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arm64/kexec: Add core kexec support
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> Reviewed-by: James Morse <james.morse@arm.com> [catalin.marinas@arm.com: removed dead code following James Morse's comments] Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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‎arch/arm64/Kconfig

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@@ -665,6 +665,16 @@ config PARAVIRT_TIME_ACCOUNTING
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If in doubt, say N here.
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config KEXEC
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depends on PM_SLEEP_SMP
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select KEXEC_CORE
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bool "kexec system call"
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---help---
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kexec is a system call that implements the ability to shutdown your
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current kernel, and to start another kernel. It is like a reboot
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but it is independent of the system firmware. And like a reboot
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you can start any kernel with it, not just Linux.
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config XEN_DOM0
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def_bool y
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depends on XEN

‎arch/arm64/include/asm/kexec.h

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/*
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* kexec for arm64
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*
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* Copyright (C) Linaro.
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* Copyright (C) Huawei Futurewei Technologies.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef _ARM64_KEXEC_H
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#define _ARM64_KEXEC_H
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/* Maximum physical address we can use pages from */
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#define KEXEC_SOURCE_MEMORY_LIMIT (-1UL)
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/* Maximum address we can reach in physical address mode */
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#define KEXEC_DESTINATION_MEMORY_LIMIT (-1UL)
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/* Maximum address we can use for the control code buffer */
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#define KEXEC_CONTROL_MEMORY_LIMIT (-1UL)
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#define KEXEC_CONTROL_PAGE_SIZE 4096
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#define KEXEC_ARCH KEXEC_ARCH_AARCH64
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#ifndef __ASSEMBLY__
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/**
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* crash_setup_regs() - save registers for the panic kernel
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*
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* @newregs: registers are saved here
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* @oldregs: registers to be saved (may be %NULL)
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*/
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static inline void crash_setup_regs(struct pt_regs *newregs,
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struct pt_regs *oldregs)
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{
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/* Empty routine needed to avoid build errors. */
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}
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#endif /* __ASSEMBLY__ */
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#endif

‎arch/arm64/kernel/Makefile

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@@ -46,6 +46,8 @@ arm64-obj-$(CONFIG_ARM64_ACPI_PARKING_PROTOCOL) += acpi_parking_protocol.o
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arm64-obj-$(CONFIG_PARAVIRT) += paravirt.o
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arm64-obj-$(CONFIG_RANDOMIZE_BASE) += kaslr.o
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arm64-obj-$(CONFIG_HIBERNATION) += hibernate.o hibernate-asm.o
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arm64-obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o \
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cpu-reset.o
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obj-y += $(arm64-obj-y) vdso/
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obj-m += $(arm64-obj-m)

