// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2012 Google, Inc.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

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

#include "ram_internal.h"

/**
 * struct persistent_ram_buffer - persistent circular RAM buffer
 *
 * @sig: Signature to indicate header (PERSISTENT_RAM_SIG xor PRZ-type value)
 * @start: First valid byte in the buffer.
 * @size: Number of valid bytes in the buffer.
 * @data: The contents of the buffer.
 */
struct persistent_ram_buffer {
        uint32_t    sig;
        atomic_t    start;
        atomic_t    size;
        uint8_t     data[];
};

#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 size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a)
{
        int old;
        int new;
        unsigned long flags = 0;

        if (!(prz->flags & PRZ_FLAG_NO_LOCK))
                raw_spin_lock_irqsave(&prz->buffer_lock, flags);

        old = atomic_read(&prz->buffer->start);
        new = old + a;
        while (unlikely(new >= prz->buffer_size))
                new -= prz->buffer_size;
        atomic_set(&prz->buffer->start, new);

        if (!(prz->flags & PRZ_FLAG_NO_LOCK))
                raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);

        return old;
}

/* increase the size counter until it hits the max size */
static void buffer_size_add(struct persistent_ram_zone *prz, size_t a)
{
        size_t old;
        size_t new;
        unsigned long flags = 0;

        if (!(prz->flags & PRZ_FLAG_NO_LOCK))
                raw_spin_lock_irqsave(&prz->buffer_lock, flags);

        old = atomic_read(&prz->buffer->size);
        if (old == prz->buffer_size)
                goto exit;

        new = old + a;
        if (new > prz->buffer_size)
                new = prz->buffer_size;
        atomic_set(&prz->buffer->size, new);

exit:
        if (!(prz->flags & PRZ_FLAG_NO_LOCK))
                raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
}

static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz,
        uint8_t *data, size_t len, uint8_t *ecc)
{
        int i;

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

static int persistent_ram_decode_rs8(struct persistent_ram_zone *prz,
        void *data, size_t len, uint8_t *ecc)
{
        int i;

        for (i = 0; i < prz->ecc_info.ecc_size; i++)
                prz->ecc_info.par[i] = ecc[i];
        return decode_rs8(prz->rs_decoder, data, prz->ecc_info.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_info.block_size;
        int ecc_size = prz->ecc_info.ecc_size;
        int size = ecc_block_size;

        if (!ecc_size)
                return;

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

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

static int persistent_ram_init_ecc(struct persistent_ram_zone *prz,
                                   struct persistent_ram_ecc_info *ecc_info)
{
        int numerr;
        struct persistent_ram_buffer *buffer = prz->buffer;
        size_t ecc_blocks;
        size_t ecc_total;

        if (!ecc_info || !ecc_info->ecc_size)
                return 0;

        prz->ecc_info.block_size = ecc_info->block_size ?: 128;
        prz->ecc_info.ecc_size = ecc_info->ecc_size ?: 16;
        prz->ecc_info.symsize = ecc_info->symsize ?: 8;
        prz->ecc_info.poly = ecc_info->poly ?: 0x11d;

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

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

        /* allocate workspace instead of using stack VLA */
        prz->ecc_info.par = kmalloc_objs(*prz->ecc_info.par,
                                         prz->ecc_info.ecc_size);
        if (!prz->ecc_info.par) {
                pr_err("cannot allocate ECC parity workspace\n");
                return -ENOMEM;
        }

        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("error in header, %d\n", numerr);
                prz->corrected_bytes += numerr;
        } else if (numerr < 0) {
                pr_info_ratelimited("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->ecc_info.ecc_size)
                return 0;

        if (prz->corrected_bytes || prz->bad_blocks)
                ret = snprintf(str, len, ""
                        "\nECC: %d Corrected bytes, %d unrecoverable blocks\n",
                        prz->corrected_bytes, prz->bad_blocks);
        else
                ret = snprintf(str, len, "\nECC: No 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_toio(buffer->data + start, s, count);
        persistent_ram_update_ecc(prz, start, count);
}

static int notrace persistent_ram_update_user(struct persistent_ram_zone *prz,
        const void __user *s, unsigned int start, unsigned int count)
{
        struct persistent_ram_buffer *buffer = prz->buffer;
        int ret = unlikely(copy_from_user(buffer->data + start, s, count)) ?
                -EFAULT : 0;
        persistent_ram_update_ecc(prz, start, count);
        return ret;
}

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 the existing buffer is differently sized, free it so a new
         * one is allocated. This can happen when persistent_ram_save_old()
         * is called early in boot and later for a timer-triggered
         * survivable crash when the crash dumps don't match in size
         * (which would be extremely unlikely given kmsg buffers usually
         * exceed prz buffer sizes).
         */
        if (prz->old_log && prz->old_log_size != size)
                persistent_ram_free_old(prz);

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

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

int notrace persistent_ram_write_user(struct persistent_ram_zone *prz,
        const void __user *s, unsigned int count)
{
        int rem, ret = 0, 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)) {
                ret = persistent_ram_update_user(prz, s, start, rem);
                s += rem;
                c -= rem;
                start = 0;
        }
        if (likely(!ret))
                ret = persistent_ram_update_user(prz, s, start, c);

        persistent_ram_update_header_ecc(prz);

        return unlikely(ret) ? ret : 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)
{
        kvfree(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);
}

