[PATCH V2 6/7] arm64/kexec: Add core kexec support

[Geoff Levand <geoff@infradead.org>]

Add three new files, kexec.h, machine_kexec.c and relocate_kernel.S to the
arm64 architecture that add support for the kexec re-boot mechanism
(CONFIG_KEXEC) on arm64 platforms.

Signed-off-by: Geoff Levand <geoff@infradead.org>
---
V2: 
  o Add comment about soft_restart().
  o Fold kexec_list_walk() and flush callback into kexec_list_flush().
  o Add arm64_ prefix to global variables.

 arch/arm64/Kconfig                  |   9 ++
 arch/arm64/include/asm/kexec.h      |  47 +++++++++
 arch/arm64/kernel/Makefile          |   1 +
 arch/arm64/kernel/machine_kexec.c   | 171 +++++++++++++++++++++++++++++++++
 arch/arm64/kernel/relocate_kernel.S | 184 ++++++++++++++++++++++++++++++++++++
 include/uapi/linux/kexec.h          |   1 +
 6 files changed, 413 insertions(+)
 create mode 100644 arch/arm64/include/asm/kexec.h
 create mode 100644 arch/arm64/kernel/machine_kexec.c
 create mode 100644 arch/arm64/kernel/relocate_kernel.S

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index f0d3a2d..af03449 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -313,6 +313,15 @@ config ARCH_HAS_CACHE_LINE_SIZE
 
 source "mm/Kconfig"
 
+config KEXEC
+	depends on (!SMP || PM_SLEEP_SMP)
+	bool "kexec system call"
+	---help---
+	  kexec is a system call that implements the ability to shutdown your
+	  current kernel, and to start another kernel.  It is like a reboot
+	  but it is independent of the system firmware.   And like a reboot
+	  you can start any kernel with it, not just Linux.
+
 config XEN_DOM0
 	def_bool y
 	depends on XEN
diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
new file mode 100644
index 0000000..e7bd7ab
--- /dev/null
+++ b/arch/arm64/include/asm/kexec.h
@@ -0,0 +1,47 @@
+/*
+ * kexec for arm64
+ *
+ * Copyright (C) Linaro.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#if !defined(_ARM64_KEXEC_H)
+#define _ARM64_KEXEC_H
+
+/* Maximum physical address we can use pages from */
+
+#define KEXEC_SOURCE_MEMORY_LIMIT (-1UL)
+
+/* Maximum address we can reach in physical address mode */
+
+#define KEXEC_DESTINATION_MEMORY_LIMIT (-1UL)
+
+/* Maximum address we can use for the control code buffer */
+
+#define KEXEC_CONTROL_MEMORY_LIMIT (-1UL)
+
+#define KEXEC_CONTROL_PAGE_SIZE	4096
+
+#define KEXEC_ARCH KEXEC_ARCH_ARM64
+
+#if !defined(__ASSEMBLY__)
+
+/**
+ * crash_setup_regs() - save registers for the panic kernel
+ *
+ * @newregs: registers are saved here
+ * @oldregs: registers to be saved (may be %NULL)
+ */
+
+static inline void crash_setup_regs(struct pt_regs *newregs,
+				    struct pt_regs *oldregs)
+{
+	/* Empty routine needed to avoid build errors. */
+}
+
+#endif /* !defined(__ASSEMBLY__) */
+
+#endif
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 6e9538c..77a7351 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -30,6 +30,7 @@ arm64-obj-$(CONFIG_CPU_IDLE)		+= cpuidle.o
 arm64-obj-$(CONFIG_JUMP_LABEL)		+= jump_label.o
 arm64-obj-$(CONFIG_KGDB)		+= kgdb.o
 arm64-obj-$(CONFIG_EFI)			+= efi.o efi-stub.o efi-entry.o
+arm64-obj-$(CONFIG_KEXEC)		+= machine_kexec.o relocate_kernel.o
 
