* LLVM=1 patches for 4.19
@ 2020-09-25 0:04 Nick Desaulniers
2020-09-25 8:54 ` Greg KH
0 siblings, 1 reply; 2+ messages in thread
From: Nick Desaulniers @ 2020-09-25 0:04 UTC (permalink / raw)
To: Greg KH, Sasha Levin
Cc: Masahiro Yamada, # 3.4.x, clang-built-linux, Nathan Chancellor
[-- Attachment #1: Type: text/plain, Size: 2673 bytes --]
Dear stable kernel maintainers,
Please consider the attached mbox file, which contains 10 patches which
cherry pick cleanly onto 4.19.y:
1. commit 8708e13c6a06 ("MAINTAINERS: add CLANG/LLVM BUILD SUPPORT info")
2. commit 7bac98707f65 ("kbuild: add OBJSIZE variable for the size tool")
3. commit fcf1b6a35c ("Documentation/llvm: add documentation on
building w/ Clang/LLVM")
4. commit 0f44fbc162b7 ("Documentation/llvm: fix the name of llvm-size")
5. commit 63b903dfebde ("net: wan: wanxl: use allow to pass
CROSS_COMPILE_M68k for rebuilding firmware")
6. commit 734f3719d343 ("net: wan: wanxl: use $(M68KCC) instead of
$(M68KAS) for rebuilding firmware")
7. commit eefb8c124fd9 ("x86/boot: kbuild: allow readelf executable to
be specified")
8. commit aa824e0c962b ("kbuild: remove AS variable")
9. commit 7e20e47c70f8 ("kbuild: replace AS=clang with LLVM_IAS=1")
10. commit a0d1c951ef08 ("kbuild: support LLVM=1 to switch the default
tools to Clang/LLVM")
The series is analogous to the previous accepted series sent for 5.4,
though this series is for 4.19.y:
https://lore.kernel.org/stable/CAKwvOd=Ko_UHWF-bYotqjPVw=chW_KMUFuBp_o8uOg0wOyHyWA@mail.gmail.com/T/#u
I don't plan to backport the series any further than 4.19.
This series improves/simplifies building kernels with Clang and LLVM
utilities; it will help the various CI systems testing kernels built
with Clang+LLVM utilities, and
we will make immediate use of it in Android (see also:
https://android-review.googlesource.com/c/platform/prebuilts/clang/host/linux-x86/+/1405387).
We can always carry it out of tree in Android, but I think the series
is fairly tame, and would prefer not to.
Some differences in this series from the one sent for 5.4:
additional backports:
1. commit 8708e13c6a06 ("MAINTAINERS: add CLANG/LLVM BUILD SUPPORT info")
2. commit 7bac98707f65 ("kbuild: add OBJSIZE variable for the size tool")
which landed in v5.2-rc7 and v5.3-rc4 respectively. It also drops the
5.4 backport of
1. commit e9781b52d4e0 ("kbuild: add PYTHON2 and PYTHON3 variables")
which was not necessary, as it was backported to 5.4 to resolve merge
conflicts which occurred anyways in this series due to not backporting
to 4.19 the following commits which caused minor conflicts:
1. commit e83b9f55448a ("kbuild: add ability to generate BTF type info
for vmlinux")
2. commit cd238effefa2 ("docs: kbuild: convert docs to ReST and rename
to *.rst")
Put another way, because I avoided backporting e83b9f55448a and
cd238effefa2, most of the patches needed to be slightly modified in
small ways (noted in each commit message), such that there was no
point in backporting e9781b52d4e0.
--
Thanks,
~Nick Desaulniers
[-- Attachment #2: llvm_1.4.19.mbox --]
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From d3071fb4072453db06bf003873bdf26c45aae33e Mon Sep 17 00:00:00 2001
From: Nick Desaulniers <ndesaulniers@google.com>
Date: Fri, 28 Jun 2019 12:07:12 -0700
Subject: [PATCH 01/10] MAINTAINERS: add CLANG/LLVM BUILD SUPPORT info
commit 8708e13c6a0600625eea3aebd027c0715a5d2bb2 upstream.
Add keyword support so that our mailing list gets cc'ed for clang/llvm
patches. We're pretty active on our mailing list so far as code review.
There are numerous Googlers like myself that are paid to support
building the Linux kernel with Clang and LLVM.
