alistair23-linux/arch/arm64/kernel/relocate_kernel.S

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * kexec for arm64
 *
 * Copyright (C) Linaro.
 * Copyright (C) Huawei Futurewei Technologies.
 */

#include <linux/kexec.h>
#include <linux/linkage.h>

#include <asm/assembler.h>
#include <asm/kexec.h>
#include <asm/page.h>
#include <asm/sysreg.h>

/*
 * arm64_relocate_new_kernel - Put a 2nd stage image in place and boot it.
 *
 * The memory that the old kernel occupies may be overwritten when coping the
 * new image to its final location.  To assure that the
 * arm64_relocate_new_kernel routine which does that copy is not overwritten,
 * all code and data needed by arm64_relocate_new_kernel must be between the
 * symbols arm64_relocate_new_kernel and arm64_relocate_new_kernel_end.  The
 * machine_kexec() routine will copy arm64_relocate_new_kernel to the kexec
 * control_code_page, a special page which has been set up to be preserved
 * during the copy operation.
 */
ENTRY(arm64_relocate_new_kernel)

	/* Setup the list loop variables. */
	mov	x18, x2				/* x18 = dtb address */
	mov	x17, x1				/* x17 = kimage_start */
	mov	x16, x0				/* x16 = kimage_head */
	raw_dcache_line_size x15, x0		/* x15 = dcache line size */
	mov	x14, xzr			/* x14 = entry ptr */
	mov	x13, xzr			/* x13 = copy dest */

	/* Clear the sctlr_el2 flags. */
	mrs	x0, CurrentEL
	cmp	x0, #CurrentEL_EL2
	b.ne	1f
	mrs	x0, sctlr_el2
	ldr	x1, =SCTLR_ELx_FLAGS
	bic	x0, x0, x1
	pre_disable_mmu_workaround
	msr	sctlr_el2, x0
	isb
1:

	/* Check if the new image needs relocation. */
	tbnz	x16, IND_DONE_BIT, .Ldone

.Lloop:
	and	x12, x16, PAGE_MASK		/* x12 = addr */

	/* Test the entry flags. */
.Ltest_source:
	tbz	x16, IND_SOURCE_BIT, .Ltest_indirection

	/* Invalidate dest page to PoC. */
	mov     x0, x13
	add     x20, x0, #PAGE_SIZE
	sub     x1, x15, #1
	bic     x0, x0, x1
2:	dc      ivac, x0
	add     x0, x0, x15
	cmp     x0, x20
	b.lo    2b
	dsb     sy

	mov x20, x13
	mov x21, x12
	copy_page x20, x21, x0, x1, x2, x3, x4, x5, x6, x7

	/* dest += PAGE_SIZE */
	add	x13, x13, PAGE_SIZE
	b	.Lnext

.Ltest_indirection:
	tbz	x16, IND_INDIRECTION_BIT, .Ltest_destination

	/* ptr = addr */
	mov	x14, x12
	b	.Lnext

.Ltest_destination:
	tbz	x16, IND_DESTINATION_BIT, .Lnext

	/* dest = addr */
	mov	x13, x12

.Lnext:
	/* entry = *ptr++ */
	ldr	x16, [x14], #8

	/* while (!(entry & DONE)) */
	tbz	x16, IND_DONE_BIT, .Lloop

.Ldone:
	/* wait for writes from copy_page to finish */
	dsb	nsh
	ic	iallu
	dsb	nsh
	isb

	/* Start new image. */
	mov	x0, x18
	mov	x1, xzr
	mov	x2, xzr
	mov	x3, xzr
	br	x17

ENDPROC(arm64_relocate_new_kernel)

.ltorg

.align 3	/* To keep the 64-bit values below naturally aligned. */

.Lcopy_end:
.org	KEXEC_CONTROL_PAGE_SIZE

/*
 * arm64_relocate_new_kernel_size - Number of bytes to copy to the
 * control_code_page.
 */
.globl arm64_relocate_new_kernel_size
arm64_relocate_new_kernel_size:
	.quad	.Lcopy_end - arm64_relocate_new_kernel