// SPDX-License-Identifier: GPL-2.0-only
/*
 * dell_rbu.c
 * Bios Update driver for Dell systems
 * Author: Dell Inc
 *         Abhay Salunke <abhay_salunke@dell.com>
 *
 * Copyright (C) 2005 Dell Inc.
 *
 * Remote BIOS Update (rbu) driver is used for updating DELL BIOS by
 * creating entries in the /sys file systems on Linux 2.6 and higher
 * kernels. The driver supports two mechanism to update the BIOS namely
 * contiguous and packetized. Both these methods still require having some
 * application to set the CMOS bit indicating the BIOS to update itself
 * after a reboot.
 *
 * Contiguous method:
 * This driver writes the incoming data in a monolithic image by allocating
 * contiguous physical pages large enough to accommodate the incoming BIOS
 * image size.
 *
 * Packetized method:
 * The driver writes the incoming packet image by allocating a new packet
 * on every time the packet data is written. This driver requires an
 * application to break the BIOS image in to fixed sized packet chunks.
 *
 * See Documentation/admin-guide/dell_rbu.rst for more info.
 */

#define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt

#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/blkdev.h>
#include <linux/platform_device.h>
#include <linux/spinlock.h>
#include <linux/moduleparam.h>
#include <linux/firmware.h>
#include <linux/dma-mapping.h>
#include <asm/set_memory.h>

MODULE_AUTHOR("Abhay Salunke <abhay_salunke@dell.com>");
MODULE_DESCRIPTION("Driver for updating BIOS image on DELL systems");
MODULE_LICENSE("GPL");
MODULE_VERSION("3.3");

#define BIOS_SCAN_LIMIT 0xffffffff
#define MAX_IMAGE_LENGTH 16
static struct _rbu_data {
        void *image_update_buffer;
        unsigned long image_update_buffer_size;
        unsigned long bios_image_size;
        int image_update_ordernum;
        spinlock_t lock;
        unsigned long packet_read_count;
        unsigned long num_packets;
        unsigned long packetsize;
        unsigned long imagesize;
        int entry_created;
} rbu_data;

static char image_type[MAX_IMAGE_LENGTH + 1] = "mono";
module_param_string(image_type, image_type, sizeof (image_type), 0);
MODULE_PARM_DESC(image_type, "BIOS image type. choose- mono or packet or init");

static unsigned long allocation_floor = 0x100000;
module_param(allocation_floor, ulong, 0644);
MODULE_PARM_DESC(allocation_floor, "Minimum address for allocations when using Packet mode");

struct packet_data {
        struct list_head list;
        size_t length;
        void *data;
        int ordernum;
};

static struct list_head packet_data_list;

static struct platform_device *rbu_device;
static int context;

static void init_packet_head(void)
{
        INIT_LIST_HEAD(&packet_data_list);
        rbu_data.packet_read_count = 0;
        rbu_data.num_packets = 0;
        rbu_data.packetsize = 0;
        rbu_data.imagesize = 0;
}

static int create_packet(void *data, size_t length) __must_hold(&rbu_data.lock)
{
        struct packet_data *newpacket;
        int ordernum = 0;
        int retval = 0;
        unsigned int packet_array_size = 0;
        void **invalid_addr_packet_array = NULL;
        void *packet_data_temp_buf = NULL;
        unsigned int idx = 0;

        pr_debug("entry\n");

        if (!rbu_data.packetsize) {
                pr_debug("packetsize not specified\n");
                retval = -EINVAL;
                goto out_noalloc;
        }

        spin_unlock(&rbu_data.lock);

        newpacket = kzalloc_obj(struct packet_data);

        if (!newpacket) {
                pr_warn("failed to allocate new packet\n");
                retval = -ENOMEM;
                spin_lock(&rbu_data.lock);
                goto out_noalloc;
        }

        ordernum = get_order(length);

