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 (augmented rbtree) used to store the PAT memory type
9 * reservations.
10 */
11
12 #include <linux/seq_file.h>
13 #include <linux/debugfs.h>
14 #include <linux/kernel.h>
15 #include <linux/rbtree_augmented.h>
16 #include <linux/sched.h>
17 #include <linux/gfp.h>
18
19 #include <asm/pgtable.h>
20 #include <asm/pat.h>
21
22 #include "pat_internal.h"
23
24 /*
25 * The memtype tree keeps track of memory type for specific
26 * physical memory areas. Without proper tracking, conflicting memory
27 * types in different mappings can cause CPU cache corruption.
28 *
29 * The tree is an interval tree (augmented rbtree) with tree ordered
30 * on starting address. Tree can contain multiple entries for
31 * different regions which overlap. All the aliases have the same
32 * cache attributes of course.
33 *
34 * memtype_lock protects the rbtree.
35 */
36
37 static struct rb_root memtype_rbroot = RB_ROOT;
38
is_node_overlap(struct memtype * node,u64 start,u64 end)39 static int is_node_overlap(struct memtype *node, u64 start, u64 end)
40 {
41 if (node->start >= end || node->end <= start)
42 return 0;
43
44 return 1;
45 }
46
get_subtree_max_end(struct rb_node * node)47 static u64 get_subtree_max_end(struct rb_node *node)
48 {
49 u64 ret = 0;
50 if (node) {
51 struct memtype *data = rb_entry(node, struct memtype, rb);
52 ret = data->subtree_max_end;
53 }
54 return ret;
55 }
56
57 #define NODE_END(node) ((node)->end)
58
RB_DECLARE_CALLBACKS_MAX(static,memtype_rb_augment_cb,struct memtype,rb,u64,subtree_max_end,NODE_END)59 RB_DECLARE_CALLBACKS_MAX(static, memtype_rb_augment_cb,
60 struct memtype, rb, u64, subtree_max_end, NODE_END)
61
62 /* Find the first (lowest start addr) overlapping range from rb tree */
63 static struct memtype *memtype_rb_lowest_match(struct rb_root *root,
64 u64 start, u64 end)
65 {
66 struct rb_node *node = root->rb_node;
67 struct memtype *last_lower = NULL;
68
69 while (node) {
70 struct memtype *data = rb_entry(node, struct memtype, rb);
71
72 if (get_subtree_max_end(node->rb_left) > start) {
73 /* Lowest overlap if any must be on left side */
74 node = node->rb_left;
75 } else if (is_node_overlap(data, start, end)) {
76 last_lower = data;
77 break;
78 } else if (start >= data->start) {
79 /* Lowest overlap if any must be on right side */
80 node = node->rb_right;
81 } else {
82 break;
83 }
84 }
85 return last_lower; /* Returns NULL if there is no overlap */
86 }
87
88 enum {
89 MEMTYPE_EXACT_MATCH = 0,
90 MEMTYPE_END_MATCH = 1
91 };
92
memtype_rb_match(struct rb_root * root,u64 start,u64 end,int match_type)93 static struct memtype *memtype_rb_match(struct rb_root *root,
94 u64 start, u64 end, int match_type)
95 {
96 struct memtype *match;
97
98 match = memtype_rb_lowest_match(root, start, end);
99 while (match != NULL && match->start < end) {
100 struct rb_node *node;
101
102 if ((match_type == MEMTYPE_EXACT_MATCH) &&
103 (match->start == start) && (match->end == end))
104 return match;
105
106 if ((match_type == MEMTYPE_END_MATCH) &&
107 (match->start < start) && (match->end == end))
108 return match;
109
110 node = rb_next(&match->rb);
111 if (node)
112 match = rb_entry(node, struct memtype, rb);
113 else
114 match = NULL;
115 }
116
117 return NULL; /* Returns NULL if there is no match */
118 }
119
memtype_rb_check_conflict(struct rb_root * root,u64 start,u64 end,enum page_cache_mode reqtype,enum page_cache_mode * newtype)120 static int memtype_rb_check_conflict(struct rb_root *root,
121 u64 start, u64 end,
122 enum page_cache_mode reqtype,
123 enum page_cache_mode *newtype)
124 {
125 struct rb_node *node;
126 struct memtype *match;
127 enum page_cache_mode found_type = reqtype;
128
129 match = memtype_rb_lowest_match(&memtype_rbroot, start, end);
130 if (match == NULL)
131 goto success;
132