Link: http://lkml.kernel.org/r/20190620001907.255803-1-ndesaulniers@google.com
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
MAINTAINERS | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index b9f9da0b886f..9388564b7ab5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3613,6 +3613,14 @@ M: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
S: Maintained
F: .clang-format
+CLANG/LLVM BUILD SUPPORT
+L: clang-built-linux@googlegroups.com
+W: https://clangbuiltlinux.github.io/
+B: https://github.com/ClangBuiltLinux/linux/issues
+C: irc://chat.freenode.net/clangbuiltlinux
+S: Supported
+K: \b(?i:clang|llvm)\b
+
CLEANCACHE API
M: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
L: linux-kernel@vger.kernel.org
--
2.28.0.681.g6f77f65b4e-goog
From 5151ab575e2c0da8f78910529ccd2ca5c14be7e6 Mon Sep 17 00:00:00 2001
From: Vasily Gorbik <gor@linux.ibm.com>
Date: Mon, 21 Jan 2019 13:54:39 +0100
Subject: [PATCH 02/10] kbuild: add OBJSIZE variable for the size tool
commit 7bac98707f65b93bf994ef4e99b1eb9e7dbb9c32 upstream.
Define and export OBJSIZE variable for "size" tool from binutils to be
used in architecture specific Makefiles (naming the variable just "SIZE"
would be too risky). In particular this tool is useful to perform checks
that early boot code is not using bss section (which might have not been
zeroed yet or intersects with initrd or other files boot loader might
have put right after the linux kernel).
Link: http://lkml.kernel.org/r/patch-1.thread-2257a1.git-188f5a3d81d5.your-ad-here.call-01565088755-ext-5120@work.hours
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
[nd: conflict in exported vars list from not backporting commit
e83b9f55448a ("kbuild: add ability to generate BTF type info for vmlinux")]
---
Makefile | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
index aaeb3f3dbcea..9b758549c7ce 100644
--- a/Makefile
+++ b/Makefile
@@ -377,6 +377,7 @@ NM = $(CROSS_COMPILE)nm
STRIP = $(CROSS_COMPILE)strip
OBJCOPY = $(CROSS_COMPILE)objcopy
OBJDUMP = $(CROSS_COMPILE)objdump
+OBJSIZE = $(CROSS_COMPILE)size
LEX = flex
YACC = bison
AWK = awk
@@ -433,7 +434,7 @@ GCC_PLUGINS_CFLAGS :=
CLANG_FLAGS :=
export ARCH SRCARCH CONFIG_SHELL HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE AS LD CC
-export CPP AR NM STRIP OBJCOPY OBJDUMP KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS
+export CPP AR NM STRIP OBJCOPY OBJDUMP OBJSIZE KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS
export MAKE LEX YACC AWK GENKSYMS INSTALLKERNEL PERL PYTHON PYTHON2 PYTHON3 UTS_MACHINE
export HOSTCXX KBUILD_HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS
--
2.28.0.681.g6f77f65b4e-goog
From f34e416b022fd5580abaf568300236f44121ca8e Mon Sep 17 00:00:00 2001
From: Nick Desaulniers <ndesaulniers@google.com>
Date: Wed, 26 Feb 2020 15:23:36 -0800
Subject: [PATCH 03/10] Documentation/llvm: add documentation on building w/
Clang/LLVM
commit fcf1b6a35c16ac500fa908a4022238e5d666eabf upstream.
added to kbuild documentation. Provides more official info on building
kernels with Clang and LLVM than our wiki.
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
[nd: hunk against Documentation/kbuild/index.rst dropped due to not backporting
commit cd238effefa2 ("docs: kbuild: convert docs to ReST and rename to *.rst")]
---
Documentation/kbuild/llvm.rst | 80 +++++++++++++++++++++++++++++++++++
MAINTAINERS | 1 +
2 files changed, 81 insertions(+)
create mode 100644 Documentation/kbuild/llvm.rst
diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst
new file mode 100644
index 000000000000..d6c79eb4e23e
--- /dev/null
+++ b/Documentation/kbuild/llvm.rst
@@ -0,0 +1,80 @@
+==============================
+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. These can be invoked as
+additional parameters to `make`.
