[PATCH v15 05/15] arm64: kexec: skip relocation code for inplace kexec

From: Pavel Tatashin
Date: Tue Jun 08 2021 - 20:44:47 EST


In case of kdump or when segments are already in place the relocation
is not needed, therefore the setup of relocation function and call to
it can be skipped.

Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Suggested-by: James Morse <james.morse@xxxxxxx>
---
arch/arm64/kernel/machine_kexec.c | 34 ++++++++++++++++++-----------
arch/arm64/kernel/relocate_kernel.S | 3 ---
2 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index 3a034bc25709..15c126e09686 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -139,21 +139,23 @@ int machine_kexec_post_load(struct kimage *kimage)
{
void *reloc_code = page_to_virt(kimage->control_code_page);

- /* If in place flush new kernel image, else flush lists and buffers */
- if (kimage->head & IND_DONE)
+ /* If in place, relocation is not used, only flush next kernel */
+ if (kimage->head & IND_DONE) {
kexec_segment_flush(kimage);
- else
- kexec_list_flush(kimage);
+ kexec_image_info(kimage);
+ return 0;
+ }

memcpy(reloc_code, arm64_relocate_new_kernel,
arm64_relocate_new_kernel_size);
kimage->arch.kern_reloc = __pa(reloc_code);
- kexec_image_info(kimage);

/* Flush the reloc_code in preparation for its execution. */
__flush_dcache_area(reloc_code, arm64_relocate_new_kernel_size);
flush_icache_range((uintptr_t)reloc_code, (uintptr_t)reloc_code +
arm64_relocate_new_kernel_size);
+ kexec_list_flush(kimage);
+ kexec_image_info(kimage);

return 0;
}
@@ -180,19 +182,25 @@ void machine_kexec(struct kimage *kimage)
local_daif_mask();

/*
- * cpu_soft_restart will shutdown the MMU, disable data caches, then
- * transfer control to the kern_reloc which contains a copy of
- * the arm64_relocate_new_kernel routine. arm64_relocate_new_kernel
- * uses physical addressing to relocate the new image to its final
- * position and transfers control to the image entry point when the
- * relocation is complete.
+ * Both restart and cpu_soft_restart will shutdown the MMU, disable data
+ * caches. However, restart will start new kernel or purgatory directly,
+ * cpu_soft_restart will transfer control to arm64_relocate_new_kernel
* In kexec case, kimage->start points to purgatory assuming that
* kernel entry and dtb address are embedded in purgatory by
* userspace (kexec-tools).
* In kexec_file case, the kernel starts directly without purgatory.
*/
- cpu_soft_restart(kimage->arch.kern_reloc, kimage->head, kimage->start,
- kimage->arch.dtb_mem);
+ if (kimage->head & IND_DONE) {
+ typeof(__cpu_soft_restart) *restart;
+
+ cpu_install_idmap();
+ restart = (void *)__pa_symbol(function_nocfi(__cpu_soft_restart));
+ restart(is_hyp_nvhe(), kimage->start, kimage->arch.dtb_mem,
+ 0, 0);
+ } else {
+ cpu_soft_restart(kimage->arch.kern_reloc, kimage->head,
+ kimage->start, kimage->arch.dtb_mem);
+ }

BUG(); /* Should never get here. */
}
diff --git a/arch/arm64/kernel/relocate_kernel.S b/arch/arm64/kernel/relocate_kernel.S
index b78ea5de97a4..8058fabe0a76 100644
--- a/arch/arm64/kernel/relocate_kernel.S
+++ b/arch/arm64/kernel/relocate_kernel.S
@@ -32,8 +32,6 @@ SYM_CODE_START(arm64_relocate_new_kernel)
mov x16, x0 /* x16 = kimage_head */
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, x1 /* x15 = dcache line size */
.Lloop:
and x12, x16, PAGE_MASK /* x12 = addr */
@@ -65,7 +63,6 @@ SYM_CODE_START(arm64_relocate_new_kernel)
.Lnext:
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
ic iallu
--
2.25.1