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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

1.4 KiB

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List of files in the vdso, has to be asm only for now

obj-vdso64 = note.o sigtramp.o restart_syscall.o

Build rules

targets := $(obj-vdso64) vdso64.so obj-vdso64 := $(addprefix $(obj)/, $(obj-vdso64))

ccflags-y := -shared -fno-common -fno-builtin ccflags-y += -nostdlib -Wl,-soname=linux-vdso64.so.1
$(call ld-option, -Wl$(comma)--hash-style=sysv) asflags-y := -D__VDSO64__ -s

KBUILD_AFLAGS += -DBUILD_VDSO KBUILD_CFLAGS += -DBUILD_VDSO -DDISABLE_BRANCH_PROFILING

VDSO_LIBGCC := $(shell $(CC) -print-libgcc-file-name)

obj-y += vdso64_wrapper.o extra-y += vdso64.lds CPPFLAGS_vdso64.lds += -P -C -U$(ARCH)

$(obj)/vdso64_wrapper.o : $(obj)/vdso64.so FORCE

Force dependency (incbin is bad)

link rule for the .so file, .lds has to be first

$(obj)/vdso64.so: $(obj)/vdso64.lds $(obj-vdso64) $(VDSO_LIBGCC) FORCE $(call if_changed,vdso64ld)

assembly rules for the .S files

$(obj-vdso64): %.o: %.S FORCE $(call if_changed_dep,vdso64as)

actual build commands

quiet_cmd_vdso64ld = VDSO64L $@ cmd_vdso64ld = $(CC) $(c_flags) -Wl,-T $(filter-out FORCE, $^) -o $@ quiet_cmd_vdso64as = VDSO64A $@ cmd_vdso64as = $(CC) $(a_flags) -c -o $@ $<

Generate VDSO offsets using helper script

gen-vdsosym := $(src)/gen_vdso_offsets.sh quiet_cmd_vdsosym = VDSOSYM $@ cmd_vdsosym = $(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@

include/generated/vdso64-offsets.h: $(obj)/vdso64.so FORCE $(call if_changed,vdsosym)

1.4 KiB Raw Blame History