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From: Mark Rutland <mark.rutland@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: catalin.marinas@arm.com, james.morse@arm.com,
	mark.rutland@arm.com, maz@kernel.org, will@kernel.org,
	joey.gouly@arm.com
Subject: [PATCH v2 19/19] arm64: idle: don't instrument idle code with KCOV
Date: Wed, 19 May 2021 13:39:02 +0100	[thread overview]
Message-ID: <20210519123902.2452-20-mark.rutland@arm.com> (raw)
In-Reply-To: <20210519123902.2452-1-mark.rutland@arm.com>

The low-level idle code in arch_cpu_idle() and its callees runs at a
time where where portions of the kernel environment aren't available.
For example, RCU may not be watching, and lockdep state may be
out-of-sync with the hardware. Due to this, it is not sound to
instrument this code.

We generally avoid instrumentation by marking the entry functions as
`noinstr`, but currently this doesn't inhibit KCOV instrumentation.
Prevent this by factoring these functions into a new idle.c so that we
can disable KCOV for the entire compilation unit, as is done for the
core idle code in kernel/sched/idle.c.

We'd like to keep instrumentation of the rest of process.c, and for the
existing code in cpuidle.c, so a new compilation unit is preferable. The
arch_cpu_idle_dead() function in process.c is a cpu hotplug function
that is safe to instrument, so it is left as-is in process.c.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
---
 arch/arm64/kernel/Makefile  |  3 +-
 arch/arm64/kernel/idle.c    | 69 +++++++++++++++++++++++++++++++++++++++++++++
 arch/arm64/kernel/process.c | 57 -------------------------------------
 3 files changed, 71 insertions(+), 58 deletions(-)
 create mode 100644 arch/arm64/kernel/idle.c

diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 294063032428..708df7de84d1 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -15,6 +15,7 @@ CFLAGS_REMOVE_syscall.o	 = -fstack-protector -fstack-protector-strong
 CFLAGS_syscall.o	+= -fno-stack-protector
 
 KCOV_INSTRUMENT_entry.o := n
+KCOV_INSTRUMENT_idle.o := n
 
 # Object file lists.
 obj-y			:= debug-monitors.o entry.o irq.o fpsimd.o		\
@@ -24,7 +25,7 @@ obj-y			:= debug-monitors.o entry.o irq.o fpsimd.o		\
 			   return_address.o cpuinfo.o cpu_errata.o		\
 			   cpufeature.o alternative.o cacheinfo.o		\
 			   smp.o smp_spin_table.o topology.o smccc-call.o	\
-			   syscall.o proton-pack.o idreg-override.o
+			   syscall.o proton-pack.o idreg-override.o idle.o
 
 targets			+= efi-entry.o
 
diff --git a/arch/arm64/kernel/idle.c b/arch/arm64/kernel/idle.c
new file mode 100644
index 000000000000..45c79204dc40
--- /dev/null
+++ b/arch/arm64/kernel/idle.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Low-level idle sequences
+ */
+
+#include <linux/cpu.h>
+#include <linux/irqflags.h>
+
+#include <asm/arch_gicv3.h>
+#include <asm/barrier.h>
+#include <asm/cpufeature.h>
+#include <asm/sysreg.h>
+
+static void noinstr __cpu_do_idle(void)
+{
+	dsb(sy);
+	wfi();
+}
+
+static void noinstr __cpu_do_idle_irqprio(void)
+{
+	unsigned long pmr;
+	unsigned long daif_bits;
+
+	daif_bits = read_sysreg(daif);
+	write_sysreg(daif_bits | PSR_I_BIT | PSR_F_BIT, daif);
+
+	/*
+	 * Unmask PMR before going idle to make sure interrupts can
+	 * be raised.
+	 */
+	pmr = gic_read_pmr();
+	gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET);
+
+	__cpu_do_idle();
+
+	gic_write_pmr(pmr);
+	write_sysreg(daif_bits, daif);
+}
+
+/*
+ *	cpu_do_idle()
+ *
+ *	Idle the processor (wait for interrupt).
+ *
+ *	If the CPU supports priority masking we must do additional work to
+ *	ensure that interrupts are not masked at the PMR (because the core will
+ *	not wake up if we block the wake up signal in the interrupt controller).
+ */
+void noinstr cpu_do_idle(void)
+{
+	if (system_uses_irq_prio_masking())
+		__cpu_do_idle_irqprio();
+	else
+		__cpu_do_idle();
+}
+
+/*
+ * This is our default idle handler.
+ */
+void noinstr arch_cpu_idle(void)
+{
+	/*
+	 * This should do all the clock switching and wait for interrupt
+	 * tricks
+	 */
+	cpu_do_idle();
+	raw_local_irq_enable();
+}
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 2e7337709155..72c5d80f03fa 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -73,63 +73,6 @@ EXPORT_SYMBOL_GPL(pm_power_off);
 