+
+ make CC=clang AS=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \\
+ OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-objsize \\
+ READELF=llvm-readelf HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar \\
+ HOSTLD=ld.lld
+
+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/
diff --git a/MAINTAINERS b/MAINTAINERS
index 9388564b7ab5..1061db6fbc32 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3620,6 +3620,7 @@ B: https://github.com/ClangBuiltLinux/linux/issues
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>
--
2.28.0.681.g6f77f65b4e-goog
From c7487d79af045e280f4ec85c866241e7846970a1 Mon Sep 17 00:00:00 2001
From: Fangrui Song <maskray@google.com>
Date: Thu, 2 Apr 2020 10:38:42 -0700
Subject: [PATCH 04/10] Documentation/llvm: fix the name of llvm-size
commit 0f44fbc162b737ff6251ae248184390ae2279fee upstream.
The tool is called llvm-size, not llvm-objsize.
Fixes: fcf1b6a35c16 ("Documentation/llvm: add documentation on building w/ Clang/LLVM")
Signed-off-by: Fangrui Song <maskray@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
Documentation/kbuild/llvm.rst | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst
index d6c79eb4e23e..eefbdfa3e4d9 100644
--- a/Documentation/kbuild/llvm.rst
+++ b/Documentation/kbuild/llvm.rst
@@ -51,7 +51,7 @@ LLVM has substitutes for GNU binutils utilities. These can be invoked as
additional parameters to `make`.
make CC=clang AS=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \\
- OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-objsize \\
+ OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-size \\
READELF=llvm-readelf HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar \\
HOSTLD=ld.lld
--
2.28.0.681.g6f77f65b4e-goog
From 76a29f2333427490c3319b353a0d4ad85aa35e79 Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <masahiroy@kernel.org>
Date: Thu, 26 Mar 2020 14:57:15 +0900
Subject: [PATCH 05/10] net: wan: wanxl: use allow to pass CROSS_COMPILE_M68k
for rebuilding firmware
commit 63b903dfebdea92aa92ad337d8451a6fbfeabf9d upstream.
As far as I understood from the Kconfig help text, this build rule is
used to rebuild the driver firmware, which runs on an old m68k-based
chip. So, you need m68k tools for the firmware rebuild.
wanxl.c is a PCI driver, but CONFIG_M68K does not select CONFIG_HAVE_PCI.
So, you cannot enable CONFIG_WANXL_BUILD_FIRMWARE for ARCH=m68k. In other
words, ifeq ($(ARCH),m68k) is false here.
I am keeping the dead code for now, but rebuilding the firmware requires
'as68k' and 'ld68k', which I do not have in hand.
Instead, the kernel.org m68k GCC [1] successfully built it.
Allowing a user to pass in CROSS_COMPILE_M68K= is handier.
[1] https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/9.2.0/x86_64-gcc-9.2.0-nolibc-m68k-linux.tar.xz
Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
drivers/net/wan/Kconfig | 2 +-
drivers/net/wan/Makefile | 12 ++++++------
2 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/net/wan/Kconfig b/drivers/net/wan/Kconfig
index 4e9fe75d7067..21190dfbabb1 100644
--- a/drivers/net/wan/Kconfig
+++ b/drivers/net/wan/Kconfig
@@ -199,7 +199,7 @@ config WANXL_BUILD_FIRMWARE
depends on WANXL && !PREVENT_FIRMWARE_BUILD
help
Allows you to rebuild firmware run by the QUICC processor.
- It requires as68k, ld68k and hexdump programs.
+ It requires m68k toolchains and hexdump programs.
You should never need this option, say N.
