[v18,03/13] arm64/kexec: Add core kexec support

Geoff,

On Thu, Jun 09, 2016 at 08:08:44PM +0000, Geoff Levand wrote:
> 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                  |  10 ++

>  arch/arm64/include/asm/kexec.h      |  48 ++++++++++

>  arch/arm64/kernel/Makefile          |   2 +

>  arch/arm64/kernel/machine_kexec.c   | 185 ++++++++++++++++++++++++++++++++++++

>  arch/arm64/kernel/relocate_kernel.S | 131 +++++++++++++++++++++++++

>  include/uapi/linux/kexec.h          |   1 +

>  6 files changed, 377 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 5a0a691..330786d 100644

> --- a/arch/arm64/Kconfig

> +++ b/arch/arm64/Kconfig

> @@ -664,6 +664,16 @@ config PARAVIRT_TIME_ACCOUNTING

>  

>  	  If in doubt, say N here.

>  

> +config KEXEC

> +	depends on PM_SLEEP_SMP

> +	select KEXEC_CORE

> +	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..04744dc

> --- /dev/null

> +++ b/arch/arm64/include/asm/kexec.h

> @@ -0,0 +1,48 @@

> +/*

> + * kexec for arm64

> + *

> + * Copyright (C) Linaro.

> + * Copyright (C) Huawei Futurewei Technologies.

> + *

> + * 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.

> + */

> +

> +#ifndef _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_AARCH64

> +

> +#ifndef __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 /* __ASSEMBLY__ */

> +

> +#endif

> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile

> index 2173149..7700c0c 100644

> --- a/arch/arm64/kernel/Makefile

> +++ b/arch/arm64/kernel/Makefile

> @@ -46,6 +46,8 @@ arm64-obj-$(CONFIG_ARM64_ACPI_PARKING_PROTOCOL)	+= acpi_parking_protocol.o

>  arm64-obj-$(CONFIG_PARAVIRT)		+= paravirt.o

>  arm64-obj-$(CONFIG_RANDOMIZE_BASE)	+= kaslr.o

>  arm64-obj-$(CONFIG_HIBERNATION)		+= hibernate.o hibernate-asm.o

> +arm64-obj-$(CONFIG_KEXEC)		+= machine_kexec.o relocate_kernel.o	\

> +					   cpu-reset.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..05f7c21

> --- /dev/null

> +++ b/arch/arm64/kernel/machine_kexec.c

> @@ -0,0 +1,185 @@

> +/*

> + * kexec for arm64

> + *

> + * Copyright (C) Linaro.

> + * Copyright (C) Huawei Futurewei Technologies.

> + *

> + * 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/highmem.h>

> +#include <linux/kexec.h>

> +#include <linux/of_fdt.h>

> +#include <linux/slab.h>

> +#include <linux/smp.h>

> +#include <linux/uaccess.h>

> +

> +#include <asm/cacheflush.h>

> +#include <asm/cpu_ops.h>

> +#include <asm/mmu_context.h>

> +#include <asm/system_misc.h>

> +

> +#include "cpu-reset.h"

> +

> +/* Global variables for the arm64_relocate_new_kernel routine. */

> +extern const unsigned char arm64_relocate_new_kernel[];

> +extern const unsigned long arm64_relocate_new_kernel_size;

> +

> +static unsigned long kimage_start;

> +

> +void machine_kexec_cleanup(struct kimage *kimage)

> +{

> +	/* 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.

> + * Forbid loading a kexec kernel if we have no way of hotplugging cpus or cpus

> + * are stuck in the kernel. This avoids a panic once we hit machine_kexec().

> + */

> +int machine_kexec_prepare(struct kimage *kimage)

> +{

> +	kimage_start = kimage->start;

> +

> +	if (kimage->type != KEXEC_TYPE_CRASH) {

> +		if (cpus_are_stuck_in_kernel()) {

> +			pr_err("Can't kexec: failed CPUs are stuck in the kernel.\n");

> +			return -EBUSY;

> +		}

> +

> +		if (num_online_cpus() > 1) {

> +#ifdef CONFIG_HOTPLUG_CPU

> +			/* any_cpu as we don't mind being preempted */

> +			int any_cpu = raw_smp_processor_id();

> +

> +			if (cpu_ops[any_cpu]->cpu_die)

> +				return 0;

> +#endif /* CONFIG_HOTPLUG_CPU */

> +

> +			pr_err("Can't kexec: no mechanism to offline secondary CPUs.\n");

> +			return -EBUSY;

> +		}

> +	}

> +

> +	return 0;

> +}

> +

> +/**

> + * kexec_list_flush - Helper to flush the kimage list to PoC.

> + */

> +static void kexec_list_flush(struct kimage *kimage)

> +{

> +	kimage_entry_t *entry;

> +	unsigned int flag;

> +

> +	for (entry = &kimage->head, flag = 0; flag != IND_DONE; entry++) {

> +		void *addr = kmap(phys_to_page(*entry & PAGE_MASK));

> +

> +		flag = *entry & IND_FLAGS;

I found a bug here when I tested the kernel *without* CONFIG_SPARSEMEM_VMEMMAP.
We need to check 'flag == IND_DONE' first before calculating
phys_to_page(*entry & PAGE_MASK), otherwise we will see a kernel page fault
(around the address 0x0) in case of IND_DONE.
This bug was harmless with CONFIG_SPARSEMEM_VMEMMAP because phys_to_page()
macro doesn't contain any memory access and 'addr' can be bogus but never used
in IND_DONE.

See my fix.
(As James mentioned before, we may use phys_to_virt() instead of kmap() here.)

Thanks,
-Takahiro AKASHI

-- 
2.8.1

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[v18,03/13] arm64/kexec: Add core kexec support

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