 obj-y					+= $(arm64-obj-y) vdso/
 obj-m					+= $(arm64-obj-m)
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
new file mode 100644
index 0000000..8924bb0
--- /dev/null
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -0,0 +1,171 @@
+/*
+ * kexec for arm64
+ *
+ * Copyright (C) Linaro.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kexec.h>
+#include <linux/of_fdt.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#include <asm/cacheflush.h>
+#include <asm/system_misc.h>
+
+/* Global variables for the relocate_kernel routine. */
+
+extern const unsigned char relocate_new_kernel[];
+extern const unsigned long relocate_new_kernel_size;
+extern unsigned long arm64_kexec_dtb_addr;
+extern unsigned long arm64_kexec_kimage_head;
+extern unsigned long arm64_kexec_kimage_start;
+
+/**
+ * kexec_is_dtb - Helper routine to check the device tree header signature.
+ */
+
+static bool kexec_is_dtb(const void *dtb)
+{
+	__be32 magic;
+
+	return get_user(magic, (__be32 *)dtb) ? false :
+		(be32_to_cpu(magic) == OF_DT_HEADER);
+}
+
+/**
+ * kexec_find_dtb_seg - Helper routine to find the dtb segment.
+ */
+
+static const struct kexec_segment *kexec_find_dtb_seg(
+	const struct kimage *image)
+{
+	int i;
+
+	for (i = 0; i < image->nr_segments; i++) {
+		if (kexec_is_dtb(image->segment[i].buf))
+			return &image->segment[i];
+	}
+
+	return NULL;
+}
+
+void machine_kexec_cleanup(struct kimage *image)
+{
+	/* Empty routine needed to avoid build errors. */
+}
+
+/**
+ * machine_kexec_prepare - Prepare for a kexec reboot.
+ *
+ * Called from the core kexec code when a kernel image is loaded.
+ */
+
+int machine_kexec_prepare(struct kimage *image)
+{
+	const struct kexec_segment *dtb_seg;
+
+	dtb_seg = kexec_find_dtb_seg(image);
+
+	if (!dtb_seg)
+		return -EINVAL;
+
+	arm64_kexec_dtb_addr = dtb_seg->mem;
+	arm64_kexec_kimage_start = image->start;
+
+	return 0;
+}
+
+/**
+ * kexec_list_flush - Helper to flush the kimage list to PoC.
+ */
+
+static void kexec_list_flush(unsigned long kimage_head)
+{
+	void *dest;
+	unsigned long *entry;
+
+	for (entry = &kimage_head, dest = NULL; ; entry++) {
+		unsigned int flag = *entry & 
+			(IND_DESTINATION | IND_INDIRECTION | IND_DONE |
+			IND_SOURCE);
+		void *addr = phys_to_virt(*entry & PAGE_MASK);
+
+		switch (flag) {
+		case IND_INDIRECTION:
+			entry = (unsigned long *)addr - 1;
+			__flush_dcache_area(addr, PAGE_SIZE);
+			break;
+		case IND_DESTINATION:
+			dest = addr;
+			break;
+		case IND_SOURCE:
+			__flush_dcache_area(addr, PAGE_SIZE);
+			dest += PAGE_SIZE;
+			break;
+		case IND_DONE:
+			return;
+		default:
+			break;
+		}
+	}
+}
+
+/**
+ * machine_kexec - Do the kexec reboot.
+ *
+ * Called from the core kexec code for a sys_reboot with LINUX_REBOOT_CMD_KEXEC.
+ */
+
+void machine_kexec(struct kimage *image)
+{
+	phys_addr_t reboot_code_buffer_phys;
+	void *reboot_code_buffer;