        /*
         * BIOS errata mean we cannot allocate packets below 1MB or they will
         * be overwritten by BIOS.
         *
         * array to temporarily hold packets
         * that are below the allocation floor
         *
         * NOTE: very simplistic because we only need the floor to be at 1MB
         *       due to BIOS errata. This shouldn't be used for higher floors
         *       or you will run out of mem trying to allocate the array.
         */
        packet_array_size = max_t(unsigned int, allocation_floor / rbu_data.packetsize, 1);
        invalid_addr_packet_array = kcalloc(packet_array_size, sizeof(void *),
                                                GFP_KERNEL);

        if (!invalid_addr_packet_array) {
                pr_warn("failed to allocate invalid_addr_packet_array\n");
                retval = -ENOMEM;
                spin_lock(&rbu_data.lock);
                goto out_alloc_packet;
        }

        while (!packet_data_temp_buf) {
                packet_data_temp_buf = (unsigned char *)
                        __get_free_pages(GFP_KERNEL, ordernum);
                if (!packet_data_temp_buf) {
                        pr_warn("failed to allocate new packet\n");
                        retval = -ENOMEM;
                        spin_lock(&rbu_data.lock);
                        goto out_alloc_packet_array;
                }

                if ((unsigned long)virt_to_phys(packet_data_temp_buf)
                                < allocation_floor) {
                        pr_debug("packet 0x%lx below floor at 0x%lx\n",
                                        (unsigned long)virt_to_phys(
                                                packet_data_temp_buf),
                                        allocation_floor);
                        invalid_addr_packet_array[idx++] = packet_data_temp_buf;
                        packet_data_temp_buf = NULL;
                }
        }
        /*
         * set to uncachable or it may never get written back before reboot
         */
        set_memory_uc((unsigned long)packet_data_temp_buf, 1 << ordernum);

        spin_lock(&rbu_data.lock);

        newpacket->data = packet_data_temp_buf;

        pr_debug("newpacket at physical addr %lx\n",
                (unsigned long)virt_to_phys(newpacket->data));

        /* packets may not have fixed size */
        newpacket->length = length;
        newpacket->ordernum = ordernum;
        ++rbu_data.num_packets;

        /* initialize the newly created packet headers */
        INIT_LIST_HEAD(&newpacket->list);
        list_add_tail(&newpacket->list, &packet_data_list);

        memcpy(newpacket->data, data, length);

        pr_debug("exit\n");

out_alloc_packet_array:
        /* always free packet array */
        while (idx--) {
                pr_debug("freeing unused packet below floor 0x%lx\n",
                        (unsigned long)virt_to_phys(invalid_addr_packet_array[idx]));
                free_pages((unsigned long)invalid_addr_packet_array[idx], ordernum);
        }
        kfree(invalid_addr_packet_array);

out_alloc_packet:
        /* if error, free data */
        if (retval)
                kfree(newpacket);

out_noalloc:
        return retval;
}

static int packetize_data(const u8 *data, size_t length)
{
        int rc = 0;
        int done = 0;
        int packet_length;
        u8 *temp;
        u8 *end = (u8 *) data + length;
        pr_debug("data length %zd\n", length);
        if (!rbu_data.packetsize) {
                pr_warn("packetsize not specified\n");
                return -EIO;
        }

        temp = (u8 *) data;

        /* packetize the hunk */
        while (!done) {
                if ((temp + rbu_data.packetsize) < end)
                        packet_length = rbu_data.packetsize;
                else {
                        /* this is the last packet */
                        packet_length = end - temp;
                        done = 1;
                }

                rc = create_packet(temp, packet_length);
                if (rc)
                        return rc;

                pr_debug("%p:%td\n", temp, (end - temp));
                temp += packet_length;
        }

        rbu_data.imagesize = length;

        return rc;
}

static int do_packet_read(char *data, struct packet_data *newpacket,
        int length, int bytes_read, int *list_read_count)
{
        void *ptemp_buf;
        int bytes_copied = 0;
        int j = 0;

        *list_read_count += newpacket->length;

        if (*list_read_count > bytes_read) {
                /* point to the start of unread data */
                j = newpacket->length - (*list_read_count - bytes_read);
                /* point to the offset in the packet buffer */
                ptemp_buf = (u8 *) newpacket->data + j;
                /*
                 * check if there is enough room in
                 * * the incoming buffer
                 */
                if (length > (*list_read_count - bytes_read))
                        /*
                         * copy what ever is there in this
                         * packet and move on
                         */
                        bytes_copied = (*list_read_count - bytes_read);
                else
                        /* copy the remaining */
                        bytes_copied = length;
                memcpy(data, ptemp_buf, bytes_copied);
        }
        return bytes_copied;
}

static int packet_read_list(char *data, size_t *pread_length)
{
        struct packet_data *newpacket;
        int temp_count = 0;
        int bytes_copied = 0;
        int bytes_read = 0;
        int remaining_bytes = 0;
        char *pdest = data;