#define MEM_TYPE_WCOMBINE       0
#define MEM_TYPE_NONCACHED      1
#define MEM_TYPE_NORMAL         2

static void *persistent_ram_vmap(phys_addr_t start, size_t size,
                unsigned int memtype)
{
        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);

        switch (memtype) {
        case MEM_TYPE_NORMAL:
                prot = PAGE_KERNEL;
                break;
        case MEM_TYPE_NONCACHED:
                prot = pgprot_noncached(PAGE_KERNEL);
                break;
        case MEM_TYPE_WCOMBINE:
                prot = pgprot_writecombine(PAGE_KERNEL);
                break;
        default:
                pr_err("invalid mem_type=%d\n", memtype);
                return NULL;
        }

        pages = kmalloc_objs(struct page *, page_count);
        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);
        }
        /*
         * VM_IOREMAP used here to bypass this region during vread()
         * and kmap_atomic() (i.e. kcore) to avoid __va() failures.
         */
        vaddr = vmap(pages, page_count, VM_MAP | VM_IOREMAP, prot);
        kfree(pages);

        /*
         * vmap() may fail and return NULL. Do not add the offset in this
         * case, otherwise a NULL mapping would appear successful.
         */
        if (!vaddr)
                return NULL;

        /*
         * Since vmap() uses page granularity, we must add the offset
         * into the page here, to get the byte granularity address
         * into the mapping to represent the actual "start" location.
         */
        return vaddr + offset_in_page(start);
}

static void *persistent_ram_iomap(phys_addr_t start, size_t size,
                unsigned int memtype, char *label)
{
        void *va;

        if (!request_mem_region(start, size, label ?: "ramoops")) {
                pr_err("request mem region (%s 0x%llx@0x%llx) failed\n",
                        label ?: "ramoops",
                        (unsigned long long)size, (unsigned long long)start);
                return NULL;
        }

        if (memtype)
                va = ioremap(start, size);
        else
                va = ioremap_wc(start, size);

        /*
         * Since request_mem_region() and ioremap() are byte-granularity
         * there is no need handle anything special like we do when the
         * vmap() case in persistent_ram_vmap() above.
         */
        return va;
}

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

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

        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;
        prz->buffer_size = size - sizeof(struct persistent_ram_buffer);

        return 0;
}

static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig,
                                    struct persistent_ram_ecc_info *ecc_info)
{
        int ret;
        bool zap = !!(prz->flags & PRZ_FLAG_ZAP_OLD);

        ret = persistent_ram_init_ecc(prz, ecc_info);
        if (ret) {
                pr_warn("ECC failed %s\n", prz->label);
                return ret;
        }

        sig ^= PERSISTENT_RAM_SIG;

        if (prz->buffer->sig == sig) {
                if (buffer_size(prz) == 0 && buffer_start(prz) == 0) {
                        pr_debug("found existing empty buffer\n");
                        return 0;
                }

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

        /* Reset missing, invalid, or single-use memory area. */
        if (zap)
                persistent_ram_zap(prz);

        return 0;
}

void persistent_ram_free(struct persistent_ram_zone **_prz)
{
        struct persistent_ram_zone *prz;

        if (!_prz)
                return;

        prz = *_prz;
        if (!prz)
                return;

        if (prz->vaddr) {
                if (pfn_valid(prz->paddr >> PAGE_SHIFT)) {
                        /* We must vunmap() at page-granularity. */
                        vunmap(prz->vaddr - offset_in_page(prz->paddr));
                } else {
                        iounmap(prz->vaddr);
                        release_mem_region(prz->paddr, prz->size);
                }
                prz->vaddr = NULL;
        }
        if (prz->rs_decoder) {
                free_rs(prz->rs_decoder);
                prz->rs_decoder = NULL;
        }
        kfree(prz->ecc_info.par);
        prz->ecc_info.par = NULL;

        persistent_ram_free_old(prz);
        kfree(prz->label);
        kfree(prz);
        *_prz = NULL;
}

struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
                        u32 sig, struct persistent_ram_ecc_info *ecc_info,
                        unsigned int memtype, u32 flags, char *label)
{
        struct persistent_ram_zone *prz;
        int ret = -ENOMEM;

        prz = kzalloc_obj(struct persistent_ram_zone);
        if (!prz) {
                pr_err("failed to allocate persistent ram zone\n");
                goto err;
        }

        /* Initialize general buffer state. */
        raw_spin_lock_init(&prz->buffer_lock);
        prz->flags = flags;
        prz->label = kstrdup(label, GFP_KERNEL);
        if (!prz->label)
                goto err;

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

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

        pr_debug("attached %s 0x%zx@0x%llx: %zu header, %zu data, %zu ecc (%d/%d)\n",
                prz->label, prz->size, (unsigned long long)prz->paddr,
                sizeof(*prz->buffer), prz->buffer_size,
                prz->size - sizeof(*prz->buffer) - prz->buffer_size,
                prz->ecc_info.ecc_size, prz->ecc_info.block_size);

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