Commit 8eb7e28d authored by Jun Yao's avatar Jun Yao Committed by Catalin Marinas
Browse files

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: default avatarJun Yao <yaojun8558363@gmail.com>
Reviewed-by: default avatarJames Morse <james.morse@arm.com>
[Mark: simplify linker script, commit message]
Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 2330b7ca

arch/arm64/kernel/head.S

+7 −5
Original line number Diff line number Diff line
@@ -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

arch/arm64/kernel/vmlinux.lds.S

+17 −16
Original line number Diff line number Diff line
@@ -138,6 +138,23 @@ SECTIONS 
	EXCEPTION_TABLE(8)		/* __init_begin will be marked RO NX */

	NOTES



	. = ALIGN(PAGE_SIZE);

	idmap_pg_dir = .;

	. += IDMAP_DIR_SIZE;



#ifdef CONFIG_UNMAP_KERNEL_AT_EL0

	tramp_pg_dir = .;

	. += PAGE_SIZE;

#endif



#ifdef CONFIG_ARM64_SW_TTBR0_PAN

	reserved_ttbr0 = .;

	. += RESERVED_TTBR0_SIZE;

#endif

	swapper_pg_dir = .;

	. += PAGE_SIZE;

	swapper_pg_end = .;



	. = ALIGN(SEGMENT_ALIGN);

	__init_begin = .;

	__inittext_begin = .;
@@ -216,22 +233,6 @@ SECTIONS 
	BSS_SECTION(0, 0, 0)



	. = ALIGN(PAGE_SIZE);

	idmap_pg_dir = .;

	. += IDMAP_DIR_SIZE;



#ifdef CONFIG_UNMAP_KERNEL_AT_EL0

	tramp_pg_dir = .;

	. += PAGE_SIZE;

#endif



#ifdef CONFIG_ARM64_SW_TTBR0_PAN

	reserved_ttbr0 = .;

	. += RESERVED_TTBR0_SIZE;

#endif

	swapper_pg_dir = .;

	. += PAGE_SIZE;

	swapper_pg_end = .;



	init_pg_dir = .;

	. += INIT_DIR_SIZE;

	init_pg_end = .;

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