diff mbox series

[RFC,2/4] of: Add a common kexec FDT setup function

Message ID 20201211221006.1052453-3-robh@kernel.org (mailing list archive)
State New, archived
Headers show
Series Kexec FDT setup consolidation | expand

Commit Message

Rob Herring (Arm) Dec. 11, 2020, 10:10 p.m. UTC 
Both arm64 and powerpc do essentially the same FDT /chosen setup for
kexec. We can simply combine everything each arch does. The differences
are either omissions that arm64 should have or additional properties
that will be ignored.

The differences relative to the arm64 version:
- If /chosen doesn't exist, it will be created (should never happen).
- Any old dtb and initrd reserved memory will be released.
- The new initrd and elfcorehdr are marked reserved.
- "linux,booted-from-kexec" is set.

The differences relative to the powerpc version:
- "kaslr-seed" and "rng-seed" may be set.
- "linux,elfcorehdr" is set.
- Any existing "linux,usable-memory-range" is removed.

Signed-off-by: Rob Herring <robh@kernel.org>
---
This could be taken a step further and do the allocation of the new
FDT. The difference is arm64 uses vmalloc and powerpc uses kmalloc. The
arm64 version also retries with a bigger allocation. That seems
unnecessary.
---
 drivers/of/Makefile |   1 +
 drivers/of/kexec.c  | 228 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/of.h  |   5 +
 3 files changed, 234 insertions(+)
 create mode 100644 drivers/of/kexec.c

Comments

Lakshmi Ramasubramanian Dec. 12, 2020, 1:18 a.m. UTC | #1 
On 12/11/20 2:10 PM, Rob Herring wrote:

Hi Rob,

> Both arm64 and powerpc do essentially the same FDT /chosen setup for
> kexec. We can simply combine everything each arch does. The differences
> are either omissions that arm64 should have or additional properties
> that will be ignored.
> 
> The differences relative to the arm64 version:
> - If /chosen doesn't exist, it will be created (should never happen).
> - Any old dtb and initrd reserved memory will be released.
> - The new initrd and elfcorehdr are marked reserved.
> - "linux,booted-from-kexec" is set.
> 
> The differences relative to the powerpc version:
> - "kaslr-seed" and "rng-seed" may be set.
> - "linux,elfcorehdr" is set.
> - Any existing "linux,usable-memory-range" is removed.
> 
> Signed-off-by: Rob Herring <robh@kernel.org>
> ---
> This could be taken a step further and do the allocation of the new
> FDT. The difference is arm64 uses vmalloc and powerpc uses kmalloc. The
> arm64 version also retries with a bigger allocation. That seems
> unnecessary.
> ---
>   drivers/of/Makefile |   1 +
>   drivers/of/kexec.c  | 228 ++++++++++++++++++++++++++++++++++++++++++++
>   include/linux/of.h  |   5 +
>   3 files changed, 234 insertions(+)
>   create mode 100644 drivers/of/kexec.c
> 
> diff --git a/drivers/of/Makefile b/drivers/of/Makefile
> index 6e1e5212f058..8ce11955afde 100644
> --- a/drivers/of/Makefile
> +++ b/drivers/of/Makefile
> @@ -13,5 +13,6 @@ obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o
>   obj-$(CONFIG_OF_RESOLVE)  += resolver.o
>   obj-$(CONFIG_OF_OVERLAY) += overlay.o
>   obj-$(CONFIG_OF_NUMA) += of_numa.o
> +obj-$(CONFIG_KEXEC_FILE) += kexec.o

For the functions moved from powerpc & arm64 to "drivers/of/kexec.c" in 
this patch, compiling kexec.c when CONFIG_KEXEC_FILE is enabled is fine. 
But when more functions (such as remove_ima_buffer()) are moved to this 
file, Makefile needs to be updated for other ima kexec related CONFIGs.

Why not compile kexec.c when CONFIG_OF_FLATTREE is enabled, and handle 
other CONFIGs using IS_ENABLED (like you'd suggested earlier)?

