1// SPDX-License-Identifier: GPL-2.0
2#include <linux/memblock.h>
3#include <linux/compiler.h>
4#include <linux/fs.h>
5#include <linux/init.h>
6#include <linux/ksm.h>
7#include <linux/mm.h>
8#include <linux/mmzone.h>
9#include <linux/huge_mm.h>
10#include <linux/proc_fs.h>
11#include <linux/seq_file.h>
12#include <linux/hugetlb.h>
13#include <linux/memremap.h>
14#include <linux/memcontrol.h>
15#include <linux/mmu_notifier.h>
16#include <linux/page_idle.h>
17#include <linux/kernel-page-flags.h>
18#include <linux/uaccess.h>
19#include "internal.h"
20
21#define KPMSIZE sizeof(u64)
22#define KPMMASK (KPMSIZE - 1)
23
24enum kpage_operation {
25 KPAGE_FLAGS,
26 KPAGE_COUNT,
27 KPAGE_CGROUP,
28};
29
30static inline unsigned long get_max_dump_pfn(void)
31{
32#ifdef CONFIG_SPARSEMEM
33 /*
34 * The memmap of early sections is completely populated and marked
35 * online even if max_pfn does not fall on a section boundary -
36 * pfn_to_online_page() will succeed on all pages. Allow inspecting
37 * these memmaps.
38 */
39 return round_up(max_pfn, PAGES_PER_SECTION);
40#else
41 return max_pfn;
42#endif
43}
44
45static u64 get_kpage_count(const struct page *page)
46{
47 struct page_snapshot ps;
48 u64 ret;
49
50 snapshot_page(ps: &ps, page);
51
52 if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT))
53 ret = folio_precise_page_mapcount(folio: &ps.folio_snapshot,
54 page: &ps.page_snapshot);
55 else
56 ret = folio_average_page_mapcount(folio: &ps.folio_snapshot);
57
58 return ret;
59}
60
61static ssize_t kpage_read(struct file *file, char __user *buf,
62 size_t count, loff_t *ppos,
63 enum kpage_operation op)
64{
65 const unsigned long max_dump_pfn = get_max_dump_pfn();
66 u64 __user *out = (u64 __user *)buf;
67 struct page *page;
68 unsigned long src = *ppos;
69 unsigned long pfn;
70 ssize_t ret = 0;
71 u64 info;
72
73 pfn = src / KPMSIZE;
74 if (src & KPMMASK || count & KPMMASK)
75 return -EINVAL;
76 if (src >= max_dump_pfn * KPMSIZE)
77 return 0;
78 count = min_t(unsigned long, count, (max_dump_pfn * KPMSIZE) - src);
79
80 while (count > 0) {
81 /*
82 * TODO: ZONE_DEVICE support requires to identify
83 * memmaps that were actually initialized.
84 */
85 page = pfn_to_online_page(pfn);
86
87 if (page) {
88 switch (op) {
89 case KPAGE_FLAGS:
90 info = stable_page_flags(page);
91 break;
92 case KPAGE_COUNT:
93 info = get_kpage_count(page);
94 break;
95 case KPAGE_CGROUP:
96 info = page_cgroup_ino(page);
97 break;
98 default:
99 info = 0;
100 break;
101 }
102 } else
103 info = 0;
104
105 if (put_user(info, out)) {
106 ret = -EFAULT;
107 break;
108 }
109
110 pfn++;
111 out++;
112 count -= KPMSIZE;
113
114 cond_resched();
115 }
116
117 *ppos += (char __user *)out - buf;
118 if (!ret)
119 ret = (char __user *)out - buf;
120 return ret;
121}
122
123/* /proc/kpagecount - an array exposing page mapcounts
124 *
125 * Each entry is a u64 representing the corresponding
126 * physical page mapcount.
