fs/proc/page.c

   1 #include <linux/bootmem.h>
   2 #include <linux/compiler.h>
   3 #include <linux/fs.h>
   4 #include <linux/init.h>
   5 #include <linux/ksm.h>
   6 #include <linux/mm.h>
   7 #include <linux/mmzone.h>
   8 #include <linux/huge_mm.h>
   9 #include <linux/proc_fs.h>
  10 #include <linux/seq_file.h>
  11 #include <linux/hugetlb.h>
  12 #include <linux/kernel-page-flags.h>
  13 #include <asm/uaccess.h>
  14 #include "internal.h"
  15
  16 #define KPMSIZE sizeof(u64)
  17 #define KPMMASK (KPMSIZE - 1)
  18
  19 /* /proc/kpagecount - an array exposing page counts
  20  *
  21  * Each entry is a u64 representing the corresponding
  22  * physical page count.
  23  */
  24 static ssize_t kpagecount_read(struct file *file, char __user *buf,
  25                              size_t count, loff_t *ppos)
  26 {
  27         u64 __user *out = (u64 __user *)buf;
  28         struct page *ppage;
  29         unsigned long src = *ppos;
  30         unsigned long pfn;
  31         ssize_t ret = 0;
  32         u64 pcount;
  33
  34         pfn = src / KPMSIZE;
  35         count = min_t(size_t, count, (max_pfn * KPMSIZE) - src);
  36         if (src & KPMMASK || count & KPMMASK)
  37                 return -EINVAL;
  38
  39         while (count > 0) {
  40                 if (pfn_valid(pfn))
  41                         ppage = pfn_to_page(pfn);
  42                 else
  43                         ppage = NULL;
  44                 if (!ppage || PageSlab(ppage))
  45                         pcount = 0;
  46                 else
  47                         pcount = page_mapcount(ppage);
  48
  49                 if (put_user(pcount, out)) {
  50                         ret = -EFAULT;
  51                         break;
  52                 }
  53
  54                 pfn++;
  55                 out++;
  56                 count -= KPMSIZE;
  57         }
  58
  59         *ppos += (char __user *)out - buf;
  60         if (!ret)
  61                 ret = (char __user *)out - buf;
  62         return ret;
  63 }
  64
  65 static const struct file_operations proc_kpagecount_operations = {
  66         .llseek = mem_lseek,
  67         .read = kpagecount_read,
  68 };
  69
  70 /* /proc/kpageflags - an array exposing page flags
  71  *
  72  * Each entry is a u64 representing the corresponding
  73  * physical page flags.
  74  */
  75
  76 static inline u64 kpf_copy_bit(u64 kflags, int ubit, int kbit)
  77 {
  78         return ((kflags >> kbit) & 1) << ubit;
  79 }
  80
  81 u64 stable_page_flags(struct page *page)
  82 {
  83         u64 k;
  84         u64 u;
  85
  86         /*
  87          * pseudo flag: KPF_NOPAGE
  88          * it differentiates a memory hole from a page with no flags
  89          */
  90         if (!page)
  91                 return 1 << KPF_NOPAGE;
  92
  93         k = page->flags;
  94         u = 0;
  95
  96         /*
  97          * pseudo flags for the well known (anonymous) memory mapped pages
  98          *
  99          * Note that page->_mapcount is overloaded in SLOB/SLUB/SLQB, so the
 100          * simple test in page_mapped() is not enough.
 101          */
 102         if (!PageSlab(page) && page_mapped(page))
 103                 u |= 1 << KPF_MMAP;
 104         if (PageAnon(page))
 105                 u |= 1 << KPF_ANON;
 106         if (PageKsm(page))
 107                 u |= 1 << KPF_KSM;
 108
 109         /*
 110          * compound pages: export both head/tail info
 111          * they together define a compound page's start/end pos and order
 112          */
 113         if (PageHead(page))
 114                 u |= 1 << KPF_COMPOUND_HEAD;
 115         if (PageTail(page))
 116                 u |= 1 << KPF_COMPOUND_TAIL;
 117         if (PageHuge(page))
 118                 u |= 1 << KPF_HUGE;
 119         /*
 120          * PageTransCompound can be true for non-huge compound pages (slab
 121          * pages or pages allocated by drivers with __GFP_COMP) because it
 122          * just checks PG_head/PG_tail, so we need to check PageLRU/PageAnon
 123          * to make sure a given page is a thp, not a non-huge compound page.