>   
>   obj-$(CONFIG_OF_UNITTEST) += unittest-data/
> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
> new file mode 100644
> index 000000000000..66787be081fe
> --- /dev/null
> +++ b/drivers/of/kexec.c
> @@ -0,0 +1,228 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2020 Arm Limited
> + *
> + * Based on arch/arm64/kernel/machine_kexec_file.c:
> + *  Copyright (C) 2018 Linaro Limited
> + *
> + * And arch/powerpc/kexec/file_load.c:
> + *  Copyright (C) 2016  IBM Corporation
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/kexec.h>
> +#include <linux/libfdt.h>
> +#include <linux/of.h>
> +#include <linux/of_fdt.h>
> +#include <linux/random.h>
> +#include <linux/types.h>
> +
> +/* relevant device tree properties */
> +#define FDT_PROP_KEXEC_ELFHDR	"linux,elfcorehdr"
> +#define FDT_PROP_MEM_RANGE	"linux,usable-memory-range"
> +#define FDT_PROP_INITRD_START	"linux,initrd-start"
> +#define FDT_PROP_INITRD_END	"linux,initrd-end"
> +#define FDT_PROP_BOOTARGS	"bootargs"
> +#define FDT_PROP_KASLR_SEED	"kaslr-seed"
> +#define FDT_PROP_RNG_SEED	"rng-seed"
> +#define RNG_SEED_SIZE		128

> +
> +/**
> + * fdt_find_and_del_mem_rsv - delete memory reservation with given address and size
> + *
> + * Return: 0 on success, or negative errno on error.
> + */
> +static int fdt_find_and_del_mem_rsv(void *fdt, unsigned long start, unsigned long size)
> +{
> +	int i, ret, num_rsvs = fdt_num_mem_rsv(fdt);
> +
> +	for (i = 0; i < num_rsvs; i++) {
> +		u64 rsv_start, rsv_size;
> +
> +		ret = fdt_get_mem_rsv(fdt, i, &rsv_start, &rsv_size);
> +		if (ret) {
> +			pr_err("Malformed device tree.\n");
> +			return -EINVAL;
> +		}
> +
> +		if (rsv_start == start && rsv_size == size) {
> +			ret = fdt_del_mem_rsv(fdt, i);
> +			if (ret) {
> +				pr_err("Error deleting device tree reservation.\n");
> +				return -EINVAL;
> +			}
> +
> +			return 0;
> +		}
> +	}
> +
> +	return -ENOENT;
> +}
> +
> +/*
> + * of_kexec_setup_new_fdt - modify /chosen and memory reservation for the next kernel
> + *
> + * @image:		kexec image being loaded.
> + * @fdt:		Flattened device tree for the next kernel.
> + * @initrd_load_addr:	Address where the next initrd will be loaded.
> + * @initrd_len:		Size of the next initrd, or 0 if there will be none.
> + * @cmdline:		Command line for the next kernel, or NULL if there will
> + *			be none.
nit: alignment of the parameter description seems to be off. But it 
could be due to my mail client.

