Merge master.kernel.org:/home/rmk/linux-2.6-arm

[linux-2.6] / kernel / power / swsusp.c

/*
 * linux/kernel/power/swsusp.c
 *
 * This file provides code to write suspend image to swap and read it back.
 *
 * Copyright (C) 1998-2001 Gabor Kuti <seasons@fornax.hu>
 * Copyright (C) 1998,2001-2005 Pavel Machek <pavel@suse.cz>
 *
 * This file is released under the GPLv2.
 *
 * I'd like to thank the following people for their work:
 *
 * Pavel Machek <pavel@ucw.cz>:
 * Modifications, defectiveness pointing, being with me at the very beginning,
 * suspend to swap space, stop all tasks. Port to 2.4.18-ac and 2.5.17.
 *
 * Steve Doddi <dirk@loth.demon.co.uk>:
 * Support the possibility of hardware state restoring.
 *
 * Raph <grey.havens@earthling.net>:
 * Support for preserving states of network devices and virtual console
 * (including X and svgatextmode)
 *
 * Kurt Garloff <garloff@suse.de>:
 * Straightened the critical function in order to prevent compilers from
 * playing tricks with local variables.
 *
 * Andreas Mohr <a.mohr@mailto.de>
 *
 * Alex Badea <vampire@go.ro>:
 * Fixed runaway init
 *
 * Andreas Steinmetz <ast@domdv.de>:
 * Added encrypted suspend option
 *
 * More state savers are welcome. Especially for the scsi layer...
 *
 * For TODOs,FIXMEs also look in Documentation/power/swsusp.txt
 */

#include <linux/module.h>
#include <linux/mm.h>
#include <linux/suspend.h>
#include <linux/smp_lock.h>
#include <linux/file.h>
#include <linux/utsname.h>
#include <linux/version.h>
#include <linux/delay.h>
#include <linux/bitops.h>
#include <linux/spinlock.h>
#include <linux/genhd.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/swap.h>
#include <linux/pm.h>
#include <linux/device.h>
#include <linux/buffer_head.h>
#include <linux/swapops.h>
#include <linux/bootmem.h>
#include <linux/syscalls.h>
#include <linux/highmem.h>
#include <linux/bio.h>

#include <asm/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <asm/io.h>

#include <linux/random.h>
#include <linux/crypto.h>
#include <asm/scatterlist.h>

#include "power.h"

#define CIPHER "aes"
#define MAXKEY 32
#define MAXIV  32

extern char resume_file[];

/* Local variables that should not be affected by save */
unsigned int nr_copy_pages __nosavedata = 0;

/* Suspend pagedir is allocated before final copy, therefore it
   must be freed after resume

   Warning: this is even more evil than it seems. Pagedirs this file
   talks about are completely different from page directories used by
   MMU hardware.
 */
suspend_pagedir_t *pagedir_nosave __nosavedata = NULL;

#define SWSUSP_SIG      "S1SUSPEND"

static struct swsusp_header {
        char reserved[PAGE_SIZE - 20 - MAXKEY - MAXIV - sizeof(swp_entry_t)];
        u8 key_iv[MAXKEY+MAXIV];
        swp_entry_t swsusp_info;
        char    orig_sig[10];
        char    sig[10];
} __attribute__((packed, aligned(PAGE_SIZE))) swsusp_header;

static struct swsusp_info swsusp_info;

/*
 * Saving part...
 */

/* We memorize in swapfile_used what swap devices are used for suspension */
#define SWAPFILE_UNUSED    0
#define SWAPFILE_SUSPEND   1    /* This is the suspending device */
#define SWAPFILE_IGNORED   2    /* Those are other swap devices ignored for suspension */

static unsigned short swapfile_used[MAX_SWAPFILES];
static unsigned short root_swap;

static int write_page(unsigned long addr, swp_entry_t *loc);
static int bio_read_page(pgoff_t page_off, void *page);

static u8 key_iv[MAXKEY+MAXIV];