 124          */
 125         else if (PageTransCompound(page)) {
 126                 struct page *head = compound_head(page);
 127
 128                 if (PageLRU(head) || PageAnon(head))
 129                         u |= 1 << KPF_THP;
 130                 else if (is_huge_zero_page(head)) {
 131                         u |= 1 << KPF_ZERO_PAGE;
 132                         u |= 1 << KPF_THP;
 133                 }
 134         } else if (is_zero_pfn(page_to_pfn(page)))
 135                 u |= 1 << KPF_ZERO_PAGE;
 136
 137
 138         /*
 139          * Caveats on high order pages: page->_count will only be set
 140          * -1 on the head page; SLUB/SLQB do the same for PG_slab;
 141          * SLOB won't set PG_slab at all on compound pages.
 142          */
 143         if (PageBuddy(page))
 144                 u |= 1 << KPF_BUDDY;
 145
 146         if (PageBalloon(page))
 147                 u |= 1 << KPF_BALLOON;
 148
 149         u |= kpf_copy_bit(k, KPF_LOCKED,        PG_locked);
 150
 151         u |= kpf_copy_bit(k, KPF_SLAB,          PG_slab);
 152
 153         u |= kpf_copy_bit(k, KPF_ERROR,         PG_error);
 154         u |= kpf_copy_bit(k, KPF_DIRTY,         PG_dirty);
 155         u |= kpf_copy_bit(k, KPF_UPTODATE,      PG_uptodate);
 156         u |= kpf_copy_bit(k, KPF_WRITEBACK,     PG_writeback);
 157
 158         u |= kpf_copy_bit(k, KPF_LRU,           PG_lru);
 159         u |= kpf_copy_bit(k, KPF_REFERENCED,    PG_referenced);
 160         u |= kpf_copy_bit(k, KPF_ACTIVE,        PG_active);
 161         u |= kpf_copy_bit(k, KPF_RECLAIM,       PG_reclaim);
 162
 163         u |= kpf_copy_bit(k, KPF_SWAPCACHE,     PG_swapcache);
 164         u |= kpf_copy_bit(k, KPF_SWAPBACKED,    PG_swapbacked);
 165
 166         u |= kpf_copy_bit(k, KPF_UNEVICTABLE,   PG_unevictable);
 167         u |= kpf_copy_bit(k, KPF_MLOCKED,       PG_mlocked);
 168
 169 #ifdef CONFIG_MEMORY_FAILURE
 170         u |= kpf_copy_bit(k, KPF_HWPOISON,      PG_hwpoison);
 171 #endif
 172
 173 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
 174         u |= kpf_copy_bit(k, KPF_UNCACHED,      PG_uncached);
 175 #endif
 176
 177         u |= kpf_copy_bit(k, KPF_RESERVED,      PG_reserved);
 178         u |= kpf_copy_bit(k, KPF_MAPPEDTODISK,  PG_mappedtodisk);
 179         u |= kpf_copy_bit(k, KPF_PRIVATE,       PG_private);
 180         u |= kpf_copy_bit(k, KPF_PRIVATE_2,     PG_private_2);
 181         u |= kpf_copy_bit(k, KPF_OWNER_PRIVATE, PG_owner_priv_1);
 182         u |= kpf_copy_bit(k, KPF_ARCH,          PG_arch_1);
 183
 184         return u;
 185 };
 186
 187 static ssize_t kpageflags_read(struct file *file, char __user *buf,
 188                              size_t count, loff_t *ppos)
 189 {
 190         u64 __user *out = (u64 __user *)buf;
 191         struct page *ppage;
 192         unsigned long src = *ppos;
 193         unsigned long pfn;
 194         ssize_t ret = 0;
 195
 196         pfn = src / KPMSIZE;
 197         count = min_t(unsigned long, count, (max_pfn * KPMSIZE) - src);
 198         if (src & KPMMASK || count & KPMMASK)
 199                 return -EINVAL;
 200
 201         while (count > 0) {
 202                 if (pfn_valid(pfn))
 203                         ppage = pfn_to_page(pfn);
 204                 else
 205                         ppage = NULL;
 206
 207                 if (put_user(stable_page_flags(ppage), out)) {
 208                         ret = -EFAULT;
 209                         break;
 210                 }
 211
 212                 pfn++;
 213                 out++;
 214                 count -= KPMSIZE;
 215         }
 216
 217         *ppos += (char __user *)out - buf;
 218         if (!ret)
 219                 ret = (char __user *)out - buf;
 220         return ret;
 221 }
 222
 223 static const struct file_operations proc_kpageflags_operations = {
 224         .llseek = mem_lseek,
 225         .read = kpageflags_read,
 226 };
 227
 228 static int __init proc_page_init(void)
 229 {
 230         proc_create("kpagecount", S_IRUSR, NULL, &proc_kpagecount_operations);
 231         proc_create("kpageflags", S_IRUSR, NULL, &proc_kpageflags_operations);
 232         return 0;
 233 }
 234 fs_initcall(proc_page_init);