> + *
> + * Return: 0 on success, or negative errno on error.
> + */
> +int of_kexec_setup_new_fdt(const struct kimage *image, void *fdt,
> +			   unsigned long initrd_load_addr, unsigned long initrd_len,
> +			   const char *cmdline)
> +{
> +	int ret, chosen_node;
> +	const void *prop;
> +
> +	/* Remove memory reservation for the current device tree. */
> +	ret = fdt_find_and_del_mem_rsv(fdt, __pa(initial_boot_params),
> +				       fdt_totalsize(initial_boot_params));
> +	if (ret == -EINVAL)
> +		return ret;
> +
> +	chosen_node = fdt_path_offset(fdt, "/chosen");
> +	if (chosen_node == -FDT_ERR_NOTFOUND)
> +		chosen_node = fdt_add_subnode(fdt, fdt_path_offset(fdt, "/"),
> +					      "chosen");
> +	if (chosen_node < 0) {
> +		ret = chosen_node;
> +		goto out;
> +	}
> +
> +	ret = fdt_delprop(fdt, chosen_node, FDT_PROP_KEXEC_ELFHDR);
> +	if (ret && ret != -FDT_ERR_NOTFOUND)
> +		goto out;
> +	ret = fdt_delprop(fdt, chosen_node, FDT_PROP_MEM_RANGE);
> +	if (ret && ret != -FDT_ERR_NOTFOUND)
> +		goto out;
> +
> +	/* Did we boot using an initrd? */
> +	prop = fdt_getprop(fdt, chosen_node, "linux,initrd-start", NULL);
> +	if (prop) {
> +		u64 tmp_start, tmp_end, tmp_size;
> +
> +		tmp_start = fdt64_to_cpu(*((const fdt64_t *) prop));
> +
> +		prop = fdt_getprop(fdt, chosen_node, "linux,initrd-end", NULL);
> +		if (!prop)
> +			return -EINVAL;
> +
> +		tmp_end = fdt64_to_cpu(*((const fdt64_t *) prop));
> +
> +		/*
> +		 * kexec reserves exact initrd size, while firmware may
> +		 * reserve a multiple of PAGE_SIZE, so check for both.
> +		 */
> +		tmp_size = tmp_end - tmp_start;
> +		ret = fdt_find_and_del_mem_rsv(fdt, tmp_start, tmp_size);
> +		if (ret == -ENOENT)
> +			ret = fdt_find_and_del_mem_rsv(fdt, tmp_start,
> +						       round_up(tmp_size, PAGE_SIZE));
> +		if (ret == -EINVAL)
> +			return ret;
> +	}
> +
> +	/* add initrd-* */
> +	if (initrd_load_addr) {
> +		ret = fdt_setprop_u64(fdt, chosen_node, FDT_PROP_INITRD_START,
> +				      initrd_load_addr);
> +		if (ret)
> +			goto out;
> +
> +		ret = fdt_setprop_u64(fdt, chosen_node, FDT_PROP_INITRD_END,
> +				      initrd_load_addr + initrd_len);
> +		if (ret)
> +			goto out;
> +
> +		ret = fdt_add_mem_rsv(fdt, initrd_load_addr, initrd_len);
> +		if (ret)
> +			goto out;
> +
> +	} else {
> +		ret = fdt_delprop(fdt, chosen_node, FDT_PROP_INITRD_START);
> +		if (ret && (ret != -FDT_ERR_NOTFOUND))
> +			goto out;
> +
> +		ret = fdt_delprop(fdt, chosen_node, FDT_PROP_INITRD_END);
> +		if (ret && (ret != -FDT_ERR_NOTFOUND))
> +			goto out;
> +	}
> +
> +	if (image->type == KEXEC_TYPE_CRASH) {
> +		/* add linux,elfcorehdr */
> +		ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
> +				FDT_PROP_KEXEC_ELFHDR,
> +				image->arch.elf_headers_mem,
> +				image->arch.elf_headers_sz);
> +		if (ret)
> +			goto out;
> +
> +		/*
> +		 * Avoid elfcorehdr from being stomped on in kdump kernel by
> +		 * setting up memory reserve map.
> +		 */
> +		ret = fdt_add_mem_rsv(fdt, image->arch.elf_headers_mem,
> +				      image->arch.elf_headers_sz);
Return value from fdt_add_mem_rsv() should be checked.

