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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: Pavel Tatashin <pasha.tatashin@soleen.com>
Link: https://lore.kernel.org/r/20210125191923.1060122-12-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Pavel Tatashin 2021-01-25 14:19:16 -05:00 committed by Will Deacon
parent 77a43be116
commit dbd82fee0f
1 changed files with 8 additions and 28 deletions
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36
arch/arm64/kernel/relocate_kernel.S
View File

@ -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