1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Handle caching attributes in page tables (PAT)
4 *
5 * Authors: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
6 * Suresh B Siddha <suresh.b.siddha@intel.com>
7 *
8 * Interval tree used to store the PAT memory type reservations.
9 */
10
11 #include <linux/seq_file.h>
12 #include <linux/debugfs.h>
13 #include <linux/kernel.h>
14 #include <linux/interval_tree_generic.h>
15 #include <linux/sched.h>
16 #include <linux/gfp.h>
17 #include <linux/pgtable.h>
18
19 #include <asm/memtype.h>
20
21 #include "memtype.h"
22
23 /*
24 * The memtype tree keeps track of memory type for specific
25 * physical memory areas. Without proper tracking, conflicting memory
26 * types in different mappings can cause CPU cache corruption.
27 *
28 * The tree is an interval tree (augmented rbtree) which tree is ordered
29 * by the starting address. The tree can contain multiple entries for
30 * different regions which overlap. All the aliases have the same
31 * cache attributes of course, as enforced by the PAT logic.
32 *
33 * memtype_lock protects the rbtree.
34 */
35
36 static inline u64 interval_start(struct memtype *entry)
37 {
38 return entry->start;
39 }
40
41 static inline u64 interval_end(struct memtype *entry)
42 {
43 return entry->end - 1;
44 }
45
46 INTERVAL_TREE_DEFINE(struct memtype, rb, u64, subtree_max_end,
47 interval_start, interval_end,
48 static, interval)
49
50 static struct rb_root_cached memtype_rbroot = RB_ROOT_CACHED;
51
52 enum {
53 MEMTYPE_EXACT_MATCH = 0,
54 MEMTYPE_END_MATCH = 1
55 };
56
57 static struct memtype *memtype_match(u64 start, u64 end, int match_type)
58 {
59 struct memtype *entry_match;
60
61 entry_match = interval_iter_first(&memtype_rbroot, start, end-1);
62
63 while (entry_match != NULL && entry_match->start < end) {
64 if ((match_type == MEMTYPE_EXACT_MATCH) &&
65 (entry_match->start == start) && (entry_match->end == end))
66 return entry_match;
67
68 if ((match_type == MEMTYPE_END_MATCH) &&
69 (entry_match->start < start) && (entry_match->end == end))
70 return entry_match;
71
72 entry_match = interval_iter_next(entry_match, start, end-1);
73 }
74
75 return NULL; /* Returns NULL if there is no match */
76 }
77
78 static int memtype_check_conflict(u64 start, u64 end,
79 enum page_cache_mode reqtype,
80 enum page_cache_mode *newtype)
81 {
82 struct memtype *entry_match;
83 enum page_cache_mode found_type = reqtype;
84
85 entry_match = interval_iter_first(&memtype_rbroot, start, end-1);
86 if (entry_match == NULL)
87 goto success;
88
89 if (entry_match->type != found_type && newtype == NULL)
90 goto failure;
91
92 dprintk("Overlap at 0x%Lx-0x%Lx\n", entry_match->start, entry_match->end);
93 found_type = entry_match->type;
94
95 entry_match = interval_iter_next(entry_match, start, end-1);
96 while (entry_match) {
97 if (entry_match->type != found_type)
98 goto failure;
99
100 entry_match = interval_iter_next(entry_match, start, end-1);
101 }
102 success:
103 if (newtype)
104 *newtype = found_type;
105
106 return 0;
107
108 failure:
109 pr_info("x86/PAT: %s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
110 current->comm, current->pid, start, end,
111 cattr_name(found_type), cattr_name(entry_match->type));
112
113 return -EBUSY;
114 }
115
116 int memtype_check_insert(struct memtype *entry_new, enum page_cache_mode *ret_type)
117 {
118 int err = 0;
119
120 err = memtype_check_conflict(entry_new->start, entry_new->end, entry_new->type, ret_type);
121 if (err)
122 return err;
123
124 if (ret_type)
125 entry_new->type = *ret_type;
126
127 interval_insert(entry_new, &memtype_rbroot);
128 return 0;
129 }
130
131 struct memtype *memtype_erase(u64 start, u64 end)
132 {
133 struct memtype *entry_old;
134
135 /*
136 * Since the memtype_rbroot tree allows overlapping ranges,
137 * memtype_erase() checks with EXACT_MATCH first, i.e. free
138 * a whole node for the munmap case. If no such entry is found,
139 * it then checks with END_MATCH, i.e. shrink the size of a node
140 * from the end for the mremap case.
141 */
142 entry_old = memtype_match(start, end, MEMTYPE_EXACT_MATCH);
143 if (!entry_old) {
144 entry_old = memtype_match(start, end, MEMTYPE_END_MATCH);
145 if (!entry_old)
146 return ERR_PTR(-EINVAL);
147 }
148
149 if (entry_old->start == start) {
150 /* munmap: erase this node */
151 interval_remove(entry_old, &memtype_rbroot);
152 } else {
153 /* mremap: update the end value of this node */
154 interval_remove(entry_old, &memtype_rbroot);
155 entry_old->end = start;
156 interval_insert(entry_old, &memtype_rbroot);
157
158 return NULL;
159 }
160
161 return entry_old;
162 }
163
164 struct memtype *memtype_lookup(u64 addr)
165 {
166 return interval_iter_first(&memtype_rbroot, addr, addr + PAGE_SIZE-1);
167 }
168
169 /*
170 * Debugging helper, copy the Nth entry of the tree into a
171 * a copy for printout. This allows us to print out the tree
172 * via debugfs, without holding the memtype_lock too long:
173 */
174 #ifdef CONFIG_DEBUG_FS
175 int memtype_copy_nth_element(struct memtype *entry_out, loff_t pos)
176 {
177 struct memtype *entry_match;
178 int i = 1;
179
180 entry_match = interval_iter_first(&memtype_rbroot, 0, ULONG_MAX);
181
182 while (entry_match && pos != i) {
183 entry_match = interval_iter_next(entry_match, 0, ULONG_MAX);
184 i++;
185 }
186
187 if (entry_match) { /* pos == i */
188 *entry_out = *entry_match;
189 return 0;
190 } else {
191 return 1;
192 }
193 }
194 #endif
195
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