The dependency will be checked anyway after Kbuild descends into a
sub-directory. Skip object/source dependency checks in top Makefile.

VPATH can be simpler since the top Makefile no longer checks the
presence of the source file, which is located in in the external
module directory.

One good thing is, it can compile an object from a generated source
file.

  $ make crypto/rsapubkey.asn1.o
    ...
  ASN.1   crypto/rsapubkey.asn1.c
  CC      crypto/rsapubkey.asn1.o
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

The previous commit made 'MAKEFLAGS += -rR' effective in the top
Makefile regardless of O= option, GNU Make versions.

The top Makefile does not need to cancel implicit rules for makefiles.

There is still one place where an empty rule is useful. Since -rR is
effective only after sub-make, GNU Make would try implicit rules to
update the top Makefile. Although it is not a big overhead, cancel it
just in case.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Adding -rR to MAKEFLAGS is important because we do not want to
be bothered by built-in implicit rules or variables.

One problem that used to exist in older GNU Make versions is

  MAKEFLAGS += -rR

... does not become effective in the current Makefile. When you are
building with O= option, it becomes effective in the top Makefile
since it recurses via 'sub-make' target. Otherwise, the top Makefile
tries implicit rules. That is why we explicitly add empty rules for
Makefiles, but we often miss to do that.

In fact, adding -d option to older GNU Make versions shows it is
trying a bunch of implicit pattern rules.

 Considering target file `scripts/Makefile.kcov'.
  Looking for an implicit rule for `scripts/Makefile.kcov'.
  Trying pattern rule with stem `Makefile.kcov'.
  Trying implicit prerequisite `scripts/Makefile.kcov.o'.
  Trying pattern rule with stem `Makefile.kcov'.
  Trying implicit prerequisite `scripts/Makefile.kcov.c'.
  Trying pattern rule with stem `Makefile.kcov'.
  Trying implicit prerequisite `scripts/Makefile.kcov.cc'.
  Trying pattern rule with stem `Makefile.kcov'.
  Trying implicit prerequisite `scripts/Makefile.kcov.C'.
  ...

This issue was fixed by GNU Make commit 58dae243526b ("[Savannah #20501]
Handle adding -r/-R to MAKEFLAGS in the makefile"). So, it is no longer
a problem if you use GNU Make 4.0 or later. However, older versions are
still widely used.

So, I decided to patch the kernel Makefile to invoke sub-make regardless
of O= option. This will allow further cleanups.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

This would disturb the change the sub-make part. Move it near the
tools/ target.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Since -Wmaybe-uninitialized was introduced by GCC 4.7, we have patched
various false positives:

 - commit e74fc973 ("Turn off -Wmaybe-uninitialized when building
   with -Os") turned off this option for -Os.

 - commit 815eb71e ("Kbuild: disable 'maybe-uninitialized' warning
   for CONFIG_PROFILE_ALL_BRANCHES") turned off this option for
   CONFIG_PROFILE_ALL_BRANCHES

 - commit a76bcf55 ("Kbuild: enable -Wmaybe-uninitialized warning
   for "make W=1"") turned off this option for GCC < 4.9
   Arnd provided more explanation in https://lkml.org/lkml/2017/3/14/903

I think this looks better by shifting the logic from Makefile to Kconfig.

Link: https://github.com/ClangBuiltLinux/linux/issues/350Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>

- $(word 1, <text>) is equivalent to $(firstword <text>)

 - hardcode "gcc" instead of $(CC)

 - minimize the shell script part

A little more notes in case $(filter-out -%, ...) is not clear.

arch/mips/Makefile passes prefixes depending on the configuration.

CROSS_COMPILE := $(call cc-cross-prefix, $(tool-archpref)-linux- \
    $(tool-archpref)-linux-gnu- $(tool-archpref)-unknown-linux-gnu-)

In the Kconfig stage (e.g. when you run 'make defconfig'), neither
CONFIG_32BIT nor CONFIG_64BIT is defined. So, $(tool-archpref) is
empty. As a result, "-linux -linux-gnu- -unknown-linux-gnu" is passed
into cc-cross-prefix. The command 'which' assumes arguments starting
with a hyphen as command options, then emits the following messages:

  Illegal option -l
  Illegal option -l
  Illegal option -u

I think it is strange to define CROSS_COMPILE depending on the CONFIG
options since you need to feed $(CC) to Kconfig, but it is how MIPS
Makefile currently works. Anyway, it would not hurt to filter-out
invalid strings beforehand.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

The genksyms source was integrated into the kernel tree in 2003.