> +
> +		/* add linux,usable-memory-range */
> +		ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
> +				FDT_PROP_MEM_RANGE,
> +				crashk_res.start,
> +				crashk_res.end - crashk_res.start + 1);
> +		if (ret)
> +			goto out;
> +	}
> +
> +	/* add bootargs */
> +	if (cmdline) {
> +		ret = fdt_setprop_string(fdt, chosen_node, FDT_PROP_BOOTARGS, cmdline);
> +		if (ret)
> +			goto out;
> +	} else {
> +		ret = fdt_delprop(fdt, chosen_node, FDT_PROP_BOOTARGS);
> +		if (ret && (ret != -FDT_ERR_NOTFOUND))
> +			goto out;
> +	}
> +
> +	/* add kaslr-seed */
> +	ret = fdt_delprop(fdt, chosen_node, FDT_PROP_KASLR_SEED);
> +	if (ret == -FDT_ERR_NOTFOUND)
> +		ret = 0;
> +	else if (ret)
> +		goto out;
> +
> +	if (rng_is_initialized()) {
> +		u64 seed = get_random_u64();
> +		ret = fdt_setprop_u64(fdt, chosen_node, FDT_PROP_KASLR_SEED, seed);
> +		if (ret)
> +			goto out;
> +	} else {
> +		pr_notice("RNG is not initialised: omitting \"%s\" property\n",
> +				FDT_PROP_KASLR_SEED);
> +	}
> +
> +	/* add rng-seed */
> +	if (rng_is_initialized()) {
> +		void *rng_seed;
> +		ret = fdt_setprop_placeholder(fdt, chosen_node, FDT_PROP_RNG_SEED,
> +				RNG_SEED_SIZE, &rng_seed);
> +		if (ret)
> +			goto out;
> +		get_random_bytes(rng_seed, RNG_SEED_SIZE);
> +	} else {
> +		pr_notice("RNG is not initialised: omitting \"%s\" property\n",
> +				FDT_PROP_RNG_SEED);
> +	}
> +
> +	ret = fdt_setprop(fdt, chosen_node, "linux,booted-from-kexec", NULL, 0);
> +
> +out:
> +	if (ret)
> +		return (ret == -FDT_ERR_NOSPACE) ? -ENOMEM : -EINVAL;
> +
> +	return 0;
> +}
> diff --git a/include/linux/of.h b/include/linux/of.h
> index 5d51891cbf1a..3375f5295875 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -558,6 +558,11 @@ int of_map_id(struct device_node *np, u32 id,
>   	       const char *map_name, const char *map_mask_name,
>   	       struct device_node **target, u32 *id_out);
>   
> +struct kimage;
> +int of_kexec_setup_new_fdt(const struct kimage *image, void *fdt,
> +			   unsigned long initrd_load_addr, unsigned long initrd_len,
> +			   const char *cmdline);

of_kexec_setup_new_fdt() should only be declared if CONFIG_KEXEC_FILE is 
enabled. Right?

  -lakshmi

> +
>   #else /* CONFIG_OF */
>   
>   static inline void of_core_init(void)
>
Thiago Jung Bauermann Dec. 12, 2020, 2:17 a.m. UTC | #2 
Lakshmi Ramasubramanian <nramas@linux.microsoft.com> writes:

> On 12/11/20 2:10 PM, Rob Herring wrote:
>
> Hi Rob,
>
>> Both arm64 and powerpc do essentially the same FDT /chosen setup for
>> kexec. We can simply combine everything each arch does. The differences
>> are either omissions that arm64 should have or additional properties
>> that will be ignored.
>> The differences relative to the arm64 version:
>> - If /chosen doesn't exist, it will be created (should never happen).
>> - Any old dtb and initrd reserved memory will be released.
>> - The new initrd and elfcorehdr are marked reserved.
>> - "linux,booted-from-kexec" is set.
>> The differences relative to the powerpc version:
>> - "kaslr-seed" and "rng-seed" may be set.
>> - "linux,elfcorehdr" is set.
>> - Any existing "linux,usable-memory-range" is removed.
>> Signed-off-by: Rob Herring <robh@kernel.org>
>> ---
>> This could be taken a step further and do the allocation of the new
>> FDT. The difference is arm64 uses vmalloc and powerpc uses kmalloc. The
>> arm64 version also retries with a bigger allocation. That seems
>> unnecessary.
>> ---
>>   drivers/of/Makefile |   1 +
>>   drivers/of/kexec.c  | 228 ++++++++++++++++++++++++++++++++++++++++++++
>>   include/linux/of.h  |   5 +
>>   3 files changed, 234 insertions(+)
>>   create mode 100644 drivers/of/kexec.c
>> diff --git a/drivers/of/Makefile b/drivers/of/Makefile
>> index 6e1e5212f058..8ce11955afde 100644
>> --- a/drivers/of/Makefile
>> +++ b/drivers/of/Makefile
>> @@ -13,5 +13,6 @@ obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o
>>   obj-$(CONFIG_OF_RESOLVE)  += resolver.o
>>   obj-$(CONFIG_OF_OVERLAY) += overlay.o
>>   obj-$(CONFIG_OF_NUMA) += of_numa.o
>> +obj-$(CONFIG_KEXEC_FILE) += kexec.o
>
> For the functions moved from powerpc & arm64 to "drivers/of/kexec.c" in this
> patch, compiling kexec.c when CONFIG_KEXEC_FILE is enabled is fine. But when
> more functions (such as remove_ima_buffer()) are moved to this file, Makefile
> needs to be updated for other ima kexec related CONFIGs.

