// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2016 IBM Corporation
 *
 * Authors:
 * Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
 * Mimi Zohar <zohar@linux.vnet.ibm.com>
 */

#include <linux/seq_file.h>
#include <linux/vmalloc.h>
#include <linux/kexec.h>
#include <linux/of.h>
#include <linux/ima.h>
#include <linux/mm.h>
#include <linux/overflow.h>
#include <linux/reboot.h>
#include <asm/page.h>
#include "ima.h"

#ifdef CONFIG_IMA_KEXEC
#define IMA_KEXEC_EVENT_LEN 256

static bool ima_kexec_update_registered;
static struct seq_file ima_kexec_file;
static size_t kexec_segment_size;
static void *ima_kexec_buffer;

static void ima_free_kexec_file_buf(struct seq_file *sf)
{
        vfree(sf->buf);
        sf->buf = NULL;
        sf->size = 0;
        sf->read_pos = 0;
        sf->count = 0;
}

void ima_measure_kexec_event(const char *event_name)
{
        char ima_kexec_event[IMA_KEXEC_EVENT_LEN];
        size_t buf_size = 0;
        long len;
        int n;

        buf_size = ima_get_binary_runtime_size();
        len = atomic_long_read(&ima_htable.len);

        n = scnprintf(ima_kexec_event, IMA_KEXEC_EVENT_LEN,
                      "kexec_segment_size=%lu;ima_binary_runtime_size=%lu;"
                      "ima_runtime_measurements_count=%ld;",
                      kexec_segment_size, buf_size, len);

        ima_measure_critical_data("ima_kexec", event_name, ima_kexec_event, n, false, NULL, 0);
}

static int ima_alloc_kexec_file_buf(size_t segment_size)
{
        /*
         * kexec 'load' may be called multiple times.
         * Free and realloc the buffer only if the segment_size is
         * changed from the previous kexec 'load' call.
         */
        if (ima_kexec_file.buf && ima_kexec_file.size == segment_size)
                goto out;

        ima_free_kexec_file_buf(&ima_kexec_file);

        /* segment size can't change between kexec load and execute */
        ima_kexec_file.buf = vmalloc(segment_size);
        if (!ima_kexec_file.buf)
                return -ENOMEM;

        ima_kexec_file.size = segment_size;

out:
        ima_kexec_file.read_pos = 0;
        ima_kexec_file.count = sizeof(struct ima_kexec_hdr);    /* reserved space */
        ima_measure_kexec_event("kexec_load");

        return 0;
}

static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
                                     unsigned long segment_size)
{
        struct ima_queue_entry *qe;
        struct ima_kexec_hdr khdr;
        int ret = 0;

        /* segment size can't change between kexec load and execute */
        if (!ima_kexec_file.buf) {
                pr_err("Kexec file buf not allocated\n");
                return -EINVAL;
        }

        memset(&khdr, 0, sizeof(khdr));
        khdr.version = 1;
        /* This is an append-only list, no need to hold the RCU read lock */
        list_for_each_entry_rcu(qe, &ima_measurements, later, true) {
                if (ima_kexec_file.count < ima_kexec_file.size) {
                        khdr.count++;
                        ima_measurements_show(&ima_kexec_file, qe);
                } else {
                        ret = -EINVAL;
                        break;
                }
        }

        /*
         * fill in reserved space with some buffer details
         * (eg. version, buffer size, number of measurements)
         */
        khdr.buffer_size = ima_kexec_file.count;
        if (ima_canonical_fmt) {
                khdr.version = cpu_to_le16(khdr.version);
                khdr.count = cpu_to_le64(khdr.count);
                khdr.buffer_size = cpu_to_le64(khdr.buffer_size);
        }
        memcpy(ima_kexec_file.buf, &khdr, sizeof(khdr));

        print_hex_dump_debug("ima dump: ", DUMP_PREFIX_NONE, 16, 1,
                             ima_kexec_file.buf, ima_kexec_file.count < 100 ?
                             ima_kexec_file.count : 100,
                             true);

        *buffer_size = ima_kexec_file.count;
        *buffer = ima_kexec_file.buf;

        return ret;
}

/*
 * Called during kexec_file_load so that IMA can add a segment to the kexec
 * image for the measurement list for the next kernel.
 *
 * This function assumes that kexec_lock is held.
 */
void ima_add_kexec_buffer(struct kimage *image)
{
        struct kexec_buf kbuf = { .image = image, .buf_align = PAGE_SIZE,
                                  .buf_min = 0, .buf_max = ULONG_MAX,
                                  .top_down = true };
        unsigned long binary_runtime_size;
        unsigned long extra_memory;

        /* use more understandable variable names than defined in kbuf */
        size_t kexec_buffer_size = 0;
        void *kexec_buffer = NULL;
        int ret;

        if (image->type == KEXEC_TYPE_CRASH)
                return;