#ifdef CONFIG_SWSUSP_ENCRYPT

static int crypto_init(int mode, void **mem)
{
        int error = 0;
        int len;
        char *modemsg;
        struct crypto_tfm *tfm;

        modemsg = mode ? "suspend not possible" : "resume not possible";

        tfm = crypto_alloc_tfm(CIPHER, CRYPTO_TFM_MODE_CBC);
        if(!tfm) {
                printk(KERN_ERR "swsusp: no tfm, %s\n", modemsg);
                error = -EINVAL;
                goto out;
        }

        if(MAXKEY < crypto_tfm_alg_min_keysize(tfm)) {
                printk(KERN_ERR "swsusp: key buffer too small, %s\n", modemsg);
                error = -ENOKEY;
                goto fail;
        }

        if (mode)
                get_random_bytes(key_iv, MAXKEY+MAXIV);

        len = crypto_tfm_alg_max_keysize(tfm);
        if (len > MAXKEY)
                len = MAXKEY;

        if (crypto_cipher_setkey(tfm, key_iv, len)) {
                printk(KERN_ERR "swsusp: key setup failure, %s\n", modemsg);
                error = -EKEYREJECTED;
                goto fail;
        }

        len = crypto_tfm_alg_ivsize(tfm);

        if (MAXIV < len) {
                printk(KERN_ERR "swsusp: iv buffer too small, %s\n", modemsg);
                error = -EOVERFLOW;
                goto fail;
        }

        crypto_cipher_set_iv(tfm, key_iv+MAXKEY, len);

        *mem=(void *)tfm;

        goto out;

fail:   crypto_free_tfm(tfm);
out:    return error;
}

static __inline__ void crypto_exit(void *mem)
{
        crypto_free_tfm((struct crypto_tfm *)mem);
}

static __inline__ int crypto_write(struct pbe *p, void *mem)
{
        int error = 0;
        struct scatterlist src, dst;

        src.page   = virt_to_page(p->address);
        src.offset = 0;
        src.length = PAGE_SIZE;
        dst.page   = virt_to_page((void *)&swsusp_header);
        dst.offset = 0;
        dst.length = PAGE_SIZE;

        error = crypto_cipher_encrypt((struct crypto_tfm *)mem, &dst, &src,
                                        PAGE_SIZE);

        if (!error)
                error = write_page((unsigned long)&swsusp_header,
                                &(p->swap_address));
        return error;
}

static __inline__ int crypto_read(struct pbe *p, void *mem)
{
        int error = 0;
        struct scatterlist src, dst;

        error = bio_read_page(swp_offset(p->swap_address), (void *)p->address);
        if (!error) {
                src.offset = 0;
                src.length = PAGE_SIZE;
                dst.offset = 0;
                dst.length = PAGE_SIZE;
                src.page = dst.page = virt_to_page((void *)p->address);

                error = crypto_cipher_decrypt((struct crypto_tfm *)mem, &dst,
                                                &src, PAGE_SIZE);
        }
        return error;
}
#else
static __inline__ int crypto_init(int mode, void *mem)
{
        return 0;
}

static __inline__ void crypto_exit(void *mem)
{
}

static __inline__ int crypto_write(struct pbe *p, void *mem)
{
        return write_page(p->address, &(p->swap_address));
}

static __inline__ int crypto_read(struct pbe *p, void *mem)
{
        return bio_read_page(swp_offset(p->swap_address), (void *)p->address);
}
#endif

static int mark_swapfiles(swp_entry_t prev)
{
        int error;

        rw_swap_page_sync(READ,
                          swp_entry(root_swap, 0),
                          virt_to_page((unsigned long)&swsusp_header));
        if (!memcmp("SWAP-SPACE",swsusp_header.sig, 10) ||
            !memcmp("SWAPSPACE2",swsusp_header.sig, 10)) {
                memcpy(swsusp_header.orig_sig,swsusp_header.sig, 10);
                memcpy(swsusp_header.sig,SWSUSP_SIG, 10);
                memcpy(swsusp_header.key_iv, key_iv, MAXKEY+MAXIV);
                swsusp_header.swsusp_info = prev;
                error = rw_swap_page_sync(WRITE,
                                          swp_entry(root_swap, 0),
                                          virt_to_page((unsigned long)
                                                       &swsusp_header));
        } else {
                pr_debug("swsusp: Partition is not swap space.\n");
                error = -ENODEV;
        }
        return error;
}

