $(obj)/ prefix
works for both cases with the help of VPATH.
As mentioned above, $(obj) and $(src) are the same at this point, hence
this commit has no functional change.
I did not modify scripts/Makefile.userprogs because there is no use
case where userspace C files are generated.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
`rustc` (like Cargo) may take advantage of the jobserver at any time
(e.g. for backend parallelism, or eventually frontend too). In the kernel,
we call `rustc` with `-Ccodegen-units=1` (and `-Zthreads` is 1 so far),
so we do not expect parallelism. However, in the upcoming Rust 1.76.0, a
warning is emitted by `rustc` [1] when it cannot connect to the jobserver
it was passed (in many cases, but not all: compiling and `--print sysroot`
do, but `--version` does not). And given GNU Make always passes
the jobserver in the environment variable (even when a line is deemed
non-recursive), `rustc` will end up complaining about it (in particular
in Make 4.3 where there is only the simple pipe jobserver style).
One solution is to remove the jobserver from `MAKEFLAGS`. However, we
can mark the lines with calls to `rustc` (and Cargo) as recursive, which
looks simpler. This is being documented as a recommendation in `rustc`
[2] and allows us to be ready for the time we may use parallelism inside
`rustc` (potentially now, if a user passes `-Zthreads`). Thus do so.
Similarly, do the same for `rustdoc` and `cargo` calls.
Finally, there is one case that the solution does not cover, which is the
`$(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>
Currently, rustc defaults to invoking `cc`, even if `HOSTCC` is defined,
resulting in build failures in hermetic environments where `cc` does not
exist. This includes both hostprogs and proc-macros.
Since we are setting the linker to `HOSTCC`, we set the linker flavor to
`gcc` explicitly. The linker-flavor selects both which linker to search
for if the linker is unset, and which kind of linker flags to pass.
Without this flag, `rustc` would attempt to determine which flags to
pass based on the name of the binary passed as `HOSTCC`. `gcc` is the
name of the linker-flavor used by `rustc` for all C compilers, including
both `gcc` and `clang`.
Signed-off-by: Matthew Maurer <mmaurer@google.com>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Tested-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
`rustc` outputs by default the temporary files (i.e. the ones saved
by `-Csave-temps`, such as `*.rcgu*` files) in the current working
directory when `-o` and `--out-dir` are not given (even if
`--emit=x=path` is given, i.e. it does not use those for temporaries).
Since out-of-tree modules are compiled from the `linux` tree,
`rustc` then tries to create them there, which may not be accessible.
Thus pass `--out-dir` explicitly, even if it is just for the temporary
files.
Similarly, do so for Rust host programs too.
Reported-by: Raphael Nestler <raphael.nestler@gmail.com>
Closes: https://github.com/Rust-for-Linux/linux/issues/1015
Reported-by: Andrea Righi <andrea.righi@canonical.com>
Tested-by: Raphael Nestler <raphael.nestler@gmail.com> # non-hostprogs
Tested-by: Andrea Righi <andrea.righi@canonical.com> # non-hostprogs
Fixes: 295d8398c6 ("kbuild: specify output names separately for each emission type from rustc")
Cc: stable@vger.kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
rustc may put comments in dep-info, so sed is used to drop them before
passing it to fixdep.
Now that fixdep can remove comments, Makefiles do not need to run sed.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
In Kbuild, two different rules must not write to the same file, but
it happens when compiling rust source files.
For example, set CONFIG_SAMPLE_RUST_MINIMAL=m and run the following:
$ make -j$(nproc) samples/rust/rust_minimal.o samples/rust/rust_minimal.rsi \
samples/rust/rust_minimal.s samples/rust/rust_minimal.ll
[snip]
RUSTC [M] samples/rust/rust_minimal.o
RUSTC [M] samples/rust/rust_minimal.rsi
RUSTC [M] samples/rust/rust_minimal.s
RUSTC [M] samples/rust/rust_minimal.ll
mv: cannot stat 'samples/rust/rust_minimal.d': No such file or directory
make[3]: *** [scripts/Makefile.build:334: samples/rust/rust_minimal.ll] Error 1
make[3]: *** Waiting for unfinished jobs....
mv: cannot stat 'samples/rust/rust_minimal.d': No such file or directory
make[3]: *** [scripts/Makefile.build:309: samples/rust/rust_minimal.o] Error 1
mv: cannot stat 'samples/rust/rust_minimal.d': No such file or directory
make[3]: *** [scripts/Makefile.build:326: samples/rust/rust_minimal.s] Error 1
make[2]: *** [scripts/Makefile.build:504: samples/rust] Error 2
make[1]: *** [scripts/Makefile.build:504: samples] Error 2
make: *** [Makefile:2008: .] Error 2
The reason for the error is that 4 threads running in parallel renames
the same file, samples/rust/rust_minimal.d.
