Pull Kbuild fixes from Masahiro Yamada:

 - Eliminate the fdtoverlay command duplication in scripts/Makefile.lib

 - Fix 'make compile_commands.json' for external modules

 - Ensure scripts/kconfig/merge_config.sh handles missing newlines

 - Fix some build errors on macOS

* tag 'kbuild-fixes-v6.11-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kbuild: fix typos "prequisites" to "prerequisites"
  Documentation/llvm: turn make command for ccache into code block
  kbuild: avoid scripts/kallsyms parsing /dev/null
  treewide: remove unnecessary <linux/version.h> inclusion
  scripts: kconfig: merge_config: config files: add a trailing newline
  Makefile: add $(srctree) to dependency of compile_commands.json target
  kbuild: clean up code duplication in cmd_fdtoverlay

Cleaning up the symbols causes various issues afterwards. Let's sort
the list based on original name.

Signed-off-by: Song Liu <song@kernel.org>
Fixes: 8cc32a9bbf29 ("kallsyms: strip LTO-only suffixes from promoted global functions")
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Tested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20240807220513.3100483-2-song@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

On macOS, as reported by Daniel Gomez, getline() sets ENOTTY to errno
if it is requested to read from /dev/null.

If this is worth fixing, I would rather pass an empty file to
scripts/kallsyms instead of adding the ugly #ifdef __APPLE__.

Fixes: c442db3f49f2 ("kbuild: remove PROVIDE() for kallsyms symbols")
Reported-by: Daniel Gomez <da.gomez@samsung.com>
Closes: https://lore.kernel.org/all/20240807-macos-build-support-v1-12-4cd1ded85694@samsung.com/
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Reviewed-by: Daniel Gomez <da.gomez@samsung.com>

Commit cf8e8658100d ("arch: Remove Itanium (IA-64) architecture")
removed the last use of the absolute kallsyms.

Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/all/20240221202655.2423854-1-jannh@google.com/
[masahiroy@kernel.org: rebase the code and reword the commit description]
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

CONFIG_DEBUG_INFO_BTF=y requires one additional link step.
(.tmp_vmlinux.btf)

CONFIG_KALLSYMS=y requires two additional link steps.
(.tmp_vmlinux.kallsyms1 and .tmp_vmlinux.kallsyms2)

Enabling both requires three additional link steps.

When CONFIG_DEBUG_INFO_BTF=y and CONFIG_KALLSYMS=y, the current build
process is as follows:

    KSYMS   .tmp_vmlinux.kallsyms0.S
    AS      .tmp_vmlinux.kallsyms0.o
    LD      .tmp_vmlinux.btf             # temporary vmlinux for BTF
    BTF     .btf.vmlinux.bin.o
    LD      .tmp_vmlinux.kallsyms1       # temporary vmlinux for kallsyms step 1
    NM      .tmp_vmlinux.kallsyms1.syms
    KSYMS   .tmp_vmlinux.kallsyms1.S
    AS      .tmp_vmlinux.kallsyms1.o
    LD      .tmp_vmlinux.kallsyms2       # temporary vmlinux for kallsyms step 2
    NM      .tmp_vmlinux.kallsyms2.syms
    KSYMS   .tmp_vmlinux.kallsyms2.S
    AS      .tmp_vmlinux.kallsyms2.o
    LD      vmlinux                      # final vmlinux

This is redundant because the BTF generation and the kallsyms step 1 can
be performed against the same temporary vmlinux.

When both CONFIG_DEBUG_INFO_BTF and CONFIG_KALLSYMS are enabled, we can
reduce the number of link steps by one.

