/*
 * kernel/power/tuxonice_copy_before_write.c
 *
 * Copyright (C) 2015 Nigel Cunningham (nigel at nigelcunningham com au)
 *
 * This file is released under the GPLv2.
 *
 * Routines (apart from the fault handling code) to deal with allocating memory
 * for copying pages before they are modified, restoring the contents and getting
 * the contents written to disk.
 */

#include <linux/percpu-defs.h>
#include <linux/sched.h>
#include <linux/tuxonice.h>
#include "tuxonice_alloc.h"
#include "tuxonice_modules.h"
#include "tuxonice_sysfs.h"
#include "tuxonice.h"

DEFINE_PER_CPU(struct toi_cbw_state, toi_cbw_states);
#define CBWS_PER_PAGE (PAGE_SIZE / sizeof(struct toi_cbw))
#define toi_cbw_pool_size 100

static void _toi_free_cbw_data(struct toi_cbw_state *state)
{
    struct toi_cbw *page_ptr, *ptr, *next;

    page_ptr = ptr = state->first;

    while(ptr) {
        next = ptr->next;

        if (ptr->virt) {
            toi__free_page(40, virt_to_page(ptr->virt));
        }
        if ((((unsigned long) ptr) & PAGE_MASK) != (unsigned long) page_ptr) {
            /* Must be on a new page - free the previous one. */
            toi__free_page(40, virt_to_page(page_ptr));
            page_ptr = ptr;
        }
        ptr = next;
    }

    if (page_ptr) {
        toi__free_page(40, virt_to_page(page_ptr));
    }

    state->first = state->next = state->last = NULL;
    state->size = 0;
}

void toi_free_cbw_data(void)
{
    int i;

    for_each_online_cpu(i) {
        struct toi_cbw_state *state = &per_cpu(toi_cbw_states, i);

        if (!state->first)
            continue;

        state->enabled = 0;

        while (state->active) {
            schedule();
        }

        _toi_free_cbw_data(state);
    }
}

static int _toi_allocate_cbw_data(struct toi_cbw_state *state)
{
    while(state->size < toi_cbw_pool_size) {
        int i;
        struct toi_cbw *ptr;

        ptr = (struct toi_cbw *) toi_get_zeroed_page(40, GFP_KERNEL);

        if (!ptr) {
            return -ENOMEM;
        }

        if (!state->first) {
            state->first = state->next = state->last = ptr;
        }

        for (i = 0; i < CBWS_PER_PAGE; i++) {
            struct toi_cbw *cbw = &ptr[i];

            cbw->virt = (char *) toi_get_zeroed_page(40, GFP_KERNEL);
            if (!cbw->virt) {
                state->size += i;
                printk("Out of memory allocating CBW pages.\n");
                return -ENOMEM;
            }

            if (cbw == state->first)
                continue;

            state->last->next = cbw;
            state->last = cbw;
        }

        state->size += CBWS_PER_PAGE;
    }

    state->enabled = 1;

    return 0;
}


int toi_allocate_cbw_data(void)
{
    int i, result;

    for_each_online_cpu(i) {
        struct toi_cbw_state *state = &per_cpu(toi_cbw_states, i);

        result = _toi_allocate_cbw_data(state);

        if (result)
            return result;
    }

    return 0;
}

void toi_cbw_restore(void)
{
    if (!toi_keeping_image)
        return;

}

void toi_cbw_write(void)
{
    if (!toi_keeping_image)
        return;

}

/**
 * toi_cbw_test_read - Test copy before write on one page
 *
 * Allocate copy before write buffers, then make one page only copy-before-write
 * and attempt to write to it. We should then be able to retrieve the original
 * version from the cbw buffer and the modified version from the page itself.
 */
static int toi_cbw_test_read(const char *buffer, int count)
{
    unsigned long virt = toi_get_zeroed_page(40, GFP_KERNEL);
    char *original = "Original contents";
    char *modified = "Modified material";
    struct page *page = virt_to_page(virt);
    int i, len = 0, found = 0, pfn = page_to_pfn(page);

    if (!page) {
        printk("toi_cbw_test_read: Unable to allocate a page for testing.\n");
        return -ENOMEM;
    }

    memcpy((char *) virt, original, strlen(original));

    if (toi_allocate_cbw_data()) {
        printk("toi_cbw_test_read: Unable to allocate cbw data.\n");
        return -ENOMEM;
    }

    toi_reset_dirtiness_one(pfn, 0);

    SetPageTOI_CBW(page);

    memcpy((char *) virt, modified, strlen(modified));

    if (strncmp((char *) virt, modified, strlen(modified))) {
        len += sprintf((char *) buffer + len, "Failed to write to page after protecting it.\n");
    }

    for_each_online_cpu(i) {
        struct toi_cbw_state *state = &per_cpu(toi_cbw_states, i);
        struct toi_cbw *ptr = state->first, *last_ptr = ptr;

        if (!found) {
            while (ptr) {
                if (ptr->pfn == pfn) {
                    found = 1;
                    if (strncmp(ptr->virt, original, strlen(original))) {
                        len += sprintf((char *) buffer + len, "Contents of original buffer are not original.\n");
                    } else {
                        len += sprintf((char *) buffer + len, "Test passed. Buffer changed and original contents preserved.\n");
                    }
                    break;
                }

                last_ptr = ptr;
                ptr = ptr->next;
            }
        }

        if (!last_ptr)
            len += sprintf((char *) buffer + len, "All available CBW buffers on cpu %d used.\n", i);
    }

    if (!found)
        len += sprintf((char *) buffer + len, "Copy before write buffer not found.\n");

    toi_free_cbw_data();

    return len;
}

/*
 * This array contains entries that are automatically registered at
 * boot. Modules and the console code register their own entries separately.
 */
static struct toi_sysfs_data sysfs_params[] = {
        SYSFS_CUSTOM("test", SYSFS_RW, toi_cbw_test_read,
                        NULL, SYSFS_NEEDS_SM_FOR_READ, NULL),
};

static struct toi_module_ops toi_cbw_ops = {
        .type                                        = MISC_HIDDEN_MODULE,
        .name                                        = "copy_before_write debugging",
        .directory                                = "cbw",
        .module                                        = THIS_MODULE,
        .early                                        = 1,

        .sysfs_data                = sysfs_params,
        .num_sysfs_entries        = sizeof(sysfs_params) /
                sizeof(struct toi_sysfs_data),
};

int toi_cbw_init(void)
{
        int result = toi_register_module(&toi_cbw_ops);
        return result;
}