/*
 * Copyright (C) IBM Corporation, 2014, 2017
 * Anton Blanchard, Rashmica Gupta.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#define pr_fmt(fmt) "memtrace: " fmt

#include <linux/bitops.h>
#include <linux/string.h>
#include <linux/memblock.h>
#include <linux/init.h>
#include <linux/moduleparam.h>
#include <linux/fs.h>
#include <linux/debugfs.h>
#include <linux/slab.h>
#include <linux/memory.h>
#include <linux/memory_hotplug.h>
#include <asm/machdep.h>
#include <asm/debugfs.h>

/* This enables us to keep track of the memory removed from each node. */
struct memtrace_entry {
        void *mem;
        u64 start;
        u64 size;
        u32 nid;
        struct dentry *dir;
        char name[16];
};

static u64 memtrace_size;

static struct memtrace_entry *memtrace_array;
static unsigned int memtrace_array_nr;


static ssize_t memtrace_read(struct file *filp, char __user *ubuf,
                             size_t count, loff_t *ppos)
{
        struct memtrace_entry *ent = filp->private_data;

        return simple_read_from_buffer(ubuf, count, ppos, ent->mem, ent->size);
}

static bool valid_memtrace_range(struct memtrace_entry *dev,
                                 unsigned long start, unsigned long size)
{
        if ((start >= dev->start) &&
            ((start + size) <= (dev->start + dev->size)))
                return true;

        return false;
}

static int memtrace_mmap(struct file *filp, struct vm_area_struct *vma)
{
        unsigned long size = vma->vm_end - vma->vm_start;
        struct memtrace_entry *dev = filp->private_data;

        if (!valid_memtrace_range(dev, vma->vm_pgoff << PAGE_SHIFT, size))
                return -EINVAL;

        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

        if (remap_pfn_range(vma, vma->vm_start,
                            vma->vm_pgoff + (dev->start >> PAGE_SHIFT),
                            size, vma->vm_page_prot))
                return -EAGAIN;

        return 0;
}

static const struct file_operations memtrace_fops = {
        .llseek = default_llseek,
        .read   = memtrace_read,
        .mmap   = memtrace_mmap,
        .open   = simple_open,
};

static void flush_memory_region(u64 base, u64 size)
{
        unsigned long line_size = ppc64_caches.l1d.size;
        u64 end = base + size;
        u64 addr;

        base = round_down(base, line_size);
        end = round_up(end, line_size);

        for (addr = base; addr < end; addr += line_size)
                asm volatile("dcbf 0,%0" : "=r" (addr) :: "memory");
}

static int check_memblock_online(struct memory_block *mem, void *arg)
{
        if (mem->state != MEM_ONLINE)
                return -1;

        return 0;
}

static int change_memblock_state(struct memory_block *mem, void *arg)
{
        unsigned long state = (unsigned long)arg;

        mem->state = state;

        return 0;
}

static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages)
{
        u64 end_pfn = start_pfn + nr_pages - 1;

        if (walk_memory_range(start_pfn, end_pfn, NULL,
            check_memblock_online))
                return false;

        walk_memory_range(start_pfn, end_pfn, (void *)MEM_GOING_OFFLINE,
                          change_memblock_state);

        if (offline_pages(start_pfn, nr_pages)) {
                walk_memory_range(start_pfn, end_pfn, (void *)MEM_ONLINE,
                                  change_memblock_state);
                return false;
        }

        walk_memory_range(start_pfn, end_pfn, (void *)MEM_OFFLINE,
                          change_memblock_state);