127 */
128static ssize_t kpagecount_read(struct file *file, char __user *buf,
129 size_t count, loff_t *ppos)
130{
131 return kpage_read(file, buf, count, ppos, op: KPAGE_COUNT);
132}
133
134static const struct proc_ops kpagecount_proc_ops = {
135 .proc_flags = PROC_ENTRY_PERMANENT,
136 .proc_lseek = mem_lseek,
137 .proc_read = kpagecount_read,
138};
139
140
141static inline u64 kpf_copy_bit(u64 kflags, int ubit, int kbit)
142{
143 return ((kflags >> kbit) & 1) << ubit;
144}
145
146u64 stable_page_flags(const struct page *page)
147{
148 const struct folio *folio;
149 struct page_snapshot ps;
150 unsigned long k;
151 unsigned long mapping;
152 bool is_anon;
153 u64 u = 0;
154
155 /*
156 * pseudo flag: KPF_NOPAGE
157 * it differentiates a memory hole from a page with no flags
158 */
159 if (!page)
160 return 1 << KPF_NOPAGE;
161
162 snapshot_page(ps: &ps, page);
163 folio = &ps.folio_snapshot;
164
165 k = folio->flags.f;
166 mapping = (unsigned long)folio->mapping;
167 is_anon = mapping & FOLIO_MAPPING_ANON;
168
169 /*
170 * pseudo flags for the well known (anonymous) memory mapped pages
171 */
172 if (folio_mapped(folio))
173 u |= 1 << KPF_MMAP;
174 if (is_anon) {
175 u |= 1 << KPF_ANON;
176 if (mapping & FOLIO_MAPPING_KSM)
177 u |= 1 << KPF_KSM;
178 }
179
180 /*
181 * compound pages: export both head/tail info
182 * they together define a compound page's start/end pos and order
183 */
184 if (ps.idx == 0)
185 u |= kpf_copy_bit(kflags: k, KPF_COMPOUND_HEAD, kbit: PG_head);
186 else
187 u |= 1 << KPF_COMPOUND_TAIL;
188 if (folio_test_hugetlb(folio))
189 u |= 1 << KPF_HUGE;
190 else if (folio_test_large(folio) &&
191 folio_test_large_rmappable(folio)) {
192 /* Note: we indicate any THPs here, not just PMD-sized ones */
193 u |= 1 << KPF_THP;
194 } else if (is_huge_zero_pfn(pfn: ps.pfn)) {
195 u |= 1 << KPF_ZERO_PAGE;
196 u |= 1 << KPF_THP;
197 } else if (is_zero_pfn(pfn: ps.pfn)) {
198 u |= 1 << KPF_ZERO_PAGE;
199 }
200
201 if (ps.flags & PAGE_SNAPSHOT_PG_BUDDY)
202 u |= 1 << KPF_BUDDY;
203
204 if (folio_test_offline(folio))
205 u |= 1 << KPF_OFFLINE;
206 if (folio_test_pgtable(folio))
207 u |= 1 << KPF_PGTABLE;
208 if (folio_test_slab(folio))
209 u |= 1 << KPF_SLAB;
210
211#if defined(CONFIG_PAGE_IDLE_FLAG) && defined(CONFIG_64BIT)
212 u |= kpf_copy_bit(kflags: k, KPF_IDLE, kbit: PG_idle);
213#else
214 if (ps.flags & PAGE_SNAPSHOT_PG_IDLE)
215 u |= 1 << KPF_IDLE;
216#endif
217
218 u |= kpf_copy_bit(kflags: k, KPF_LOCKED, kbit: PG_locked);
219 u |= kpf_copy_bit(kflags: k, KPF_DIRTY, kbit: PG_dirty);
220 u |= kpf_copy_bit(kflags: k, KPF_UPTODATE, kbit: PG_uptodate);
221 u |= kpf_copy_bit(kflags: k, KPF_WRITEBACK, kbit: PG_writeback);
222
223 u |= kpf_copy_bit(kflags: k, KPF_LRU, kbit: PG_lru);