IMA kexec is only available if CONFIG_KEXEC_FILE is enabled, so I don't
understand what problem you are seeing.
Lakshmi Ramasubramanian Dec. 12, 2020, 5:46 a.m. UTC | #3 
On 12/11/20 6:17 PM, Thiago Jung Bauermann wrote:
> 
> Lakshmi Ramasubramanian <nramas@linux.microsoft.com> writes:
> 
>> On 12/11/20 2:10 PM, Rob Herring wrote:
>>
>> Hi Rob,
>>
>>> Both arm64 and powerpc do essentially the same FDT /chosen setup for
>>> kexec. We can simply combine everything each arch does. The differences
>>> are either omissions that arm64 should have or additional properties
>>> that will be ignored.
>>> The differences relative to the arm64 version:
>>> - If /chosen doesn't exist, it will be created (should never happen).
>>> - Any old dtb and initrd reserved memory will be released.
>>> - The new initrd and elfcorehdr are marked reserved.
>>> - "linux,booted-from-kexec" is set.
>>> The differences relative to the powerpc version:
>>> - "kaslr-seed" and "rng-seed" may be set.
>>> - "linux,elfcorehdr" is set.
>>> - Any existing "linux,usable-memory-range" is removed.
>>> Signed-off-by: Rob Herring <robh@kernel.org>
>>> ---
>>> This could be taken a step further and do the allocation of the new
>>> FDT. The difference is arm64 uses vmalloc and powerpc uses kmalloc. The
>>> arm64 version also retries with a bigger allocation. That seems
>>> unnecessary.
>>> ---
>>>    drivers/of/Makefile |   1 +
>>>    drivers/of/kexec.c  | 228 ++++++++++++++++++++++++++++++++++++++++++++
>>>    include/linux/of.h  |   5 +
>>>    3 files changed, 234 insertions(+)
>>>    create mode 100644 drivers/of/kexec.c
>>> diff --git a/drivers/of/Makefile b/drivers/of/Makefile
>>> index 6e1e5212f058..8ce11955afde 100644
>>> --- a/drivers/of/Makefile
>>> +++ b/drivers/of/Makefile
>>> @@ -13,5 +13,6 @@ obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o
>>>    obj-$(CONFIG_OF_RESOLVE)  += resolver.o
>>>    obj-$(CONFIG_OF_OVERLAY) += overlay.o
>>>    obj-$(CONFIG_OF_NUMA) += of_numa.o
>>> +obj-$(CONFIG_KEXEC_FILE) += kexec.o
>>
>> For the functions moved from powerpc & arm64 to "drivers/of/kexec.c" in this
>> patch, compiling kexec.c when CONFIG_KEXEC_FILE is enabled is fine. But when
>> more functions (such as remove_ima_buffer()) are moved to this file, Makefile
>> needs to be updated for other ima kexec related CONFIGs.
> 
> IMA kexec is only available if CONFIG_KEXEC_FILE is enabled, so I don't
> understand what problem you are seeing.
> 

delete_fdt_mem_rsv() and setup_fdt() functions are defined when 
CONFIG_KEXEC_FILE is enabled. So there is no problem with this patch as 
such.