        /* check if we have any packets */
        if (0 == rbu_data.num_packets)
                return -ENOMEM;

        remaining_bytes = *pread_length;
        bytes_read = rbu_data.packet_read_count;

        list_for_each_entry(newpacket, &packet_data_list, list) {
                bytes_copied = do_packet_read(pdest, newpacket,
                        remaining_bytes, bytes_read, &temp_count);
                remaining_bytes -= bytes_copied;
                bytes_read += bytes_copied;
                pdest += bytes_copied;
                /*
                 * check if we reached end of buffer before reaching the
                 * last packet
                 */
                if (remaining_bytes == 0)
                        break;
        }
        /*finally set the bytes read */
        *pread_length = bytes_read - rbu_data.packet_read_count;
        rbu_data.packet_read_count = bytes_read;
        return 0;
}

static void packet_empty_list(void)
{
        struct packet_data *newpacket, *tmp;

        list_for_each_entry_safe(newpacket, tmp, &packet_data_list, list) {
                list_del(&newpacket->list);

                /*
                 * zero out the RBU packet memory before freeing
                 * to make sure there are no stale RBU packets left in memory
                 */
                memset(newpacket->data, 0, newpacket->length);
                set_memory_wb((unsigned long)newpacket->data,
                        1 << newpacket->ordernum);
                free_pages((unsigned long) newpacket->data,
                        newpacket->ordernum);
                kfree(newpacket);
        }
        rbu_data.packet_read_count = 0;
        rbu_data.num_packets = 0;
        rbu_data.imagesize = 0;
}

/*
 * img_update_free: Frees the buffer allocated for storing BIOS image
 * Always called with lock held and returned with lock held
 */
static void img_update_free(void)
{
        if (!rbu_data.image_update_buffer)
                return;
        /*
         * zero out this buffer before freeing it to get rid of any stale
         * BIOS image copied in memory.
         */
        memset(rbu_data.image_update_buffer, 0,
                rbu_data.image_update_buffer_size);
        free_pages((unsigned long) rbu_data.image_update_buffer,
                rbu_data.image_update_ordernum);

        /*
         * Re-initialize the rbu_data variables after a free
         */
        rbu_data.image_update_ordernum = -1;
        rbu_data.image_update_buffer = NULL;
        rbu_data.image_update_buffer_size = 0;
        rbu_data.bios_image_size = 0;
}

/*
 * img_update_realloc: This function allocates the contiguous pages to
 * accommodate the requested size of data. The memory address and size
 * values are stored globally and on every call to this function the new
 * size is checked to see if more data is required than the existing size.
 * If true the previous memory is freed and new allocation is done to
 * accommodate the new size. If the incoming size is less then than the
 * already allocated size, then that memory is reused. This function is
 * called with lock held and returns with lock held.
 */
static int img_update_realloc(unsigned long size)
{
        unsigned char *image_update_buffer = NULL;
        unsigned long img_buf_phys_addr;
        int ordernum;

        /*
         * check if the buffer of sufficient size has been
         * already allocated
         */
        if (rbu_data.image_update_buffer_size >= size) {
                /*
                 * check for corruption
                 */
                if ((size != 0) && (rbu_data.image_update_buffer == NULL)) {
                        pr_err("corruption check failed\n");
                        return -EINVAL;
                }
                /*
                 * we have a valid pre-allocated buffer with
                 * sufficient size
                 */
                return 0;
        }

