arm64/mm: move runtime pgds to rodata

Now that deliberate writes to swapper_pg_dir are made via the fixmap, we
can defend against errant writes by moving it into the rodata section.
Since tramp_pg_dir and reserved_ttbr0 must be at a fixed offset from
swapper_pg_dir, and are not modified at runtime, these are also moved
into the rodata section. Likewise, idmap_pg_dir is not modified at
runtime, and is moved into rodata.

Signed-off-by: Jun Yao <yaojun8558363@gmail.com>
Reviewed-by: James Morse <james.morse@arm.com>
[Mark: simplify linker script, commit message]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 7 insertions, 5 deletions

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 7bf52ee0a805..4471f570a295 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -287,18 +287,20 @@ __create_page_tables:
 	mov	x28, lr
 
 	/*
-	 * Invalidate the idmap and swapper page tables to avoid potential
-	 * dirty cache lines being evicted.
+	 * Invalidate the init page tables to avoid potential dirty cache lines
+	 * being evicted. Other page tables are allocated in rodata as part of
+	 * the kernel image, and thus are clean to the PoC per the boot
+	 * protocol.
 	 */
-	adrp	x0, idmap_pg_dir
+	adrp	x0, init_pg_dir
 	adrp	x1, init_pg_end
 	sub	x1, x1, x0
 	bl	__inval_dcache_area
 
 	/*
-	 * Clear the idmap and swapper page tables.
+	 * Clear the init page tables.
 	 */
-	adrp	x0, idmap_pg_dir
+	adrp	x0, init_pg_dir
 	adrp	x1, init_pg_end
 	sub	x1, x1, x0
 1:	stp	xzr, xzr, [x0], #16