arm64: mm: Add arm64_kernel_unmapped_at_el0 helper

In order for code such as TLB invalidation to operate efficiently when
the decision to map the kernel at EL0 is determined at runtime, this
patch introduces a helper function, arm64_kernel_unmapped_at_el0, to
determine whether or not the kernel is mapped whilst running in userspace.

Currently, this just reports the value of CONFIG_UNMAP_KERNEL_AT_EL0,
but will later be hooked up to a fake CPU capability using a static key.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Tested-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 01bfb184f2a842bde6c2248c273cd84786fb148b..c07954638658e6db2befab48e3e89bed64b227d1 100644 (file)
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -19,6 +19,8 @@
 #define MMCF_AARCH32   0x1     /* mm context flag for AArch32 executables */
 #define USER_ASID_FLAG (UL(1) << 48)
 
+#ifndef __ASSEMBLY__
+
 typedef struct {
        atomic64_t      id;
        void            *vdso;
@@ -32,6 +34,11 @@ typedef struct {
  */
 #define ASID(mm)       ((mm)->context.id.counter & 0xffff)
 
+static inline bool arm64_kernel_unmapped_at_el0(void)
+{
+       return IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0);
+}
+
 extern void paging_init(void);
 extern void bootmem_init(void);
 extern void __iomem *early_io_map(phys_addr_t phys, unsigned long virt);
@@ -42,4 +49,5 @@ extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
 extern void *fixmap_remap_fdt(phys_addr_t dt_phys);
 extern void mark_linear_text_alias_ro(void);
 
+#endif /* !__ASSEMBLY__ */
 #endif