Commit dbd82fee authored by Pavel Tatashin's avatar Pavel Tatashin Committed by Will Deacon
Browse files

arm64: kexec: arm64_relocate_new_kernel clean-ups and optimizations 



In preparation to bigger changes to arm64_relocate_new_kernel that would
enable this function to do MMU backed memory copy, do few clean-ups and
optimizations. These include:

1. Call raw_dcache_line_size()  only when relocation is actually going to
   happen. i.e. kdump type kexec, does not need it.

2.  copy_page(dest, src, tmps...) increments dest and src by PAGE_SIZE, so
    no need to store dest prior to calling copy_page and increment it
    after. Also, src is not used after a copy, not need to copy either.

3. For consistency use comment on the same line with instruction when it
   describes the instruction itself.

4. Some comment corrections

Signed-off-by: default avatarPavel Tatashin <pasha.tatashin@soleen.com>
Link: https://lore.kernel.org/r/20210125191923.1060122-12-pasha.tatashin@soleen.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 77a43be1

arch/arm64/kernel/relocate_kernel.S

+8 −28
Original line number Diff line number Diff line
@@ -17,28 +17,24 @@ 
/*

 * 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

 * The memory that the old kernel occupies may be overwritten when copying 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.

 * safe memory that has been set up to be preserved during the copy operation.

 */

SYM_CODE_START(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 */



	/* Check if the new image needs relocation. */

	tbnz	x16, IND_DONE_BIT, .Ldone



	raw_dcache_line_size x15, x0		/* x15 = dcache line size */

.Lloop:

	and	x12, x16, PAGE_MASK		/* x12 = addr */
@@ -57,34 +53,18 @@ SYM_CODE_START(arm64_relocate_new_kernel) 
	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

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

	b	.Lnext



.Ltest_indirection:

	tbz	x16, IND_INDIRECTION_BIT, .Ltest_destination



	/* ptr = addr */

	mov	x14, x12

	mov	x14, x12			/* ptr = addr */

	b	.Lnext



.Ltest_destination:

	tbz	x16, IND_DESTINATION_BIT, .Lnext



	/* dest = addr */

	mov	x13, x12



	mov	x13, x12			/* dest = addr */

.Lnext:

	/* entry = *ptr++ */

	ldr	x16, [x14], #8



	/* while (!(entry & DONE)) */

	tbz	x16, IND_DONE_BIT, .Lloop



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

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

.Ldone:

	/* wait for writes from copy_page to finish */

	dsb	nsh