diff --git a/drivers/net/wan/Makefile b/drivers/net/wan/Makefile
index 9532e69fda87..c21b7345b50b 100644
--- a/drivers/net/wan/Makefile
+++ b/drivers/net/wan/Makefile
@@ -41,17 +41,17 @@ $(obj)/wanxl.o: $(obj)/wanxlfw.inc
ifeq ($(CONFIG_WANXL_BUILD_FIRMWARE),y)
ifeq ($(ARCH),m68k)
- AS68K = $(AS)
- LD68K = $(LD)
+ M68KAS = $(AS)
+ M68KLD = $(LD)
else
- AS68K = as68k
- LD68K = ld68k
+ M68KAS = $(CROSS_COMPILE_M68K)as
+ M68KLD = $(CROSS_COMPILE_M68K)ld
endif
quiet_cmd_build_wanxlfw = BLD FW $@
cmd_build_wanxlfw = \
- $(CPP) -D__ASSEMBLY__ -Wp,-MD,$(depfile) -I$(srctree)/include/uapi $< | $(AS68K) -m68360 -o $(obj)/wanxlfw.o; \
- $(LD68K) --oformat binary -Ttext 0x1000 $(obj)/wanxlfw.o -o $(obj)/wanxlfw.bin; \
+ $(CPP) -D__ASSEMBLY__ -Wp,-MD,$(depfile) -I$(srctree)/include/uapi $< | $(M68KAS) -m68360 -o $(obj)/wanxlfw.o; \
+ $(M68KLD) --oformat binary -Ttext 0x1000 $(obj)/wanxlfw.o -o $(obj)/wanxlfw.bin; \
hexdump -ve '"\n" 16/1 "0x%02X,"' $(obj)/wanxlfw.bin | sed 's/0x ,//g;1s/^/static const u8 firmware[]={/;$$s/,$$/\n};\n/' >$(obj)/wanxlfw.inc; \
rm -f $(obj)/wanxlfw.bin $(obj)/wanxlfw.o
--
2.28.0.681.g6f77f65b4e-goog
From 2468f4ebe56b9bc2d18884e1726b35041fdb18fa Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <masahiroy@kernel.org>
Date: Thu, 26 Mar 2020 14:57:16 +0900
Subject: [PATCH 06/10] net: wan: wanxl: use $(M68KCC) instead of $(M68KAS) for
rebuilding firmware
commit 734f3719d3438f9cc181d674c33ca9762e9148a1 upstream.
The firmware source, wanxlfw.S, is currently compiled by the combo of
$(CPP) and $(M68KAS). This is not what we usually do for compiling *.S
files. In fact, this Makefile is the only user of $(AS) in the kernel
build.
Instead of combining $(CPP) and (AS) from different tool sets, using
$(M68KCC) as an assembler driver is simpler, and saner.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
drivers/net/wan/Makefile | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/net/wan/Makefile b/drivers/net/wan/Makefile
index c21b7345b50b..0500282e176e 100644
--- a/drivers/net/wan/Makefile
+++ b/drivers/net/wan/Makefile
@@ -41,16 +41,16 @@ $(obj)/wanxl.o: $(obj)/wanxlfw.inc
ifeq ($(CONFIG_WANXL_BUILD_FIRMWARE),y)
ifeq ($(ARCH),m68k)
- M68KAS = $(AS)
+ M68KCC = $(CC)
M68KLD = $(LD)
else
- M68KAS = $(CROSS_COMPILE_M68K)as
+ M68KCC = $(CROSS_COMPILE_M68K)gcc
M68KLD = $(CROSS_COMPILE_M68K)ld
endif
quiet_cmd_build_wanxlfw = BLD FW $@
cmd_build_wanxlfw = \
- $(CPP) -D__ASSEMBLY__ -Wp,-MD,$(depfile) -I$(srctree)/include/uapi $< | $(M68KAS) -m68360 -o $(obj)/wanxlfw.o; \
+ $(M68KCC) -D__ASSEMBLY__ -Wp,-MD,$(depfile) -I$(srctree)/include/uapi -c -o $(obj)/wanxlfw.o $<; \
$(M68KLD) --oformat binary -Ttext 0x1000 $(obj)/wanxlfw.o -o $(obj)/wanxlfw.bin; \
hexdump -ve '"\n" 16/1 "0x%02X,"' $(obj)/wanxlfw.bin | sed 's/0x ,//g;1s/^/static const u8 firmware[]={/;$$s/,$$/\n};\n/' >$(obj)/wanxlfw.inc; \
rm -f $(obj)/wanxlfw.bin $(obj)/wanxlfw.o
--
2.28.0.681.g6f77f65b4e-goog
From 8fe85728b46a8ee90265696c9876a72596415044 Mon Sep 17 00:00:00 2001
From: Dmitry Golovin <dima@golovin.in>
Date: Thu, 5 Dec 2019 00:54:41 +0200
Subject: [PATCH 07/10] x86/boot: kbuild: allow readelf executable to be
specified
commit eefb8c124fd969e9a174ff2bedff86aa305a7438 upstream.
Introduce a new READELF variable to top-level Makefile, so the name of
readelf binary can be specified.
Before this change the name of the binary was hardcoded to
"$(CROSS_COMPILE)readelf" which might not be present for every
toolchain.
This allows to build with LLVM Object Reader by using make parameter
READELF=llvm-readelf.
