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>

$(shell ...) expands to empty. There is no need to assign it to _dummy.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>

Use pattern rules to unify similar build rules among n32, n64, and o32.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

There is no good reason to generate the syscall offset macros by
scripting since they are not derived from the syscall tables.

Define __NR_*_Linux macros directly in arch/mips/include/asm/unistd.h,
and clean up the Makefile and the shell script.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Many architectures duplicate similar shell scripts.

This commit converts mips to use scripts/syscallhdr.sh.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Many architectures duplicate similar shell scripts.

This commit converts mips to use scripts/syscalltbl.sh. This also
unifies syscall_table_32_o32.h and syscall_table_64_o32.h into
syscall_table_o32.h.

The offset parameters are unneeded here; __SYSCALL(nr, entry) is defined
as 'PTR entry', so the parameter 'nr' is not used in the first place.

With this commit, syscall tables and generated files are straight
mapped,  which makes things easier to understand.

  syscall_n32.tbl  -->  syscall_table_n32.h
  syscall_n64.tbl  -->  syscall_table_n64.h
  syscall_o32.tbl  -->  syscall_table_o32.h

Then, the abi parameters are also unneeded.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Pull Kbuild updates from Masahiro Yamada:

 - Fix false-positive build warnings for ARCH=ia64 builds

 - Optimize dictionary size for module compression with xz

 - Check the compiler and linker versions in Kconfig

 - Fix misuse of extra-y

 - Support DWARF v5 debug info

 - Clamp SUBLEVEL to 255 because stable releases 4.4.x and 4.9.x
   exceeded the limit

 - Add generic syscall{tbl,hdr}.sh for cleanups across arches

 - Minor cleanups of genksyms

 - Minor cleanups of Kconfig

* tag 'kbuild-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (38 commits)
  initramfs: Remove redundant dependency of RD_ZSTD on BLK_DEV_INITRD
  kbuild: remove deprecated 'always' and 'hostprogs-y/m'
  kbuild: parse C= and M= before changing the working directory
  kbuild: reuse this-makefile to define abs_srctree
  kconfig: unify rule of config, menuconfig, nconfig, gconfig, xconfig
  kconfig: omit --oldaskconfig option for 'make config'
  kconfig: fix 'invalid option' for help option
  kconfig: remove dead code in conf_askvalue()
  kconfig: clean up nested if-conditionals in check_conf()
  kconfig: Remove duplicate call to sym_get_string_value()
  Makefile: Remove # characters from compiler string
  Makefile: reuse CC_VERSION_TEXT
  kbuild: check the minimum linker version in Kconfig
  kbuild: remove ld-version macro
  scripts: add generic syscallhdr.sh
  scripts: add generic syscalltbl.sh
  arch: syscalls: remove $(srctree)/ prefix from syscall tables
  arch: syscalls: add missing FORCE and fix 'targets' to make if_changed work
  gen_compile_commands: prune some directories
  kbuild: simplify access to the kernel's version
  ...

The 'syscall' variables are not directly used in the commands.
Remove the $(srctree)/ prefix because we can rely on VPATH.

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

The rules in these Makefiles cannot detect the command line change
because the prerequisite 'FORCE' is missing.

Adding 'FORCE' will result in the headers being rebuilt every time
because the 'targets' additions are also wrong; the file paths in
'targets' must be relative to the current Makefile.

Fix all of them so the if_changed rules work correctly.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>

unistd_nr_{n32,n64,o32}.h are needed only by include/asm/unistd.h,
which is a kernel-side header file, and their contents is generally
not for userland use.
Move their target destination from include/generated/uapi/asm/ to
include/generated/asm/ to disable exporting them as UAPI headers.

Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>