I was thinking when other arch independent functions such as 
do_get_kexec_buffer() and remove_ima_buffer() are moved to 
"drivers/of/kexec.c", they need to be defined only when 
CONFIG_HAVE_IMA_KEXEC is enabled.

If CONFIG_HAVE_IMA_KEXEC is enabled, CONFIG_KEXEC_FILE is also enabled. 
So there shouldn't be a problem moving those functions to 
"drivers/of/kexec.c". You are right Thiago. Thanks.

  -lakshmi
Thiago Jung Bauermann Dec. 22, 2020, 9:48 p.m. UTC | #4 
Rob Herring <robh@kernel.org> writes:

> Both arm64 and powerpc do essentially the same FDT /chosen setup for
> kexec. We can simply combine everything each arch does. The differences
> are either omissions that arm64 should have or additional properties
> that will be ignored.
>
> The differences relative to the arm64 version:
> - If /chosen doesn't exist, it will be created (should never happen).
> - Any old dtb and initrd reserved memory will be released.
> - The new initrd and elfcorehdr are marked reserved.
> - "linux,booted-from-kexec" is set.
>
> The differences relative to the powerpc version:
> - "kaslr-seed" and "rng-seed" may be set.
> - "linux,elfcorehdr" is set.

I especially like the elfcorehdr property. It always bothered me that we
pass it on the kernel command line, since it's not something that could
or should be set by an admin.

> - Any existing "linux,usable-memory-range" is removed.
>
> Signed-off-by: Rob Herring <robh@kernel.org>
> ---
> This could be taken a step further and do the allocation of the new
> FDT. The difference is arm64 uses vmalloc and powerpc uses kmalloc. The
> arm64 version also retries with a bigger allocation. That seems
> unnecessary.
> ---
>  drivers/of/Makefile |   1 +
>  drivers/of/kexec.c  | 228 ++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/of.h  |   5 +
>  3 files changed, 234 insertions(+)
>  create mode 100644 drivers/of/kexec.c

Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
diff mbox series

Patch

diff --git a/drivers/of/Makefile b/drivers/of/Makefile
index 6e1e5212f058..8ce11955afde 100644
--- a/drivers/of/Makefile
+++ b/drivers/of/Makefile
@@ -13,5 +13,6 @@  obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o
 obj-$(CONFIG_OF_RESOLVE)  += resolver.o
 obj-$(CONFIG_OF_OVERLAY) += overlay.o
 obj-$(CONFIG_OF_NUMA) += of_numa.o
+obj-$(CONFIG_KEXEC_FILE) += kexec.o
 
