ram_core.c

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/*
 * Copyright (C) 2012 Google, Inc.
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#include <linux/device.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/list.h>
#include <linux/memblock.h>
#include <linux/rslib.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/pstore_ram.h>
#include <asm/page.h>

struct persistent_ram_buffer {
    uint32_t    sig;
    atomic_t    start;
    atomic_t    size;
    uint8_t     data[0];
};

#define PERSISTENT_RAM_SIG (0x43474244) /* DBGC */

static inline size_t buffer_size(struct persistent_ram_zone *prz)
{
    return atomic_read(&prz->buffer->size);
}

static inline size_t buffer_start(struct persistent_ram_zone *prz)
{
    return atomic_read(&prz->buffer->start);
}

/* increase and wrap the start pointer, returning the old value */
static inline size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a)
{
    int old;
    int new;

    do {
        old = atomic_read(&prz->buffer->start);
        new = old + a;
        while (unlikely(new > prz->buffer_size))
            new -= prz->buffer_size;
    } while (atomic_cmpxchg(&prz->buffer->start, old, new) != old);

    return old;
}

/* increase the size counter until it hits the max size */
static inline void buffer_size_add(struct persistent_ram_zone *prz, size_t a)
{
    size_t old;
    size_t new;

    if (atomic_read(&prz->buffer->size) == prz->buffer_size)
        return;

    do {
        old = atomic_read(&prz->buffer->size);
        new = old + a;
        if (new > prz->buffer_size)
            new = prz->buffer_size;
    } while (atomic_cmpxchg(&prz->buffer->size, old, new) != old);
}

static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz,
    uint8_t *data, size_t len, uint8_t *ecc)
{
    int i;
    uint16_t par[prz->ecc_size];

    /* Initialize the parity buffer */
    memset(par, 0, sizeof(par));
    encode_rs8(prz->rs_decoder, data, len, par, 0);
    for (i = 0; i < prz->ecc_size; i++)
        ecc[i] = par[i];
}

static int persistent_ram_decode_rs8(struct persistent_ram_zone *prz,
    void *data, size_t len, uint8_t *ecc)
{
    int i;
    uint16_t par[prz->ecc_size];

    for (i = 0; i < prz->ecc_size; i++)
        par[i] = ecc[i];
    return decode_rs8(prz->rs_decoder, data, par, len,
                NULL, 0, NULL, 0, NULL);
}

static void notrace persistent_ram_update_ecc(struct persistent_ram_zone *prz,
    unsigned int start, unsigned int count)
{
    struct persistent_ram_buffer *buffer = prz->buffer;
    uint8_t *buffer_end = buffer->data + prz->buffer_size;
    uint8_t *block;
    uint8_t *par;
    int ecc_block_size = prz->ecc_block_size;
    int ecc_size = prz->ecc_size;
    int size = prz->ecc_block_size;

    if (!prz->ecc_size)
        return;

    block = buffer->data + (start & ~(ecc_block_size - 1));
    par = prz->par_buffer + (start / ecc_block_size) * prz->ecc_size;

    do {
        if (block + ecc_block_size > buffer_end)
            size = buffer_end - block;
        persistent_ram_encode_rs8(prz, block, size, par);
        block += ecc_block_size;
        par += ecc_size;
    } while (block < buffer->data + start + count);
}

static void persistent_ram_update_header_ecc(struct persistent_ram_zone *prz)
{
    struct persistent_ram_buffer *buffer = prz->buffer;

    if (!prz->ecc_size)
        return;

    persistent_ram_encode_rs8(prz, (uint8_t *)buffer, sizeof(*buffer),
                  prz->par_header);
}

static void persistent_ram_ecc_old(struct persistent_ram_zone *prz)
{
    struct persistent_ram_buffer *buffer = prz->buffer;
    uint8_t *block;
    uint8_t *par;

    if (!prz->ecc_size)
        return;

    block = buffer->data;
    par = prz->par_buffer;
    while (block < buffer->data + buffer_size(prz)) {
        int numerr;
        int size = prz->ecc_block_size;
        if (block + size > buffer->data + prz->buffer_size)
            size = buffer->data + prz->buffer_size - block;
        numerr = persistent_ram_decode_rs8(prz, block, size, par);
        if (numerr > 0) {
            pr_devel("persistent_ram: error in block %p, %d\n",
                   block, numerr);
            prz->corrected_bytes += numerr;
        } else if (numerr < 0) {
            pr_devel("persistent_ram: uncorrectable error in block %p\n",
                block);
            prz->bad_blocks++;
        }
        block += prz->ecc_block_size;
        par += prz->ecc_size;
    }
}