133 if (match->type != found_type && newtype == NULL)
134 goto failure;
135
136 dprintk("Overlap at 0x%Lx-0x%Lx\n", match->start, match->end);
137 found_type = match->type;
138
139 node = rb_next(&match->rb);
140 while (node) {
141 match = rb_entry(node, struct memtype, rb);
142
143 if (match->start >= end) /* Checked all possible matches */
144 goto success;
145
146 if (is_node_overlap(match, start, end) &&
147 match->type != found_type) {
148 goto failure;
149 }
150
151 node = rb_next(&match->rb);
152 }
153 success:
154 if (newtype)
155 *newtype = found_type;
156
157 return 0;
158
159 failure:
160 pr_info("x86/PAT: %s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
161 current->comm, current->pid, start, end,
162 cattr_name(found_type), cattr_name(match->type));
163 return -EBUSY;
164 }
165
memtype_rb_insert(struct rb_root * root,struct memtype * newdata)166 static void memtype_rb_insert(struct rb_root *root, struct memtype *newdata)
167 {
168 struct rb_node **node = &(root->rb_node);
169 struct rb_node *parent = NULL;
170
171 while (*node) {
172 struct memtype *data = rb_entry(*node, struct memtype, rb);
173
174 parent = *node;
175 if (data->subtree_max_end < newdata->end)
176 data->subtree_max_end = newdata->end;
177 if (newdata->start <= data->start)
178 node = &((*node)->rb_left);
179 else if (newdata->start > data->start)
180 node = &((*node)->rb_right);
181 }
182
183 newdata->subtree_max_end = newdata->end;
184 rb_link_node(&newdata->rb, parent, node);
185 rb_insert_augmented(&newdata->rb, root, &memtype_rb_augment_cb);
186 }
187
rbt_memtype_check_insert(struct memtype * new,enum page_cache_mode * ret_type)188 int rbt_memtype_check_insert(struct memtype *new,
189 enum page_cache_mode *ret_type)
190 {
191 int err = 0;
192
193 err = memtype_rb_check_conflict(&memtype_rbroot, new->start, new->end,
194 new->type, ret_type);
195
196 if (!err) {
197 if (ret_type)
198 new->type = *ret_type;
199
200 new->subtree_max_end = new->end;
201 memtype_rb_insert(&memtype_rbroot, new);
202 }
203 return err;
204 }
205
rbt_memtype_erase(u64 start,u64 end)206 struct memtype *rbt_memtype_erase(u64 start, u64 end)
207 {
208 struct memtype *data;
209
210 /*
211 * Since the memtype_rbroot tree allows overlapping ranges,
212 * rbt_memtype_erase() checks with EXACT_MATCH first, i.e. free
213 * a whole node for the munmap case. If no such entry is found,
214 * it then checks with END_MATCH, i.e. shrink the size of a node
215 * from the end for the mremap case.
216 */
217 data = memtype_rb_match(&memtype_rbroot, start, end,
218 MEMTYPE_EXACT_MATCH);
219 if (!data) {
220 data = memtype_rb_match(&memtype_rbroot, start, end,
221 MEMTYPE_END_MATCH);
222 if (!data)
223 return ERR_PTR(-EINVAL);
224 }
225
226 if (data->start == start) {
227 /* munmap: erase this node */
228 rb_erase_augmented(&data->rb, &memtype_rbroot,
229 &memtype_rb_augment_cb);
230 } else {
231 /* mremap: update the end value of this node */
232 rb_erase_augmented(&data->rb, &memtype_rbroot,
233 &memtype_rb_augment_cb);
234 data->end = start;
235 data->subtree_max_end = data->end;
236 memtype_rb_insert(&memtype_rbroot, data);
237 return NULL;
238 }
239
240 return data;
241 }
242
rbt_memtype_lookup(u64 addr)243 struct memtype *rbt_memtype_lookup(u64 addr)
244 {
245 return memtype_rb_lowest_match(&memtype_rbroot, addr, addr + PAGE_SIZE);
246 }
247
248 #if defined(CONFIG_DEBUG_FS)
rbt_memtype_copy_nth_element(struct memtype * out,loff_t pos)249 int rbt_memtype_copy_nth_element(struct memtype *out, loff_t pos)
250 {
251 struct rb_node *node;
252 int i = 1;
253
254 node = rb_first(&memtype_rbroot);
255 while (node && pos != i) {
256 node = rb_next(node);
257 i++;
258 }
259
260 if (node) { /* pos == i */
261 struct memtype *this = rb_entry(node, struct memtype, rb);
262 *out = *this;
263 return 0;
264 } else {
265 return 1;
266 }
267 }
268 #endif
269