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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Nathan Chancellor <natechancellor@gmail.com>,
	Peter Smith <peter.smith@linaro.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Sasha Levin <sashal@kernel.org>,
	linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: [PATCH AUTOSEL 4.9 21/45] kbuild: Add -Werror=unknown-warning-option to CLANG_FLAGS
Date: Fri, 19 Jul 2019 00:12:40 -0400	[thread overview]
Message-ID: <20190719041304.18849-21-sashal@kernel.org> (raw)
In-Reply-To: <20190719041304.18849-1-sashal@kernel.org>

From: Nathan Chancellor <natechancellor@gmail.com>

[ Upstream commit 589834b3a0097a4908f4112eac0ca2feb486fa32 ]

In commit ebcc5928c5d9 ("arm64: Silence gcc warnings about arch ABI
drift"), the arm64 Makefile added -Wno-psabi to KBUILD_CFLAGS, which is
a GCC only option so clang rightfully complains:

warning: unknown warning option '-Wno-psabi' [-Wunknown-warning-option]

https://clang.llvm.org/docs/DiagnosticsReference.html#wunknown-warning-option

However, by default, this is merely a warning so the build happily goes
on with a slew of these warnings in the process.

Commit c3f0d0bc5b01 ("kbuild, LLVMLinux: Add -Werror to cc-option to
support clang") worked around this behavior in cc-option by adding
-Werror so that unknown flags cause an error. However, this all happens
silently and when an unknown flag is added to the build unconditionally
like -Wno-psabi, cc-option will always fail because there is always an
unknown flag in the list of flags. This manifested as link time failures
in the arm64 libstub because -fno-stack-protector didn't get added to
KBUILD_CFLAGS.

To avoid these weird cryptic failures in the future, make clang behave
like gcc and immediately error when it encounters an unknown flag by
adding -Werror=unknown-warning-option to CLANG_FLAGS. This can be added
unconditionally for clang because it is supported by at least 3.0.0,
according to godbolt [1] and 4.0.0, according to its documentation [2],
which is far earlier than we typically support.

[1]: https://godbolt.org/z/7F7rm3
[2]: https://releases.llvm.org/4.0.0/tools/clang/docs/DiagnosticsReference.html#wunknown-warning-option

Link: https://github.com/ClangBuiltLinux/linux/issues/511
Link: https://github.com/ClangBuiltLinux/linux/issues/517
Suggested-by: Peter Smith <peter.smith@linaro.org>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Makefile b/Makefile
index c80dad45334e..60b562dbd97f 100644
--- a/Makefile
+++ b/Makefile
@@ -515,6 +515,7 @@ ifneq ($(GCC_TOOLCHAIN),)
 CLANG_FLAGS	+= --gcc-toolchain=$(GCC_TOOLCHAIN)
 endif
 CLANG_FLAGS	+= -no-integrated-as
+CLANG_FLAGS	+= -Werror=unknown-warning-option
 KBUILD_CFLAGS	+= $(CLANG_FLAGS)
 KBUILD_AFLAGS	+= $(CLANG_FLAGS)
 endif
-- 
2.20.1


  parent reply	other threads:[~2019-07-19  4:18 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-19  4:12 [PATCH AUTOSEL 4.9 01/45] drm/panel: simple: Fix panel_simple_dsi_probe Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 02/45] usb: core: hub: Disable hub-initiated U1/U2 Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 03/45] tty: max310x: Fix invalid baudrate divisors calculator Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 04/45] pinctrl: rockchip: fix leaked of_node references Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 05/45] tty: serial: cpm_uart - fix init when SMC is relocated Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 06/45] drm/edid: Fix a missing-check bug in drm_load_edid_firmware() Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 07/45] drm/bridge: tc358767: read display_props in get_modes() Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 08/45] drm/bridge: sii902x: pixel clock unit is 10kHz instead of 1kHz Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 09/45] memstick: Fix error cleanup path of memstick_init Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 10/45] tty/serial: digicolor: Fix digicolor-usart already registered warning Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 11/45] tty: serial: msm_serial: avoid system lockup condition Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 12/45] serial: 8250: Fix TX interrupt handling condition Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 13/45] drm/virtio: Add memory barriers for capset cache Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 14/45] phy: renesas: rcar-gen2: Fix memory leak at error paths Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 15/45] drm/rockchip: Properly adjust to a true clock in adjusted_mode Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 16/45] tty: serial_core: Set port active bit in uart_port_activate Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 17/45] usb: gadget: Zero ffs_io_data Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 18/45] powerpc/pci/of: Fix OF flags parsing for 64bit BARs Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 19/45] PCI: sysfs: Ignore lockdep for remove attribute Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 20/45] iio: st_accel: fix iio_triggered_buffer_{pre,post}enable positions Sasha Levin
2019-07-19  4:12 ` Sasha Levin [this message]
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 22/45] PCI: xilinx-nwl: Fix Multi MSI data programming Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 23/45] iio: iio-utils: Fix possible incorrect mask calculation Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 24/45] recordmcount: Fix spurious mcount entries on powerpc Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 25/45] mfd: core: Set fwnode for created devices Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 26/45] mfd: arizona: Fix undefined behavior Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 27/45] mfd: hi655x-pmic: Fix missing return value check for devm_regmap_init_mmio_clk Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 28/45] um: Silence lockdep complaint about mmap_sem Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 29/45] powerpc/4xx/uic: clear pending interrupt after irq type/pol change Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 30/45] RDMA/i40iw: Set queue pair state when being queried Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 31/45] serial: sh-sci: Terminate TX DMA during buffer flushing Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 32/45] serial: sh-sci: Fix TX DMA buffer flushing and workqueue races Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 33/45] PCI: tegra: Enable Relaxed Ordering only for Tegra20 & Tegra30 Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 34/45] kallsyms: exclude kasan local symbols on s390 Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 35/45] perf test mmap-thread-lookup: Initialize variable to suppress memory sanitizer warning Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 36/45] RDMA/rxe: Fill in wc byte_len with IB_WC_RECV_RDMA_WITH_IMM Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 37/45] powerpc/boot: add {get, put}_unaligned_be32 to xz_config.h Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 38/45] f2fs: avoid out-of-range memory access Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 39/45] mailbox: handle failed named mailbox channel request Sasha Levin
2019-07-19  4:12 ` [PATCH AUTOSEL 4.9 40/45] powerpc/eeh: Handle hugepages in ioremap space Sasha Levin
2019-07-19  4:13 ` [PATCH AUTOSEL 4.9 41/45] sh: prevent warnings when using iounmap Sasha Levin
2019-07-19  4:13 ` [PATCH AUTOSEL 4.9 42/45] mm/kmemleak.c: fix check for softirq context Sasha Levin
2019-07-19  4:13 ` [PATCH AUTOSEL 4.9 43/45] 9p: pass the correct prototype to read_cache_page Sasha Levin
2019-07-19  4:13 ` [PATCH AUTOSEL 4.9 44/45] mm/mmu_notifier: use hlist_add_head_rcu() Sasha Levin
2019-07-19  4:13 ` [PATCH AUTOSEL 4.9 45/45] locking/lockdep: Fix lock used or unused stats error Sasha Levin

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