In Makefiles, $(error ), $(warning ), and $(info ) expand to the empty
string, as explained in the GNU Make manual [1]:
 "The result of the expansion of this function is the empty string."

Therefore, they are no-op except for logging purposes.

$(shell ...) expands to the output of the command. It expands to the
empty string when the command does not print anything to stdout.
Hence, $(shell mkdir ...) is no-op except for creating the directory.

Remove meaningless assignments.

[1]: https://www.gnu.org/software/make/manual/make.html#Make-Control-Functions

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20240221134201.2656908-1-masahiroy@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-kbuild@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-perf-users@vger.kernel.org

As Dmitry described in [1] changelog the current way of detecting
-s option is broken for new make.

Changing the tools/build -s option detection the same way as it was
fixed for root Makefile in [1].

[1] 4bf73588165b ("kbuild: Port silent mode detection to future gnu make.")

Cc: Dmitry Goncharov <dgoncharov@users.sf.net>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: KP Singh <kpsingh@chromium.org>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Stanislav Fomichev <sdf@google.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Quentin Monnet <quentin@isovalent.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: bpf@vger.kernel.org
Cc: linux-perf-users@vger.kernel.org
Link: https://lore.kernel.org/r/20231008212251.236023-3-jolsa@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

The next cset needs to compare if a flex version is greater or
equal/less than another, but since there is no canonical, generally
available way to compare versions in the command line (sort -V, yeah,
but...), just use awk to canonicalize the versions like is also done in
scripts/rust_is_available.sh.

There was a problem spotted in linux-next where a bashism, here
documents, aka the '<<<' stdin redirector, for strings to be used as the
stdin for awk. Use $(shell echo | awk ...) instead.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Pull sh updates from John Paul Adrian Glaubitz:
 "This is a bit larger than my previous one and mainly consists of
  clean-up work in the arch/sh directory by Geert Uytterhoeven and Randy
  Dunlap.

  Additionally, this fixes a bug in the Storage Queue code that was
  discovered while I was reviewing a patch to switch the code to the
  bitmap API by Christophe Jaillet.

  So this contains both a fix for the original bug in the Storage Queue
  code that can be backported later as well as the Christophe's patch to
  swich the code to the bitmap API.

  Summary:

   - Use generic GCC library routines

   - sq: Use the bitmap API when applicable

   - sq: Fix incorrect element size for allocating bitmap buffer

   - pci: Remove unused variable in SH-7786 PCI Express code

   - mcount.S: fix build error when PRINTK is not enabled

   - remove sh5/sh64 last fragments

   - math-emu: fix macro redefined warning

   - init: use OF_EARLY_FLATTREE for early init

   - nmi_debug: fix return value of __setup handler

   - SH2007: drop the bad URL info"

* tag 'sh-for-v6.4-tag1' of git://git.kernel.org/pub/scm/linux/kernel/git/glaubitz/sh-linux:
  sh: Replace <uapi/asm/types.h> by <asm-generic/int-ll64.h>
  sh: Use generic GCC library routines
  sh: sq: Use the bitmap API when applicable
  sh: sq: Fix incorrect element size for allocating bitmap buffer
  sh: pci: Remove unused variable in SH-7786 PCI Express code
  sh: mcount.S: fix build error when PRINTK is not enabled
  sh: remove sh5/sh64 last fragments
  sh: math-emu: fix macro redefined warning
  sh: init: use OF_EARLY_FLATTREE for early init
  sh: nmi_debug: fix return value of __setup handler
  sh: SH2007: drop the bad URL info

A previous patch removed most of the sh5 (sh64) support from the
kernel tree. Now remove the last stragglers.

