Merge tag 'kbuild-v5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - do not generate unneeded top-level built-in.a

 - let git ignore O= directory entirely

 - optimize scripts/kallsyms slightly

 - exclude DWARF info from *.s regardless of config options

 - fix GCC toolchain search path for Clang to prepare ld.lld support

 - do not generate modules.order when CONFIG_MODULES is disabled

 - simplify single target rules and remove VPATH for external module
   build

 - allow to add optional flags to dpkg-buildpackage when building
   deb-pkg

 - move some compiler option tests from Makefile to Kconfig

 - various Makefile cleanups

* tag 'kbuild-v5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (40 commits)
  kbuild: remove scripts/basic/% build target
  kbuild: use -Werror=implicit-... instead of -Werror-implicit-...
  kbuild: clean up scripts/gcc-version.sh
  kbuild: remove cc-version macro
  kbuild: update comment block of scripts/clang-version.sh
  kbuild: remove commented-out INITRD_COMPRESS
  kbuild: move -gsplit-dwarf, -gdwarf-4 option tests to Kconfig
  kbuild: [bin]deb-pkg: add DPKG_FLAGS variable
  kbuild: move ".config not found!" message from Kconfig to Makefile
  kbuild: invoke syncconfig if include/config/auto.conf.cmd is missing
  kbuild: simplify single target rules
  kbuild: remove empty rules for makefiles
  kbuild: make -r/-R effective in top Makefile for old Make versions
  kbuild: move tools_silent to a more relevant place
  kbuild: compute false-positive -Wmaybe-uninitialized cases in Kconfig
  kbuild: refactor cc-cross-prefix implementation
  kbuild: hardcode genksyms path and remove GENKSYMS variable
  scripts/gdb: refactor rules for symlink creation
  kbuild: create symlink to vmlinux-gdb.py in scripts_gdb target
  scripts/gdb: do not descend into scripts/gdb from scripts
  ...
This commit is contained in:
Linus Torvalds
2019-03-10 17:48:21 -07:00
33 changed files with 262 additions and 362 deletions

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@@ -15,7 +15,7 @@ DT_TMP_SCHEMA := processed-schema.yaml
extra-y += $(DT_TMP_SCHEMA)
quiet_cmd_mk_schema = SCHEMA $@
cmd_mk_schema = $(DT_MK_SCHEMA) $(DT_MK_SCHEMA_FLAGS) -o $@ $(filter-out FORCE, $^)
cmd_mk_schema = $(DT_MK_SCHEMA) $(DT_MK_SCHEMA_FLAGS) -o $@ $(real-prereqs)
DT_DOCS = $(shell \
cd $(srctree)/$(src) && \

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@@ -232,17 +232,12 @@ KBUILD_LDS
--------------------------------------------------
The linker script with full path. Assigned by the top-level Makefile.
KBUILD_VMLINUX_INIT
KBUILD_VMLINUX_OBJS
--------------------------------------------------
All object files for the init (first) part of vmlinux.
Files specified with KBUILD_VMLINUX_INIT are linked first.
KBUILD_VMLINUX_MAIN
--------------------------------------------------
All object files for the main part of vmlinux.
All object files for vmlinux. They are linked to vmlinux in the same
order as listed in KBUILD_VMLINUX_OBJS.
KBUILD_VMLINUX_LIBS
--------------------------------------------------
All .a "lib" files for vmlinux.
KBUILD_VMLINUX_INIT, KBUILD_VMLINUX_MAIN, and KBUILD_VMLINUX_LIBS together
specify all the object files used to link vmlinux.
All .a "lib" files for vmlinux. KBUILD_VMLINUX_OBJS and KBUILD_VMLINUX_LIBS
together specify all the object files used to link vmlinux.

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@@ -154,13 +154,8 @@ more details, with real examples.
Kbuild compiles all the $(obj-y) files. It then calls
"$(AR) rcSTP" to merge these files into one built-in.a file.
This is a thin archive without a symbol table, which makes it
unsuitable as a linker input.
The scripts/link-vmlinux.sh script later makes an aggregate
built-in.a with "${AR} rcsTP", which creates the thin archive
with a symbol table and an index, making it a valid input for
the final vmlinux link passes.
This is a thin archive without a symbol table. It will be later
linked into vmlinux by scripts/link-vmlinux.sh
The order of files in $(obj-y) is significant. Duplicates in
the lists are allowed: the first instance will be linked into
@@ -504,23 +499,6 @@ more details, with real examples.
In the above example, -Wno-unused-but-set-variable will be added to
KBUILD_CFLAGS only if gcc really accepts it.
cc-version
cc-version returns a numerical version of the $(CC) compiler version.
The format is <major><minor> where both are two digits. So for example
gcc 3.41 would return 0341.
cc-version is useful when a specific $(CC) version is faulty in one
area, for example -mregparm=3 was broken in some gcc versions
even though the option was accepted by gcc.
Example:
#arch/x86/Makefile
cflags-y += $(shell \
if [ $(cc-version) -ge 0300 ] ; then \
echo "-mregparm=3"; fi ;)
In the above example, -mregparm=3 is only used for gcc version greater
than or equal to gcc 3.0.
cc-ifversion
cc-ifversion tests the version of $(CC) and equals the fourth parameter
if version expression is true, or the fifth (if given) if the version

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@@ -140,7 +140,7 @@ executed to make module versioning work.
make -C $KDIR M=$PWD bar.lst
make -C $KDIR M=$PWD baz.o
make -C $KDIR M=$PWD foo.ko
make -C $KDIR M=$PWD /
make -C $KDIR M=$PWD ./
=== 3. Creating a Kbuild File for an External Module