+
+	BUG_ON(num_online_cpus() > 1);
+
+	arm64_kexec_kimage_head = image->head;
+
+	reboot_code_buffer_phys = page_to_phys(image->control_code_page);
+	reboot_code_buffer = phys_to_virt(reboot_code_buffer_phys);
+
+	/*
+	 * Copy relocate_new_kernel to the reboot_code_buffer for use
+	 * after the kernel is shut down.
+	 */
+
+	memcpy(reboot_code_buffer, relocate_new_kernel,
+		relocate_new_kernel_size);
+
+	/* Flush the reboot_code_buffer in preparation for its execution. */
+
+	__flush_dcache_area(reboot_code_buffer, relocate_new_kernel_size);
+
+	/* Flush the kimage list. */
+
+	kexec_list_flush(image->head);
+
+	pr_info("Bye!\n");
+
+	/* Disable all DAIF exceptions. */
+	
+	asm volatile ("msr daifset, #0xf" : : : "memory");
+
+	/*
+	 * soft_restart() will shutdown the MMU, disable data caches, then
+	 * transfer control to the reboot_code_buffer which contains a copy of
+	 * the relocate_new_kernel routine.  relocate_new_kernel will use
+	 * physical addressing to relocate the new kernel to its final position
+	 * and then will transfer control to the entry point of the new kernel.
+	 */
+
+	soft_restart(reboot_code_buffer_phys);
+}
+
+void machine_crash_shutdown(struct pt_regs *regs)
+{
+	/* Empty routine needed to avoid build errors. */
+}
diff --git a/arch/arm64/kernel/relocate_kernel.S b/arch/arm64/kernel/relocate_kernel.S
new file mode 100644
index 0000000..ac68322
--- /dev/null
+++ b/arch/arm64/kernel/relocate_kernel.S
@@ -0,0 +1,184 @@
+/*
+ * kexec for arm64
+ *
+ * Copyright (C) Linaro.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <asm/assembler.h>
+#include <asm/kexec.h>
+#include <asm/memory.h>
+#include <asm/page.h>
+#include <asm/proc-macros.S>
+
+/* The list entry flags. */
+
+#define IND_DESTINATION_BIT 0
+#define IND_INDIRECTION_BIT 1
+#define IND_DONE_BIT        2
+#define IND_SOURCE_BIT      3
+
+/*
+ * relocate_new_kernel - Put the 2nd stage kernel image in place and boot it.
+ *
+ * The memory that the old kernel occupies may be overwritten when coping the
+ * new kernel to its final location.  To assure that the relocate_new_kernel
+ * routine which does that copy is not overwritten all code and data needed
+ * by relocate_new_kernel must be between the symbols relocate_new_kernel and
+ * relocate_new_kernel_end.  The machine_kexec() routine will copy
+ * relocate_new_kernel to the kexec control_code_page, a special page which
+ * has been set up to be preserved during the kernel copy operation.
+ */
+
+.globl relocate_new_kernel
+relocate_new_kernel:
+
+	/* Setup the list loop variables. */
+
+	ldr	x18, arm64_kexec_kimage_head	/* x18 = list entry */
+	dcache_line_size x17, x0		/* x17 = dcache line size */
+	mov	x16, xzr			/* x16 = segment start */
+	mov	x15, xzr			/* x15 = entry ptr */
+	mov	x14, xzr			/* x14 = copy dest */
+
+	/* Check if the new kernel needs relocation. */
+
+	cbz	x18, .Ldone