/*
 * Check whether the swap device is the specified resume
 * device, irrespective of whether they are specified by
 * identical names.
 *
 * (Thus, device inode aliasing is allowed.  You can say /dev/hda4
 * instead of /dev/ide/host0/bus0/target0/lun0/part4 [if using devfs]
 * and they'll be considered the same device.  This is *necessary* for
 * devfs, since the resume code can only recognize the form /dev/hda4,
 * but the suspend code would see the long name.)
 */
static int is_resume_device(const struct swap_info_struct *swap_info)
{
        struct file *file = swap_info->swap_file;
        struct inode *inode = file->f_dentry->d_inode;

        return S_ISBLK(inode->i_mode) &&
                swsusp_resume_device == MKDEV(imajor(inode), iminor(inode));
}

static int swsusp_swap_check(void) /* This is called before saving image */
{
        int i, len;

        len=strlen(resume_file);
        root_swap = 0xFFFF;

        spin_lock(&swap_lock);
        for (i=0; i<MAX_SWAPFILES; i++) {
                if (!(swap_info[i].flags & SWP_WRITEOK)) {
                        swapfile_used[i]=SWAPFILE_UNUSED;
                } else {
                        if (!len) {
                                printk(KERN_WARNING "resume= option should be used to set suspend device" );
                                if (root_swap == 0xFFFF) {
                                        swapfile_used[i] = SWAPFILE_SUSPEND;
                                        root_swap = i;
                                } else
                                        swapfile_used[i] = SWAPFILE_IGNORED;
                        } else {
                                /* we ignore all swap devices that are not the resume_file */
                                if (is_resume_device(&swap_info[i])) {
                                        swapfile_used[i] = SWAPFILE_SUSPEND;
                                        root_swap = i;
                                } else {
                                        swapfile_used[i] = SWAPFILE_IGNORED;
                                }
                        }
                }
        }
        spin_unlock(&swap_lock);
        return (root_swap != 0xffff) ? 0 : -ENODEV;
}

/**
 * This is called after saving image so modification
 * will be lost after resume... and that's what we want.
 * we make the device unusable. A new call to
 * lock_swapdevices can unlock the devices.
 */
static void lock_swapdevices(void)
{
        int i;

        spin_lock(&swap_lock);
        for (i = 0; i< MAX_SWAPFILES; i++)
                if (swapfile_used[i] == SWAPFILE_IGNORED) {
                        swap_info[i].flags ^= SWP_WRITEOK;
                }
        spin_unlock(&swap_lock);
}

/**
 *      write_page - Write one page to a fresh swap location.
 *      @addr:  Address we're writing.
 *      @loc:   Place to store the entry we used.
 *
 *      Allocate a new swap entry and 'sync' it. Note we discard -EIO
 *      errors. That is an artifact left over from swsusp. It did not
 *      check the return of rw_swap_page_sync() at all, since most pages
 *      written back to swap would return -EIO.
 *      This is a partial improvement, since we will at least return other
 *      errors, though we need to eventually fix the damn code.
 */
static int write_page(unsigned long addr, swp_entry_t *loc)
{
        swp_entry_t entry;
        int error = 0;

        entry = get_swap_page();
        if (swp_offset(entry) &&
            swapfile_used[swp_type(entry)] == SWAPFILE_SUSPEND) {
                error = rw_swap_page_sync(WRITE, entry,
                                          virt_to_page(addr));
                if (error == -EIO)
                        error = 0;
                if (!error)
                        *loc = entry;
        } else
                error = -ENOSPC;
        return error;
}

