arm64/mm: Restructure arch_validate_flags() for extensibility

Currently arch_validate_flags() is written in a very non-extensible
fashion, returning immediately if MTE is not supported and writing the MTE
check as a direct return. Since we will want to add more checks for GCS
refactor the existing code to be more extensible, no functional change
intended.

Reviewed-by: Thiago Jung Bauermann <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
Signed-off-by: Mark Brown <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Catalin Marinas <[email protected]>

Author: broonie

arch/arm64/include/asm/mman.h

@@ -62,11 +62,17 @@ static inline bool arch_validate_prot(unsigned long prot,
 
 static inline bool arch_validate_flags(unsigned long vm_flags)
 {
-	if (!system_supports_mte())
-		return true;
+	if (system_supports_mte()) {
+		/*
+		 * only allow VM_MTE if VM_MTE_ALLOWED has been set
+		 * previously
+		 */
+		if ((vm_flags & VM_MTE) && !(vm_flags & VM_MTE_ALLOWED))
+			return false;
+	}
+
+	return true;
 
-	/* only allow VM_MTE if VM_MTE_ALLOWED has been set previously */
-	return !(vm_flags & VM_MTE) || (vm_flags & VM_MTE_ALLOWED);
 }
 #define arch_validate_flags(vm_flags) arch_validate_flags(vm_flags)