[PATCH 5/8] arm64/kexec: Add core kexec support

Geoff Levand
2015-01-17T00:23:34Z

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>
---
arch/arm64/Kconfig | 9 ++
arch/arm64/include/asm/kexec.h | 47 +++++++++++
arch/arm64/kernel/Makefile | 1 +
arch/arm64/kernel/machine_kexec.c | 155 ++++++++++++++++++++++++++++++++++
arch/arm64/kernel/relocate_kernel.S | 160 ++++++++++++++++++++++++++++++++++++
include/uapi/linux/kexec.h | 1 +
6 files changed, 373 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 b1f9a20..d9eb9cd 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -474,6 +474,15 @@ config SECCOMP
and the task is only allowed to execute a few safe syscalls
defined by each seccomp mode.

+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 77d3d95..eff1625 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -34,6 +34,7 @@ arm64-obj-$(CONFIG_KGDB) += kgdb.o
arm64-obj-$(CONFIG_EFI) += efi.o efi-stub.o efi-entry.o
arm64-obj-$(CONFIG_PCI) += pci.o
arm64-obj-$(CONFIG_ARMV8_DEPRECATED) += armv8_deprecated.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..b0e5d76
--- /dev/null
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -0,0 +1,155 @@
+/*
+ * 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 = kexec_find_dtb_seg(image);
+
+ arm64_kexec_dtb_addr = dtb_seg ? dtb_seg->mem : 0;
+ 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:
+ BUG();
+ }
+ }
+}
+
+/**
+ * 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..1c1514d
--- /dev/null
+++ b/arch/arm64/kernel/relocate_kernel.S
@@ -0,0 +1,160 @@
+/*
+ * 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 a 2nd stage kernel image in place and boot it.
+ *
+ * The memory that the old kernel occupies may be overwritten when coping the
+ * new image 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 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 image 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
+
+ mov x20, x14 /* x20 = copy dest */
+ mov x21, x13 /* x21 = copy src */
+
+ /* Invalidate dest page to PoC. */
+ mov x0, x20
+ add x19, x0, #PAGE_SIZE
+ sub x1, x17, #1
+ bic x0, x0, x1
+1: dc ivac, x0
+ add x0, x0, x17
+ cmp x0, x19
+ b.lo 1b
+ dsb sy
+
+ /* Copy page. */
+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
+
+ 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:
+ dsb sy
+ isb
+ ic ialluis
+ dsb sy
+ isb
+
+ /* Start new image. */
+ ldr x4, arm64_kexec_kimage_start
+ ldr x0, arm64_kexec_dtb_addr
+ mov x1, xzr
+ mov x2, xzr
+ mov x3, xzr
+ br x4
+
+.align 3 /* To keep the 64-bit values below naturally aligned. */
+
+/* The machine_kexec routines set these variables. */
+
+/*
+ * arm64_kexec_kimage_start - Copy of image->start, the entry point of the new
+ * image.
+ */
+.globl arm64_kexec_kimage_start
+arm64_kexec_kimage_start:
+ .quad 0x0
+
+/*
+ * arm64_kexec_dtb_addr - Physical address of a 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
+
+.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
--
2.1.0