/**
 *      data_free - Free the swap entries used by the saved image.
 *
 *      Walk the list of used swap entries and free each one.
 *      This is only used for cleanup when suspend fails.
 */
static void data_free(void)
{
        swp_entry_t entry;
        struct pbe *p;

        for_each_pbe (p, pagedir_nosave) {
                entry = p->swap_address;
                if (entry.val)
                        swap_free(entry);
                else
                        break;
        }
}

/**
 *      data_write - Write saved image to swap.
 *
 *      Walk the list of pages in the image and sync each one to swap.
 */
static int data_write(void)
{
        int error = 0, i = 0;
        unsigned int mod = nr_copy_pages / 100;
        struct pbe *p;
        void *tfm;

        if ((error = crypto_init(1, &tfm)))
                return error;

        if (!mod)
                mod = 1;

        printk( "Writing data to swap (%d pages)...     ", nr_copy_pages );
        for_each_pbe (p, pagedir_nosave) {
                if (!(i%mod))
                        printk( "\b\b\b\b%3d%%", i / mod );
                if ((error = crypto_write(p, tfm))) {
                        crypto_exit(tfm);
                        return error;
                }
                i++;
        }
        printk("\b\b\b\bdone\n");
        crypto_exit(tfm);
        return error;
}

static void dump_info(void)
{
        pr_debug(" swsusp: Version: %u\n",swsusp_info.version_code);
        pr_debug(" swsusp: Num Pages: %ld\n",swsusp_info.num_physpages);
        pr_debug(" swsusp: UTS Sys: %s\n",swsusp_info.uts.sysname);
        pr_debug(" swsusp: UTS Node: %s\n",swsusp_info.uts.nodename);
        pr_debug(" swsusp: UTS Release: %s\n",swsusp_info.uts.release);
        pr_debug(" swsusp: UTS Version: %s\n",swsusp_info.uts.version);
        pr_debug(" swsusp: UTS Machine: %s\n",swsusp_info.uts.machine);
        pr_debug(" swsusp: UTS Domain: %s\n",swsusp_info.uts.domainname);
        pr_debug(" swsusp: CPUs: %d\n",swsusp_info.cpus);
        pr_debug(" swsusp: Image: %ld Pages\n",swsusp_info.image_pages);
        pr_debug(" swsusp: Pagedir: %ld Pages\n",swsusp_info.pagedir_pages);
}

static void init_header(void)
{
        memset(&swsusp_info, 0, sizeof(swsusp_info));
        swsusp_info.version_code = LINUX_VERSION_CODE;
        swsusp_info.num_physpages = num_physpages;
        memcpy(&swsusp_info.uts, &system_utsname, sizeof(system_utsname));

        swsusp_info.suspend_pagedir = pagedir_nosave;
        swsusp_info.cpus = num_online_cpus();
        swsusp_info.image_pages = nr_copy_pages;
}

static int close_swap(void)
{
        swp_entry_t entry;
        int error;

        dump_info();
        error = write_page((unsigned long)&swsusp_info, &entry);
        if (!error) {
                printk( "S" );
                error = mark_swapfiles(entry);
                printk( "|\n" );
        }
        return error;
}

/**
 *      free_pagedir_entries - Free pages used by the page directory.
 *
 *      This is used during suspend for error recovery.
 */

static void free_pagedir_entries(void)
{
        int i;

        for (i = 0; i < swsusp_info.pagedir_pages; i++)
                swap_free(swsusp_info.pagedir[i]);
}


/**
 *      write_pagedir - Write the array of pages holding the page directory.
 *      @last:  Last swap entry we write (needed for header).
 */

static int write_pagedir(void)
{
        int error = 0;
        unsigned int n = 0;
        struct pbe *pbe;

        printk( "Writing pagedir...");
        for_each_pb_page (pbe, pagedir_nosave) {
                if ((error = write_page((unsigned long)pbe, &swsusp_info.pagedir[n++])))
                        return error;
        }

        swsusp_info.pagedir_pages = n;
        printk("done (%u pages)\n", n);
        return error;
}