‎arch/arm64/kernel/machine_kexec.c

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/*
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* kexec for arm64
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*
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* Copyright (C) Linaro.
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* Copyright (C) Huawei Futurewei Technologies.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/kexec.h>
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#include <linux/smp.h>
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#include <asm/cacheflush.h>
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#include <asm/cpu_ops.h>
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#include <asm/mmu_context.h>
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#include "cpu-reset.h"
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/* Global variables for the arm64_relocate_new_kernel routine. */
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extern const unsigned char arm64_relocate_new_kernel[];
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extern const unsigned long arm64_relocate_new_kernel_size;
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static unsigned long kimage_start;
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void machine_kexec_cleanup(struct kimage *kimage)
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{
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/* Empty routine needed to avoid build errors. */
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}
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/**
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* machine_kexec_prepare - Prepare for a kexec reboot.
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*
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* Called from the core kexec code when a kernel image is loaded.
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* Forbid loading a kexec kernel if we have no way of hotplugging cpus or cpus
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* are stuck in the kernel. This avoids a panic once we hit machine_kexec().
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*/
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int machine_kexec_prepare(struct kimage *kimage)
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{
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kimage_start = kimage->start;
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if (kimage->type != KEXEC_TYPE_CRASH && cpus_are_stuck_in_kernel()) {
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pr_err("Can't kexec: CPUs are stuck in the kernel.\n");
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return -EBUSY;
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}
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return 0;
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}
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/**
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* kexec_list_flush - Helper to flush the kimage list and source pages to PoC.
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*/
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static void kexec_list_flush(struct kimage *kimage)
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{
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kimage_entry_t *entry;
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for (entry = &kimage->head; ; entry++) {
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unsigned int flag;
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void *addr;
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/* flush the list entries. */
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__flush_dcache_area(entry, sizeof(kimage_entry_t));
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flag = *entry & IND_FLAGS;
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if (flag == IND_DONE)
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break;
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addr = phys_to_virt(*entry & PAGE_MASK);
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switch (flag) {
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case IND_INDIRECTION:
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/* Set entry point just before the new list page. */
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entry = (kimage_entry_t *)addr - 1;
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break;
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case IND_SOURCE:
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/* flush the source pages. */
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__flush_dcache_area(addr, PAGE_SIZE);
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break;
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case IND_DESTINATION:
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break;
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default:
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BUG();
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}
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}
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}
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/**
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* kexec_segment_flush - Helper to flush the kimage segments to PoC.
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*/
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static void kexec_segment_flush(const struct kimage *kimage)
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{
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unsigned long i;
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pr_debug("%s:\n", __func__);
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for (i = 0; i < kimage->nr_segments; i++) {
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pr_debug(" segment[%lu]: %016lx - %016lx, 0x%lx bytes, %lu pages\n",
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i,
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kimage->segment[i].mem,
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kimage->segment[i].mem + kimage->segment[i].memsz,
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kimage->segment[i].memsz,
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kimage->segment[i].memsz / PAGE_SIZE);
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__flush_dcache_area(phys_to_virt(kimage->segment[i].mem),
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kimage->segment[i].memsz);
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}
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}
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/**
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* machine_kexec - Do the kexec reboot.
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*
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* Called from the core kexec code for a sys_reboot with LINUX_REBOOT_CMD_KEXEC.
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*/
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void machine_kexec(struct kimage *kimage)
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{
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phys_addr_t reboot_code_buffer_phys;
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void *reboot_code_buffer;
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/*
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* New cpus may have become stuck_in_kernel after we loaded the image.
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*/
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BUG_ON(cpus_are_stuck_in_kernel() || (num_online_cpus() > 1));
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reboot_code_buffer_phys = page_to_phys(kimage->control_code_page);
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reboot_code_buffer = phys_to_virt(reboot_code_buffer_phys);
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/*
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* Copy arm64_relocate_new_kernel to the reboot_code_buffer for use
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* after the kernel is shut down.
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*/
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memcpy(reboot_code_buffer, arm64_relocate_new_kernel,
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arm64_relocate_new_kernel_size);
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/* Flush the reboot_code_buffer in preparation for its execution. */
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__flush_dcache_area(reboot_code_buffer, arm64_relocate_new_kernel_size);
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flush_icache_range((uintptr_t)reboot_code_buffer,
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arm64_relocate_new_kernel_size);
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/* Flush the kimage list and its buffers. */
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kexec_list_flush(kimage);
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/* Flush the new image if already in place. */
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if (kimage->head & IND_DONE)
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kexec_segment_flush(kimage);
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pr_info("Bye!\n");
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/* Disable all DAIF exceptions. */
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asm volatile ("msr daifset, #0xf" : : : "memory");
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/*
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* cpu_soft_restart will shutdown the MMU, disable data caches, then
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* transfer control to the reboot_code_buffer which contains a copy of
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* the arm64_relocate_new_kernel routine. arm64_relocate_new_kernel
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* uses physical addressing to relocate the new image to its final
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* position and transfers control to the image entry point when the
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* relocation is complete.
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*/
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cpu_soft_restart(1, reboot_code_buffer_phys, kimage->head,
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kimage_start, 0);
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BUG(); /* Should never get here. */
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}
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void machine_crash_shutdown(struct pt_regs *regs)
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{
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/* Empty routine needed to avoid build errors. */
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}

