[PATCH v8 07/13] arm64: kexec_file: invoke the kernel without purgatory

[AKASHI Takahiro]

On arm64, purugatory would do almosty nothing. So just invoke the second
kernel by jumping into the entry code directly.

While, in this case, cpu_soft_restart() must be called in a specific way,
it still stays compatible with kexec as far as the fifth argument is null.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
---
 arch/arm64/kernel/cpu-reset.S       |  6 +++---
 arch/arm64/kernel/machine_kexec.c   | 11 +++++++++--
 arch/arm64/kernel/relocate_kernel.S |  3 ++-
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/cpu-reset.S b/arch/arm64/kernel/cpu-reset.S
index 8021b46c9743..46fd9ea66ae8 100644
--- a/arch/arm64/kernel/cpu-reset.S
+++ b/arch/arm64/kernel/cpu-reset.S
@@ -24,9 +24,9 @@
  *
  * @el2_switch: Flag to indicate a swich to EL2 is needed.
  * @entry: Location to jump to for soft reset.
- * arg0: First argument passed to @entry.
- * arg1: Second argument passed to @entry.
- * arg2: Third argument passed to @entry.
+ * arg0: First argument passed to @entry. (rellocator's address)
+ * arg1: Second argument passed to @entry.(physcal kernel entry)
+ * arg2: Third argument passed to @entry. (physical dtb address)
  *
  * Put the CPU into the same state as it would be if it had been reset, and
  * branch to what would be the reset vector. It must be executed with the
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index f76ea92dff91..f7dbba00be10 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -205,10 +205,17 @@ void machine_kexec(struct kimage *kimage)
 	 * 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.
+	 * In case of kexec_file_load syscall, we directly start the kernel,
+	 * skipping purgatory.
 	 */
-
 	cpu_soft_restart(kimage != kexec_crash_image,
-		reboot_code_buffer_phys, kimage->head, kimage->start, 0);
+		reboot_code_buffer_phys, kimage->head, kimage->start,
+#ifdef CONFIG_KEXEC_FILE
+				kimage->purgatory_info.purgatory_buf ?
+						0 : kimage->arch.dtb_mem);
+#else
+				0);
+#endif
 
 	BUG(); /* Should never get here. */
 }
diff --git a/arch/arm64/kernel/relocate_kernel.S b/arch/arm64/kernel/relocate_kernel.S
index f407e422a720..95fd94209aae 100644
--- a/arch/arm64/kernel/relocate_kernel.S
+++ b/arch/arm64/kernel/relocate_kernel.S
@@ -32,6 +32,7 @@
 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 */
@@ -107,7 +108,7 @@ ENTRY(arm64_relocate_new_kernel)
 	isb
 
 	/* Start new image. */
-	mov	x0, xzr
+	mov	x0, x18
 	mov	x1, xzr
 	mov	x2, xzr
 	mov	x3, xzr
-- 
2.16.2