1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (c) 2024 Google LLC. All rights reserved.
4 * Author(s): Kalesh Singh <[email protected]>
5 */
6
7 #ifndef PGSIZE_HELPER_H
8 #define PGSIZE_HELPER_H
9
10 #include <stdlib.h>
11 #include <string.h>
12 #include <unistd.h>
13
14 #define MAX_PAGE_SIZE (64*1024)
15
16 #if defined(__x86_64__)
17 /*
18 * Android emulates the userspace page size on some x86_64 emulators.
19 * The kernel page size still remains 4KiB (0x1000).
20 */
kernel_page_size(void)21 static inline size_t kernel_page_size(void)
22 {
23 return 0x1000;
24 }
25
26 /* Handle upto MAX_PAGE_SIZE emulation on 4KiB kernel base page size system */
27 #define DECLARE_MINCORE_VECTOR(vec_name, num_pages) \
28 unsigned char vec_name[(num_pages) * (MAX_PAGE_SIZE / 4096)]
29
30 #else /* !defined(__x86_64__) */
31
kernel_page_size(void)32 static inline size_t kernel_page_size(void)
33 {
34 return getpagesize();
35 }
36
37 #define DECLARE_MINCORE_VECTOR(vec_name, num_pages) unsigned char vec_name[(num_pages)]
38 #endif /* defined(__x86_64__) */
39
40 /*
41 * NOTE: For all cases except Android x86_64 page size emulators,
42 * kernel_page_size == page_size, and the below macros are effectively
43 * no-ops.
44 */
45
46 /* The number of kernel pages covered by size */
nr_kernel_pages(size_t size)47 static inline size_t nr_kernel_pages(size_t size)
48 {
49 return size / kernel_page_size();
50 }
51
52 /* The number of kernel pages in a @nr_pages userspace pages */
nr_pgs_to_nr_kernel_pgs(size_t nr_pages)53 static size_t nr_pgs_to_nr_kernel_pgs(size_t nr_pages)
54 {
55 return nr_pages * nr_kernel_pages(getpagesize());
56 }
57
58 /* The number of userspace pages in a @nr_pages kernel pages */
nr_kernel_pgs_to_nr_pgs(size_t nr_pages)59 static size_t nr_kernel_pgs_to_nr_pgs(size_t nr_pages)
60 {
61 return nr_pages / nr_kernel_pages(getpagesize());
62 }
63
64 /*
65 * Test populating the last partial 4KiB page if the page size is emulated,
66 * instead of the first. This faults in the preceding pages for convenient
67 * test accounting.
68 */
69 #define MLOCK_PAGE_SIZE_EMULATION_OFFSET(tcases) \
70 do { \
71 if (getpagesize() != kernel_page_size()) { \
72 for (int i = 0; i < ARRAY_SIZE(tcases); i++) { \
73 struct tcase *test = tcases + i; \
74 if (test->offset > 0) test->offset = pgsz - kernel_page_size() + test->offset; \
75 } \
76 } \
77 } while (0)
78
79 /*
80 * Make the backing file large enough to cover the last corresponding kernel page.
81 *
82 * This is an artifact of x86_64 page size emulation on Android, to handle
83 * file_map_fault's, which does allow access to the partial page after the end
84 * of the file.
85 */
86 #define SAFE_FILE_PRINTF_PGSIZE_EMULATION(file, str) \
87 do { \
88 if (kernel_page_size() == getpagesize()) { \
89 SAFE_FILE_PRINTF(file, str); \
90 } else { \
91 int str_len = strlen(str); \
92 int nr_writes = ((kernel_page_size() \
93 * (nr_pgs_to_nr_kernel_pgs(1) - 1)) / str_len) + 1; \
94 int total_len = str_len * nr_writes; \
95 char *buffer = SAFE_MALLOC(total_len + 1); \
96 for (int i = 0; i < nr_writes; i++) \
97 strcat(buffer, str); \
98 SAFE_FILE_PRINTF(file, buffer); \
99 free(buffer); \
100 } \
101 } while (0)
102 #endif /* PGSIZE_HELPER_H */
103