/**
 *      write_suspend_image - Write entire image and metadata.
 *
 */
static int write_suspend_image(void)
{
        int error;

        init_header();
        if ((error = data_write()))
                goto FreeData;

        if ((error = write_pagedir()))
                goto FreePagedir;

        if ((error = close_swap()))
                goto FreePagedir;
 Done:
        memset(key_iv, 0, MAXKEY+MAXIV);
        return error;
 FreePagedir:
        free_pagedir_entries();
 FreeData:
        data_free();
        goto Done;
}

/**
 *      enough_swap - Make sure we have enough swap to save the image.
 *
 *      Returns TRUE or FALSE after checking the total amount of swap
 *      space avaiable.
 *
 *      FIXME: si_swapinfo(&i) returns all swap devices information.
 *      We should only consider resume_device.
 */

int enough_swap(unsigned int nr_pages)
{
        struct sysinfo i;

        si_swapinfo(&i);
        pr_debug("swsusp: available swap: %lu pages\n", i.freeswap);
        return i.freeswap > (nr_pages + PAGES_FOR_IO +
                (nr_pages + PBES_PER_PAGE - 1) / PBES_PER_PAGE);
}


/* It is important _NOT_ to umount filesystems at this point. We want
 * them synced (in case something goes wrong) but we DO not want to mark
 * filesystem clean: it is not. (And it does not matter, if we resume
 * correctly, we'll mark system clean, anyway.)
 */
int swsusp_write(void)
{
        int error;

        lock_swapdevices();
        error = write_suspend_image();
        /* This will unlock ignored swap devices since writing is finished */
        lock_swapdevices();
        return error;

}



int swsusp_suspend(void)
{
        int error;
        if ((error = arch_prepare_suspend()))
                return error;
        local_irq_disable();
        /* At this point, device_suspend() has been called, but *not*
         * device_power_down(). We *must* device_power_down() now.
         * Otherwise, drivers for some devices (e.g. interrupt controllers)
         * become desynchronized with the actual state of the hardware
         * at resume time, and evil weirdness ensues.
         */
        if ((error = device_power_down(PMSG_FREEZE))) {
                printk(KERN_ERR "Some devices failed to power down, aborting suspend\n");
                local_irq_enable();
                return error;
        }

        if ((error = swsusp_swap_check())) {
                printk(KERN_ERR "swsusp: cannot find swap device, try swapon -a.\n");
                device_power_up();
                local_irq_enable();
                return error;
        }

        save_processor_state();
        if ((error = swsusp_arch_suspend()))
                printk(KERN_ERR "Error %d suspending\n", error);
        /* Restore control flow magically appears here */
        restore_processor_state();
        restore_highmem();
        device_power_up();
        local_irq_enable();
        return error;
}

int swsusp_resume(void)
{
        int error;
        local_irq_disable();
        if (device_power_down(PMSG_FREEZE))
                printk(KERN_ERR "Some devices failed to power down, very bad\n");
        /* We'll ignore saved state, but this gets preempt count (etc) right */
        save_processor_state();
        error = swsusp_arch_resume();
        /* Code below is only ever reached in case of failure. Otherwise
         * execution continues at place where swsusp_arch_suspend was called
         */
        BUG_ON(!error);
        /* The only reason why swsusp_arch_resume() can fail is memory being
         * very tight, so we have to free it as soon as we can to avoid
         * subsequent failures
         */
        swsusp_free();
        restore_processor_state();
        restore_highmem();
        touch_softlockup_watchdog();
        device_power_up();
        local_irq_enable();
        return error;
}