This does not happen when compiling C or assembly files because
-Wp,-MMD,$(depfile) explicitly specifies the dependency filepath.
$(depfile) is a unique path for each target.
Currently, rustc is only given --out-dir and --emit=<list-of-types>
So, all the rust build rules output the dep-info into the default
<CRATE_NAME>.d, which causes the path conflict.
Fortunately, the --emit option is able to specify the output path
individually, with the form --emit=<type>=<path>.
Add --emit=dep-info=$(depfile) to the common part. Also, remove the
redundant --out-dir because the output path is specified for each type.
The code gets much cleaner because we do not need to rename *.d files.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
The conditional:
ifneq ($(hostprogs),)
... is evaluated to true if $(hostprogs) does not contain any word but
whitespace characters.
ifneq ($(strip $(hostprogs)),)
... is a safe way to avoid interpreting whitespace as a non-empty value,
but I'd rather want to use the side-effect of $(sort ...) to do the
equivalent.
$(sort ...) is used in scripts/Makefile.host in order to drop duplication
in $(hostprogs). It is also useful to strip excessive spaces.
Move $(sort ...) before evaluating the ifneq.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
The host shared library rules are currently implemented in
scripts/Makefile.host, but actually GCC-plugin is the only user of
them. (The VDSO .so files are built for the target by different
build rules) Hence, they do not need to be treewide available.
Move all the relevant build rules to scripts/gcc-plugins/Makefile.
I also optimized the build steps so *.so is directly built from .c
because every upstream plugin is compiled from a single source file.
I am still keeping the multi-file plugin support, which Kees Cook
mentioned might be needed by out-of-tree plugins.
(https://lkml.org/lkml/2019/1/11/1107)
If the plugin, foo.so, is compiled from two files foo.c and foo2.c,
then you can do like follows:
foo-objs := foo.o foo2.o
Single-file plugins do not need the *-objs notation.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
This omits system headers from the generated header dependency.
System headers are not updated unless you upgrade the compiler. Nor do
they contain CONFIG options, so fixdep does not need to parse them.
Having said that, the effect of this optimization will be quite small
because the kernel code generally does not include system headers
except <stdarg.h>. Host programs include a lot of system headers,
but there are not so many in the kernel tree.
At first, keeping system headers in .*.cmd files might be useful to
detect the compiler update, but there is no guarantee that <stdarg.h>
is included from every file. So, I implemented a more reliable way in
the previous commit.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Nobody was opposed to raising minimum GCC version to 4.8 [1]
So, we will drop GCC <= 4.7 support sooner or later.
We always use C++ compiler for building plugins for GCC >= 4.8.
This commit drops the plugin support for GCC <= 4.7 a bit earlier,
which allows us to dump lots of code.
[1] https://lkml.org/lkml/2020/1/23/545
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
In old days, the "host-progs" syntax was used for specifying host
programs. It was renamed to the current "hostprogs-y" in 2004.
It is typically useful in scripts/Makefile because it allows Kbuild to
selectively compile host programs based on the kernel configuration.
This commit renames like follows:
always -> always-y
hostprogs-y -> hostprogs
So, scripts/Makefile will look like this:
always-$(CONFIG_BUILD_BIN2C) += ...
always-$(CONFIG_KALLSYMS) += ...
...
hostprogs := $(always-y) $(always-m)
I think this makes more sense because a host program is always a host
program, irrespective of the kernel configuration. We want to specify
which ones to compile by CONFIG options, so always-y will be handier.
The "always", "hostprogs-y", "hostprogs-m" will be kept for backward
compatibility for a while.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Kbuild provides per-file compiler flag addition/removal:
CFLAGS_<basetarget>.o
CFLAGS_REMOVE_<basetarget>.o
AFLAGS_<basetarget>.o
AFLAGS_REMOVE_<basetarget>.o
CPPFLAGS_<basetarget>.lds
HOSTCFLAGS_<basetarget>.o
HOSTCXXFLAGS_<basetarget>.o
The <basetarget> is the filename of the target with its directory and
suffix stripped.
This syntax comes into a trouble when two files with the same basename
appear in one Makefile, for example:
obj-y += foo.o
obj-y += dir/foo.o
CFLAGS_foo.o := <some-flags>
Here, the <some-flags> applies to both foo.o and dir/foo.o
The real world problem is:
scripts/kconfig/util.c
scripts/kconfig/lxdialog/util.c
Both files are compiled into scripts/kconfig/mconf, but only the
latter should be given with the ncurses flags.
It is more sensible to use the relative path to the Makefile, like this:
obj-y += foo.o
CFLAGS_foo.o := <some-flags>
obj-y += dir/foo.o
CFLAGS_dir/foo.o := <other-flags>
At first, I attempted to replace $(basetarget) with $*. The $* variable
is replaced with the stem ('%') part in a pattern rule. This works with
most of cases, but does not for explicit rules.