        /*
         * Reserve extra memory for measurements added during kexec.
         */
        if (CONFIG_IMA_KEXEC_EXTRA_MEMORY_KB <= 0)
                extra_memory = PAGE_SIZE / 2;
        else
                extra_memory = CONFIG_IMA_KEXEC_EXTRA_MEMORY_KB * 1024;

        binary_runtime_size = ima_get_binary_runtime_size() + extra_memory;

        if (binary_runtime_size >= ULONG_MAX - PAGE_SIZE)
                kexec_segment_size = ULONG_MAX;
        else
                kexec_segment_size = ALIGN(binary_runtime_size, PAGE_SIZE);

        if ((kexec_segment_size == ULONG_MAX) ||
            ((kexec_segment_size >> PAGE_SHIFT) > totalram_pages() / 2)) {
                pr_err("Binary measurement list too large.\n");
                return;
        }

        ret = ima_alloc_kexec_file_buf(kexec_segment_size);
        if (ret < 0) {
                pr_err("Not enough memory for the kexec measurement buffer.\n");
                return;
        }

        kbuf.buffer = kexec_buffer;
        kbuf.bufsz = kexec_buffer_size;
        kbuf.memsz = kexec_segment_size;
        image->is_ima_segment_index_set = false;
        ret = kexec_add_buffer(&kbuf);
        if (ret) {
                pr_err("Error passing over kexec measurement buffer.\n");
                vfree(kexec_buffer);
                return;
        }

        image->ima_buffer_addr = kbuf.mem;
        image->ima_buffer_size = kexec_segment_size;
        image->ima_buffer = kexec_buffer;
        image->ima_segment_index = image->nr_segments - 1;
        image->is_ima_segment_index_set = true;

        kexec_dprintk("kexec measurement buffer for the loaded kernel at 0x%lx.\n",
                      kbuf.mem);
}

/*
 * Called during kexec execute so that IMA can update the measurement list.
 */
static int ima_update_kexec_buffer(struct notifier_block *self,
                                   unsigned long action, void *data)
{
        size_t buf_size = 0;
        int ret = NOTIFY_OK;
        void *buf = NULL;

        if (!kexec_in_progress) {
                pr_info("No kexec in progress.\n");
                return ret;
        }

        if (!ima_kexec_buffer) {
                pr_err("Kexec buffer not set.\n");
                return ret;
        }

        ret = ima_dump_measurement_list(&buf_size, &buf, kexec_segment_size);

        if (ret)
                pr_err("Dump measurements failed. Error:%d\n", ret);

        if (buf_size != 0)
                memcpy(ima_kexec_buffer, buf, buf_size);

        kimage_unmap_segment(ima_kexec_buffer);
        ima_kexec_buffer = NULL;

        return ret;
}

static struct notifier_block update_buffer_nb = {
        .notifier_call = ima_update_kexec_buffer,
        .priority = INT_MIN
};

/*
 * Create a mapping for the source pages that contain the IMA buffer
 * so we can update it later.
 */
void ima_kexec_post_load(struct kimage *image)
{
        if (ima_kexec_buffer) {
                kimage_unmap_segment(ima_kexec_buffer);
                ima_kexec_buffer = NULL;
        }

        if (!image->ima_buffer_addr)
                return;

        ima_kexec_buffer = kimage_map_segment(image, image->ima_segment_index);
        if (!ima_kexec_buffer) {
                pr_err("Could not map measurements buffer.\n");
                return;
        }

        if (!ima_kexec_update_registered) {
                register_reboot_notifier(&update_buffer_nb);
                ima_kexec_update_registered = true;
        }
}

#endif /* IMA_KEXEC */

/*
 * Restore the measurement list from the previous kernel.
 */
void __init ima_load_kexec_buffer(void)
{
        void *kexec_buffer = NULL;
        size_t kexec_buffer_size = 0;
        int rc;

        rc = ima_get_kexec_buffer(&kexec_buffer, &kexec_buffer_size);
        switch (rc) {
        case 0:
                rc = ima_restore_measurement_list(kexec_buffer_size,
                                                  kexec_buffer);
                if (rc != 0)
                        pr_err("Failed to restore the measurement list: %d\n",
                                rc);

                ima_free_kexec_buffer();
                break;
        case -ENOTSUPP:
                pr_debug("Restoring the measurement list not supported\n");
                break;
        case -ENOENT:
                pr_debug("No measurement list to restore\n");
                break;
        default:
                pr_debug("Error restoring the measurement list: %d\n", rc);
        }
}

/*
 * ima_validate_range - verify a physical buffer lies in addressable RAM
 * @phys: physical start address of the buffer from previous kernel
 * @size: size of the buffer
 *
 * On success return 0. On failure returns -EINVAL so callers can skip
 * restoring.
 */
int ima_validate_range(phys_addr_t phys, size_t size)
{
        unsigned long start_pfn, end_pfn;
        phys_addr_t end_phys;

        if (check_add_overflow(phys, (phys_addr_t)size - 1, &end_phys))
                return -EINVAL;

        start_pfn = PHYS_PFN(phys);
        end_pfn = PHYS_PFN(end_phys);

#ifdef CONFIG_X86
        if (!pfn_range_is_mapped(start_pfn, end_pfn))
#else
        if (!page_is_ram(start_pfn) || !page_is_ram(end_pfn))
#endif
        {
                pr_warn("IMA: previous kernel measurement buffer %pa (size 0x%zx) lies outside available memory\n",
                        &phys, size);
                return -EINVAL;
        }

        return 0;
}