        /*
         * free any previously allocated buffer
         */
        img_update_free();

        spin_unlock(&rbu_data.lock);

        ordernum = get_order(size);
        image_update_buffer =
                (unsigned char *)__get_free_pages(GFP_DMA32, ordernum);
        spin_lock(&rbu_data.lock);
        if (!image_update_buffer) {
                pr_debug("Not enough memory for image update: size = %ld\n", size);
                return -ENOMEM;
        }

        img_buf_phys_addr = (unsigned long)virt_to_phys(image_update_buffer);
        if (WARN_ON_ONCE(img_buf_phys_addr > BIOS_SCAN_LIMIT))
                return -EINVAL; /* can't happen per definition */

        rbu_data.image_update_buffer = image_update_buffer;
        rbu_data.image_update_buffer_size = size;
        rbu_data.bios_image_size = rbu_data.image_update_buffer_size;
        rbu_data.image_update_ordernum = ordernum;
        return 0;
}

static ssize_t read_packet_data(char *buffer, loff_t pos, size_t count)
{
        int retval;
        size_t bytes_left;
        size_t data_length;
        char *ptempBuf = buffer;

        /* check to see if we have something to return */
        if (rbu_data.num_packets == 0) {
                pr_debug("no packets written\n");
                retval = -ENOMEM;
                goto read_rbu_data_exit;
        }

        if (pos > rbu_data.imagesize) {
                retval = 0;
                pr_warn("data underrun\n");
                goto read_rbu_data_exit;
        }

        bytes_left = rbu_data.imagesize - pos;
        data_length = min(bytes_left, count);

        retval = packet_read_list(ptempBuf, &data_length);
        if (retval < 0)
                goto read_rbu_data_exit;

        if ((pos + count) > rbu_data.imagesize) {
                rbu_data.packet_read_count = 0;
                /* this was the last copy */
                retval = bytes_left;
        } else
                retval = count;

      read_rbu_data_exit:
        return retval;
}

static ssize_t read_rbu_mono_data(char *buffer, loff_t pos, size_t count)
{
        /* check to see if we have something to return */
        if ((rbu_data.image_update_buffer == NULL) ||
                (rbu_data.bios_image_size == 0)) {
                pr_debug("image_update_buffer %p, bios_image_size %lu\n",
                        rbu_data.image_update_buffer,
                        rbu_data.bios_image_size);
                return -ENOMEM;
        }

        return memory_read_from_buffer(buffer, count, &pos,
                        rbu_data.image_update_buffer, rbu_data.bios_image_size);
}

static ssize_t data_read(struct file *filp, struct kobject *kobj,
                         const struct bin_attribute *bin_attr,
                         char *buffer, loff_t pos, size_t count)
{
        ssize_t ret_count = 0;

        spin_lock(&rbu_data.lock);

        if (!strcmp(image_type, "mono"))
                ret_count = read_rbu_mono_data(buffer, pos, count);
        else if (!strcmp(image_type, "packet"))
                ret_count = read_packet_data(buffer, pos, count);
        else
                pr_debug("invalid image type specified\n");

        spin_unlock(&rbu_data.lock);
        return ret_count;
}
static const BIN_ATTR_RO(data, 0);

static void callbackfn_rbu(const struct firmware *fw, void *context)
{
        rbu_data.entry_created = 0;

        if (!fw)
                return;

        if (!fw->size)
                goto out;

        spin_lock(&rbu_data.lock);
        if (!strcmp(image_type, "mono")) {
                if (!img_update_realloc(fw->size))
                        memcpy(rbu_data.image_update_buffer,
                                fw->data, fw->size);
        } else if (!strcmp(image_type, "packet")) {
                /*
                 * we need to free previous packets if a
                 * new hunk of packets needs to be downloaded
                 */
                packet_empty_list();
                if (packetize_data(fw->data, fw->size))
                        /* Incase something goes wrong when we are
                         * in middle of packetizing the data, we
                         * need to free up whatever packets might
                         * have been created before we quit.
                         */
                        packet_empty_list();
        } else
                pr_debug("invalid image type specified\n");
        spin_unlock(&rbu_data.lock);
 out:
        release_firmware(fw);
}

static ssize_t image_type_read(struct file *filp, struct kobject *kobj,
                               const struct bin_attribute *bin_attr,
                               char *buffer, loff_t pos, size_t count)
{
        int size = 0;
        if (!pos)
                size = scnprintf(buffer, count, "%s\n", image_type);
        return size;
}

