[PATCH 06/11] x86/xip: after paging trampoline, discard PMDs above _brk

[Jim Kukunas <james.t.kukunas@linux.intel.com>]

In the likely case that XIP_BASE is above PAGE_OFFSET, we
want to discard any early identity mappings. So rather than
keeping every PMD above PAGE_OFFSET, only copy the ones from
PAGE_OFFSET to the last PMD of _end. At this point, the linear
address space should look normal.

Signed-off-by: Jim Kukunas <james.t.kukunas@linux.intel.com>
---
 arch/x86/include/asm/pgtable.h | 7 +++++++
 arch/x86/kernel/setup.c        | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index a0c35bf..5eaba7d 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -660,6 +660,13 @@ static inline int pgd_none(pgd_t pgd)
 #define KERNEL_PGD_BOUNDARY	pgd_index(PAGE_OFFSET)
 #define KERNEL_PGD_PTRS		(PTRS_PER_PGD - KERNEL_PGD_BOUNDARY)
 
+#ifdef CONFIG_XIP_KERNEL
+#define BOOT_PGD_COPY_PTRS \
+	((pgd_index((unsigned long)_end)  - pgd_index(PAGE_OFFSET)) + 4)
+#else
+#define BOOT_PGD_COPY_PTRS	KERNEL_PGD_PTRS
+#endif
+
 #ifndef __ASSEMBLY__
 
 extern int direct_gbpages;
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index e2d85c4..d276ebf 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -894,7 +894,7 @@ void __init setup_arch(char **cmdline_p)
 	 */
 	clone_pgd_range(swapper_pg_dir     + KERNEL_PGD_BOUNDARY,
 			initial_page_table + KERNEL_PGD_BOUNDARY,
-			KERNEL_PGD_PTRS);
+			BOOT_PGD_COPY_PTRS);
 
 	load_cr3(swapper_pg_dir);
 	/*
-- 
2.1.0