I do not expect anybody still using the external /sbin/genksyms.
Kbuild does not need to provide the ability to override GENKSYMS.

Let's remove the GENKSYMS variable, and use the hardcoded path.

Since it occurred in the pre-git era, I attached the commit message
in case somebody is interested in the historical background.

  | Author: Kai Germaschewski <kai@tp1.ruhr-uni-bochum.de>
  | Date:   Wed Feb 19 04:17:28 2003 -0600
  |
  | kbuild: [PATCH] put genksyms in scripts dir
  |
  | This puts genksyms into scripts/genksyms/.
  |
  | genksyms used to be maintained externally, though the only possible user
  | was the kernel build. Moving it into the kernel sources makes it easier to
  | keep it uptodate, like for example updating it to generate linker scripts
  | directly instead of postprocessing the generated header file fragments
  | with sed, as we do currently.
  |
  | Also, genksyms does not handle __typeof__, which needs to be fixed since
  | some of the exported symbol in the kernel are defined using __typeof__.
  |
  | (Rusty Russell/me)
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

gdb-scripts is not a real object, but (ab)used like a phony target.

Rewrite the code in a more Kbuild-ish way. Add symlinks to extra-y
and use if_changed.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

It is weird to create gdb stuff as a side-effect of vmlinux.

Move it to a more relevant place.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

Currently, Kbuild descends from scripts/Makefile to scripts/gdb/Makefile
just for creating symbolic links, but it does not need to do it so early.

Merge the two descending paths to simplify the code.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

Every time we add/remove a target, we need to touch the header part,
including renumbering. This is not so important information.

Numbering targets is rather misleading because they are not necessarily
generated in this order. For example, 1) and 2) can be executed
simultaneously when the -j option is given.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

scripts/gdb/linux/constants.py is never used in the kernel build
process. There is no good reason to create it so early.

Get it out of the 'prepare' stage.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

Commit 06300b21 ("kbuild: support building individual files for
external modules") introduced the '/' target. It works only for
external modules to build all .o files, but skip the modpost stage.

However, 'make /' looks a bit weird to me. 'make ./' is more sensible
if you want to build all objects under the current directory, and it
works as expected.

Let's change '/' into a phony target that is an alias of './', but
I may feel like deprecating it in the future.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

It is fine to set KBUILD_MODULES=1 when CONFIG_MODULES is disabled.
It is actually how "make allnoconfig all" works.

On the other hand, KBUILD_MODULES=1 is unneeded for the %.ko pattern.
It is just a matter of whether modules.order is generated or not.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Do not generate pointless modules.order when the module support is
disabled.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

'$(MAKE) KBUILD_SRC=' changes the working directory back and forth
between objtree and srctree.

It is better to recurse to the top-level Makefile directly.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

This causes an issue when trying to build with `make LD=ld.lld` if
ld.lld and the rest of your cross tools aren't in the same directory
(ex. /usr/local/bin) (as is the case for Android's build system), as the
GCC_TOOLCHAIN_DIR then gets set based on `which $(LD)` which will point
where LLVM tools are, not GCC/binutils tools are located.

Instead, select the GCC_TOOLCHAIN_DIR based on another tool provided by
binutils for which LLVM does not provide a substitute for, such as
elfedit.