+	tbnz	x18, IND_DONE_BIT, .Ldone
+
+.Lloop:
+	and	x13, x18, PAGE_MASK		/* x13 = addr */
+
+	/* Test the entry flags. */
+
+.Ltest_source:
+	tbz	x18, IND_SOURCE_BIT, .Ltest_indirection
+
+	/* copy_page(x20 = dest, x21 = src) */
+
+	mov x20, x14
+	mov x21, x13
+
+1:	ldp	x22, x23, [x21]
+	ldp	x24, x25, [x21, #16]
+	ldp	x26, x27, [x21, #32]
+	ldp	x28, x29, [x21, #48]
+	add	x21, x21, #64
+	stnp	x22, x23, [x20]
+	stnp	x24, x25, [x20, #16]
+	stnp	x26, x27, [x20, #32]
+	stnp	x28, x29, [x20, #48]
+	add	x20, x20, #64
+	tst	x21, #(PAGE_SIZE - 1)
+	b.ne	1b
+
+	/* dest += PAGE_SIZE */
+
+	add	x14, x14, PAGE_SIZE
+	b	.Lnext
+
+.Ltest_indirection:
+	tbz	x18, IND_INDIRECTION_BIT, .Ltest_destination
+
+	/* ptr = addr */
+
+	mov	x15, x13
+	b	.Lnext
+
+.Ltest_destination:
+	tbz	x18, IND_DESTINATION_BIT, .Lnext
+
+	/* flush segment */
+
+	bl	.Lflush
+	mov	x16, x13
+
+	/* dest = addr */
+
+	mov	x14, x13
+
+.Lnext:
+	/* entry = *ptr++ */
+
+	ldr	x18, [x15], #8
+
+	/* while (!(entry & DONE)) */
+
+	tbz	x18, IND_DONE_BIT, .Lloop
+
+.Ldone:
+	/* flush last segment */
+
+	bl	.Lflush
+
+	dsb	sy
+	isb
+	ic	ialluis
+	dsb	sy
+	isb
+
+	/* start_new_kernel */
+
+	ldr	x4, arm64_kexec_kimage_start
+	ldr	x0, arm64_kexec_dtb_addr
+	mov	x1, xzr
+	mov	x2, xzr
+	mov	x3, xzr
+	br	x4
+
+/* flush - x17 = line size, x16 = start addr, x14 = end addr. */
+
+.Lflush:
+	cbz	x16, 2f
+	mov	x0, x16
+	sub	x1, x17, #1
+	bic	x0, x0, x1
+1:	dc	civac, x0
+	add	x0, x0, x17
+	cmp	x0, x14
+	b.lo	1b
+2:	ret
+
+.align 3	/* To keep the 64-bit values below naturally aligned. */
+
+/* The machine_kexec routines set these variables. */
+
+/*
+ * arm64_kexec_dtb_addr - Physical address of the new kernel's device tree.
+ */
+
+.globl arm64_kexec_dtb_addr
+arm64_kexec_dtb_addr:
+	.quad	0x0
+
+/*
+ * arm64_kexec_kimage_head - Copy of image->head, the list of kimage entries.
+ */
+
+.globl arm64_kexec_kimage_head
+arm64_kexec_kimage_head:
+	.quad	0x0
+
+/*
+ * arm64_kexec_kimage_start - Copy of image->start, the entry point of the new
+ * kernel.
+ */
+
+.globl arm64_kexec_kimage_start
+arm64_kexec_kimage_start:
+	.quad	0x0
+
+.Lrelocate_new_kernel_end:
+
+/*
+ * relocate_new_kernel_size - Number of bytes to copy to the control_code_page.
+ */
+
+.globl relocate_new_kernel_size
+relocate_new_kernel_size:
+	.quad .Lrelocate_new_kernel_end - relocate_new_kernel
+
+.org	KEXEC_CONTROL_PAGE_SIZE
diff --git a/include/uapi/linux/kexec.h b/include/uapi/linux/kexec.h
index 6925f5b..04626b9 100644
--- a/include/uapi/linux/kexec.h
+++ b/include/uapi/linux/kexec.h
@@ -39,6 +39,7 @@
 #define KEXEC_ARCH_SH      (42 << 16)
 #define KEXEC_ARCH_MIPS_LE (10 << 16)
 #define KEXEC_ARCH_MIPS    ( 8 << 16)
+#define KEXEC_ARCH_ARM64   (183 << 16)
 
 /* The artificial cap on the number of segments passed to kexec_load. */
 #define KEXEC_SEGMENT_MAX 16
-- 
1.9.1




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