From: Ard Biesheuvel <ardb@kernel.org>
To: linux@armlinux.org.uk
Cc: linux-arm-kernel@lists.infradead.org,
Ard Biesheuvel <ardb@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Sudeep Holla <sudeep.holla@arm.com>,
Cristian Marussi <cristian.marussi@arm.com>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Arnd Bergmann <arnd@arndb.de>,
Linus Walleij <linus.walleij@linaro.org>,
Masami Hiramatsu <mhiramat@kernel.org>
Subject: [PATCH v2 10/12] drivers/firmware/scmi: disable ftrace for Clang Thumb2 builds
Date: Mon, 31 Jan 2022 18:03:45 +0100 [thread overview]
Message-ID: <20220131170347.381551-11-ardb@kernel.org> (raw)
In-Reply-To: <20220131170347.381551-1-ardb@kernel.org>
The SMC calling convention designates R0-R7 as input registers in
AArch32 mode, and this conflicts with the compiler's use of R7 as a
frame pointer when building in Thumb2 mode. Generally, we don't enable
the frame pointer, and GCC happily enables the -pg profiling hooks
without them. However, Clang refuses, and errors out with the message
below:
drivers/firmware/arm_scmi/smc.c:152:2: error: write to reserved register 'R7'
arm_smccc_1_1_invoke(scmi_info->func_id, 0, 0, 0, 0, 0, 0, 0, &res);
^
include/linux/arm-smccc.h:550:4: note: expanded from macro 'arm_smccc_1_1_invoke'
arm_smccc_1_1_smc(__VA_ARGS__); \
^
Let's just disable ftrace for the compilation unit when building this
configuration.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
drivers/firmware/arm_scmi/Makefile | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
index 1dcf123d64ab..52b9078bfe96 100644
--- a/drivers/firmware/arm_scmi/Makefile
+++ b/drivers/firmware/arm_scmi/Makefile
@@ -11,3 +11,10 @@ scmi-module-objs := $(scmi-bus-y) $(scmi-driver-y) $(scmi-protocols-y) \
$(scmi-transport-y)
obj-$(CONFIG_ARM_SCMI_PROTOCOL) += scmi-module.o
obj-$(CONFIG_ARM_SCMI_POWER_DOMAIN) += scmi_pm_domain.o
+
+ifeq ($(CONFIG_THUMB2_KERNEL)$(CONFIG_CC_IS_CLANG),yy)
+# The use of R7 in the SMCCC conflicts with the compiler's use of R7 as a frame
+# pointer in Thumb2 mode, which is forcibly enabled by Clang when profiling
+# hooks are inserted via the -pg switch.
+CFLAGS_REMOVE_smc.o += $(CC_FLAGS_FTRACE)
+endif
--
2.30.2
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next prev parent reply other threads:[~2022-01-31 17:24 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-31 17:03 [PATCH v2 00/12] ARM: ftrace fixes and cleanups Ard Biesheuvel
2022-01-31 17:03 ` [PATCH v2 01/12] ARM: ftrace: ensure that ADR take Thumb bit into account Ard Biesheuvel
2022-01-31 17:03 ` [PATCH v2 02/12] ARM: ftrace: use ADD not POP to counter PUSH at entry Ard Biesheuvel
2022-01-31 17:03 ` [PATCH v2 03/12] ARM: ftrace: use trampolines to keep .init.text in branching range Ard Biesheuvel
2022-01-31 17:03 ` [PATCH v2 04/12] ARM: ftrace: avoid redundant loads or clobbering IP Ard Biesheuvel
2022-01-31 17:03 ` [PATCH v2 05/12] ARM: ftrace: avoid unnecessary literal loads Ard Biesheuvel
2022-01-31 17:03 ` [PATCH v2 06/12] ARM: ftrace: enable HAVE_FUNCTION_GRAPH_FP_TEST Ard Biesheuvel
2022-01-31 17:03 ` [PATCH v2 07/12] ARM: unwind: track location of LR value in stack frame Ard Biesheuvel
2022-01-31 17:03 ` [PATCH v2 08/12] ARM: ftrace: enable the graph tracer with the EABI unwinder Ard Biesheuvel
2022-01-31 17:03 ` [PATCH v2 09/12] ARM: kprobes: treat R7 as the frame pointer register in Thumb2 builds Ard Biesheuvel
2022-01-31 18:31 ` Nick Desaulniers
2022-02-01 7:42 ` Ard Biesheuvel
2022-02-01 13:18 ` Masami Hiramatsu
2022-02-01 14:05 ` Ard Biesheuvel
2022-02-02 6:10 ` Masami Hiramatsu
2022-02-02 8:00 ` Ard Biesheuvel
2022-01-31 17:03 ` Ard Biesheuvel [this message]
2022-01-31 18:37 ` [PATCH v2 10/12] drivers/firmware/scmi: disable ftrace for Clang " Nick Desaulniers
2022-02-01 8:12 ` Ard Biesheuvel
2022-01-31 22:04 ` Sudeep Holla
2022-01-31 17:03 ` [PATCH v2 11/12] ARM: cacheflush: avoid clobbering the frame pointer in Thumb2 mode Ard Biesheuvel
2022-01-31 18:40 ` Nick Desaulniers
2022-01-31 17:03 ` [PATCH v2 12/12] Revert "ARM: 9144/1: forbid ftrace with clang and thumb2_kernel" Ard Biesheuvel
2022-01-31 18:42 ` Nick Desaulniers
2022-01-31 17:21 ` [PATCH v2 00/12] ARM: ftrace fixes and cleanups Steven Rostedt
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