Commit 2bf31a4a authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Catalin Marinas
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arm64: avoid dynamic relocations in early boot code 



Before implementing KASLR for arm64 by building a self-relocating PIE
executable, we have to ensure that values we use before the relocation
routine is executed are not subject to dynamic relocation themselves.
This applies not only to virtual addresses, but also to values that are
supplied by the linker at build time and relocated using R_AARCH64_ABS64
relocations.

So instead, use assemble time constants, or force the use of static
relocations by folding the constants into the instructions.

Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 6ad1fe5d

arch/arm64/kernel/efi-entry.S

+1 −1
Original line number Diff line number Diff line
@@ -61,7 +61,7 @@ ENTRY(entry) 
	 */

	mov	x20, x0		// DTB address

	ldr	x0, [sp, #16]	// relocated _text address

	ldr	x21, =stext_offset

	movz	x21, #:abs_g0:stext_offset

	add	x21, x0, x21



	/*

arch/arm64/kernel/head.S

+26 −13
Original line number Diff line number Diff line
@@ -67,12 +67,11 @@ 
 * in the entry routines.

 */

	__HEAD



_head:

	/*

	 * DO NOT MODIFY. Image header expected by Linux boot-loaders.

	 */

#ifdef CONFIG_EFI

efi_head:

	/*

	 * This add instruction has no meaningful effect except that

	 * its opcode forms the magic "MZ" signature required by UEFI.
@@ -94,14 +93,14 @@ efi_head: 
	.byte	0x4d

	.byte	0x64

#ifdef CONFIG_EFI

	.long	pe_header - efi_head		// Offset to the PE header.

	.long	pe_header - _head		// Offset to the PE header.

#else

	.word	0				// reserved

#endif



#ifdef CONFIG_EFI

	.globl	__efistub_stext_offset

	.set	__efistub_stext_offset, stext - efi_head

	.set	__efistub_stext_offset, stext - _head

	.align 3

pe_header:

	.ascii	"PE"
@@ -124,7 +123,7 @@ optional_header: 
	.long	_end - stext			// SizeOfCode

	.long	0				// SizeOfInitializedData

	.long	0				// SizeOfUninitializedData

	.long	__efistub_entry - efi_head	// AddressOfEntryPoint

	.long	__efistub_entry - _head		// AddressOfEntryPoint

	.long	__efistub_stext_offset		// BaseOfCode



extra_header_fields:
@@ -139,7 +138,7 @@ extra_header_fields: 
	.short	0				// MinorSubsystemVersion

	.long	0				// Win32VersionValue



	.long	_end - efi_head			// SizeOfImage

	.long	_end - _head			// SizeOfImage



	// Everything before the kernel image is considered part of the header

	.long	__efistub_stext_offset		// SizeOfHeaders
@@ -219,11 +218,13 @@ ENTRY(stext) 
	 * On return, the CPU will be ready for the MMU to be turned on and

	 * the TCR will have been set.

	 */

	ldr	x27, =__mmap_switched		// address to jump to after

	ldr	x27, 0f				// address to jump to after

						// MMU has been enabled

	adr_l	lr, __enable_mmu		// return (PIC) address

	b	__cpu_setup			// initialise processor

ENDPROC(stext)

	.align	3

0:	.quad	__mmap_switched - (_head - TEXT_OFFSET) + KIMAGE_VADDR



/*

 * Preserve the arguments passed by the bootloader in x0 .. x3
@@ -391,7 +392,8 @@ __create_page_tables: 
	mov	x0, x26				// swapper_pg_dir

	ldr	x5, =KIMAGE_VADDR

	create_pgd_entry x0, x5, x3, x6

	ldr	x6, =KERNEL_END			// __va(KERNEL_END)

	ldr	w6, kernel_img_size

	add	x6, x6, x5

	mov	x3, x24				// phys offset

	create_block_map x0, x7, x3, x5, x6
@@ -408,6 +410,9 @@ __create_page_tables: 
	mov	lr, x27

	ret

ENDPROC(__create_page_tables)



kernel_img_size:

	.long	_end - (_head - TEXT_OFFSET)

	.ltorg



/*
@@ -415,6 +420,10 @@ ENDPROC(__create_page_tables) 
 */

	.set	initial_sp, init_thread_union + THREAD_START_SP

__mmap_switched:

	adr_l	x8, vectors			// load VBAR_EL1 with virtual

	msr	vbar_el1, x8			// vector table address

	isb



	// Clear BSS

	adr_l	x0, __bss_start

	mov	x1, xzr
@@ -610,13 +619,19 @@ ENTRY(secondary_startup) 
	adrp	x26, swapper_pg_dir

	bl	__cpu_setup			// initialise processor



	ldr	x21, =secondary_data

	ldr	x27, =__secondary_switched	// address to jump to after enabling the MMU

	ldr	x8, =KIMAGE_VADDR

	ldr	w9, 0f

	sub	x27, x8, w9, sxtw		// address to jump to after enabling the MMU

	b	__enable_mmu

ENDPROC(secondary_startup)

0:	.long	(_text - TEXT_OFFSET) - __secondary_switched



ENTRY(__secondary_switched)

	ldr	x0, [x21]			// get secondary_data.stack

	adr_l	x5, vectors

	msr	vbar_el1, x5

	isb



	ldr_l	x0, secondary_data		// get secondary_data.stack

	mov	sp, x0

	and	x0, x0, #~(THREAD_SIZE - 1)

	msr	sp_el0, x0			// save thread_info
@@ -641,8 +656,6 @@ __enable_mmu: 
	ubfx	x2, x1, #ID_AA64MMFR0_TGRAN_SHIFT, 4

	cmp	x2, #ID_AA64MMFR0_TGRAN_SUPPORTED

	b.ne	__no_granule_support

	ldr	x5, =vectors

	msr	vbar_el1, x5

	msr	ttbr0_el1, x25			// load TTBR0

	msr	ttbr1_el1, x26			// load TTBR1

	isb

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