/**
 *      On resume, for storing the PBE list and the image,
 *      we can only use memory pages that do not conflict with the pages
 *      which had been used before suspend.
 *
 *      We don't know which pages are usable until we allocate them.
 *
 *      Allocated but unusable (ie eaten) memory pages are marked so that
 *      swsusp_free() can release them
 */

unsigned long get_safe_page(gfp_t gfp_mask)
{
        unsigned long m;

        do {
                m = get_zeroed_page(gfp_mask);
                if (m && PageNosaveFree(virt_to_page(m)))
                        /* This is for swsusp_free() */
                        SetPageNosave(virt_to_page(m));
        } while (m && PageNosaveFree(virt_to_page(m)));
        if (m) {
                /* This is for swsusp_free() */
                SetPageNosave(virt_to_page(m));
                SetPageNosaveFree(virt_to_page(m));
        }
        return m;
}

/**
 *      check_pagedir - We ensure here that pages that the PBEs point to
 *      won't collide with pages where we're going to restore from the loaded
 *      pages later
 */

static int check_pagedir(struct pbe *pblist)
{
        struct pbe *p;

        /* This is necessary, so that we can free allocated pages
         * in case of failure
         */
        for_each_pbe (p, pblist)
                p->address = 0UL;

        for_each_pbe (p, pblist) {
                p->address = get_safe_page(GFP_ATOMIC);
                if (!p->address)
                        return -ENOMEM;
        }
        return 0;
}

/**
 *      swsusp_pagedir_relocate - It is possible, that some memory pages
 *      occupied by the list of PBEs collide with pages where we're going to
 *      restore from the loaded pages later.  We relocate them here.
 */

static struct pbe *swsusp_pagedir_relocate(struct pbe *pblist)
{
        struct zone *zone;
        unsigned long zone_pfn;
        struct pbe *pbpage, *tail, *p;
        void *m;
        int rel = 0;

        if (!pblist) /* a sanity check */
                return NULL;

        pr_debug("swsusp: Relocating pagedir (%lu pages to check)\n",
                        swsusp_info.pagedir_pages);

        /* Clear page flags */

        for_each_zone (zone) {
                for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
                        if (pfn_valid(zone_pfn + zone->zone_start_pfn))
                                ClearPageNosaveFree(pfn_to_page(zone_pfn +
                                        zone->zone_start_pfn));
        }

        /* Mark orig addresses */

        for_each_pbe (p, pblist)
                SetPageNosaveFree(virt_to_page(p->orig_address));

        tail = pblist + PB_PAGE_SKIP;

        /* Relocate colliding pages */

        for_each_pb_page (pbpage, pblist) {
                if (PageNosaveFree(virt_to_page((unsigned long)pbpage))) {
                        m = (void *)get_safe_page(GFP_ATOMIC | __GFP_COLD);
                        if (!m)
                                return NULL;
                        memcpy(m, (void *)pbpage, PAGE_SIZE);
                        if (pbpage == pblist)
                                pblist = (struct pbe *)m;
                        else
                                tail->next = (struct pbe *)m;
                        pbpage = (struct pbe *)m;

                        /* We have to link the PBEs again */
                        for (p = pbpage; p < pbpage + PB_PAGE_SKIP; p++)
                                if (p->next) /* needed to save the end */
                                        p->next = p + 1;

                        rel++;
                }
                tail = pbpage + PB_PAGE_SKIP;
        }

        /* This is for swsusp_free() */
        for_each_pb_page (pbpage, pblist) {
                SetPageNosave(virt_to_page(pbpage));
                SetPageNosaveFree(virt_to_page(pbpage));
        }

        printk("swsusp: Relocated %d pages\n", rel);

        return pblist;
}

/*
 *      Using bio to read from swap.
 *      This code requires a bit more work than just using buffer heads
 *      but, it is the recommended way for 2.5/2.6.
 *      The following are to signal the beginning and end of I/O. Bios
 *      finish asynchronously, while we want them to happen synchronously.
 *      A simple atomic_t, and a wait loop take care of this problem.
 */

static atomic_t io_done = ATOMIC_INIT(0);

static int end_io(struct bio *bio, unsigned int num, int err)
{
        if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
                panic("I/O error reading memory image");
        atomic_set(&io_done, 0);
        return 0;
}

static struct block_device *resume_bdev;