224 u |= kpf_copy_bit(kflags: k, KPF_REFERENCED, kbit: PG_referenced);
225 u |= kpf_copy_bit(kflags: k, KPF_ACTIVE, kbit: PG_active);
226 u |= kpf_copy_bit(kflags: k, KPF_RECLAIM, kbit: PG_reclaim);
227
228#define SWAPCACHE ((1 << PG_swapbacked) | (1 << PG_swapcache))
229 if ((k & SWAPCACHE) == SWAPCACHE)
230 u |= 1 << KPF_SWAPCACHE;
231 u |= kpf_copy_bit(kflags: k, KPF_SWAPBACKED, kbit: PG_swapbacked);
232
233 u |= kpf_copy_bit(kflags: k, KPF_UNEVICTABLE, kbit: PG_unevictable);
234 u |= kpf_copy_bit(kflags: k, KPF_MLOCKED, kbit: PG_mlocked);
235
236#ifdef CONFIG_MEMORY_FAILURE
237 if (u & (1 << KPF_HUGE))
238 u |= kpf_copy_bit(kflags: k, KPF_HWPOISON, kbit: PG_hwpoison);
239 else
240 u |= kpf_copy_bit(kflags: ps.page_snapshot.flags.f, KPF_HWPOISON, kbit: PG_hwpoison);
241#endif
242
243 u |= kpf_copy_bit(kflags: k, KPF_RESERVED, kbit: PG_reserved);
244 u |= kpf_copy_bit(kflags: k, KPF_OWNER_2, kbit: PG_owner_2);
245 u |= kpf_copy_bit(kflags: k, KPF_PRIVATE, kbit: PG_private);
246 u |= kpf_copy_bit(kflags: k, KPF_PRIVATE_2, kbit: PG_private_2);
247 u |= kpf_copy_bit(kflags: k, KPF_OWNER_PRIVATE, kbit: PG_owner_priv_1);
248 u |= kpf_copy_bit(kflags: k, KPF_ARCH, kbit: PG_arch_1);
249#ifdef CONFIG_ARCH_USES_PG_ARCH_2
250 u |= kpf_copy_bit(kflags: k, KPF_ARCH_2, kbit: PG_arch_2);
251#endif
252#ifdef CONFIG_ARCH_USES_PG_ARCH_3
253 u |= kpf_copy_bit(k, KPF_ARCH_3, PG_arch_3);
254#endif
255
256 return u;
257}
258EXPORT_SYMBOL_GPL(stable_page_flags);
259
260/* /proc/kpageflags - an array exposing page flags
261 *
262 * Each entry is a u64 representing the corresponding
263 * physical page flags.
264 */
265static ssize_t kpageflags_read(struct file *file, char __user *buf,
266 size_t count, loff_t *ppos)
267{
268 return kpage_read(file, buf, count, ppos, op: KPAGE_FLAGS);
269}
270
271static const struct proc_ops kpageflags_proc_ops = {
272 .proc_flags = PROC_ENTRY_PERMANENT,
273 .proc_lseek = mem_lseek,
274 .proc_read = kpageflags_read,
275};
276
277#ifdef CONFIG_MEMCG
278static ssize_t kpagecgroup_read(struct file *file, char __user *buf,
279 size_t count, loff_t *ppos)
280{
281 return kpage_read(file, buf, count, ppos, op: KPAGE_CGROUP);
282}
283static const struct proc_ops kpagecgroup_proc_ops = {
284 .proc_flags = PROC_ENTRY_PERMANENT,
285 .proc_lseek = mem_lseek,
286 .proc_read = kpagecgroup_read,
287};
288#endif /* CONFIG_MEMCG */
289
290static int __init proc_page_init(void)
291{
292 proc_create(name: "kpagecount", S_IRUSR, NULL, proc_ops: &kpagecount_proc_ops);
293 proc_create(name: "kpageflags", S_IRUSR, NULL, proc_ops: &kpageflags_proc_ops);
294#ifdef CONFIG_MEMCG
295 proc_create(name: "kpagecgroup", S_IRUSR, NULL, proc_ops: &kpagecgroup_proc_ops);
296#endif
297 return 0;
298}
299fs_initcall(proc_page_init);
300

source code of linux/fs/proc/page.c