static ssize_t image_type_write(struct file *filp, struct kobject *kobj,
                                const struct bin_attribute *bin_attr,
                                char *buffer, loff_t pos, size_t count)
{
        int rc = count;
        int req_firm_rc = 0;
        int i;
        spin_lock(&rbu_data.lock);
        /*
         * Find the first newline or space
         */
        for (i = 0; i < count; ++i)
                if (buffer[i] == '\n' || buffer[i] == ' ') {
                        buffer[i] = '\0';
                        break;
                }
        if (i == count)
                buffer[count] = '\0';

        if (strstr(buffer, "mono"))
                strcpy(image_type, "mono");
        else if (strstr(buffer, "packet"))
                strcpy(image_type, "packet");
        else if (strstr(buffer, "init")) {
                /*
                 * If due to the user error the driver gets in a bad
                 * state where even though it is loaded , the
                 * /sys/class/firmware/dell_rbu entries are missing.
                 * to cover this situation the user can recreate entries
                 * by writing init to image_type.
                 */
                if (!rbu_data.entry_created) {
                        spin_unlock(&rbu_data.lock);
                        req_firm_rc = request_firmware_nowait(THIS_MODULE,
                                FW_ACTION_NOUEVENT, "dell_rbu",
                                &rbu_device->dev, GFP_KERNEL, &context,
                                callbackfn_rbu);
                        if (req_firm_rc) {
                                pr_err("request_firmware_nowait failed %d\n", rc);
                                rc = -EIO;
                        } else
                                rbu_data.entry_created = 1;

                        spin_lock(&rbu_data.lock);
                }
        } else {
                pr_warn("image_type is invalid\n");
                spin_unlock(&rbu_data.lock);
                return -EINVAL;
        }

        /* we must free all previous allocations */
        packet_empty_list();
        img_update_free();
        spin_unlock(&rbu_data.lock);

        return rc;
}
static const BIN_ATTR_RW(image_type, 0);

static ssize_t packet_size_read(struct file *filp, struct kobject *kobj,
                                const struct bin_attribute *bin_attr,
                                char *buffer, loff_t pos, size_t count)
{
        int size = 0;
        if (!pos) {
                spin_lock(&rbu_data.lock);
                size = scnprintf(buffer, count, "%lu\n", rbu_data.packetsize);
                spin_unlock(&rbu_data.lock);
        }
        return size;
}

static ssize_t packet_size_write(struct file *filp, struct kobject *kobj,
                                 const struct bin_attribute *bin_attr,
                                 char *buffer, loff_t pos, size_t count)
{
        unsigned long temp;
        spin_lock(&rbu_data.lock);
        packet_empty_list();
        sscanf(buffer, "%lu", &temp);
        if (temp < 0xffffffff)
                rbu_data.packetsize = temp;

        spin_unlock(&rbu_data.lock);
        return count;
}
static const BIN_ATTR_RW(packet_size, 0);

static const struct bin_attribute *const rbu_bin_attrs[] = {
        &bin_attr_data,
        &bin_attr_image_type,
        &bin_attr_packet_size,
        NULL
};

static const struct attribute_group rbu_group = {
        .bin_attrs = rbu_bin_attrs,
};

static int __init dcdrbu_init(void)
{
        int rc;
        spin_lock_init(&rbu_data.lock);

        init_packet_head();
        rbu_device = platform_device_register_simple("dell_rbu", PLATFORM_DEVID_NONE, NULL, 0);
        if (IS_ERR(rbu_device)) {
                pr_err("platform_device_register_simple failed\n");
                return PTR_ERR(rbu_device);
        }

        rc = sysfs_create_group(&rbu_device->dev.kobj, &rbu_group);
        if (rc)
                goto out_devreg;

        rbu_data.entry_created = 0;
        return 0;

out_devreg:
        platform_device_unregister(rbu_device);
        return rc;
}

static __exit void dcdrbu_exit(void)
{
        spin_lock(&rbu_data.lock);
        packet_empty_list();
        img_update_free();
        spin_unlock(&rbu_data.lock);
        sysfs_remove_group(&rbu_device->dev.kobj, &rbu_group);
        platform_device_unregister(rbu_device);
}

module_exit(dcdrbu_exit);
module_init(dcdrbu_init);