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

[Rob Herring]

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@xxxxxxxxxx>
---
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
 
 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)
-- 
2.25.1