page.c

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#include <linux/bootmem.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/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/hugetlb.h>
#include <linux/kernel-page-flags.h>
#include <asm/uaccess.h>
#include "internal.h"

#define KPMSIZE sizeof(u64)
#define KPMMASK (KPMSIZE - 1)

/* /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)
{
    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;
    count = min_t(size_t, count, (max_pfn * KPMSIZE) - src);
    if (src & KPMMASK || count & KPMMASK)
        return -EINVAL;

    while (count > 0) {
        if (pfn_valid(pfn))
            ppage = pfn_to_page(pfn);
        else
            ppage = NULL;
        if (!ppage || PageSlab(ppage))
            pcount = 0;
        else
            pcount = page_mapcount(ppage);

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

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

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

static const struct file_operations proc_kpagecount_operations = {
    .llseek = mem_lseek,
    .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 to make
     * sure a given page is a thp, not a non-huge compound page.
     */
    else if (PageTransCompound(page) && PageLRU(compound_trans_head(page)))
        u |= 1 << KPF_THP;

    /*
     * Caveats on high order pages: page->_count 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;

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

    u |= kpf_copy_bit(k, KPF_SLAB,      PG_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);

    u |= kpf_copy_bit(k, KPF_SWAPCACHE, PG_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);

    return u;
};

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

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

    while (count > 0) {
        if (pfn_valid(pfn))
            ppage = pfn_to_page(pfn);
        else
            ppage = NULL;

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

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

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

static const struct file_operations proc_kpageflags_operations = {
    .llseek = mem_lseek,
    .read = kpageflags_read,
};

static int __init proc_page_init(void)
{
    proc_create("kpagecount", S_IRUSR, NULL, &proc_kpagecount_operations);
    proc_create("kpageflags", S_IRUSR, NULL, &proc_kpageflags_operations);
    return 0;
}
module_init(proc_page_init);