arm64: make is_ttbrX_addr() noinstr-safe

We use is_ttbr0_addr() in noinstr code, but as it's only marked as
inline, it's theoretically possible for the compiler to place it
out-of-line and instrument it, which would be problematic.

Mark is_ttbr0_addr() as __always_inline such that that can safely be
used from noinstr code. For consistency, do the same to is_ttbr1_addr().
Note that while is_ttbr1_addr() calls arch_kasan_reset_tag(), this is a
macro (and its callees are either macros or __always_inline), so there
is not a risk of transient instrumentation.

Signed-off-by: Mark Rutland <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

Author: mrutland-arm

arch/arm64/include/asm/processor.h

@@ -308,13 +308,13 @@ static inline void compat_start_thread(struct pt_regs *regs, unsigned long pc,
 }
 #endif
 
-static inline bool is_ttbr0_addr(unsigned long addr)
+static __always_inline bool is_ttbr0_addr(unsigned long addr)
 {
 	/* entry assembly clears tags for TTBR0 addrs */
 	return addr < TASK_SIZE;
 }
 
-static inline bool is_ttbr1_addr(unsigned long addr)
+static __always_inline bool is_ttbr1_addr(unsigned long addr)
 {
 	/* TTBR1 addresses may have a tag if KASAN_SW_TAGS is in use */
 	return arch_kasan_reset_tag(addr) >= PAGE_OFFSET;