// 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/memremap.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)

enum kpage_operation {
        KPAGE_FLAGS,
        KPAGE_COUNT,
        KPAGE_CGROUP,
};

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
}

static u64 get_kpage_count(const struct page *page)
{
        struct page_snapshot ps;
        u64 ret;

        snapshot_page(&ps, page);

        if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT))
                ret = folio_precise_page_mapcount(&ps.folio_snapshot,
                                                  &ps.page_snapshot);
        else
                ret = folio_average_page_mapcount(&ps.folio_snapshot);

        return ret;
}

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

        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.
                 */
                page = pfn_to_online_page(pfn);

                if (page) {
                        switch (op) {
                        case KPAGE_FLAGS:
                                info = stable_page_flags(page);
                                break;
                        case KPAGE_COUNT:
                                info = get_kpage_count(page);
                                break;
                        case KPAGE_CGROUP:
                                info = page_cgroup_ino(page);
                                break;
                        default:
                                info = 0;
                                break;
                        }
                } else
                        info = 0;

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

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

                cond_resched();
        }

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

/* /proc/kpagecount - an array exposing page mapcounts
 *
 * Each entry is a u64 representing the corresponding
 * physical page mapcount.
 */
static ssize_t kpagecount_read(struct file *file, char __user *buf,
                size_t count, loff_t *ppos)
{
        return kpage_read(file, buf, count, ppos, KPAGE_COUNT);
}

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


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

u64 stable_page_flags(const struct page *page)
{
        const struct folio *folio;
        struct page_snapshot ps;
        unsigned long k;
        unsigned long mapping;
        bool is_anon;
        u64 u = 0;

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

        snapshot_page(&ps, page);
        folio = &ps.folio_snapshot;

        k = folio->flags.f;
        mapping = (unsigned long)folio->mapping;
        is_anon = mapping & FOLIO_MAPPING_ANON;

        /*
         * pseudo flags for the well known (anonymous) memory mapped pages
         */
        if (folio_mapped(folio))
                u |= 1 << KPF_MMAP;
        if (is_anon) {
                u |= 1 << KPF_ANON;
                if (mapping & FOLIO_MAPPING_KSM)
                        u |= 1 << KPF_KSM;
        }

        /*
         * compound pages: export both head/tail info
         * they together define a compound page's start/end pos and order
         */
        if (ps.idx == 0)
                u |= kpf_copy_bit(k, KPF_COMPOUND_HEAD, PG_head);
        else
                u |= 1 << KPF_COMPOUND_TAIL;
        if (folio_test_hugetlb(folio))
                u |= 1 << KPF_HUGE;
        else if (folio_test_large(folio) &&
                 folio_test_large_rmappable(folio)) {
                /* Note: we indicate any THPs here, not just PMD-sized ones */
                u |= 1 << KPF_THP;
        } else if (is_huge_zero_pfn(ps.pfn)) {
                u |= 1 << KPF_ZERO_PAGE;
                u |= 1 << KPF_THP;
        } else if (is_zero_pfn(ps.pfn)) {
                u |= 1 << KPF_ZERO_PAGE;
        }

        if (ps.flags & PAGE_SNAPSHOT_PG_BUDDY)
                u |= 1 << KPF_BUDDY;

        if (folio_test_offline(folio))
                u |= 1 << KPF_OFFLINE;
        if (folio_test_pgtable(folio))
                u |= 1 << KPF_PGTABLE;
        if (folio_test_slab(folio))
                u |= 1 << KPF_SLAB;

#if defined(CONFIG_PAGE_IDLE_FLAG) && defined(CONFIG_64BIT)
        u |= kpf_copy_bit(k, KPF_IDLE,          PG_idle);
#else
        if (ps.flags & PAGE_SNAPSHOT_PG_IDLE)
                u |= 1 << KPF_IDLE;
#endif

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

#define SWAPCACHE ((1 << PG_swapbacked) | (1 << PG_swapcache))
        if ((k & SWAPCACHE) == SWAPCACHE)
                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
        if (u & (1 << KPF_HUGE))
                u |= kpf_copy_bit(k, KPF_HWPOISON,      PG_hwpoison);
        else
                u |= kpf_copy_bit(ps.page_snapshot.flags.f, KPF_HWPOISON, PG_hwpoison);
#endif

        u |= kpf_copy_bit(k, KPF_RESERVED,      PG_reserved);
        u |= kpf_copy_bit(k, KPF_OWNER_2,       PG_owner_2);
        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_ARCH_USES_PG_ARCH_2
        u |= kpf_copy_bit(k, KPF_ARCH_2,        PG_arch_2);
#endif
#ifdef CONFIG_ARCH_USES_PG_ARCH_3
        u |= kpf_copy_bit(k, KPF_ARCH_3,        PG_arch_3);
#endif

        return u;
}
EXPORT_SYMBOL_GPL(stable_page_flags);

/* /proc/kpageflags - an array exposing page flags
 *
 * Each entry is a u64 representing the corresponding
 * physical page flags.
 */
static ssize_t kpageflags_read(struct file *file, char __user *buf,
                size_t count, loff_t *ppos)
{
        return kpage_read(file, buf, count, ppos, KPAGE_FLAGS);
}

static const struct proc_ops kpageflags_proc_ops = {
        .proc_flags     = PROC_ENTRY_PERMANENT,
        .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)
{
        return kpage_read(file, buf, count, ppos, KPAGE_CGROUP);
}
static const struct proc_ops kpagecgroup_proc_ops = {
        .proc_flags     = PROC_ENTRY_PERMANENT,
        .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);