From: Mark Rutland mark.rutland@arm.com
[ Upstream commit bf6fa2c0dda751863c3446aa64d733013bec4a19 ]
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 Signed-off-by: Sasha Levin sashal@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 \