Fixes: 785f11aa ("kbuild: Add better clang cross build support")
Link: https://github.com/ClangBuiltLinux/linux/issues/341Suggested-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Modern gcc adds view assignments, reset assertion checking in .loc
directives and a couple more additional debug markers, which clutters
the asm output unnecessarily:

For example:

  bsp_resume:
  .LFB3466:
          .loc 1 1868 1 is_stmt 1 view -0
          .cfi_startproc
          .loc 1 1869 2 view .LVU73
  # arch/x86/kernel/cpu/common.c:1869:    if (this_cpu->c_bsp_resume)
          .loc 1 1869 14 is_stmt 0 view .LVU74
          movq    this_cpu(%rip), %rax    # this_cpu, this_cpu
          movq    64(%rax), %rax  # this_cpu.94_1->c_bsp_resume, _2
  # arch/x86/kernel/cpu/common.c:1869:    if (this_cpu->c_bsp_resume)
          .loc 1 1869 5 view .LVU75
          testq   %rax, %rax      # _2
          je      .L8     #,
          .loc 1 1870 3 is_stmt 1 view .LVU76
          movq    $boot_cpu_data, %rdi    #,
          jmp     __x86_indirect_thunk_rax

or
        .loc 2 57 9 view .LVU478
        .loc 2 57 9 view .LVU479
        .loc 2 57 9 view .LVU480
        .loc 2 57 9 view .LVU481
  .LBB1385:
  .LBB1383:
  .LBB1379:
  .LBB1377:
  .LBB1375:
        .loc 2 57 9 view .LVU482
        .loc 2 57 9 view .LVU483
        movl	%edi, %edx	# cpu, cpu
  .LVL87:
        .loc 2 57 9 is_stmt 0 view .LVU484

That MOV in there is drowned in debugging information and latter makes
it hard to follow the asm. And that DWARF info is not really needed for
asm output staring.

Disable the debug information generation which clutters the asm output
unnecessarily:

  bsp_resume:
  # arch/x86/kernel/cpu/common.c:1869:    if (this_cpu->c_bsp_resume)
          movq    this_cpu(%rip), %rax    # this_cpu, this_cpu
          movq    64(%rax), %rax  # this_cpu.94_1->c_bsp_resume, _2
  # arch/x86/kernel/cpu/common.c:1869:    if (this_cpu->c_bsp_resume)
          testq   %rax, %rax      # _2
          je      .L8     #,
  # arch/x86/kernel/cpu/common.c:1870:            this_cpu->c_bsp_resume(&boot_cpu_data);
          movq    $boot_cpu_data, %rdi    #,
          jmp     __x86_indirect_thunk_rax
  .L8:
  # arch/x86/kernel/cpu/common.c:1871: }
          rep ret
          .size   bsp_resume, .-bsp_resume

  [ bp: write commit message. ]
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Borislav Petkov <bp@suse.de>

<asm/bitsperlong.h> is enough to include the definition of
BITS_PER_LONG.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Global variables in the .bss section are zeroed out before the program
starts to run.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Fix the following sparse warnings:

scripts/kallsyms.c:65:5: warning: symbol 'token_profit' was not declared. Should it be static?
scripts/kallsyms.c:68:15: warning: symbol 'best_table' was not declared. Should it be static?
scripts/kallsyms.c:69:15: warning: symbol 'best_table_len' was not declared. Should it be static?

Also, remove 'inline' from is_arm_mapping_symbol(). The compiler
will inline it anyway when it is appropriate to do so.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

When compiling into output directory using O=, many files
created under KBUILD_OUTPUT that git considers
as new ones; git clients, ex. "git gui" lists it, and it clutters
file list making it difficult to see what was really changed

Generate .gitignore in output directory that ignores all
its content
Signed-off-by: Vladimir Kondratiev <vladimir.kondratiev@linux.intel.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

There is no build order among the following:
  prepare3
  outputmakefile
  asm-generic
  $(version_h)
  $(autoksyms_h)
  include/generated/utsrelease.h

It is meaningless to insert the prepare2 target between the first
three and the last three.

The comment says, "prepare2 creates a makefile if using a separate
output directory." Let me explain it more precisely. The prepare
targets cannot be executed without the .config file. Because the
configuration targets depend on the outputmakefile target, the
generated makefile is already there before the parepare2 is run.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

The commands surrounded by ( ) are executed in a subshell, but in
most cases, we do not need to spawn an extra subshell.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

In Kbuild, if_changed and friends must have FORCE as a prerequisite.