Link: https://github.com/ClangBuiltLinux/linux/issues/771
Signed-off-by: Dmitry Golovin <dima@golovin.in>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
[nd: conflict in exported vars list from not backporting commit
e83b9f55448a ("kbuild: add ability to generate BTF type info for vmlinux")]
---
Makefile | 3 ++-
arch/x86/boot/compressed/Makefile | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/Makefile b/Makefile
index 9b758549c7ce..2135f3df0eee 100644
--- a/Makefile
+++ b/Makefile
@@ -378,6 +378,7 @@ STRIP = $(CROSS_COMPILE)strip
OBJCOPY = $(CROSS_COMPILE)objcopy
OBJDUMP = $(CROSS_COMPILE)objdump
OBJSIZE = $(CROSS_COMPILE)size
+READELF = $(CROSS_COMPILE)readelf
LEX = flex
YACC = bison
AWK = awk
@@ -434,7 +435,7 @@ GCC_PLUGINS_CFLAGS :=
CLANG_FLAGS :=
export ARCH SRCARCH CONFIG_SHELL HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE AS LD CC
-export CPP AR NM STRIP OBJCOPY OBJDUMP OBJSIZE KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS
+export CPP AR NM STRIP OBJCOPY OBJDUMP OBJSIZE READELF KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS
export MAKE LEX YACC AWK GENKSYMS INSTALLKERNEL PERL PYTHON PYTHON2 PYTHON3 UTS_MACHINE
export HOSTCXX KBUILD_HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 466f66c8a7f8..10c8d6a2b20b 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -100,7 +100,7 @@ vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_thunk_$(BITS).o
quiet_cmd_check_data_rel = DATAREL $@
define cmd_check_data_rel
for obj in $(filter %.o,$^); do \
- ${CROSS_COMPILE}readelf -S $$obj | grep -qF .rel.local && { \
+ $(READELF) -S $$obj | grep -qF .rel.local && { \
echo "error: $$obj has data relocations!" >&2; \
exit 1; \
} || true; \
--
2.28.0.681.g6f77f65b4e-goog
From 57f3e5a88befcfe332b0157e6904b5f3be2bff5f Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <masahiroy@kernel.org>
Date: Thu, 26 Mar 2020 14:57:18 +0900
Subject: [PATCH 08/10] kbuild: remove AS variable
commit aa824e0c962b532d5073cbb41b2efcd6f5e72bae upstream.
As commit 5ef872636ca7 ("kbuild: get rid of misleading $(AS) from
documents") noted, we rarely use $(AS) directly in the kernel build.
Now that the only/last user of $(AS) in drivers/net/wan/Makefile was
converted to $(CC), $(AS) is no longer used in the build process.
You can still pass in AS=clang, which is just a switch to turn on
the LLVM integrated assembler.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
[nd: conflict in exported vars list from not backporting commit
e83b9f55448a ("kbuild: add ability to generate BTF type info for vmlinux")]
---
Makefile | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/Makefile b/Makefile
index 2135f3df0eee..08f47c559548 100644
--- a/Makefile
+++ b/Makefile
@@ -368,7 +368,6 @@ KBUILD_HOSTLDFLAGS := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
KBUILD_HOSTLDLIBS := $(HOST_LFS_LIBS) $(HOSTLDLIBS)
# Make variables (CC, etc...)
-AS = $(CROSS_COMPILE)as
LD = $(CROSS_COMPILE)ld
CC = $(CROSS_COMPILE)gcc
CPP = $(CC) -E
@@ -434,7 +433,7 @@ KBUILD_LDFLAGS :=
GCC_PLUGINS_CFLAGS :=
CLANG_FLAGS :=
-export ARCH SRCARCH CONFIG_SHELL HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE AS LD CC
+export ARCH SRCARCH CONFIG_SHELL HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE LD CC
export CPP AR NM STRIP OBJCOPY OBJDUMP OBJSIZE READELF KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS
export MAKE LEX YACC AWK GENKSYMS INSTALLKERNEL PERL PYTHON PYTHON2 PYTHON3 UTS_MACHINE
export HOSTCXX KBUILD_HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS
--
2.28.0.681.g6f77f65b4e-goog
From 56677e12eb4216762c61c53f74e03bf41c69da39 Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <masahiroy@kernel.org>
Date: Wed, 8 Apr 2020 10:36:22 +0900
Subject: [PATCH 09/10] kbuild: replace AS=clang with LLVM_IAS=1
commit 7e20e47c70f810d678d02941fa3c671209c4ca97 upstream.