Fixes: 37744feebc08 ("sh: remove sh5 support")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@libc.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: linux-sh@vger.kernel.org
Acked-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Reviewed-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Link: https://lore.kernel.org/r/20230306040037.20350-6-rdunlap@infradead.org
Signed-off-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>

Documentation/bpf/bpf_devel_QA.rst
  b7abcd9c656b ("bpf, doc: Link to submitting-patches.rst for general patch submission info")
  d56b0c461d19 ("bpf, docs: Fix link to netdev-FAQ target")
https://lore.kernel.org/all/20230307095812.236eb1be@canb.auug.org.au/

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

We will add tools support for LoongArch (bpf, perf, objtool, etc.), add
build infrastructure and common headers for preparation.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

I cross-compile my BPF selftests with the following command:

CLANG_CROSS_FLAGS="--target=aarch64-linux-gnu --sysroot=/sysroot/" \
  make LLVM=1 CC=clang CROSS_COMPILE=aarch64-linux-gnu- SRCARCH=arm64

(Note the use of CLANG_CROSS_FLAGS to specify a custom sysroot instead
of letting clang use gcc's default sysroot)

However, CLANG_CROSS_FLAGS gets propagated to host tools builds (libbpf
and bpftool) and because they reference it directly in their Makefiles,
they end up cross-compiling host objects which results in linking
errors.

This patch ensures that CLANG_CROSS_FLAGS is reset if CROSS_COMPILE
isn't set (for example when reaching a BPF host tool build).

Signed-off-by: Florent Revest <revest@chromium.org>
Link: https://lore.kernel.org/r/20230217151832.27784-1-revest@chromium.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Pull Kbuild updates from Masahiro Yamada:

 - Add new environment variables, USERCFLAGS and USERLDFLAGS to allow
   additional flags to be passed to user-space programs.

 - Fix missing fflush() bugs in Kconfig and fixdep

 - Fix a minor bug in the comment format of the .config file

 - Make kallsyms ignore llvm's local labels, .L*

 - Fix UAPI compile-test for cross-compiling with Clang

 - Extend the LLVM= syntax to support LLVM=<suffix> form for using a
   particular version of LLVm, and LLVM=<prefix> form for using custom
   LLVM in a particular directory path.

 - Clean up Makefiles

* tag 'kbuild-v5.18-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kbuild: Make $(LLVM) more flexible
  kbuild: add --target to correctly cross-compile UAPI headers with Clang
  fixdep: use fflush() and ferror() to ensure successful write to files
  arch: syscalls: simplify uapi/kapi directory creation
  usr/include: replace extra-y with always-y
  certs: simplify empty certs creation in certs/Makefile
  certs: include certs/signing_key.x509 unconditionally
  kallsyms: ignore all local labels prefixed by '.L'
  kconfig: fix missing '# end of' for empty menu
  kconfig: add fflush() before ferror() check
  kbuild: replace $(if A,A,B) with $(or A,B)
  kbuild: Add environment variables for userprogs flags
  kbuild: unify cmd_copy and cmd_shipped

The LLVM make variable allows a developer to quickly switch between the
GNU and LLVM tools. However, it does not handle versioned binaries, such
as the ones shipped by Debian, as LLVM=1 just defines the tool variables
with the unversioned binaries.

There was some discussion during the review of the patch that introduces
LLVM=1 around versioned binaries, ultimately coming to the conclusion
that developers can just add the folder that contains the unversioned
binaries to their PATH, as Debian's versioned suffixed binaries are
really just symlinks to the unversioned binaries in /usr/lib/llvm-#/bin:

$ realpath /usr/bin/clang-14
/usr/lib/llvm-14/bin/clang

$ PATH=/usr/lib/llvm-14/bin:$PATH make ... LLVM=1

However, that can be cumbersome to developers who are constantly testing
series with different toolchains and versions. It is simple enough to
support these versioned binaries directly in the Kbuild system by
allowing the developer to specify the version suffix with LLVM=, which
is shorter than the above suggestion:

$ make ... LLVM=-14

It does not change the meaning of LLVM=1 (which will continue to use
unversioned binaries) and it does not add too much additional complexity
to the existing $(LLVM) code, while allowing developers to quickly test
their series with different versions of the whole LLVM suite of tools.

Some developers may build LLVM from source but not add the binaries to
their PATH, as they may not want to use that toolchain systemwide.
Support those developers by allowing them to supply the directory that
the LLVM tools are available in, as it is no more complex to support
than the version suffix change above.

$ make ... LLVM=/path/to/llvm/

Update and reorder the documentation to reflect these new additions.
At the same time, notate that LLVM=0 is not the same as just omitting it
altogether, which has confused people in the past.

Link: https://lore.kernel.org/r/20200317215515.226917-1-ndesaulniers@google.com/
Link: https://lore.kernel.org/r/20220224151322.072632223@infradead.org/
Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>