Hence, $(filter-out FORCE,$^) or $(filter-out $(PHONY),$^) is a common
idiom to get the names of all the prerequisites except phony targets.

Add real-prereqs as a shorthand.

Note:
We cannot replace $(filter %.o,$^) in cmd_link_multi-m because $^ may
include auto-generated dependencies from the .*.cmd file when a single
object module is changed into a multi object module. Refer to commit
69ea912f ("kbuild: remove unneeded link_multi_deps"). I added some
comment to avoid accidental breakage.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Rob Herring <robh@kernel.org>

When I was refactoring cmd_ar_builtin in scripts/Makefile.build,
I noticed the build breakage of s390.

Some Makefiles of s390 add extra dependencies to built-in.a;
built-in.a depends on timestamp files *.o.chkbss, but $(AR) does
not want to include them into built-in.a.

Insert a phony target 'chkbss' in between so that $(AR) can take
$(filter-out $(PHONY), $^) as input.

While I was here, I refactored Makefile.chkbss a little bit.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>

All the callers of size_append pass $(filter-out FORCE,$^).
Move $(filter-out FORCE,$^) to the definition of size_append.

This makes the callers cleaner because $(call ...) is unneeded
for a macro with no argument.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

The top Makefile does not need to export KBUILD_VMLINUX_INIT and
KBUILD_VMLINUX_MAIN separately.

Put every built-in.a into KBUILD_VMLINUX_OBJS. The order of
$(head-y), $(init-y), $(core-y), ... is still retained.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

The symbol table in the final archive is unneeded; the linker does not
require the symbol table after the --whole-archive option. Every object
file in the archive is included in the link anyway.

Pass thin archives from subdirectories directly to the linker, and
remove the final archiving step.

Fix up the document and comments as well.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Nicholas Piggin <npiggin@gmail.com>

When building an external module, $(obj) is the absolute path to it.

The header search paths from ccflags-y etc. should not be tweaked.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Pull x86 fixes from Thomas Gleixner:
 "A set of fixes for x86:

   - Fix the swapped outb() parameters in the KASLR code

   - Fix the PKEY handling at fork which missed to preserve the pkey
     state for the child. Comes with a test case to validate that.

   - Fix the entry stack handling for XEN PV to respect that XEN PV
     systems enter the function already on the current thread stack and
     not on the trampoline.

   - Fix kexec load failure caused by using a stale value when the
     kexec_buf structure is reused for subsequent allocations.

   - Fix a bogus sizeof() in the memory encryption code

   - Enforce PCI dependency for the Intel Low Power Subsystem

   - Enforce PCI_LOCKLESS_CONFIG when PCI is enabled"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/Kconfig: Select PCI_LOCKLESS_CONFIG if PCI is enabled
  x86/entry/64/compat: Fix stack switching for XEN PV
  x86/kexec: Fix a kexec_file_load() failure
  x86/mm/mem_encrypt: Fix erroneous sizeof()
  x86/selftests/pkeys: Fork() to check for state being preserved
  x86/pkeys: Properly copy pkey state at fork()
  x86/kaslr: Fix incorrect i8254 outb() parameters
  x86/intel/lpss: Make PCI dependency explicit

Pull x86 timer fixes from Thomas Gleixner:
 "Two commits which were missed to be sent during the merge window.

   - The TSC calibration fix turns out to be more urgent as recent
     Skylake-X systems seem to have massive trouble with calibration
     disturbance. This should go back into stable for that reason and it
     the risk of breakage is rather low.

   - Drop an unused define"

* 'x86-timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/hpet: Remove unused FSEC_PER_NSEC define
  x86/tsc: Make calibration refinement more robust

Pull timer fix from Thomas Glexiner:
 "A single regression fix to address the unintended breakage of posix
  cpu timers.