/**
 *      submit - submit BIO request.
 *      @rw:    READ or WRITE.
 *      @off    physical offset of page.
 *      @page:  page we're reading or writing.
 *
 *      Straight from the textbook - allocate and initialize the bio.
 *      If we're writing, make sure the page is marked as dirty.
 *      Then submit it and wait.
 */

static int submit(int rw, pgoff_t page_off, void *page)
{
        int error = 0;
        struct bio *bio;

        bio = bio_alloc(GFP_ATOMIC, 1);
        if (!bio)
                return -ENOMEM;
        bio->bi_sector = page_off * (PAGE_SIZE >> 9);
        bio_get(bio);
        bio->bi_bdev = resume_bdev;
        bio->bi_end_io = end_io;

        if (bio_add_page(bio, virt_to_page(page), PAGE_SIZE, 0) < PAGE_SIZE) {
                printk("swsusp: ERROR: adding page to bio at %ld\n",page_off);
                error = -EFAULT;
                goto Done;
        }

        if (rw == WRITE)
                bio_set_pages_dirty(bio);

        atomic_set(&io_done, 1);
        submit_bio(rw | (1 << BIO_RW_SYNC), bio);
        while (atomic_read(&io_done))
                yield();

 Done:
        bio_put(bio);
        return error;
}

static int bio_read_page(pgoff_t page_off, void *page)
{
        return submit(READ, page_off, page);
}

static int bio_write_page(pgoff_t page_off, void *page)
{
        return submit(WRITE, page_off, page);
}

/*
 * Sanity check if this image makes sense with this kernel/swap context
 * I really don't think that it's foolproof but more than nothing..
 */

static const char *sanity_check(void)
{
        dump_info();
        if (swsusp_info.version_code != LINUX_VERSION_CODE)
                return "kernel version";
        if (swsusp_info.num_physpages != num_physpages)
                return "memory size";
        if (strcmp(swsusp_info.uts.sysname,system_utsname.sysname))
                return "system type";
        if (strcmp(swsusp_info.uts.release,system_utsname.release))
                return "kernel release";
        if (strcmp(swsusp_info.uts.version,system_utsname.version))
                return "version";
        if (strcmp(swsusp_info.uts.machine,system_utsname.machine))
                return "machine";
#if 0
        /* We can't use number of online CPUs when we use hotplug to remove them ;-))) */
        if (swsusp_info.cpus != num_possible_cpus())
                return "number of cpus";
#endif
        return NULL;
}


static int check_header(void)
{
        const char *reason = NULL;
        int error;

        if ((error = bio_read_page(swp_offset(swsusp_header.swsusp_info), &swsusp_info)))
                return error;

        /* Is this same machine? */
        if ((reason = sanity_check())) {
                printk(KERN_ERR "swsusp: Resume mismatch: %s\n",reason);
                return -EPERM;
        }
        nr_copy_pages = swsusp_info.image_pages;
        return error;
}

static int check_sig(void)
{
        int error;

        memset(&swsusp_header, 0, sizeof(swsusp_header));
        if ((error = bio_read_page(0, &swsusp_header)))
                return error;
        if (!memcmp(SWSUSP_SIG, swsusp_header.sig, 10)) {
                memcpy(swsusp_header.sig, swsusp_header.orig_sig, 10);
                memcpy(key_iv, swsusp_header.key_iv, MAXKEY+MAXIV);
                memset(swsusp_header.key_iv, 0, MAXKEY+MAXIV);

                /*
                 * Reset swap signature now.
                 */
                error = bio_write_page(0, &swsusp_header);
        } else { 
                return -EINVAL;
        }
        if (!error)
                pr_debug("swsusp: Signature found, resuming\n");
        return error;
}