        /* RCU grace period? */
        flush_memory_region((u64)__va(start_pfn << PAGE_SHIFT),
                            nr_pages << PAGE_SHIFT);

        lock_device_hotplug();
        remove_memory(nid, start_pfn << PAGE_SHIFT, nr_pages << PAGE_SHIFT);
        unlock_device_hotplug();

        return true;
}

static u64 memtrace_alloc_node(u32 nid, u64 size)
{
        u64 start_pfn, end_pfn, nr_pages;
        u64 base_pfn;

        if (!NODE_DATA(nid) || !node_spanned_pages(nid))
                return 0;

        start_pfn = node_start_pfn(nid);
        end_pfn = node_end_pfn(nid);
        nr_pages = size >> PAGE_SHIFT;

        /* Trace memory needs to be aligned to the size */
        end_pfn = round_down(end_pfn - nr_pages, nr_pages);

        for (base_pfn = end_pfn; base_pfn > start_pfn; base_pfn -= nr_pages) {
                if (memtrace_offline_pages(nid, base_pfn, nr_pages) == true)
                        return base_pfn << PAGE_SHIFT;
        }

        return 0;
}

static int memtrace_init_regions_runtime(u64 size)
{
        u32 nid;
        u64 m;

        memtrace_array = kcalloc(num_online_nodes(),
                                sizeof(struct memtrace_entry), GFP_KERNEL);
        if (!memtrace_array) {
                pr_err("Failed to allocate memtrace_array\n");
                return -EINVAL;
        }

        for_each_online_node(nid) {
                m = memtrace_alloc_node(nid, size);

                /*
                 * A node might not have any local memory, so warn but
                 * continue on.
                 */
                if (!m) {
                        pr_err("Failed to allocate trace memory on node %d\n", nid);
                        continue;
                }

                pr_info("Allocated trace memory on node %d at 0x%016llx\n", nid, m);

                memtrace_array[memtrace_array_nr].start = m;
                memtrace_array[memtrace_array_nr].size = size;
                memtrace_array[memtrace_array_nr].nid = nid;
                memtrace_array_nr++;
        }

        return 0;
}

static struct dentry *memtrace_debugfs_dir;

static int memtrace_init_debugfs(void)
{
        int ret = 0;
        int i;

        for (i = 0; i < memtrace_array_nr; i++) {
                struct dentry *dir;
                struct memtrace_entry *ent = &memtrace_array[i];

                ent->mem = ioremap(ent->start, ent->size);
                /* Warn but continue on */
                if (!ent->mem) {
                        pr_err("Failed to map trace memory at 0x%llx\n",
                                 ent->start);
                        ret = -1;
                        continue;
                }

                snprintf(ent->name, 16, "%08x", ent->nid);
                dir = debugfs_create_dir(ent->name, memtrace_debugfs_dir);
                if (!dir)
                        return -1;

                ent->dir = dir;
                debugfs_create_file("trace", 0400, dir, ent, &memtrace_fops);
                debugfs_create_x64("start", 0400, dir, &ent->start);
                debugfs_create_x64("size", 0400, dir, &ent->size);
        }

        return ret;
}

static int memtrace_enable_set(void *data, u64 val)
{
        if (memtrace_size)
                return -EINVAL;

        if (!val)
                return -EINVAL;

        /* Make sure size is aligned to a memory block */
        if (val & (memory_block_size_bytes() - 1))
                return -EINVAL;

        if (memtrace_init_regions_runtime(val))
                return -EINVAL;

        if (memtrace_init_debugfs())
                return -EINVAL;

        memtrace_size = val;

        return 0;
}

static int memtrace_enable_get(void *data, u64 *val)
{
        *val = memtrace_size;
        return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(memtrace_init_fops, memtrace_enable_get,
                                        memtrace_enable_set, "0x%016llx\n");

static int memtrace_init(void)
{
        memtrace_debugfs_dir = debugfs_create_dir("memtrace",
                                                  powerpc_debugfs_root);
        if (!memtrace_debugfs_dir)
                return -1;

        debugfs_create_file("enable", 0600, memtrace_debugfs_dir,
                            NULL, &memtrace_init_fops);

        return 0;
}
machine_device_initcall(powernv, memtrace_init);