static int persistent_ram_init_ecc(struct persistent_ram_zone *prz,
                   int ecc_size)
{
    int numerr;
    struct persistent_ram_buffer *buffer = prz->buffer;
    int ecc_blocks;
    size_t ecc_total;
    int ecc_symsize = 8;
    int ecc_poly = 0x11d;

    if (!ecc_size)
        return 0;

    prz->ecc_block_size = 128;
    prz->ecc_size = ecc_size;

    ecc_blocks = DIV_ROUND_UP(prz->buffer_size, prz->ecc_block_size);
    ecc_total = (ecc_blocks + 1) * prz->ecc_size;
    if (ecc_total >= prz->buffer_size) {
        pr_err("%s: invalid ecc_size %u (total %zu, buffer size %zu)\n",
               __func__, prz->ecc_size, ecc_total, prz->buffer_size);
        return -EINVAL;
    }

    prz->buffer_size -= ecc_total;
    prz->par_buffer = buffer->data + prz->buffer_size;
    prz->par_header = prz->par_buffer + ecc_blocks * prz->ecc_size;

    /*
     * first consecutive root is 0
     * primitive element to generate roots = 1
     */
    prz->rs_decoder = init_rs(ecc_symsize, ecc_poly, 0, 1, prz->ecc_size);
    if (prz->rs_decoder == NULL) {
        pr_info("persistent_ram: init_rs failed\n");
        return -EINVAL;
    }

    prz->corrected_bytes = 0;
    prz->bad_blocks = 0;

    numerr = persistent_ram_decode_rs8(prz, buffer, sizeof(*buffer),
                       prz->par_header);
    if (numerr > 0) {
        pr_info("persistent_ram: error in header, %d\n", numerr);
        prz->corrected_bytes += numerr;
    } else if (numerr < 0) {
        pr_info("persistent_ram: uncorrectable error in header\n");
        prz->bad_blocks++;
    }

    return 0;
}

ssize_t persistent_ram_ecc_string(struct persistent_ram_zone *prz,
    char *str, size_t len)
{
    ssize_t ret;

    if (prz->corrected_bytes || prz->bad_blocks)
        ret = snprintf(str, len, ""
            "\n%d Corrected bytes, %d unrecoverable blocks\n",
            prz->corrected_bytes, prz->bad_blocks);
    else
        ret = snprintf(str, len, "\nNo errors detected\n");

    return ret;
}

static void notrace persistent_ram_update(struct persistent_ram_zone *prz,
    const void *s, unsigned int start, unsigned int count)
{
    struct persistent_ram_buffer *buffer = prz->buffer;
    memcpy(buffer->data + start, s, count);
    persistent_ram_update_ecc(prz, start, count);
}

void persistent_ram_save_old(struct persistent_ram_zone *prz)
{
    struct persistent_ram_buffer *buffer = prz->buffer;
    size_t size = buffer_size(prz);
    size_t start = buffer_start(prz);

    if (!size)
        return;

    if (!prz->old_log) {
        persistent_ram_ecc_old(prz);
        prz->old_log = kmalloc(size, GFP_KERNEL);
    }
    if (!prz->old_log) {
        pr_err("persistent_ram: failed to allocate buffer\n");
        return;
    }

    prz->old_log_size = size;
    memcpy(prz->old_log, &buffer->data[start], size - start);
    memcpy(prz->old_log + size - start, &buffer->data[0], start);
}

int notrace persistent_ram_write(struct persistent_ram_zone *prz,
    const void *s, unsigned int count)
{
    int rem;
    int c = count;
    size_t start;

    if (unlikely(c > prz->buffer_size)) {
        s += c - prz->buffer_size;
        c = prz->buffer_size;
    }

    buffer_size_add(prz, c);

    start = buffer_start_add(prz, c);

    rem = prz->buffer_size - start;
    if (unlikely(rem < c)) {
        persistent_ram_update(prz, s, start, rem);
        s += rem;
        c -= rem;
        start = 0;
    }
    persistent_ram_update(prz, s, start, c);

    persistent_ram_update_header_ecc(prz);

    return count;
}

size_t persistent_ram_old_size(struct persistent_ram_zone *prz)
{
    return prz->old_log_size;
}

void *persistent_ram_old(struct persistent_ram_zone *prz)
{
    return prz->old_log;
}

void persistent_ram_free_old(struct persistent_ram_zone *prz)
{
    kfree(prz->old_log);
    prz->old_log = NULL;
    prz->old_log_size = 0;
}

