// SPDX-License-Identifier: GPL-2.0
#include <linux/memblock.h>
#include <linux/compiler.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/ksm.h>
#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/huge_mm.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/hugetlb.h>
#include <linux/memcontrol.h>
#include <linux/mmu_notifier.h>
#include <linux/page_idle.h>
#include <linux/kernel-page-flags.h>
#include <linux/uaccess.h>
#include "internal.h"

#define KPMSIZE sizeof(u64)
#define KPMMASK (KPMSIZE - 1)
#define KPMBITS (KPMSIZE * BITS_PER_BYTE)

static inline unsigned long get_max_dump_pfn(void)
{
#ifdef CONFIG_SPARSEMEM
        /*
         * The memmap of early sections is completely populated and marked
         * online even if max_pfn does not fall on a section boundary -
         * pfn_to_online_page() will succeed on all pages. Allow inspecting
         * these memmaps.
         */
        return round_up(max_pfn, PAGES_PER_SECTION);
#else
        return max_pfn;
#endif
}

/* /proc/kpagecount - an array exposing page counts
 *
 * Each entry is a u64 representing the corresponding
 * physical page count.
 */
static ssize_t kpagecount_read(struct file *file, char __user *buf,
                             size_t count, loff_t *ppos)
{
        const unsigned long max_dump_pfn = get_max_dump_pfn();
        u64 __user *out = (u64 __user *)buf;
        struct page *ppage;
        unsigned long src = *ppos;
        unsigned long pfn;
        ssize_t ret = 0;
        u64 pcount;

        pfn = src / KPMSIZE;
        if (src & KPMMASK || count & KPMMASK)
                return -EINVAL;
        if (src >= max_dump_pfn * KPMSIZE)
                return 0;
        count = min_t(unsigned long, count, (max_dump_pfn * KPMSIZE) - src);

        while (count > 0) {
                /*
                 * TODO: ZONE_DEVICE support requires to identify
                 * memmaps that were actually initialized.
                 */
                ppage = pfn_to_online_page(pfn);

                if (!ppage || PageSlab(ppage) || page_has_type(ppage))
                        pcount = 0;
                else
                        pcount = page_mapcount(ppage);

                if (put_user(pcount, out)) {
                        ret = -EFAULT;
                        break;
                }

                pfn++;
                out++;
                count -= KPMSIZE;

                cond_resched();
        }

        *ppos += (char __user *)out - buf;
        if (!ret)
                ret = (char __user *)out - buf;
        return ret;
}

static const struct proc_ops kpagecount_proc_ops = {
        .proc_lseek     = mem_lseek,
        .proc_read      = kpagecount_read,
};

/* /proc/kpageflags - an array exposing page flags
 *
 * Each entry is a u64 representing the corresponding
 * physical page flags.
 */

static inline u64 kpf_copy_bit(u64 kflags, int ubit, int kbit)
{
        return ((kflags >> kbit) & 1) << ubit;
}

u64 stable_page_flags(struct page *page)
{
        u64 k;
        u64 u;

        /*
         * pseudo flag: KPF_NOPAGE
         * it differentiates a memory hole from a page with no flags
         */
        if (!page)
                return 1 << KPF_NOPAGE;

        k = page->flags;
        u = 0;

        /*
         * pseudo flags for the well known (anonymous) memory mapped pages
         *
         * Note that page->_mapcount is overloaded in SLOB/SLUB/SLQB, so the
         * simple test in page_mapped() is not enough.
         */
        if (!PageSlab(page) && page_mapped(page))
                u |= 1 << KPF_MMAP;
        if (PageAnon(page))
                u |= 1 << KPF_ANON;
        if (PageKsm(page))
                u |= 1 << KPF_KSM;

        /*
         * compound pages: export both head/tail info
         * they together define a compound page's start/end pos and order
         */
        if (PageHead(page))
                u |= 1 << KPF_COMPOUND_HEAD;
        if (PageTail(page))
                u |= 1 << KPF_COMPOUND_TAIL;
        if (PageHuge(page))
                u |= 1 << KPF_HUGE;
        /*
         * PageTransCompound can be true for non-huge compound pages (slab
         * pages or pages allocated by drivers with __GFP_COMP) because it
         * just checks PG_head/PG_tail, so we need to check PageLRU/PageAnon
         * to make sure a given page is a thp, not a non-huge compound page.
         */
        else if (PageTransCompound(page)) {
                struct page *head = compound_head(page);

                if (PageLRU(head) || PageAnon(head))
                        u |= 1 << KPF_THP;
                else if (is_huge_zero_page(head)) {
                        u |= 1 << KPF_ZERO_PAGE;
                        u |= 1 << KPF_THP;
                }
        } else if (is_zero_pfn(page_to_pfn(page)))
                u |= 1 << KPF_ZERO_PAGE;


