OpenCloudOS-Kernel/Documentation
Nathan Chancellor df05c0e949 Documentation: Raise the minimum supported version of LLVM to 11.0.0
LLVM versions prior to 11.0.0 have a harder time with dead code
elimination, which can cause issues with commonly used expressions such
as BUILD_BUG_ON and the bitmask functions/macros in bitfield.h (see the
first two issues links below).

Whenever there is an issue within LLVM that has been resolved in a later
release, the only course of action is to gate the problematic
configuration or source code on the toolchain verson or raise the
minimum supported version of LLVM for building the kernel, as LLVM has a
limited support lifetime compared to GCC. GCC major releases will
typically see a few point releases across a two year period on average
whereas LLVM major releases are only supported until the next major
release and will only see one or two point releases within that
timeframe. For example, GCC 8.1 was released in May 2018 and GCC 8.5 was
released in May 2021, whereas LLVM 12.0.0 was released in April 2021 and
its only point release, 12.0.1, was released in July 2021, giving a
minimal window for fixes to be backported.

To resolve these build errors around improper dead code elimination,
raise the minimum supported version of LLVM for building the kernel to
11.0.0. Doing so is a more proper solution than mucking around with core
kernel macros that have always worked with GCC or disabling drivers for
using these macros in a proper manner. This type of issue may continue
to crop up and require patching, which creates more debt for bumping the
minimum supported version in the future.

This should have a minimal impact to distributions. Using a script to
pull several different Docker images and check the output of
'clang --version':

archlinux:latest: clang version 13.0.0

debian:oldoldstable-slim: clang version 3.8.1-24 (tags/RELEASE_381/final)
debian:oldstable-slim: clang version 7.0.1-8+deb10u2 (tags/RELEASE_701/final)
debian:stable-slim: Debian clang version 11.0.1-2
debian:testing-slim: Debian clang version 11.1.0-4
debian:unstable-slim: Debian clang version 11.1.0-4

fedora:34: clang version 12.0.1 (Fedora 12.0.1-1.fc34)
fedora:latest: clang version 13.0.0 (Fedora 13.0.0-3.fc35)
fedora:rawhide: clang version 13.0.0 (Fedora 13.0.0-5.fc36)

opensuse/leap:15.2: clang version 9.0.1
opensuse/leap:latest: clang version 11.0.1
opensuse/tumbleweed:latest: clang version 13.0.0

ubuntu:bionic: clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final)
ubuntu:latest: clang version 10.0.0-4ubuntu1
ubuntu:hirsute: Ubuntu clang version 12.0.0-3ubuntu1~21.04.2
ubuntu:rolling: Ubuntu clang version 13.0.0-2
ubuntu:devel: Ubuntu clang version 13.0.0-9

In every case, the distribution's version of clang is either older than
the current minimum supported version of LLVM 10.0.1 or equal to or
greater than the proposed 11.0.0 so nothing should change.

Another benefit of this change is LLVM=1 works better with arm64 and
x86_64 since commit f12b034afe ("scripts/Makefile.clang: default to
LLVM_IAS=1") enabled the integrated assembler by default, which only
works well with clang 11+ (clang-10 required it to be disabled to
successfully build a kernel).

