// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) IBM Corporation, 2014, 2017
 * Anton Blanchard, Rashmica Gupta.
 */

#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 <linux/numa.h>
#include <asm/machdep.h>
#include <asm/cacheflush.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 DEFINE_MUTEX(memtrace_mutex);
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 int memtrace_mmap(struct file *filp, struct vm_area_struct *vma)
{
        struct memtrace_entry *ent = filp->private_data;

        if (ent->size < vma->vm_end - vma->vm_start)
                return -EINVAL;

        if (vma->vm_pgoff << PAGE_SHIFT >= ent->size)
                return -EINVAL;

        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
        return remap_pfn_range(vma, vma->vm_start, PHYS_PFN(ent->start) + vma->vm_pgoff,
                               vma->vm_end - vma->vm_start, vma->vm_page_prot);
}

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

#define FLUSH_CHUNK_SIZE SZ_1G
/**
 * flush_dcache_range_chunked(): Write any modified data cache blocks out to
 * memory and invalidate them, in chunks of up to FLUSH_CHUNK_SIZE
 * Does not invalidate the corresponding instruction cache blocks.
 *
 * @start: the start address
 * @stop: the stop address (exclusive)
 * @chunk: the max size of the chunks
 */
static void flush_dcache_range_chunked(unsigned long start, unsigned long stop,
                                       unsigned long chunk)
{
        unsigned long i;

        for (i = start; i < stop; i += chunk) {
                flush_dcache_range(i, min(stop, i + chunk));
                cond_resched();
        }
}

static void memtrace_clear_range(unsigned long start_pfn,
                                 unsigned long nr_pages)
{
        unsigned long pfn;

        /* As HIGHMEM does not apply, use clear_page() directly. */
        for (pfn = start_pfn; pfn < start_pfn + nr_pages; pfn++) {
                if (IS_ALIGNED(pfn, PAGES_PER_SECTION))
                        cond_resched();
                clear_page(__va(PFN_PHYS(pfn)));
        }
        /*
         * Before we go ahead and use this range as cache inhibited range
         * flush the cache.
         */
        flush_dcache_range_chunked((unsigned long)pfn_to_kaddr(start_pfn),
                                   (unsigned long)pfn_to_kaddr(start_pfn + nr_pages),
                                   FLUSH_CHUNK_SIZE);
}

static u64 memtrace_alloc_node(u32 nid, u64 size)
{
        const unsigned long nr_pages = PHYS_PFN(size);
        unsigned long pfn, start_pfn;
        struct page *page;

        /*
         * Trace memory needs to be aligned to the size, which is guaranteed
         * by alloc_contig_pages().
         */
        page = alloc_contig_pages(nr_pages, GFP_KERNEL | __GFP_THISNODE |
                                  __GFP_NOWARN, nid, NULL);
        if (!page)
                return 0;
        start_pfn = page_to_pfn(page);

        /*
         * Clear the range while we still have a linear mapping.
         *
         * TODO: use __GFP_ZERO with alloc_contig_pages() once supported.
         */
        memtrace_clear_range(start_pfn, nr_pages);

        /*
         * Set pages PageOffline(), to indicate that nobody (e.g., hibernation,
         * dumping, ...) should be touching these pages.
         */
        for (pfn = start_pfn; pfn < start_pfn + nr_pages; pfn++)
                __SetPageOffline(pfn_to_page(pfn));

        arch_remove_linear_mapping(PFN_PHYS(start_pfn), size);

        return PFN_PHYS(start_pfn);
}

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);

                ent->dir = dir;
                debugfs_create_file_unsafe("trace", 0600, 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_free(int nid, u64 start, u64 size)
{
        struct mhp_params params = { .pgprot = PAGE_KERNEL };
        const unsigned long nr_pages = PHYS_PFN(size);
        const unsigned long start_pfn = PHYS_PFN(start);
        unsigned long pfn;
        int ret;

        ret = arch_create_linear_mapping(nid, start, size, &params);
        if (ret)
                return ret;

        for (pfn = start_pfn; pfn < start_pfn + nr_pages; pfn++)
                __ClearPageOffline(pfn_to_page(pfn));

        free_contig_range(start_pfn, nr_pages);
        return 0;
}

/*
 * Iterate through the chunks of memory we allocated and attempt to expose
 * them back to the kernel.
 */
static int memtrace_free_regions(void)
{
        int i, ret = 0;
        struct memtrace_entry *ent;

        for (i = memtrace_array_nr - 1; i >= 0; i--) {
                ent = &memtrace_array[i];

                /* We have freed this chunk previously */
                if (ent->nid == NUMA_NO_NODE)
                        continue;

                /* Remove from io mappings */
                if (ent->mem) {
                        iounmap(ent->mem);
                        ent->mem = 0;
                }

                if (memtrace_free(ent->nid, ent->start, ent->size)) {
                        pr_err("Failed to free trace memory on node %d\n",
                                ent->nid);
                        ret += 1;
                        continue;
                }

                /*
                 * Memory was freed successfully so clean up references to it
                 * so on reentry we can tell that this chunk was freed.
                 */
                debugfs_remove_recursive(ent->dir);
                pr_info("Freed trace memory back on node %d\n", ent->nid);
                ent->size = ent->start = ent->nid = NUMA_NO_NODE;
        }
        if (ret)
                return ret;

        /* If all chunks of memory were freed successfully, reset globals */
        kfree(memtrace_array);
        memtrace_array = NULL;
        memtrace_size = 0;
        memtrace_array_nr = 0;
        return 0;
}

static int memtrace_enable_set(void *data, u64 val)
{
        int rc = -EAGAIN;
        u64 bytes;

        /*
         * Don't attempt to do anything if size isn't aligned to a memory
         * block or equal to zero.
         */
        bytes = memory_block_size_bytes();
        if (val & (bytes - 1)) {
                pr_err("Value must be aligned with 0x%llx\n", bytes);
                return -EINVAL;
        }

        mutex_lock(&memtrace_mutex);

        /* Free all previously allocated memory. */
        if (memtrace_size && memtrace_free_regions())
                goto out_unlock;

        if (!val) {
                rc = 0;
                goto out_unlock;
        }

        /* Allocate memory. */
        if (memtrace_init_regions_runtime(val))
                goto out_unlock;

        if (memtrace_init_debugfs())
                goto out_unlock;

        memtrace_size = val;
        rc = 0;
out_unlock:
        mutex_unlock(&memtrace_mutex);
        return rc;
}

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",
                                                  arch_debugfs_dir);

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

        return 0;
}
machine_device_initcall(powernv, memtrace_init);