linux-kernel - [PATCH 10/18] arm64: kexec: pass kimage as the only argument to relocation function

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Message-Id: <20210527150526.271941-11-pasha.tatashin@soleen.com>
Date:   Thu, 27 May 2021 11:05:18 -0400
From:   Pavel Tatashin <pasha.tatashin@...een.com>
To:     pasha.tatashin@...een.com, jmorris@...ei.org, sashal@...nel.org,
        ebiederm@...ssion.com, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org, corbet@....net,
        catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org, maz@...nel.org,
        james.morse@....com, vladimir.murzin@....com,
        matthias.bgg@...il.com, linux-mm@...ck.org, mark.rutland@....com,
        steve.capper@....com, rfontana@...hat.com, tglx@...utronix.de,
        selindag@...il.com, tyhicks@...ux.microsoft.com,
        kernelfans@...il.com, akpm@...ux-foundation.org,
        madvenka@...ux.microsoft.com
Subject: [PATCH 10/18] arm64: kexec: pass kimage as the only argument to relocation function

Currently, kexec relocation function (arm64_relocate_new_kernel) accepts
the following arguments:

head:		start of array that contains relocation information.
entry:		entry point for new kernel or purgatory.
dtb_mem:	first and only argument to entry.

The number of arguments cannot be easily expended, because this
function is also called from HVC_SOFT_RESTART, which preserves only
three arguments. And, also arm64_relocate_new_kernel is written in
assembly but called without stack, thus no place to move extra arguments
to free registers.

Soon, we will need to pass more arguments: once we enable MMU we
will need to pass information about page tables.

Pass kimage to arm64_relocate_new_kernel, and teach it to get the
required fields from kimage.

Suggested-by: James Morse <james.morse@....com>
Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
---
 arch/arm64/kernel/asm-offsets.c     |  7 +++++++
 arch/arm64/kernel/machine_kexec.c   |  6 ++++--
 arch/arm64/kernel/relocate_kernel.S | 10 ++++------
 3 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 0cb34ccb6e73..92c2ed846730 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -9,6 +9,7 @@
 
 #include <linux/arm_sdei.h>
 #include <linux/sched.h>
+#include <linux/kexec.h>
 #include <linux/mm.h>
 #include <linux/dma-mapping.h>
 #include <linux/kvm_host.h>
@@ -155,6 +156,12 @@ int main(void)
   DEFINE(PTRAUTH_USER_KEY_APIA,		offsetof(struct ptrauth_keys_user, apia));
   DEFINE(PTRAUTH_KERNEL_KEY_APIA,	offsetof(struct ptrauth_keys_kernel, apia));
   BLANK();
+#endif
+#ifdef CONFIG_KEXEC_CORE
+  DEFINE(KIMAGE_ARCH_DTB_MEM,		offsetof(struct kimage, arch.dtb_mem));
+  DEFINE(KIMAGE_HEAD,			offsetof(struct kimage, head));
+  DEFINE(KIMAGE_START,			offsetof(struct kimage, start));
+  BLANK();
 #endif
   return 0;
 }
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index bde623805866..76a757954a70 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -83,6 +83,8 @@ static void kexec_list_flush(struct kimage *kimage)
 {
 	kimage_entry_t *entry;
 
+	__flush_dcache_area(kimage, sizeof(*kimage));
+
 	for (entry = &kimage->head; ; entry++) {
 		unsigned int flag;
 		void *addr;
@@ -198,8 +200,8 @@ void machine_kexec(struct kimage *kimage)
 		restart(is_hyp_callable(), kimage->start, kimage->arch.dtb_mem,
 			0, 0);
 	} else {
-		cpu_soft_restart(kimage->arch.kern_reloc, kimage->head,
-				 kimage->start, kimage->arch.dtb_mem);
+		cpu_soft_restart(kimage->arch.kern_reloc, virt_to_phys(kimage),
+				 0, 0);
 	}
 
 	BUG(); /* Should never get here. */
diff --git a/arch/arm64/kernel/relocate_kernel.S b/arch/arm64/kernel/relocate_kernel.S
index 718037bef560..36b4496524c3 100644
--- a/arch/arm64/kernel/relocate_kernel.S
+++ b/arch/arm64/kernel/relocate_kernel.S
@@ -27,9 +27,7 @@
  */
 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 */
+	ldr	x16, [x0, #KIMAGE_HEAD]		/* x16 = kimage_head */
 	mov	x14, xzr			/* x14 = entry ptr */
 	mov	x13, xzr			/* x13 = copy dest */
 	raw_dcache_line_size x15, x1		/* x15 = dcache line size */
@@ -63,12 +61,12 @@ SYM_CODE_START(arm64_relocate_new_kernel)
 	isb
 
 	/* Start new image. */
-	mov	x0, x18
+	ldr	x4, [x0, #KIMAGE_START]		/* relocation start */
+	ldr	x0, [x0, #KIMAGE_ARCH_DTB_MEM]	/* dtb address */
 	mov	x1, xzr
 	mov	x2, xzr
 	mov	x3, xzr
-	br	x17
-
+	br	x4
 SYM_CODE_END(arm64_relocate_new_kernel)
 
 .align 3	/* To keep the 64-bit values below naturally aligned. */
-- 
2.25.1