Link: https://github.com/ClangBuiltLinux/linux/issues/1293
Link: https://github.com/ClangBuiltLinux/linux/issues/1506
Link: https://github.com/ClangBuiltLinux/linux/issues/1511
Link: fa496ce3c6
Link: https://groups.google.com/g/clang-built-linux/c/mPQb9_ZWW0s/m/W7o6S-QTBAAJ
Link: https://github.com/ClangBuiltLinux/misc-scripts
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-12-02 17:24:32 +09:00
..
ABI f2fs-for-5.16-rc1 2021-11-13 11:20:22 -08:00
PCI
RCU rcu: Fix undefined Kconfig macros 2021-09-13 16:32:46 -07:00
accounting
admin-guide platform-drivers-x86 for v5.16-2 2021-11-18 14:39:40 -08:00
arm Documentation: arm: marvell: Fix link to armada_1000_pb.pdf document 2021-11-15 02:49:56 -07:00
arm64 Merge branch 'for-next/trbe-errata' into for-next/core 2021-10-29 12:25:33 +01:00
block This is a relatively unexciting cycle for documentation. 2021-11-02 22:11:39 -07:00
bpf libbpf: update index.rst reference 2021-11-17 06:12:14 -07:00
cdrom drivers/cdrom: improved ioctl for media change detection 2021-09-14 20:05:26 -06:00
core-api Merge branch 'akpm' (patches from Andrew) 2021-11-06 14:08:17 -07:00
cpu-freq
crypto crypto: engine - Add KPP Support to Crypto Engine 2021-10-29 21:04:03 +08:00
dev-tools Merge branch 'akpm' (patches from Andrew) 2021-11-09 10:11:53 -08:00
devicetree dt-bindings: i2c: imx-lpi2c: Fix i.MX 8QM compatible matching 2021-11-23 09:54:00 +01:00
doc-guide docs: Update Sphinx requirements 2021-11-15 02:47:22 -07:00
driver-api cxl for v5.16 2021-11-08 11:49:48 -08:00
fault-injection
fb
features parisc: Move thread_info into task struct 2021-11-01 07:35:59 +01:00
filesystems docs: filesystem: cifs: ksmbd: Fix small layout issues 2021-11-25 00:09:26 -06:00
firmware-guide Documentation: ACPI: Fix non-D0 probe _DSC object example 2021-11-10 13:59:12 +01:00
firmware_class
fpga
gpu drm-misc-next for 5.16: 2021-11-05 13:50:15 +10:00
hid
hwmon Driver core changes for 5.16-rc1 2021-11-04 08:32:38 -07:00
i2c docs: i2c: smbus-protocol: mention the repeated start condition 2021-11-23 12:59:41 +01:00
ia64
ide
iio
infiniband
input
isdn
kbuild Kbuild updates for v5.16 2021-11-08 09:15:45 -08:00
kernel-hacking docs: futex: Fix kernel-doc references 2021-10-19 17:27:05 +02:00
leds leds: add new LED_FUNCTION_PLAYER for player LEDs for game controllers. 2021-10-27 09:49:29 +02:00
litmus-tests
livepatch
locking doc: drm: remove TODO entry regarding DRM_MODSET_LOCK_ALL cleanup 2021-10-01 13:01:05 -04:00
m68k
maintainer docs: use the lore redirector everywhere 2021-10-12 13:58:19 -06:00
mhi
mips
misc-devices
netlabel
networking ptp: fix filter names in the documentation 2021-11-26 11:19:19 -08:00
nios2
nvdimm
openrisc
parisc
pcmcia
power Documentation: power: Describe 'advanced' and 'simple' EM models 2021-11-10 21:26:34 +01:00
powerpc
process Documentation: Raise the minimum supported version of LLVM to 11.0.0 2021-12-02 17:24:32 +09:00
riscv
s390
scheduler sched/fair: Add document for burstable CFS bandwidth 2021-10-05 15:51:41 +02:00
scsi
security net,lsm,selinux: revert the security_sctp_assoc_established() hook 2021-11-12 12:07:02 -05:00
sh
sound ASoC: doc: update codec example code 2021-10-25 12:36:14 +01:00
sparc
sphinx
sphinx-static
spi spi: Remove unused function spi_busnum_to_master() 2021-10-07 15:45:57 +01:00
staging
target
timers Documentation/no_hz: Introduce "dyntick-idle mode" before using it 2021-09-27 11:31:11 -06:00
trace docs: ftrace: fix the wrong path of tracefs 2021-11-15 02:50:39 -07:00
translations doc/zh_CN: fix a translation error in management-style 2021-11-15 02:53:30 -07:00
usb
userspace-api Char/Misc driver update for 5.16-rc1 2021-11-04 08:21:47 -07:00
virt Merge branch 'kvm-sev-move-context' into kvm-master 2021-11-11 11:02:58 -05:00
vm mm/migrate.c: remove MIGRATE_PFN_LOCKED 2021-11-11 09:34:35 -08:00
w1 dt-bindings: w1: update w1-gpio.yaml reference 2021-09-16 21:02:09 -05:00
watchdog
x86 - Add the model number of a new, Raptor Lake CPU, to intel-family.h 2021-11-14 09:29:03 -08:00
xtensa
.gitignore
COPYING-logo
Changes
CodingStyle
Kconfig
Makefile
SubmittingPatches
arch.rst
asm-annotations.rst docs: use the lore redirector everywhere 2021-10-12 13:58:19 -06:00
atomic_bitops.txt
atomic_t.txt
conf.py docs: pdfdocs: Adjust \headheight for fancyhdr 2021-10-12 14:09:03 -06:00
docutils.conf
dontdiff
index.rst
logo.gif
memory-barriers.txt
watch_queue.rst