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Masahiro Yamada b1992c3772 kbuild: use $(src) instead of $(srctree)/$(src) for source directory

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)

When the kernel is built in a separate output directory, $(src) does
not accurately reflect the source directory location. While Kbuild
resolves this discrepancy by specifying VPATH=$(srctree) to search for
source files, it does not cover all cases. For example, when adding a
header search path for local headers, -I$(srctree)/$(src) is typically
passed to the compiler.

This introduces inconsistency between upstream and downstream Makefiles
because $(src) is used instead of $(srctree)/$(src) for the latter.

To address this inconsistency, this commit changes the semantics of
$(src) so that it always points to the directory in the source tree.

Going forward, the variables used in Makefiles will have the following
meanings:

  $(obj)     - directory in the object tree
  $(src)     - directory in the source tree  (changed by this commit)
  $(objtree) - the top of the kernel object tree
  $(srctree) - the top of the kernel source tree

Consequently, $(srctree)/$(src) in upstream Makefiles need to be replaced
with $(src).

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

2024-05-10 04:34:52 +09:00

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SPDX-License-Identifier: GPL-2.0-only

Unlike the kernel space, exported headers are written in standard C.

- Forbid C++ style comments

- Use 'inline', 'asm' instead of 'inline', 'asm'

-std=c90 (equivalent to -ansi) catches the violation of those.

We cannot go as far as adding -Wpedantic since it emits too many warnings.

UAPI_CFLAGS := -std=c90 -Wall -Werror=implicit-function-declaration

In theory, we do not care -m32 or -m64 for header compile tests.

It is here just because CONFIG_CC_CAN_LINK is tested with -m32 or -m64.

UAPI_CFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CFLAGS))

USERCFLAGS might contain sysroot location for CC.

UAPI_CFLAGS += $(USERCFLAGS)

override c_flags = $(UAPI_CFLAGS) -Wp,-MMD,$(depfile) -I $(obj) -I $(srctree)/usr/dummy-include

The following are excluded for now because they fail to build.

Do not add a new header to the blacklist without legitimate reason.

Please consider to fix the header first.

Sorted alphabetically.

no-header-test += asm/ucontext.h no-header-test += drm/vmwgfx_drm.h no-header-test += linux/am437x-vpfe.h no-header-test += linux/coda.h no-header-test += linux/cyclades.h no-header-test += linux/errqueue.h no-header-test += linux/hdlc/ioctl.h no-header-test += linux/ivtv.h no-header-test += linux/matroxfb.h no-header-test += linux/omap3isp.h no-header-test += linux/omapfb.h no-header-test += linux/patchkey.h no-header-test += linux/phonet.h no-header-test += linux/sctp.h no-header-test += linux/sysctl.h no-header-test += linux/usb/audio.h no-header-test += linux/v4l2-mediabus.h no-header-test += linux/v4l2-subdev.h no-header-test += linux/videodev2.h no-header-test += linux/vm_sockets.h no-header-test += sound/asequencer.h no-header-test += sound/asoc.h no-header-test += sound/asound.h no-header-test += sound/compress_offload.h no-header-test += sound/emu10k1.h no-header-test += sound/sfnt_info.h no-header-test += xen/evtchn.h no-header-test += xen/gntdev.h no-header-test += xen/privcmd.h

More headers are broken in some architectures

ifeq ($(SRCARCH),arc) no-header-test += linux/bpf_perf_event.h endif

ifeq ($(SRCARCH),powerpc) no-header-test += linux/bpf_perf_event.h endif

ifeq ($(SRCARCH),sparc) no-header-test += asm/uctx.h no-header-test += asm/fbio.h endif

asm-generic/.h is used by asm/.h, and should not be included directly

no-header-test += asm-generic/%

always-y := $(patsubst $(obj)/%.h,%.hdrtest, $(shell find $(obj) -name '*.h' 2>/dev/null))

Include the header twice to detect missing include guard.

quiet_cmd_hdrtest = HDRTEST $< cmd_hdrtest =
$(CC) $(c_flags) -fsyntax-only -x c /dev/null
$(if $(filter-out $(no-header-test), $*.h), -include $< -include $<);
$(PERL) $(src)/headers_check.pl $(obj) $(SRCARCH) $<;
touch $@

$(obj)/%.hdrtest: $(obj)/%.h FORCE $(call if_changed_dep,hdrtest)

Since GNU Make 4.3, $(patsubst $(obj)/%/,%,$(wildcard $(obj)/*/)) works.

To support older Make versions, use a somewhat tedious way.

clean-files += $(filter-out Makefile headers_check.pl, $(notdir $(wildcard $(obj)/*)))

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