void persistent_ram_zap(struct persistent_ram_zone *prz)
{
    atomic_set(&prz->buffer->start, 0);
    atomic_set(&prz->buffer->size, 0);
    persistent_ram_update_header_ecc(prz);
}

static void *persistent_ram_vmap(phys_addr_t start, size_t size)
{
    struct page **pages;
    phys_addr_t page_start;
    unsigned int page_count;
    pgprot_t prot;
    unsigned int i;
    void *vaddr;

    page_start = start - offset_in_page(start);
    page_count = DIV_ROUND_UP(size + offset_in_page(start), PAGE_SIZE);

    prot = pgprot_noncached(PAGE_KERNEL);

    pages = kmalloc(sizeof(struct page *) * page_count, GFP_KERNEL);
    if (!pages) {
        pr_err("%s: Failed to allocate array for %u pages\n", __func__,
            page_count);
        return NULL;
    }

    for (i = 0; i < page_count; i++) {
        phys_addr_t addr = page_start + i * PAGE_SIZE;
        pages[i] = pfn_to_page(addr >> PAGE_SHIFT);
    }
    vaddr = vmap(pages, page_count, VM_MAP, prot);
    kfree(pages);

    return vaddr;
}

static void *persistent_ram_iomap(phys_addr_t start, size_t size)
{
    if (!request_mem_region(start, size, "persistent_ram")) {
        pr_err("request mem region (0x%llx@0x%llx) failed\n",
            (unsigned long long)size, (unsigned long long)start);
        return NULL;
    }

    return ioremap(start, size);
}

static int persistent_ram_buffer_map(phys_addr_t start, phys_addr_t size,
        struct persistent_ram_zone *prz)
{
    prz->paddr = start;
    prz->size = size;

    if (pfn_valid(start >> PAGE_SHIFT))
        prz->vaddr = persistent_ram_vmap(start, size);
    else
        prz->vaddr = persistent_ram_iomap(start, size);

    if (!prz->vaddr) {
        pr_err("%s: Failed to map 0x%llx pages at 0x%llx\n", __func__,
            (unsigned long long)size, (unsigned long long)start);
        return -ENOMEM;
    }

    prz->buffer = prz->vaddr + offset_in_page(start);
    prz->buffer_size = size - sizeof(struct persistent_ram_buffer);

    return 0;
}

static int __devinit persistent_ram_post_init(struct persistent_ram_zone *prz,
                          u32 sig, int ecc_size)
{
    int ret;

    ret = persistent_ram_init_ecc(prz, ecc_size);
    if (ret)
        return ret;

    sig ^= PERSISTENT_RAM_SIG;

    if (prz->buffer->sig == sig) {
        if (buffer_size(prz) > prz->buffer_size ||
            buffer_start(prz) > buffer_size(prz))
            pr_info("persistent_ram: found existing invalid buffer,"
                " size %zu, start %zu\n",
                   buffer_size(prz), buffer_start(prz));
        else {
            pr_debug("persistent_ram: found existing buffer,"
                " size %zu, start %zu\n",
                   buffer_size(prz), buffer_start(prz));
            persistent_ram_save_old(prz);
            return 0;
        }
    } else {
        pr_debug("persistent_ram: no valid data in buffer"
            " (sig = 0x%08x)\n", prz->buffer->sig);
    }

    prz->buffer->sig = sig;
    persistent_ram_zap(prz);

    return 0;
}

void persistent_ram_free(struct persistent_ram_zone *prz)
{
    if (!prz)
        return;

    if (prz->vaddr) {
        if (pfn_valid(prz->paddr >> PAGE_SHIFT)) {
            vunmap(prz->vaddr);
        } else {
            iounmap(prz->vaddr);
            release_mem_region(prz->paddr, prz->size);
        }
        prz->vaddr = NULL;
    }
    persistent_ram_free_old(prz);
    kfree(prz);
}

struct persistent_ram_zone * __devinit persistent_ram_new(phys_addr_t start,
                              size_t size, u32 sig,
                              int ecc_size)
{
    struct persistent_ram_zone *prz;
    int ret = -ENOMEM;

    prz = kzalloc(sizeof(struct persistent_ram_zone), GFP_KERNEL);
    if (!prz) {
        pr_err("persistent_ram: failed to allocate persistent ram zone\n");
        goto err;
    }

    ret = persistent_ram_buffer_map(start, size, prz);
    if (ret)
        goto err;

    ret = persistent_ram_post_init(prz, sig, ecc_size);
    if (ret)
        goto err;

    return prz;
err:
    persistent_ram_free(prz);
    return ERR_PTR(ret);
}