[PATCH v3 08/20] arm64: mm: Add arm64_kernel_unmapped_at_el0 helper

Will Deacon
2017-12-06T12:40:30Z

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>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
arch/arm64/include/asm/mmu.h | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 01bfb184f2a8..c07954638658 100644
--- 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
--
2.1.4