This commit changes the build process as follows:

    KSYMS   .tmp_vmlinux0.kallsyms.S
    AS      .tmp_vmlinux0.kallsyms.o
    LD      .tmp_vmlinux1                # temporary vmlinux for BTF and kallsyms step 1
    BTF     .tmp_vmlinux1.btf.o
    NM      .tmp_vmlinux1.syms
    KSYMS   .tmp_vmlinux1.kallsyms.S
    AS      .tmp_vmlinux1.kallsyms.o
    LD      .tmp_vmlinux2                # temporary vmlinux for kallsyms step 2
    NM      .tmp_vmlinux2.syms
    KSYMS   .tmp_vmlinux2.kallsyms.S
    AS      .tmp_vmlinux2.kallsyms.o
    LD      vmlinux                      # final vmlinux

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>

This reimplements commit 951bcae6c5a0 ("kallsyms: Avoid weak references
for kallsyms symbols") because I am not a big fan of PROVIDE().

As an alternative solution, this commit prepends one more kallsyms step.

    KSYMS   .tmp_vmlinux.kallsyms0.S          # added
    AS      .tmp_vmlinux.kallsyms0.o          # added
    LD      .tmp_vmlinux.btf
    BTF     .btf.vmlinux.bin.o
    LD      .tmp_vmlinux.kallsyms1
    NM      .tmp_vmlinux.kallsyms1.syms
    KSYMS   .tmp_vmlinux.kallsyms1.S
    AS      .tmp_vmlinux.kallsyms1.o
    LD      .tmp_vmlinux.kallsyms2
    NM      .tmp_vmlinux.kallsyms2.syms
    KSYMS   .tmp_vmlinux.kallsyms2.S
    AS      .tmp_vmlinux.kallsyms2.o
    LD      vmlinux

Step 0 takes /dev/null as input, and generates .tmp_vmlinux.kallsyms0.o,
which has a valid kallsyms format with the empty symbol list, and can be
linked to vmlinux. Since it is really small, the added compile-time cost
is negligible.

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

Clean up the variables in scripts/link-vmlinux.sh

 - Specify the extra objects directly in vmlinux_link()
 - Move the AS rule to kallsyms()
 - Set kallsymso and btf_vmlinux_bin_o where they are generated
 - Remove unneeded variable, kallsymso_prev
 - Introduce the btf_data variable
 - Introduce the strip_debug flag instead of checking the output name

No functional change intended.

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

In commit b18b047002b7 ("kbuild: change scripts/mksysmap into sed
script"), the mksysmap script was transformed into a sed script,
made directly executable with "#!/bin/sed -f". Apparently, the path to
sed is different on NixOS.

The shebang can't use the env command, otherwise the "sed -f" command
would be treated as a single argument. This can be solved with the -S
flag, but that is a GNU extension. Explicitly use sed instead of relying
on the executable shebang to fix NixOS builds without breaking build
environments using Busybox.

Fixes: b18b047002b7 ("kbuild: change scripts/mksysmap into sed script")
Reported-by: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Richard Acayan <mailingradian@gmail.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Dmitry Safonov <0x7f454c46@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Remove the left-over of commit 51eb95e2da41 ("kbuild: Don't remove
link-vmlinux temporary files on exit/signal").

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

In convention, short logs print the output file, not the input file.

Let's change the suffix for 'AS' since it assembles *.S into *.o.

[Before]

  LD      .tmp_vmlinux.kallsyms1
  NM      .tmp_vmlinux.kallsyms1.syms
  KSYMS   .tmp_vmlinux.kallsyms1.S
  AS      .tmp_vmlinux.kallsyms1.S
  LD      .tmp_vmlinux.kallsyms2
  NM      .tmp_vmlinux.kallsyms2.syms
  KSYMS   .tmp_vmlinux.kallsyms2.S
  AS      .tmp_vmlinux.kallsyms2.S
  LD      vmlinux

[After]

  LD      .tmp_vmlinux.kallsyms1
  NM      .tmp_vmlinux.kallsyms1.syms
  KSYMS   .tmp_vmlinux.kallsyms1.S
  AS      .tmp_vmlinux.kallsyms1.o
  LD      .tmp_vmlinux.kallsyms2
  NM      .tmp_vmlinux.kallsyms2.syms
  KSYMS   .tmp_vmlinux.kallsyms2.S
  AS      .tmp_vmlinux.kallsyms2.o
  LD      vmlinux

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>