Add a method (hyp_idmap_setup) to populate a hyp pgd with an
identity mapping of the code contained in the .hyp.idmap.text
section.

Offer a method to drop this identity mapping through
hyp_idmap_teardown.

Make all the above depend on CONFIG_ARM_VIRT_EXT and CONFIG_ARM_LPAE.

Cc: Will Deacon <redacted>
Reviewed-by: Marcelo Tosatti <redacted>
Signed-off-by: Marc Zyngier <redacted>
Signed-off-by: Christoffer Dall <redacted>
---
 arch/arm/include/asm/idmap.h                |    5 ++
 arch/arm/include/asm/pgtable-3level-hwdef.h |    1 
 arch/arm/kernel/vmlinux.lds.S               |    6 ++
 arch/arm/mm/idmap.c                         |   74 +++++++++++++++++++++++----
 4 files changed, 73 insertions(+), 13 deletions(-)

diff --git a/arch/arm/include/asm/idmap.h b/arch/arm/include/asm/idmap.h
index bf863ed..36708ba 100644
--- a/arch/arm/include/asm/idmap.h
+++ b/arch/arm/include/asm/idmap.h

@@ -11,4 +11,9 @@ extern pgd_t *idmap_pgd;
 
 void setup_mm_for_reboot(void);
 
+#ifdef CONFIG_ARM_VIRT_EXT
+void hyp_idmap_teardown(pgd_t *hyp_pgd);
+void hyp_idmap_setup(pgd_t *hyp_pgd);
+#endif