/**
 *      data_read - Read image pages from swap.
 *
 *      You do not need to check for overlaps, check_pagedir()
 *      already did that.
 */

static int data_read(struct pbe *pblist)
{
        struct pbe *p;
        int error = 0;
        int i = 0;
        int mod = swsusp_info.image_pages / 100;
        void *tfm;

        if ((error = crypto_init(0, &tfm)))
                return error;

        if (!mod)
                mod = 1;

        printk("swsusp: Reading image data (%lu pages):     ",
                        swsusp_info.image_pages);

        for_each_pbe (p, pblist) {
                if (!(i % mod))
                        printk("\b\b\b\b%3d%%", i / mod);

                if ((error = crypto_read(p, tfm))) {
                        crypto_exit(tfm);
                        return error;
                }

                i++;
        }
        printk("\b\b\b\bdone\n");
        crypto_exit(tfm);
        return error;
}

/**
 *      read_pagedir - Read page backup list pages from swap
 */

static int read_pagedir(struct pbe *pblist)
{
        struct pbe *pbpage, *p;
        unsigned int i = 0;
        int error;

        if (!pblist)
                return -EFAULT;

        printk("swsusp: Reading pagedir (%lu pages)\n",
                        swsusp_info.pagedir_pages);

        for_each_pb_page (pbpage, pblist) {
                unsigned long offset = swp_offset(swsusp_info.pagedir[i++]);

                error = -EFAULT;
                if (offset) {
                        p = (pbpage + PB_PAGE_SKIP)->next;
                        error = bio_read_page(offset, (void *)pbpage);
                        (pbpage + PB_PAGE_SKIP)->next = p;
                }
                if (error)
                        break;
        }

        if (!error)
                BUG_ON(i != swsusp_info.pagedir_pages);

        return error;
}


static int check_suspend_image(void)
{
        int error = 0;

        if ((error = check_sig()))
                return error;

        if ((error = check_header()))
                return error;

        return 0;
}

static int read_suspend_image(void)
{
        int error = 0;
        struct pbe *p;

        if (!(p = alloc_pagedir(nr_copy_pages)))
                return -ENOMEM;

        if ((error = read_pagedir(p)))
                return error;

        create_pbe_list(p, nr_copy_pages);

        if (!(pagedir_nosave = swsusp_pagedir_relocate(p)))
                return -ENOMEM;

        /* Allocate memory for the image and read the data from swap */

        error = check_pagedir(pagedir_nosave);

        if (!error)
                error = data_read(pagedir_nosave);

        return error;
}

/**
 *      swsusp_check - Check for saved image in swap
 */

int swsusp_check(void)
{
        int error;

        resume_bdev = open_by_devnum(swsusp_resume_device, FMODE_READ);
        if (!IS_ERR(resume_bdev)) {
                set_blocksize(resume_bdev, PAGE_SIZE);
                error = check_suspend_image();
                if (error)
                    blkdev_put(resume_bdev);
        } else
                error = PTR_ERR(resume_bdev);

        if (!error)
                pr_debug("swsusp: resume file found\n");
        else
                pr_debug("swsusp: Error %d check for resume file\n", error);
        return error;
}

/**
 *      swsusp_read - Read saved image from swap.
 */

int swsusp_read(void)
{
        int error;

        if (IS_ERR(resume_bdev)) {
                pr_debug("swsusp: block device not initialised\n");
                return PTR_ERR(resume_bdev);
        }

        error = read_suspend_image();
        blkdev_put(resume_bdev);
        memset(key_iv, 0, MAXKEY+MAXIV);

        if (!error)
                pr_debug("swsusp: Reading resume file was successful\n");
        else
                pr_debug("swsusp: Error %d resuming\n", error);
        return error;
}

/**
 *      swsusp_close - close swap device.
 */

void swsusp_close(void)
{
        if (IS_ERR(resume_bdev)) {
                pr_debug("swsusp: block device not initialised\n");
                return;
        }

        blkdev_put(resume_bdev);
}