 obj-$(CONFIG_OF_UNITTEST) += unittest-data/
diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
new file mode 100644
index 000000000000..66787be081fe
--- /dev/null
+++ b/drivers/of/kexec.c
@@ -0,0 +1,228 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 Arm Limited
+ *
+ * Based on arch/arm64/kernel/machine_kexec_file.c:
+ *  Copyright (C) 2018 Linaro Limited
+ *
+ * And arch/powerpc/kexec/file_load.c:
+ *  Copyright (C) 2016  IBM Corporation
+ */
+
+#include <linux/kernel.h>
+#include <linux/kexec.h>
+#include <linux/libfdt.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
+#include <linux/random.h>
+#include <linux/types.h>
+
+/* relevant device tree properties */
+#define FDT_PROP_KEXEC_ELFHDR	"linux,elfcorehdr"
+#define FDT_PROP_MEM_RANGE	"linux,usable-memory-range"
+#define FDT_PROP_INITRD_START	"linux,initrd-start"
+#define FDT_PROP_INITRD_END	"linux,initrd-end"
+#define FDT_PROP_BOOTARGS	"bootargs"
+#define FDT_PROP_KASLR_SEED	"kaslr-seed"
+#define FDT_PROP_RNG_SEED	"rng-seed"
+#define RNG_SEED_SIZE		128
+
+/**
+ * fdt_find_and_del_mem_rsv - delete memory reservation with given address and size
+ *
+ * Return: 0 on success, or negative errno on error.
+ */
+static int fdt_find_and_del_mem_rsv(void *fdt, unsigned long start, unsigned long size)
+{
+	int i, ret, num_rsvs = fdt_num_mem_rsv(fdt);
+
+	for (i = 0; i < num_rsvs; i++) {
+		u64 rsv_start, rsv_size;
+
+		ret = fdt_get_mem_rsv(fdt, i, &rsv_start, &rsv_size);
+		if (ret) {
+			pr_err("Malformed device tree.\n");
+			return -EINVAL;
+		}
+
+		if (rsv_start == start && rsv_size == size) {
+			ret = fdt_del_mem_rsv(fdt, i);
+			if (ret) {
+				pr_err("Error deleting device tree reservation.\n");
+				return -EINVAL;
+			}
+
+			return 0;
+		}
+	}
+
+	return -ENOENT;
+}
+
+/*
+ * of_kexec_setup_new_fdt - modify /chosen and memory reservation for the next kernel
+ *
+ * @image:		kexec image being loaded.
+ * @fdt:		Flattened device tree for the next kernel.
+ * @initrd_load_addr:	Address where the next initrd will be loaded.
+ * @initrd_len:		Size of the next initrd, or 0 if there will be none.
+ * @cmdline:		Command line for the next kernel, or NULL if there will
+ *			be none.
+ *
+ * Return: 0 on success, or negative errno on error.
+ */
+int of_kexec_setup_new_fdt(const struct kimage *image, void *fdt,
+			   unsigned long initrd_load_addr, unsigned long initrd_len,
+			   const char *cmdline)
+{
+	int ret, chosen_node;
+	const void *prop;
+
+	/* Remove memory reservation for the current device tree. */
+	ret = fdt_find_and_del_mem_rsv(fdt, __pa(initial_boot_params),
+				       fdt_totalsize(initial_boot_params));
+	if (ret == -EINVAL)
+		return ret;
+
+	chosen_node = fdt_path_offset(fdt, "/chosen");
+	if (chosen_node == -FDT_ERR_NOTFOUND)
+		chosen_node = fdt_add_subnode(fdt, fdt_path_offset(fdt, "/"),
+					      "chosen");
+	if (chosen_node < 0) {
+		ret = chosen_node;
+		goto out;
+	}
+
+	ret = fdt_delprop(fdt, chosen_node, FDT_PROP_KEXEC_ELFHDR);
+	if (ret && ret != -FDT_ERR_NOTFOUND)
+		goto out;
+	ret = fdt_delprop(fdt, chosen_node, FDT_PROP_MEM_RANGE);
+	if (ret && ret != -FDT_ERR_NOTFOUND)
+		goto out;
+
+	/* Did we boot using an initrd? */
+	prop = fdt_getprop(fdt, chosen_node, "linux,initrd-start", NULL);
+	if (prop) {
+		u64 tmp_start, tmp_end, tmp_size;
+
+		tmp_start = fdt64_to_cpu(*((const fdt64_t *) prop));
+
+		prop = fdt_getprop(fdt, chosen_node, "linux,initrd-end", NULL);
+		if (!prop)
+			return -EINVAL;
+
+		tmp_end = fdt64_to_cpu(*((const fdt64_t *) prop));
