[PATCHv5 11/12] arm64: uaccess: remove redundant PAN toggling

[Qian Cai]

On Wed, 2020-12-02 at 13:15 +0000, Mark Rutland wrote:
> Some code (e.g. futex) needs to make privileged accesses to userspace
> memory, and uses uaccess_{enable,disable}_privileged() in order to
> permit this. All other uaccess primitives use LDTR/STTR, and never need
> to toggle PAN.
> 
> Remove the redundant PAN toggling.
[]
> -static bool __maybe_unused
> -cpufeature_pan_not_uao(const struct arm64_cpu_capabilities *entry, int __unused)
> -{
> -	return (__system_matches_cap(ARM64_HAS_PAN) &&
> !__system_matches_cap(ARM64_HAS_UAO));
> -}

With CONFIG_ARM64_PTR_AUTH=n, we now have,

arch/arm64/kernel/cpufeature.c:2649:13: warning: '__system_matches_cap' defined but not used [-Wunused-function]
 static bool __system_matches_cap(unsigned int n)
             ^~~~~~~~~~~~~~~~~~~~

Probably just need to transfer __maybe_unused to __system_matches_cap().

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 6bdb03400581..d4e4d9d388b0 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2646,7 +2646,7 @@ bool this_cpu_has_cap(unsigned int n)
  * - The SYSTEM_FEATURE cpu_hwcaps may not have been set.
  * In all other cases cpus_have_{const_}cap() should be used.
  */
-static bool __system_matches_cap(unsigned int n)
+static bool __maybe_unused __system_matches_cap(unsigned int n)
 {
 	if (n < ARM64_NCAPS) {
 		const struct arm64_cpu_capabilities *cap = cpu_hwcaps_ptrs[n];