From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Masahiro Yamada <masahiroy@kernel.org>,
Nathan Chancellor <natechancellor@gmail.com>,
Nick Desaulniers <ndesaulniers@google.com>
Subject: [PATCH 4.19 33/37] kbuild: support LLVM=1 to switch the default tools to Clang/LLVM
Date: Fri, 25 Sep 2020 14:49:01 +0200 [thread overview]
Message-ID: <20200925124725.938789823@linuxfoundation.org> (raw)
In-Reply-To: <20200925124720.972208530@linuxfoundation.org>
From: Masahiro Yamada <masahiroy@kernel.org>
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")]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
Documentation/kbuild/llvm.rst | 8 ++++++--
Makefile | 29 +++++++++++++++++++++++------
tools/objtool/Makefile | 6 ++++++
3 files changed, 35 insertions(+), 8 deletions(-)
--- 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 \\
--- a/Makefile
+++ b/Makefile
@@ -358,8 +358,13 @@ HOST_LFS_CFLAGS := $(shell getconf LFS_C
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_LDFLAG
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 = $(CROSS_COMPILE)strip
+endif
LEX = flex
YACC = bison
AWK = awk
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -7,9 +7,15 @@ ARCH := x86
endif
# always use the host compiler
+ifneq ($(LLVM),)
+HOSTAR ?= llvm-ar
+HOSTCC ?= clang
+HOSTLD ?= ld.lld
+else
HOSTAR ?= ar
HOSTCC ?= gcc
HOSTLD ?= ld
+endif
AR = $(HOSTAR)
CC = $(HOSTCC)
LD = $(HOSTLD)
next prev parent reply other threads:[~2020-09-25 12:54 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-25 12:48 [PATCH 4.19 00/37] 4.19.148-rc1 review Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 01/37] af_key: pfkey_dump needs parameter validation Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 02/37] KVM: fix memory leak in kvm_io_bus_unregister_dev() Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 03/37] kprobes: fix kill kprobe which has been marked as gone Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 04/37] mm/thp: fix __split_huge_pmd_locked() for migration PMD Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 05/37] cxgb4: Fix offset when clearing filter byte counters Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 06/37] geneve: add transport ports in route lookup for geneve Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 07/37] hdlc_ppp: add range checks in ppp_cp_parse_cr() Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 08/37] ip: fix tos reflection in ack and reset packets Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 09/37] ipv6: avoid lockdep issue in fib6_del() Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 10/37] net: DCB: Validate DCB_ATTR_DCB_BUFFER argument Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 11/37] net: dsa: rtl8366: Properly clear member config Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 12/37] net: ipv6: fix kconfig dependency warning for IPV6_SEG6_HMAC Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 13/37] net: sch_generic: aviod concurrent reset and enqueue op for lockless qdisc Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 14/37] nfp: use correct define to return NONE fec Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 15/37] tipc: Fix memory leak in tipc_group_create_member() Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 16/37] tipc: fix shutdown() of connection oriented socket Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 17/37] tipc: use skb_unshare() instead in tipc_buf_append() Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 18/37] bnxt_en: return proper error codes in bnxt_show_temp Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 19/37] bnxt_en: Protect bnxt_set_eee() and bnxt_set_pauseparam() with mutex Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 20/37] net: phy: Avoid NPD upon phy_detach() when driver is unbound Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 21/37] net: qrtr: check skb_put_padto() return value Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 22/37] net: add __must_check to skb_put_padto() Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 23/37] ipv4: Update exception handling for multipath routes via same device Greg Kroah-Hartman
2020-09-25 16:51 ` Pavel Machek
2020-09-26 15:46 ` Greg Kroah-Hartman
2020-09-29 12:26 ` Pavel Machek
2020-09-25 12:48 ` [PATCH 4.19 24/37] MAINTAINERS: add CLANG/LLVM BUILD SUPPORT info Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 25/37] kbuild: add OBJSIZE variable for the size tool Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 26/37] Documentation/llvm: add documentation on building w/ Clang/LLVM Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 27/37] Documentation/llvm: fix the name of llvm-size Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 28/37] net: wan: wanxl: use allow to pass CROSS_COMPILE_M68k for rebuilding firmware Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 29/37] net: wan: wanxl: use $(M68KCC) instead of $(M68KAS) " Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 30/37] x86/boot: kbuild: allow readelf executable to be specified Greg Kroah-Hartman
2020-09-25 12:48 ` [PATCH 4.19 31/37] kbuild: remove AS variable Greg Kroah-Hartman
2020-09-25 12:49 ` [PATCH 4.19 32/37] kbuild: replace AS=clang with LLVM_IAS=1 Greg Kroah-Hartman
2020-09-25 12:49 ` Greg Kroah-Hartman [this message]
2020-09-25 12:49 ` [PATCH 4.19 34/37] mm: memcg: fix memcg reclaim soft lockup Greg Kroah-Hartman
2020-09-25 12:49 ` [PATCH 4.19 35/37] tcp_bbr: refactor bbr_target_cwnd() for general inflight provisioning Greg Kroah-Hartman
2020-09-25 12:49 ` [PATCH 4.19 36/37] tcp_bbr: adapt cwnd based on ack aggregation estimation Greg Kroah-Hartman
2020-09-25 12:49 ` [PATCH 4.19 37/37] serial: 8250: Avoid error message on reprobe Greg Kroah-Hartman
2020-09-25 17:39 ` [PATCH 4.19 00/37] 4.19.148-rc1 review Pavel Machek
2020-09-26 15:50 ` Greg Kroah-Hartman
2020-09-25 20:02 ` Shuah Khan
2020-09-26 12:35 ` Naresh Kamboju
2020-09-26 15:42 ` Guenter Roeck
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