‎arch/arm64/kernel/relocate_kernel.S

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/*
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* kexec for arm64
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*
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* Copyright (C) Linaro.
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* Copyright (C) Huawei Futurewei Technologies.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/kexec.h>
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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#include <asm/kexec.h>
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#include <asm/page.h>
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#include <asm/sysreg.h>
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/*
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* arm64_relocate_new_kernel - Put a 2nd stage image in place and boot it.
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*
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* The memory that the old kernel occupies may be overwritten when coping the
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* new image to its final location. To assure that the
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* arm64_relocate_new_kernel routine which does that copy is not overwritten,
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* all code and data needed by arm64_relocate_new_kernel must be between the
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* symbols arm64_relocate_new_kernel and arm64_relocate_new_kernel_end. The
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* machine_kexec() routine will copy arm64_relocate_new_kernel to the kexec
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* control_code_page, a special page which has been set up to be preserved
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* during the copy operation.
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*/
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ENTRY(arm64_relocate_new_kernel)
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/* Setup the list loop variables. */
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mov x17, x1 /* x17 = kimage_start */
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mov x16, x0 /* x16 = kimage_head */
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dcache_line_size x15, x0 /* x15 = dcache line size */
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mov x14, xzr /* x14 = entry ptr */
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mov x13, xzr /* x13 = copy dest */
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/* Clear the sctlr_el2 flags. */
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mrs x0, CurrentEL
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cmp x0, #CurrentEL_EL2
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b.ne 1f
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mrs x0, sctlr_el2
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ldr x1, =SCTLR_ELx_FLAGS
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bic x0, x0, x1
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msr sctlr_el2, x0
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isb
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1:
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/* Check if the new image needs relocation. */
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tbnz x16, IND_DONE_BIT, .Ldone
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.Lloop:
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and x12, x16, PAGE_MASK /* x12 = addr */
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/* Test the entry flags. */
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.Ltest_source:
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tbz x16, IND_SOURCE_BIT, .Ltest_indirection
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/* Invalidate dest page to PoC. */
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mov x0, x13
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add x20, x0, #PAGE_SIZE
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sub x1, x15, #1
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bic x0, x0, x1
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2: dc ivac, x0
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add x0, x0, x15
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cmp x0, x20
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b.lo 2b
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dsb sy
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mov x20, x13
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mov x21, x12
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copy_page x20, x21, x0, x1, x2, x3, x4, x5, x6, x7
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/* dest += PAGE_SIZE */
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add x13, x13, PAGE_SIZE
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b .Lnext
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.Ltest_indirection:
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tbz x16, IND_INDIRECTION_BIT, .Ltest_destination
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/* ptr = addr */
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mov x14, x12
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b .Lnext
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.Ltest_destination:
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tbz x16, IND_DESTINATION_BIT, .Lnext
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/* dest = addr */
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mov x13, x12
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.Lnext:
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/* entry = *ptr++ */
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ldr x16, [x14], #8
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/* while (!(entry & DONE)) */
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tbz x16, IND_DONE_BIT, .Lloop
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.Ldone:
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/* wait for writes from copy_page to finish */
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dsb nsh
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ic iallu
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dsb nsh
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isb
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/* Start new image. */
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mov x0, xzr
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mov x1, xzr
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mov x2, xzr
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mov x3, xzr
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br x17
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ENDPROC(arm64_relocate_new_kernel)
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.ltorg
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.align 3 /* To keep the 64-bit values below naturally aligned. */
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.Lcopy_end:
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.org KEXEC_CONTROL_PAGE_SIZE
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/*
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* arm64_relocate_new_kernel_size - Number of bytes to copy to the
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* control_code_page.
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*/
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.globl arm64_relocate_new_kernel_size
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arm64_relocate_new_kernel_size:
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.quad .Lcopy_end - arm64_relocate_new_kernel

‎include/uapi/linux/kexec.h

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#define KEXEC_ARCH_SH (42 << 16)
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#define KEXEC_ARCH_MIPS_LE (10 << 16)
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#define KEXEC_ARCH_MIPS ( 8 << 16)
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#define KEXEC_ARCH_AARCH64 (183 << 16)
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/* The artificial cap on the number of segments passed to kexec_load. */
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#define KEXEC_SEGMENT_MAX 16

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