        /*
         * Caveats on high order pages: page->_refcount will only be set
         * -1 on the head page; SLUB/SLQB do the same for PG_slab;
         * SLOB won't set PG_slab at all on compound pages.
         */
        if (PageBuddy(page))
                u |= 1 << KPF_BUDDY;
        else if (page_count(page) == 0 && is_free_buddy_page(page))
                u |= 1 << KPF_BUDDY;

        if (PageOffline(page))
                u |= 1 << KPF_OFFLINE;
        if (PageTable(page))
                u |= 1 << KPF_PGTABLE;

        if (page_is_idle(page))
                u |= 1 << KPF_IDLE;

        u |= kpf_copy_bit(k, KPF_LOCKED,        PG_locked);

        u |= kpf_copy_bit(k, KPF_SLAB,          PG_slab);
        if (PageTail(page) && PageSlab(compound_head(page)))
                u |= 1 << KPF_SLAB;

        u |= kpf_copy_bit(k, KPF_ERROR,         PG_error);
        u |= kpf_copy_bit(k, KPF_DIRTY,         PG_dirty);
        u |= kpf_copy_bit(k, KPF_UPTODATE,      PG_uptodate);
        u |= kpf_copy_bit(k, KPF_WRITEBACK,     PG_writeback);

        u |= kpf_copy_bit(k, KPF_LRU,           PG_lru);
        u |= kpf_copy_bit(k, KPF_REFERENCED,    PG_referenced);
        u |= kpf_copy_bit(k, KPF_ACTIVE,        PG_active);
        u |= kpf_copy_bit(k, KPF_RECLAIM,       PG_reclaim);

        if (PageSwapCache(page))
                u |= 1 << KPF_SWAPCACHE;
        u |= kpf_copy_bit(k, KPF_SWAPBACKED,    PG_swapbacked);

        u |= kpf_copy_bit(k, KPF_UNEVICTABLE,   PG_unevictable);
        u |= kpf_copy_bit(k, KPF_MLOCKED,       PG_mlocked);

#ifdef CONFIG_MEMORY_FAILURE
        u |= kpf_copy_bit(k, KPF_HWPOISON,      PG_hwpoison);
#endif

#ifdef CONFIG_ARCH_USES_PG_UNCACHED
        u |= kpf_copy_bit(k, KPF_UNCACHED,      PG_uncached);
#endif

        u |= kpf_copy_bit(k, KPF_RESERVED,      PG_reserved);
        u |= kpf_copy_bit(k, KPF_MAPPEDTODISK,  PG_mappedtodisk);
        u |= kpf_copy_bit(k, KPF_PRIVATE,       PG_private);
        u |= kpf_copy_bit(k, KPF_PRIVATE_2,     PG_private_2);
        u |= kpf_copy_bit(k, KPF_OWNER_PRIVATE, PG_owner_priv_1);
        u |= kpf_copy_bit(k, KPF_ARCH,          PG_arch_1);
#ifdef CONFIG_64BIT
        u |= kpf_copy_bit(k, KPF_ARCH_2,        PG_arch_2);
#endif

        return u;
};

static ssize_t kpageflags_read(struct file *file, char __user *buf,
                             size_t count, loff_t *ppos)
{
        const unsigned long max_dump_pfn = get_max_dump_pfn();
        u64 __user *out = (u64 __user *)buf;
        struct page *ppage;
        unsigned long src = *ppos;
        unsigned long pfn;
        ssize_t ret = 0;

        pfn = src / KPMSIZE;
        if (src & KPMMASK || count & KPMMASK)
                return -EINVAL;
        if (src >= max_dump_pfn * KPMSIZE)
                return 0;
        count = min_t(unsigned long, count, (max_dump_pfn * KPMSIZE) - src);

        while (count > 0) {
                /*
                 * TODO: ZONE_DEVICE support requires to identify
                 * memmaps that were actually initialized.
                 */
                ppage = pfn_to_online_page(pfn);

                if (put_user(stable_page_flags(ppage), out)) {
                        ret = -EFAULT;
                        break;
                }

                pfn++;
                out++;
                count -= KPMSIZE;

                cond_resched();
        }

        *ppos += (char __user *)out - buf;
        if (!ret)
                ret = (char __user *)out - buf;
        return ret;
}

static const struct proc_ops kpageflags_proc_ops = {
        .proc_lseek     = mem_lseek,
        .proc_read      = kpageflags_read,
};

#ifdef CONFIG_MEMCG
static ssize_t kpagecgroup_read(struct file *file, char __user *buf,
                                size_t count, loff_t *ppos)
{
        const unsigned long max_dump_pfn = get_max_dump_pfn();
        u64 __user *out = (u64 __user *)buf;
        struct page *ppage;
        unsigned long src = *ppos;
        unsigned long pfn;
        ssize_t ret = 0;
        u64 ino;

        pfn = src / KPMSIZE;
        if (src & KPMMASK || count & KPMMASK)
                return -EINVAL;
        if (src >= max_dump_pfn * KPMSIZE)
                return 0;
        count = min_t(unsigned long, count, (max_dump_pfn * KPMSIZE) - src);

        while (count > 0) {
                /*
                 * TODO: ZONE_DEVICE support requires to identify
                 * memmaps that were actually initialized.
                 */
                ppage = pfn_to_online_page(pfn);

                if (ppage)
                        ino = page_cgroup_ino(ppage);
                else
                        ino = 0;

                if (put_user(ino, out)) {
                        ret = -EFAULT;
                        break;
                }

                pfn++;
                out++;
                count -= KPMSIZE;

                cond_resched();
        }

        *ppos += (char __user *)out - buf;
        if (!ret)
                ret = (char __user *)out - buf;
        return ret;
}

static const struct proc_ops kpagecgroup_proc_ops = {
        .proc_lseek     = mem_lseek,
        .proc_read      = kpagecgroup_read,
};
#endif /* CONFIG_MEMCG */

static int __init proc_page_init(void)
{
        proc_create("kpagecount", S_IRUSR, NULL, &kpagecount_proc_ops);
        proc_create("kpageflags", S_IRUSR, NULL, &kpageflags_proc_ops);
#ifdef CONFIG_MEMCG
        proc_create("kpagecgroup", S_IRUSR, NULL, &kpagecgroup_proc_ops);
#endif
        return 0;
}
fs_initcall(proc_page_init);