+
+		/*
+		 * kexec reserves exact initrd size, while firmware may
+		 * reserve a multiple of PAGE_SIZE, so check for both.
+		 */
+		tmp_size = tmp_end - tmp_start;
+		ret = fdt_find_and_del_mem_rsv(fdt, tmp_start, tmp_size);
+		if (ret == -ENOENT)
+			ret = fdt_find_and_del_mem_rsv(fdt, tmp_start,
+						       round_up(tmp_size, PAGE_SIZE));
+		if (ret == -EINVAL)
+			return ret;
+	}
+
+	/* add initrd-* */
+	if (initrd_load_addr) {
+		ret = fdt_setprop_u64(fdt, chosen_node, FDT_PROP_INITRD_START,
+				      initrd_load_addr);
+		if (ret)
+			goto out;
+
+		ret = fdt_setprop_u64(fdt, chosen_node, FDT_PROP_INITRD_END,
+				      initrd_load_addr + initrd_len);
+		if (ret)
+			goto out;
+
+		ret = fdt_add_mem_rsv(fdt, initrd_load_addr, initrd_len);
+		if (ret)
+			goto out;
+
+	} else {
+		ret = fdt_delprop(fdt, chosen_node, FDT_PROP_INITRD_START);
+		if (ret && (ret != -FDT_ERR_NOTFOUND))
+			goto out;
+
+		ret = fdt_delprop(fdt, chosen_node, FDT_PROP_INITRD_END);
+		if (ret && (ret != -FDT_ERR_NOTFOUND))
+			goto out;
+	}
+
+	if (image->type == KEXEC_TYPE_CRASH) {
+		/* add linux,elfcorehdr */
+		ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
+				FDT_PROP_KEXEC_ELFHDR,
+				image->arch.elf_headers_mem,
+				image->arch.elf_headers_sz);
+		if (ret)
+			goto out;
+
+		/*
+		 * Avoid elfcorehdr from being stomped on in kdump kernel by
+		 * setting up memory reserve map.
+		 */
+		ret = fdt_add_mem_rsv(fdt, image->arch.elf_headers_mem,
+				      image->arch.elf_headers_sz);
+
+		/* add linux,usable-memory-range */
+		ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
+				FDT_PROP_MEM_RANGE,
+				crashk_res.start,
+				crashk_res.end - crashk_res.start + 1);
+		if (ret)
+			goto out;
+	}
+
+	/* add bootargs */
+	if (cmdline) {
+		ret = fdt_setprop_string(fdt, chosen_node, FDT_PROP_BOOTARGS, cmdline);
+		if (ret)
+			goto out;
+	} else {
+		ret = fdt_delprop(fdt, chosen_node, FDT_PROP_BOOTARGS);
+		if (ret && (ret != -FDT_ERR_NOTFOUND))
+			goto out;
+	}
+
+	/* add kaslr-seed */
+	ret = fdt_delprop(fdt, chosen_node, FDT_PROP_KASLR_SEED);
+	if (ret == -FDT_ERR_NOTFOUND)
+		ret = 0;
+	else if (ret)
+		goto out;
+
+	if (rng_is_initialized()) {
+		u64 seed = get_random_u64();
+		ret = fdt_setprop_u64(fdt, chosen_node, FDT_PROP_KASLR_SEED, seed);
+		if (ret)
+			goto out;
+	} else {
+		pr_notice("RNG is not initialised: omitting \"%s\" property\n",
+				FDT_PROP_KASLR_SEED);
+	}
+
+	/* add rng-seed */
+	if (rng_is_initialized()) {
+		void *rng_seed;
+		ret = fdt_setprop_placeholder(fdt, chosen_node, FDT_PROP_RNG_SEED,
+				RNG_SEED_SIZE, &rng_seed);
+		if (ret)
+			goto out;
+		get_random_bytes(rng_seed, RNG_SEED_SIZE);
+	} else {
+		pr_notice("RNG is not initialised: omitting \"%s\" property\n",
+				FDT_PROP_RNG_SEED);
+	}
+
+	ret = fdt_setprop(fdt, chosen_node, "linux,booted-from-kexec", NULL, 0);
+
+out:
+	if (ret)
+		return (ret == -FDT_ERR_NOSPACE) ? -ENOMEM : -EINVAL;
+
+	return 0;
+}
diff --git a/include/linux/of.h b/include/linux/of.h
index 5d51891cbf1a..3375f5295875 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -558,6 +558,11 @@  int of_map_id(struct device_node *np, u32 id,
 	       const char *map_name, const char *map_mask_name,
 	       struct device_node **target, u32 *id_out);
 
+struct kimage;
+int of_kexec_setup_new_fdt(const struct kimage *image, void *fdt,
+			   unsigned long initrd_load_addr, unsigned long initrd_len,
+			   const char *cmdline);
+
 #else /* CONFIG_OF */
 
 static inline void of_core_init(void)