Commit bf6fa2c0 authored Jun 07, 2021 by Mark Rutland Committed by Will Deacon Jun 07, 2021

arm64: entry: don't instrument entry code with KCOV



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>
Link: https://lore.kernel.org/r/20210607094624.34689-20-mark.rutland@arm.com


Signed-off-by: Will Deacon <will@kernel.org>

parent 6ecbc78c

arch/arm64/kernel/Makefile

+5 −0

Original line number	Diff line number	Diff line
		@@ -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 \