// 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/memblock.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

/*
 * Additional space needed for the FDT buffer so that we can add initrd,
 * bootargs, kaslr-seed, rng-seed, useable-memory-range and elfcorehdr.
 */
#define FDT_EXTRA_SPACE 0x1000

/**
 * fdt_find_and_del_mem_rsv - delete memory reservation with given address and size
 *
 * @fdt:        Flattened device tree for the current kernel.
 * @start:      Starting address of the reserved memory.
 * @size:       Size of the reserved memory.
 *
 * 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;
}

/**
 * get_addr_size_cells - Get address and size of root node
 *
 * @addr_cells: Return address of the root node
 * @size_cells: Return size of the root node
 *
 * Return: 0 on success, or negative errno on error.
 */
static int get_addr_size_cells(int *addr_cells, int *size_cells)
{
        struct device_node *root;

        root = of_find_node_by_path("/");
        if (!root)
                return -EINVAL;

        *addr_cells = of_n_addr_cells(root);
        *size_cells = of_n_size_cells(root);

        of_node_put(root);

        return 0;
}

/**
 * do_get_kexec_buffer - Get address and size of device tree property
 *
 * @prop: Device tree property
 * @len: Size of @prop
 * @addr: Return address of the node
 * @size: Return size of the node
 *
 * Return: 0 on success, or negative errno on error.
 */
static int do_get_kexec_buffer(const void *prop, int len, unsigned long *addr,
                               size_t *size)
{
        int ret, addr_cells, size_cells;

        ret = get_addr_size_cells(&addr_cells, &size_cells);
        if (ret)
                return ret;

        if (len < 4 * (addr_cells + size_cells))
                return -ENOENT;

        *addr = of_read_number(prop, addr_cells);
        *size = of_read_number(prop + 4 * addr_cells, size_cells);

        return 0;
}

/**
 * ima_get_kexec_buffer - get IMA buffer from the previous kernel
 * @addr:       On successful return, set to point to the buffer contents.
 * @size:       On successful return, set to the buffer size.
 *
 * Return: 0 on success, negative errno on error.
 */
int ima_get_kexec_buffer(void **addr, size_t *size)
{
        int ret, len;
        unsigned long tmp_addr;
        size_t tmp_size;
        const void *prop;

        if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC))
                return -ENOTSUPP;

        prop = of_get_property(of_chosen, "linux,ima-kexec-buffer", &len);
        if (!prop)
                return -ENOENT;

        ret = do_get_kexec_buffer(prop, len, &tmp_addr, &tmp_size);
        if (ret)
                return ret;

        *addr = __va(tmp_addr);
        *size = tmp_size;

        return 0;
}

/**
 * ima_free_kexec_buffer - free memory used by the IMA buffer
 */
int ima_free_kexec_buffer(void)
{
        int ret;
        unsigned long addr;
        size_t size;
        struct property *prop;

        if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC))
                return -ENOTSUPP;

        prop = of_find_property(of_chosen, "linux,ima-kexec-buffer", NULL);
        if (!prop)
                return -ENOENT;

        ret = do_get_kexec_buffer(prop->value, prop->length, &addr, &size);
        if (ret)
                return ret;

        ret = of_remove_property(of_chosen, prop);
        if (ret)
                return ret;

        return memblock_free(addr, size);

}

/**
 * remove_ima_buffer - remove the IMA buffer property and reservation from @fdt
 *
 * @fdt: Flattened Device Tree to update
 * @chosen_node: Offset to the chosen node in the device tree
 *
 * The IMA measurement buffer is of no use to a subsequent kernel, so we always
 * remove it from the device tree.
 */
static void remove_ima_buffer(void *fdt, int chosen_node)
{
        int ret, len;
        unsigned long addr;
        size_t size;
        const void *prop;

        if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC))
                return;

        prop = fdt_getprop(fdt, chosen_node, "linux,ima-kexec-buffer", &len);
        if (!prop)
                return;

        ret = do_get_kexec_buffer(prop, len, &addr, &size);
        fdt_delprop(fdt, chosen_node, "linux,ima-kexec-buffer");
        if (ret)
                return;

        ret = fdt_find_and_del_mem_rsv(fdt, addr, size);
        if (!ret)
                pr_debug("Removed old IMA buffer reservation.\n");
}

#ifdef CONFIG_IMA_KEXEC
/**
 * setup_ima_buffer - add IMA buffer information to the fdt
 * @image:              kexec image being loaded.
 * @fdt:                Flattened device tree for the next kernel.
 * @chosen_node:        Offset to the chosen node.
 *
 * Return: 0 on success, or negative errno on error.
 */
static int setup_ima_buffer(const struct kimage *image, void *fdt,
                            int chosen_node)
{
        int ret;

        if (!image->ima_buffer_size)
                return 0;

        ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
                                       "linux,ima-kexec-buffer",
                                       image->ima_buffer_addr,
                                       image->ima_buffer_size);
        if (ret < 0)
                return -EINVAL;

        ret = fdt_add_mem_rsv(fdt, image->ima_buffer_addr,
                              image->ima_buffer_size);
        if (ret)
                return -EINVAL;

        pr_debug("IMA buffer at 0x%llx, size = 0x%zx\n",
                 image->ima_buffer_addr, image->ima_buffer_size);

        return 0;
}
#else /* CONFIG_IMA_KEXEC */
static inline int setup_ima_buffer(const struct kimage *image, void *fdt,
                                   int chosen_node)
{
        return 0;
}
#endif /* CONFIG_IMA_KEXEC */

/*
 * of_kexec_alloc_and_setup_fdt - Alloc and setup a new Flattened Device Tree
 *
 * @image:              kexec image being loaded.
 * @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.
 * @extra_fdt_size:     Additional size for the new FDT buffer.
 *
 * Return: fdt on success, or NULL errno on error.
 */
void *of_kexec_alloc_and_setup_fdt(const struct kimage *image,
                                   unsigned long initrd_load_addr,
                                   unsigned long initrd_len,
                                   const char *cmdline, size_t extra_fdt_size)
{
        void *fdt;
        int ret, chosen_node;
        const void *prop;
        size_t fdt_size;

        fdt_size = fdt_totalsize(initial_boot_params) +
                   (cmdline ? strlen(cmdline) : 0) +
                   FDT_EXTRA_SPACE +
                   extra_fdt_size;
        fdt = kvmalloc(fdt_size, GFP_KERNEL);
        if (!fdt)
                return NULL;

        ret = fdt_open_into(initial_boot_params, fdt, fdt_size);
        if (ret < 0) {
                pr_err("Error %d setting up the new device tree.\n", ret);
                goto out;
        }

        /* 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) {
                pr_err("Error removing memory reservation.\n");
                goto out;
        }

        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) {
                        ret = -EINVAL;
                        goto out;
                }

                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)
                        goto out;
        }

        /* 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->elf_load_addr,
                                image->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->elf_load_addr,
                                      image->elf_headers_sz);
                if (ret)
                        goto out;

                /* 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);
        if (ret)
                goto out;

        remove_ima_buffer(fdt, chosen_node);
        ret = setup_ima_buffer(image, fdt, fdt_path_offset(fdt, "/chosen"));

out:
        if (ret) {
                kvfree(fdt);
                fdt = NULL;
        }

        return fdt;
}