The 'AS' variable is unused for building the kernel. Only the remaining
usage is to turn on the integrated assembler. A boolean flag is a better
fit for this purpose.
AS=clang was added for experts. So, I replaced it with LLVM_IAS=1,
breaking the backward compatibility.
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
Documentation/kbuild/llvm.rst | 5 ++++-
Makefile | 2 ++
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst
index eefbdfa3e4d9..450708534860 100644
--- a/Documentation/kbuild/llvm.rst
+++ b/Documentation/kbuild/llvm.rst
@@ -50,11 +50,14 @@ LLVM Utilities
LLVM has substitutes for GNU binutils utilities. These can be invoked as
additional parameters to `make`.
- make CC=clang AS=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \\
+ 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
------------
diff --git a/Makefile b/Makefile
index 08f47c559548..0ee360e98de1 100644
--- a/Makefile
+++ b/Makefile
@@ -492,7 +492,9 @@ endif
ifneq ($(GCC_TOOLCHAIN),)
CLANG_FLAGS += --gcc-toolchain=$(GCC_TOOLCHAIN)
endif
+ifneq ($(LLVM_IAS),1)
CLANG_FLAGS += -no-integrated-as
+endif
CLANG_FLAGS += -Werror=unknown-warning-option
KBUILD_CFLAGS += $(CLANG_FLAGS)
KBUILD_AFLAGS += $(CLANG_FLAGS)
--
2.28.0.681.g6f77f65b4e-goog
From 487e2e6fe9414161b014f5772b4ed8e46cf4a0a6 Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <masahiroy@kernel.org>
Date: Wed, 8 Apr 2020 10:36:23 +0900
Subject: [PATCH 10/10] kbuild: support LLVM=1 to switch the default tools to
Clang/LLVM
commit a0d1c951ef08ed24f35129267e3595d86f57f5d3 upstream.
As Documentation/kbuild/llvm.rst implies, building the kernel with a
full set of LLVM tools gets very verbose and unwieldy.
Provide a single switch LLVM=1 to use Clang and LLVM tools instead
of GCC and Binutils. You can pass it from the command line or as an
environment variable.
Please note LLVM=1 does not turn on the integrated assembler. You need
to pass LLVM_IAS=1 to use it. When the upstream kernel is ready for the
integrated assembler, I think we can make it default.
We discussed what we need, and we agreed to go with a simple boolean
flag that switches both target and host tools:
https://lkml.org/lkml/2020/3/28/494
https://lkml.org/lkml/2020/4/3/43
Some items discussed, but not adopted:
- LLVM_DIR
When multiple versions of LLVM are installed, I just thought supporting
LLVM_DIR=/path/to/my/llvm/bin/ might be useful.
CC = $(LLVM_DIR)clang
LD = $(LLVM_DIR)ld.lld
...
However, we can handle this by modifying PATH. So, we decided to not do
this.
- LLVM_SUFFIX
Some distributions (e.g. Debian) package specific versions of LLVM with
naming conventions that use the version as a suffix.
CC = clang$(LLVM_SUFFIX)
LD = ld.lld(LLVM_SUFFIX)
...
will allow a user to pass LLVM_SUFFIX=-11 to use clang-11 etc.,
but the suffixed versions in /usr/bin/ are symlinks to binaries in
/usr/lib/llvm-#/bin/, so this can also be handled by PATH.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com> # build
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
[nd: conflict in exported vars list from not backporting commit
e83b9f55448a ("kbuild: add ability to generate BTF type info for vmlinux")]
[nd: hunk against Documentation/kbuild/kbuild.rst dropped due to not backporting
commit cd238effefa2 ("docs: kbuild: convert docs to ReST and rename to *.rst")]
---
Documentation/kbuild/llvm.rst | 8 ++++++--
Makefile | 29 +++++++++++++++++++++++------
tools/objtool/Makefile | 6 ++++++
3 files changed, 35 insertions(+), 8 deletions(-)
diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst
index 450708534860..c776b6eee969 100644
--- a/Documentation/kbuild/llvm.rst
+++ b/Documentation/kbuild/llvm.rst
@@ -47,8 +47,12 @@ example:
LLVM Utilities
--------------
-LLVM has substitutes for GNU binutils utilities. These can be invoked as
-additional parameters to `make`.
