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From: Arnd Bergmann <arnd@kernel.org>
To: Russell King <linux@armlinux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
	Ard Biesheuvel <ardb@kernel.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	llvm@lists.linux.dev
Subject: [PATCH 14/14] [RFC] ARM: forbid ftrace with clang and thumb2_kernel
Date: Tue, 28 Sep 2021 17:41:43 +0200	[thread overview]
Message-ID: <20210928154143.2106903-15-arnd@kernel.org> (raw)
In-Reply-To: <20210928154143.2106903-1-arnd@kernel.org>

From: Arnd Bergmann <arnd@arndb.de>

clang fails to build kernels with THUMB2 and FUNCTION_TRACER
enabled when there is any inline asm statement containing
the frame pointer register r7:

arch/arm/mach-versatile/dcscb.c:95:2: error: inline asm clobber list contains reserved registers: R7 [-Werror,-Winline-asm]
arch/arm/mach-exynos/mcpm-exynos.c:154:2: error: inline asm clobber list contains reserved registers: R7 [-Werror,-Winline-asm]
arch/arm/probes/kprobes/actions-thumb.c:449:3: error: inline asm clobber list contains reserved registers: R7 [-Werror,-Winline-asm]

Apparently gcc should also have warned about this, and the
configuration is actually invalid, though there is some
disagreement on the bug trackers about this.

Link: https://bugs.llvm.org/show_bug.cgi?id=45826
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94986
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/arm/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 0d4f3e2d50ad..7ea95bb40004 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -91,7 +91,7 @@ config ARM
 	select HAVE_FAST_GUP if ARM_LPAE
 	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
 	select HAVE_FUNCTION_GRAPH_TRACER if !THUMB2_KERNEL && !CC_IS_CLANG
-	select HAVE_FUNCTION_TRACER if !XIP_KERNEL
+	select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !(THUMB2_KERNEL && CC_IS_CLANG)
 	select HAVE_GCC_PLUGINS
 	select HAVE_HW_BREAKPOINT if PERF_EVENTS && (CPU_V6 || CPU_V6K || CPU_V7)
 	select HAVE_IRQ_TIME_ACCOUNTING
-- 
2.29.2


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  parent reply	other threads:[~2021-09-28 15:50 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-28 15:41 [PATCH 00/14] ARM: randconfig build fixes Arnd Bergmann
2021-09-28 15:41 ` [PATCH 01/14] ARM: RiscPC needs older gcc version Arnd Bergmann
2021-09-28 16:03   ` Arnd Bergmann
2021-09-29  8:45     ` Arnd Bergmann
2021-09-28 15:41 ` [PATCH 02/14] ARM: patch: fix BE32 compilation Arnd Bergmann
2021-09-28 21:33   ` Linus Walleij
2021-09-28 15:41 ` [PATCH 03/14] ARM: remove duplicate memcpy() definition Arnd Bergmann
2021-09-28 21:39   ` Linus Walleij
2021-09-28 15:41 ` [PATCH 04/14] ARM: kprobes: address gcc -Wempty-body warning Arnd Bergmann
2021-09-28 15:41 ` [PATCH 05/14] ARM: ARMv7-M uses BE-8, not BE-32 Arnd Bergmann
2021-09-28 15:41 ` [PATCH 06/14] ARM: disallow CONFIG_THUMB with ARMv4 Arnd Bergmann
2021-09-29 18:52   ` Nick Desaulniers
2021-10-06 16:01   ` Ard Biesheuvel
2021-09-28 15:41 ` [PATCH 07/14] ARM: fix link warning with XIP + frame-pointer Arnd Bergmann
2021-09-28 15:41 ` [PATCH 08/14] ARM: kprobes: fix arch_init_kprobes() prototype Arnd Bergmann
2021-09-28 15:41 ` [PATCH 09/14] ARM: allow compile-testing without machine record Arnd Bergmann
2021-09-28 15:41 ` [PATCH 10/14] ARM: only warn about XIP address when not compile testing Arnd Bergmann
2021-09-28 15:41 ` [PATCH 11/14] ARM: kasan: work around LPAE build warning Arnd Bergmann
2021-09-28 15:41 ` [PATCH 12/14] ARM: add CONFIG_PHYS_OFFSET default values Arnd Bergmann
2021-09-28 16:02   ` Nicolas Pitre
2021-09-28 21:44   ` Linus Walleij
2021-09-28 15:41 ` [PATCH 13/14] ARM: use .arch directives instead of assembler command line flags Arnd Bergmann
2021-09-28 17:10   ` Nick Desaulniers
2021-09-28 18:32     ` Arnd Bergmann
2021-09-29 18:11       ` Nick Desaulniers
2022-01-21 22:17   ` Nathan Chancellor
2021-09-28 15:41 ` Arnd Bergmann [this message]
2021-09-28 17:20   ` [PATCH 14/14] [RFC] ARM: forbid ftrace with clang and thumb2_kernel Nick Desaulniers

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