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From: Mark Rutland <mark.rutland@arm.com>
To: linux-arm-kernel@lists.infradead.org, will@kernel.org
Cc: catalin.marinas@arm.com, james.morse@arm.com, joey.gouly@arm.com,
	mark.rutland@arm.com, maz@kernel.org
Subject: [PATCH v4 19/20] arm64: entry: don't instrument entry code with KCOV
Date: Mon,  7 Jun 2021 10:46:23 +0100	[thread overview]
Message-ID: <20210607094624.34689-20-mark.rutland@arm.com> (raw)
In-Reply-To: <20210607094624.34689-1-mark.rutland@arm.com>

The code in entry-common.c runs at exception entry and return
boundaries, 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 disabling KCOV for the entire compilation unit.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
---
 arch/arm64/kernel/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 6cc97730790e..787c3c83edd7 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -14,6 +14,11 @@ CFLAGS_REMOVE_return_address.o = $(CC_FLAGS_FTRACE)
 CFLAGS_REMOVE_syscall.o	 = -fstack-protector -fstack-protector-strong
 CFLAGS_syscall.o	+= -fno-stack-protector
 
+# It's not safe to invoke KCOV when portions of the kernel environment aren't
+# available or are out-of-sync with HW state. Since `noinstr` doesn't always
+# inhibit KCOV instrumentation, disable it for the entire compilation unit.
+KCOV_INSTRUMENT_entry.o := n
+
 # Object file lists.
 obj-y			:= debug-monitors.o entry.o irq.o fpsimd.o		\
 			   entry-common.o entry-fpsimd.o process.o ptrace.o	\
-- 
2.11.0


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  parent reply	other threads:[~2021-06-07 10:29 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-07  9:46 [PATCH v4 00/20] arm64: entry: migrate more code to C Mark Rutland
2021-06-07  9:46 ` [PATCH v4 01/20] arm64: remove redundant local_daif_mask() in bad_mode() Mark Rutland
2021-06-07  9:46 ` [PATCH v4 02/20] arm64: entry: unmask IRQ+FIQ after EL0 handling Mark Rutland
2021-06-07  9:46 ` [PATCH v4 03/20] arm64: entry: convert SError handlers to C Mark Rutland
2021-06-07  9:46 ` [PATCH v4 04/20] arm64: entry: move arm64_preempt_schedule_irq to entry-common.c Mark Rutland
2021-06-07  9:46 ` [PATCH v4 05/20] arm64: entry: move NMI preempt logic to C Mark Rutland
2021-06-07  9:46 ` [PATCH v4 06/20] arm64: entry: add a call_on_irq_stack helper Mark Rutland
2021-06-07  9:46 ` [PATCH v4 07/20] arm64: entry: convert IRQ+FIQ handlers to C Mark Rutland
2021-06-07  9:46 ` [PATCH v4 08/20] arm64: entry: organise entry handlers consistently Mark Rutland
2021-06-07  9:46 ` [PATCH v4 09/20] arm64: entry: organise entry vectors consistently Mark Rutland
2021-06-07  9:46 ` [PATCH v4 10/20] arm64: entry: consolidate EL1 exception returns Mark Rutland
2021-06-07  9:46 ` [PATCH v4 11/20] arm64: entry: move bad_mode() to entry-common.c Mark Rutland
2021-06-07  9:46 ` [PATCH v4 12/20] arm64: entry: improve bad_mode() Mark Rutland
2021-06-07  9:46 ` [PATCH v4 13/20] arm64: entry: template the entry asm functions Mark Rutland
2021-06-07  9:46 ` [PATCH v4 14/20] arm64: entry: handle all vectors with C Mark Rutland
2021-06-07  9:46 ` [PATCH v4 15/20] arm64: entry: fold el1_inv() into el1h_64_sync_handler() Mark Rutland
2021-06-07  9:46 ` [PATCH v4 16/20] arm64: entry: split bad stack entry Mark Rutland
2021-06-07  9:46 ` [PATCH v4 17/20] arm64: entry: split SDEI entry Mark Rutland
2021-06-07  9:46 ` [PATCH v4 18/20] arm64: entry: make NMI entry/exit functions static Mark Rutland
2021-06-07  9:46 ` Mark Rutland [this message]
2021-06-07  9:46 ` [PATCH v4 20/20] arm64: idle: don't instrument idle code with KCOV Mark Rutland
2021-06-07 13:35 ` [PATCH v4 00/20] arm64: entry: migrate more code to C Will Deacon

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