+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 \\
diff --git a/Makefile b/Makefile
index 0ee360e98de1..9810cbba0cea 100644
--- a/Makefile
+++ b/Makefile
@@ -358,8 +358,13 @@ HOST_LFS_CFLAGS := $(shell getconf LFS_CFLAGS 2>/dev/null)
HOST_LFS_LDFLAGS := $(shell getconf LFS_LDFLAGS 2>/dev/null)
HOST_LFS_LIBS := $(shell getconf LFS_LIBS 2>/dev/null)
-HOSTCC = gcc
-HOSTCXX = g++
+ifneq ($(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)
@@ -368,16 +373,28 @@ KBUILD_HOSTLDFLAGS := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
KBUILD_HOSTLDLIBS := $(HOST_LFS_LIBS) $(HOSTLDLIBS)
# Make variables (CC, etc...)
-LD = $(CROSS_COMPILE)ld
-CC = $(CROSS_COMPILE)gcc
CPP = $(CC) -E
+ifneq ($(LLVM),)
+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
+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
-OBJSIZE = $(CROSS_COMPILE)size
READELF = $(CROSS_COMPILE)readelf
+OBJSIZE = $(CROSS_COMPILE)size
+STRIP = $(CROSS_COMPILE)strip
+endif
LEX = flex
YACC = bison
AWK = awk
diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index 20f67fcf378d..baa92279c137 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -7,9 +7,15 @@ ARCH := x86
endif
# always use the host compiler
+ifneq ($(LLVM),)
+HOSTAR ?= llvm-ar
+HOSTCC ?= clang
+HOSTLD ?= ld.lld
+else
HOSTAR ?= ar
HOSTCC ?= gcc
HOSTLD ?= ld
+endif
AR = $(HOSTAR)
CC = $(HOSTCC)
LD = $(HOSTLD)
--
2.28.0.681.g6f77f65b4e-goog
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: LLVM=1 patches for 4.19
2020-09-25 0:04 LLVM=1 patches for 4.19 Nick Desaulniers
@ 2020-09-25 8:54 ` Greg KH
0 siblings, 0 replies; 2+ messages in thread
From: Greg KH @ 2020-09-25 8:54 UTC (permalink / raw)
To: Nick Desaulniers
Cc: Sasha Levin, Masahiro Yamada, # 3.4.x, clang-built-linux,
Nathan Chancellor
On Thu, Sep 24, 2020 at 05:04:45PM -0700, Nick Desaulniers wrote:
> Dear stable kernel maintainers,
> Please consider the attached mbox file, which contains 10 patches which
> cherry pick cleanly onto 4.19.y:
> 1. commit 8708e13c6a06 ("MAINTAINERS: add CLANG/LLVM BUILD SUPPORT info")
> 2. commit 7bac98707f65 ("kbuild: add OBJSIZE variable for the size tool")
> 3. commit fcf1b6a35c ("Documentation/llvm: add documentation on
> building w/ Clang/LLVM")
> 4. commit 0f44fbc162b7 ("Documentation/llvm: fix the name of llvm-size")
> 5. commit 63b903dfebde ("net: wan: wanxl: use allow to pass
> CROSS_COMPILE_M68k for rebuilding firmware")
> 6. commit 734f3719d343 ("net: wan: wanxl: use $(M68KCC) instead of
> $(M68KAS) for rebuilding firmware")
> 7. commit eefb8c124fd9 ("x86/boot: kbuild: allow readelf executable to
> be specified")
> 8. commit aa824e0c962b ("kbuild: remove AS variable")
> 9. commit 7e20e47c70f8 ("kbuild: replace AS=clang with LLVM_IAS=1")
> 10. commit a0d1c951ef08 ("kbuild: support LLVM=1 to switch the default
> tools to Clang/LLVM")
>
> The series is analogous to the previous accepted series sent for 5.4,
> though this series is for 4.19.y:
> https://lore.kernel.org/stable/CAKwvOd=Ko_UHWF-bYotqjPVw=chW_KMUFuBp_o8uOg0wOyHyWA@mail.gmail.com/T/#u
>
> I don't plan to backport the series any further than 4.19.
Yeah, I wouldn't worry about anything older than 4.19.y at the moment
for stuff like this.
All look good, now queued up, thanks!
greg k-h
^ permalink raw reply [flat|nested] 2+ messages in thread
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