For example, arch/ia64/lib/Makefile reuses rule_as_o_S in its own
explicit rules, so $* will be empty, resulting in ignoring the per-file
AFLAGS.
I introduced a new variable, target-stem, which can be used also from
explicit rules.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Flex and bison are used for kconfig, dtc, genksyms, all of which are
host programs. I never imagine the kernel embeds a parser or a lexer.
Move the flex and bison rules to scripts/Makefile.host. This file is
included only when hostprogs-y etc. is present in the Makefile in the
directory. So, parsing these rules are skipped in most of directories.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Pull Kbuild updates from Masahiro Yamada:
- remove headers_{install,check}_all targets
- remove unreasonable 'depends on !UML' from CONFIG_SAMPLES
- re-implement 'make headers_install' more cleanly
- add new header-test-y syntax to compile-test headers
- compile-test exported headers to ensure they are compilable in
user-space
- compile-test headers under include/ to ensure they are self-contained
- remove -Waggregate-return, -Wno-uninitialized, -Wno-unused-value
flags
- add -Werror=unknown-warning-option for Clang
- add 128-bit built-in types support to genksyms
- fix missed rebuild of modules.builtin
- propagate 'No space left on device' error in fixdep to Make
- allow Clang to use its integrated assembler
- improve some coccinelle scripts
- add a new flag KBUILD_ABS_SRCTREE to request Kbuild to use absolute
path for $(srctree).
- do not ignore errors when compression utility is missing
- misc cleanups
* tag 'kbuild-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (49 commits)
kbuild: use -- separater intead of $(filter-out ...) for cc-cross-prefix
kbuild: Inform user to pass ARCH= for make mrproper
kbuild: fix compression errors getting ignored
kbuild: add a flag to force absolute path for srctree
kbuild: replace KBUILD_SRCTREE with boolean building_out_of_srctree
kbuild: remove src and obj from the top Makefile
scripts/tags.sh: remove unused environment variables from comments
scripts/tags.sh: drop SUBARCH support for ARM
kbuild: compile-test kernel headers to ensure they are self-contained
kheaders: include only headers into kheaders_data.tar.xz
kheaders: remove meaningless -R option of 'ls'
kbuild: support header-test-pattern-y
kbuild: do not create wrappers for header-test-y
kbuild: compile-test exported headers to ensure they are self-contained
init/Kconfig: add CONFIG_CC_CAN_LINK
kallsyms: exclude kasan local symbols on s390
kbuild: add more hints about SUBDIRS replacement
coccinelle: api/stream_open: treat all wait_.*() calls as blocking
coccinelle: put_device: Add a cast to an expression for an assignment
coccinelle: put_device: Adjust a message construction
...
Commit 25b146c5b8 ("kbuild: allow Kbuild to start from any directory")
deprecated KBUILD_SRCTREE.
It is only used in tools/testing/selftest/ to distinguish out-of-tree
build. Replace it with a new boolean flag, building_out_of_srctree.
I also replaced the conditional ($(srctree),.) because the next commit
will allow an absolute path to be used for $(srctree) even when building
in the source tree.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
The kbuild documentation clearly shows that the documents
there are written at different times: some use markdown,
some use their own peculiar logic to split sections.
Convert everything to ReST without affecting too much
the author's style and avoiding adding uneeded markups.
The conversion is actually:
- add blank lines and identation in order to identify paragraphs;
- fix tables markups;
- add some lists markups;
- mark literal blocks;
- adjust title markups.
At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
The 'addtree' and 'flags' in scripts/Kbuild.include are so compilecated
and ugly.
As I mentioned in [1], Kbuild should stop automatic prefixing of header
search path options.
I fixed up (almost) all Makefiles in the kernel. Now 'addtree' and
'flags' have been removed.
Kbuild still caters to add $(srctree)/$(src) and $(objtree)/$(obj)
to the header search path for O= building, but never touches extra
compiler options from ccflags-y etc.
[1]: https://patchwork.kernel.org/patch/9632347/
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
KBUILD_SRC was conventionally used for some different purposes:
[1] To remember the source tree path
[2] As a flag to check if sub-make is already done
[3] As a flag to check if Kbuild runs out of tree
For [1], we do not need to remember it because the top Makefile
can compute it by $(realpath $(dir $(lastword $(MAKEFILE_LIST))))
[2] has been replaced with self-commenting 'sub_make_done'.
For [3], we can distinguish in-tree/out-of-tree by comparing
$(srctree) and '.'
This commit converts [3] to prepare for the KBUILD_SRC removal.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
When building an external module, $(obj) is the absolute path to it.
The header search paths from ccflags-y etc. should not be tweaked.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
In preparation for enabling command line LDLIBS, re-name HOST_LOADLIBES
to KBUILD_HOSTLDLIBS as the internal use only flags. Also rename
existing usage to HOSTLDLIBS for consistency. This should not have any
visible effects.
Signed-off-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