  This is caused by a new sanity check in the common code, which fails
  for posix cpu timers under certain conditions because the posix cpu
  timer code never updates the variable which is checked"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  posix-cpu-timers: Unbreak timer rearming

Pull locking fixes from Thomas Gleixner:
 "A small series of fixes which all address possible missed wakeups:

   - Document and fix the wakeup ordering of wake_q

   - Add the missing barrier in rcuwait_wake_up(), which was documented
     in the comment but missing in the code

   - Fix the possible missed wakeups in the rwsem and futex code"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/rwsem: Fix (possible) missed wakeup
  futex: Fix (possible) missed wakeup
  sched/wake_q: Fix wakeup ordering for wake_q
  sched/wake_q: Document wake_q_add()
  sched/wait: Fix rcuwait_wake_up() ordering

Pull irq fixes from Thomas Gleixner:
 "A small set of fixes for the interrupt subsystem:

   - Fix a double increment in the irq descriptor allocator which
     resulted in a sanity check only being done for every second
     affinity mask

   - Add a missing device tree translation in the stm32-exti driver.
     Without that the interrupt association is completely wrong.

   - Initialize the mutex in the GIC-V3 MBI driver

   - Fix the alignment for aliasing devices in the GIC-V3-ITS driver so
     multi MSI allocations work correctly

   - Ensure that the initial affinity of a interrupt is not empty at
     startup time.

   - Drop bogus include in the madera irq chip driver

   - Fix KernelDoc regression"

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  irqchip/gic-v3-its: Align PCI Multi-MSI allocation on their size
  genirq/irqdesc: Fix double increment in alloc_descs()
  genirq: Fix the kerneldoc comment for struct irq_affinity_desc
  irqchip/madera: Drop GPIO includes
  irqchip/gic-v3-mbi: Fix uninitialized mbi_lock
  irqchip/stm32-exti: Add domain translate function
  genirq: Make sure the initial affinity is not empty

Pull EDAC fix from Borislav Petkov:
 "Fix persistent register offsets of altera_edac, from Thor Thayer"

* tag 'edac_fix_for_5.0' of git://git.kernel.org/pub/scm/linux/kernel/git/bp/bp:
  EDAC, altera: Fix S10 persistent register offset

Pull block revert from Jens Axboe:
 "Silly error snuck into a patch from the last series, let's do a revert
  to avoid a potential use-after-free"

* tag 'for-linus-20190127' of git://git.kernel.dk/linux-block:
  Revert "block: cover another queue enter recursion via BIO_QUEUE_ENTERED"

Pull KVM fixes from Paolo Bonzini:
 "Quite a few fixes for x86: nested virtualization save/restore, AMD
  nested virtualization and virtual APIC, 32-bit fixes, an important fix
  to restore operation on older processors, and a bunch of hyper-v
  bugfixes. Several are marked stable.

  There are also fixes for GCC warnings and for a GCC/objtool interaction"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: x86: Mark expected switch fall-throughs
  KVM: x86: fix TRACE_INCLUDE_PATH and remove -I. header search paths
  KVM: selftests: check returned evmcs version range
  x86/kvm/hyper-v: nested_enable_evmcs() sets vmcs_version incorrectly
  KVM: VMX: Move vmx_vcpu_run()'s VM-Enter asm blob to a helper function
  kvm: selftests: Fix region overlap check in kvm_util
  kvm: vmx: fix some -Wmissing-prototypes warnings
  KVM: nSVM: clear events pending from svm_complete_interrupts() when exiting to L1
  svm: Fix AVIC incomplete IPI emulation
  svm: Add warning message for AVIC IPI invalid target
  KVM: x86: WARN_ONCE if sending a PV IPI returns a fatal error
  KVM: x86: Fix PV IPIs for 32-bit KVM host
  x86/kvm/hyper-v: recommend using eVMCS only when it is enabled
  x86/kvm/hyper-v: don't recommend doing reset via synthetic MSR
  kvm: x86/vmx: Use kzalloc for cached_vmcs12
  KVM: VMX: Use the correct field var when clearing VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL
  KVM: x86: Fix single-step debugging
  x86/kvm/hyper-v: don't announce GUEST IDLE MSR support

Pull dma-mapping fix from Christoph Hellwig:
 "Fix a xen-swiotlb regression on arm64"

* tag 'dma-mapping-5.0-2' of git://git.infradead.org/users/hch/dma-mapping:
  arm64/xen: fix xen-swiotlb cache flushing