Merge "Merge android11-5.4.61+ (0d36496b) into msm-5.4"

    issues

    reproducible-builds

    llvm

.. only::  subproject and html

These two variables allow to override the user@host string displayed during

boot and in /proc/version. The default value is the output of the commands

whoami and host, respectively.

LLVM

----

If this variable is set to 1, Kbuild will use Clang and LLVM utilities instead

of GCC and GNU binutils to build the kernel.

==============================

Building Linux with Clang/LLVM

==============================

This document covers how to build the Linux kernel with Clang and LLVM

utilities.

About

-----

The Linux kernel has always traditionally been compiled with GNU toolchains

such as GCC and binutils. Ongoing work has allowed for `Clang

<https://clang.llvm.org/>`_ and `LLVM <https://llvm.org/>`_ utilities to be

used as viable substitutes. Distributions such as `Android

<https://www.android.com/>`_, `ChromeOS

<https://www.chromium.org/chromium-os>`_, and `OpenMandriva

<https://www.openmandriva.org/>`_ use Clang built kernels.  `LLVM is a

collection of toolchain components implemented in terms of C++ objects

<https://www.aosabook.org/en/llvm.html>`_. Clang is a front-end to LLVM that

supports C and the GNU C extensions required by the kernel, and is pronounced

"klang," not "see-lang."

Clang

-----

The compiler used can be swapped out via `CC=` command line argument to `make`.

`CC=` should be set when selecting a config and during a build.

	make CC=clang defconfig

	make CC=clang

Cross Compiling

---------------

A single Clang compiler binary will typically contain all supported backends,

which can help simplify cross compiling.

	ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make CC=clang

`CROSS_COMPILE` is not used to prefix the Clang compiler binary, instead

`CROSS_COMPILE` is used to set a command line flag: `--target <triple>`. For

example:

	clang --target aarch64-linux-gnu foo.c

LLVM Utilities

--------------

LLVM has substitutes for GNU binutils utilities. Kbuild supports `LLVM=1`

to enable them.

	make LLVM=1

They can be enabled individually. The full list of the parameters:

	make CC=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \\

	  OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-size \\

	  READELF=llvm-readelf HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar \\

	  HOSTLD=ld.lld

Currently, the integrated assembler is disabled by default. You can pass

`LLVM_IAS=1` to enable it.

Getting Help

------------

- `Website <https://clangbuiltlinux.github.io/>`_

- `Mailing List <https://groups.google.com/forum/#!forum/clang-built-linux>`_: <clang-built-linux@googlegroups.com>

- `Issue Tracker <https://github.com/ClangBuiltLinux/linux/issues>`_

- IRC: #clangbuiltlinux on chat.freenode.net

- `Telegram <https://t.me/ClangBuiltLinux>`_: @ClangBuiltLinux

- `Wiki <https://github.com/ClangBuiltLinux/linux/wiki>`_

- `Beginner Bugs <https://github.com/ClangBuiltLinux/linux/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22>`_

Getting LLVM

-------------

- http://releases.llvm.org/download.html

- https://github.com/llvm/llvm-project

- https://llvm.org/docs/GettingStarted.html

- https://llvm.org/docs/CMake.html

- https://apt.llvm.org/

- https://www.archlinux.org/packages/extra/x86_64/llvm/

- https://github.com/ClangBuiltLinux/tc-build

- https://github.com/ClangBuiltLinux/linux/wiki/Building-Clang-from-source

- https://android.googlesource.com/platform/prebuilts/clang/host/linux-x86/

C:	irc://chat.freenode.net/clangbuiltlinux

S:	Supported

K:	\b(?i:clang|llvm)\b

F:	Documentation/kbuild/llvm.rst

CLEANCACHE API

M:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

# SPDX-License-Identifier: GPL-2.0

VERSION = 5

PATCHLEVEL = 4

SUBLEVEL = 60

SUBLEVEL = 61

EXTRAVERSION =

NAME = Kleptomaniac Octopus

HOST_LFS_LDFLAGS := $(shell getconf LFS_LDFLAGS 2>/dev/null)

HOST_LFS_LIBS := $(shell getconf LFS_LIBS 2>/dev/null)

ifneq ($(LLVM),)

HOSTCC	= clang

HOSTCXX	= clang++

else

HOSTCC	= gcc

HOSTCXX	= g++

endif

KBUILD_HOSTCFLAGS   := -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 \

		-fomit-frame-pointer -std=gnu89 $(HOST_LFS_CFLAGS) \

		$(HOSTCFLAGS)

KBUILD_HOSTLDLIBS   := $(HOST_LFS_LIBS) $(HOSTLDLIBS)

# Make variables (CC, etc...)

AS		= $(CROSS_COMPILE)as

LD		= $(CROSS_COMPILE)ld

REAL_CC		= $(CROSS_COMPILE)gcc

CPP		= $(CC) -E

ifneq ($(LLVM),)

REAL_CC	= clang

LD		= ld.lld

AR		= llvm-ar

NM		= llvm-nm

OBJCOPY		= llvm-objcopy

OBJDUMP		= llvm-objdump

READELF		= llvm-readelf

OBJSIZE		= llvm-size

STRIP		= llvm-strip

else

REAL_CC		= $(CROSS_COMPILE)gcc

LD		= $(CROSS_COMPILE)ld

AR		= $(CROSS_COMPILE)ar

NM		= $(CROSS_COMPILE)nm

STRIP		= $(CROSS_COMPILE)strip

OBJCOPY		= $(CROSS_COMPILE)objcopy

OBJDUMP		= $(CROSS_COMPILE)objdump

READELF		= $(CROSS_COMPILE)readelf

OBJSIZE		= $(CROSS_COMPILE)size

STRIP		= $(CROSS_COMPILE)strip

endif

PAHOLE		= pahole

LEX		= flex

YACC		= bison

DEPMOD		= /sbin/depmod

PERL		= perl

PYTHON		= python

PYTHON2		= python2

PYTHON3		= python3

CHECK		= sparse

BASH		= bash

GCC_PLUGINS_CFLAGS :=

CLANG_FLAGS :=

export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE AS LD CC

export CPP AR NM STRIP OBJCOPY OBJDUMP OBJSIZE PAHOLE LEX YACC AWK INSTALLKERNEL

export PERL PYTHON PYTHON2 PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX

export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE LD CC

export CPP AR NM STRIP OBJCOPY OBJDUMP OBJSIZE READELF PAHOLE LEX YACC AWK INSTALLKERNEL

export PERL PYTHON PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX

export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE

export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS

ifneq ($(GCC_TOOLCHAIN),)

CLANG_FLAGS	+= --gcc-toolchain=$(GCC_TOOLCHAIN)

endif

ifeq ($(shell $(AS) --version 2>&1 | head -n 1 | grep clang),)

ifneq ($(LLVM_IAS),1)

CLANG_FLAGS	+= -no-integrated-as

endif

CLANG_FLAGS	+= -Werror=unknown-warning-option