 void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
 
-static void noinstr __cpu_do_idle(void)
-{
-	dsb(sy);
-	wfi();
-}
-
-static void noinstr __cpu_do_idle_irqprio(void)
-{
-	unsigned long pmr;
-	unsigned long daif_bits;
-
-	daif_bits = read_sysreg(daif);
-	write_sysreg(daif_bits | PSR_I_BIT | PSR_F_BIT, daif);
-
-	/*
-	 * Unmask PMR before going idle to make sure interrupts can
-	 * be raised.
-	 */
-	pmr = gic_read_pmr();
-	gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET);
-
-	__cpu_do_idle();
-
-	gic_write_pmr(pmr);
-	write_sysreg(daif_bits, daif);
-}
-
-/*
- *	cpu_do_idle()
- *
- *	Idle the processor (wait for interrupt).
- *
- *	If the CPU supports priority masking we must do additional work to
- *	ensure that interrupts are not masked at the PMR (because the core will
- *	not wake up if we block the wake up signal in the interrupt controller).
- */
-void noinstr cpu_do_idle(void)
-{
-	if (system_uses_irq_prio_masking())
-		__cpu_do_idle_irqprio();
-	else
-		__cpu_do_idle();
-}
-
-/*
- * This is our default idle handler.
- */
-void noinstr arch_cpu_idle(void)
-{
-	/*
-	 * This should do all the clock switching and wait for interrupt
-	 * tricks
-	 */
-	cpu_do_idle();
-	raw_local_irq_enable();
-}
-
 #ifdef CONFIG_HOTPLUG_CPU
 void arch_cpu_idle_dead(void)
 {
-- 
2.11.0


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      parent reply	other threads:[~2021-05-19 13:11 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-19 12:38 [PATCH v2 00/19] arm64: entry: migrate more code to C Mark Rutland
2021-05-19 12:38 ` [PATCH v2 01/19] arm64: remove redundant local_daif_mask() in bad_mode() Mark Rutland
2021-05-21 10:39   ` Joey Gouly
2021-05-19 12:38 ` [PATCH v2 02/19] arm64: entry: unmask IRQ+FIQ after EL0 handling Mark Rutland
2021-05-25 16:45   ` Joey Gouly
2021-05-19 12:38 ` [PATCH v2 03/19] arm64: entry: convert SError handlers to C Mark Rutland
2021-05-25 13:38   ` Joey Gouly
2021-05-19 12:38 ` [PATCH v2 04/19] arm64: entry: move arm64_preempt_schedule_irq to entry-common.c Mark Rutland
2021-05-21 11:00   ` Joey Gouly
2021-05-19 12:38 ` [PATCH v2 05/19] arm64: entry: move preempt logic to C Mark Rutland
2021-05-25 12:50   ` Joey Gouly
2021-05-19 12:38 ` [PATCH v2 06/19] arm64: entry: add a call_on_irq_stack helper Mark Rutland
2021-05-19 14:46   ` Mark Rutland
2021-05-19 12:38 ` [PATCH v2 07/19] arm64: entry: convert IRQ+FIQ handlers to C Mark Rutland
2021-05-21 13:19   ` Joey Gouly
2021-05-21 15:23     ` Mark Rutland
2021-05-19 12:38 ` [PATCH v2 08/19] arm64: entry: organise entry handlers consistently Mark Rutland
2021-05-21 16:04   ` Joey Gouly
2021-05-19 12:38 ` [PATCH v2 09/19] arm64: entry: organise entry vectors consistently Mark Rutland
2021-05-21 16:07   ` Joey Gouly
2021-05-19 12:38 ` [PATCH v2 10/19] arm64: entry: consolidate EL1 exception returns Mark Rutland
2021-05-21 16:22   ` Joey Gouly
2021-05-19 12:38 ` [PATCH v2 11/19] arm64: entry: move bad_mode() to entry-common.c Mark Rutland
2021-05-21 16:46   ` Joey Gouly
2021-05-19 12:38 ` [PATCH v2 12/19] arm64: entry: improve bad_mode() Mark Rutland
2021-05-21 17:02   ` Joey Gouly
2021-05-21 17:10     ` Mark Rutland
2021-05-19 12:38 ` [PATCH v2 13/19] arm64: entry: template the entry asm functions Mark Rutland
2021-05-21 17:16   ` Joey Gouly
2021-05-19 12:38 ` [PATCH v2 14/19] arm64: entry: handle all vectors with C Mark Rutland
2021-05-21 15:59   ` Joey Gouly
2021-05-21 16:41     ` Mark Rutland
2021-05-19 12:38 ` [PATCH v2 15/19] arm64: entry: split bad stack entry Mark Rutland
2021-05-25 11:25   ` Joey Gouly
2021-05-19 12:38 ` [PATCH v2 16/19] arm64: entry: split SDEI entry Mark Rutland
2021-05-25 11:49   ` Joey Gouly
2021-05-19 12:39 ` [PATCH v2 17/19] arm64: entry: make NMI entry/exit functions static Mark Rutland
2021-05-21 17:21   ` Joey Gouly
2021-05-19 12:39 ` [PATCH v2 18/19] arm64: entry: don't instrument entry code with KCOV Mark Rutland
2021-05-19 12:39 ` Mark Rutland [this message]

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