[PATCH 1/9] arm64: cpufeature: make cpus_have_cap() noinstr-safe

Mark Rutland
2022-09-01T15:15:29Z

Currently it isn't safe to use cpus_have_cap() from noinstr code as
test_bit() is explicitly instrumented, and were cpus_have_cap() placed
out-of-line, cpus_have_cap() itself could be instrumented.

Make cpus_have_cap() noinstr safe by marking it __always_inline and
using arch_test_bit().

Aside from the prevention of instrumentation, there should be no
functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
---
arch/arm64/include/asm/cpufeature.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index fd7d75a275f6c..630c337c77746 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -448,11 +448,11 @@ static __always_inline bool system_capabilities_finalized(void)
*
* Before the capability is detected, this returns false.
*/
-static inline bool cpus_have_cap(unsigned int num)
+static __always_inline bool cpus_have_cap(unsigned int num)
{
if (num >= ARM64_NCAPS)
return false;
- return test_bit(num, cpu_hwcaps);
+ return arch_test_bit(num, cpu_hwcaps);
}

/*