1 // SPDX-License-Identifier: GPL-2.0
2 #include "comm.h"
3 #include <errno.h>
4 #include <string.h>
5 #include <internal/rc_check.h>
6 #include <linux/refcount.h>
7 #include <linux/zalloc.h>
8 #include "rwsem.h"
9
DECLARE_RC_STRUCT(comm_str)10 DECLARE_RC_STRUCT(comm_str) {
11 refcount_t refcnt;
12 char str[];
13 };
14
15 static struct comm_strs {
16 struct rw_semaphore lock;
17 struct comm_str **strs;
18 int num_strs;
19 int capacity;
20 } _comm_strs;
21
22 static void comm_strs__remove_if_last(struct comm_str *cs);
23
comm_strs__init(void)24 static void comm_strs__init(void)
25 {
26 init_rwsem(&_comm_strs.lock);
27 _comm_strs.capacity = 16;
28 _comm_strs.num_strs = 0;
29 _comm_strs.strs = calloc(16, sizeof(*_comm_strs.strs));
30 }
31
comm_strs__get(void)32 static struct comm_strs *comm_strs__get(void)
33 {
34 static pthread_once_t comm_strs_type_once = PTHREAD_ONCE_INIT;
35
36 pthread_once(&comm_strs_type_once, comm_strs__init);
37
38 return &_comm_strs;
39 }
40
comm_str__refcnt(struct comm_str * cs)41 static refcount_t *comm_str__refcnt(struct comm_str *cs)
42 {
43 return &RC_CHK_ACCESS(cs)->refcnt;
44 }
45
comm_str__str(const struct comm_str * cs)46 static const char *comm_str__str(const struct comm_str *cs)
47 {
48 return &RC_CHK_ACCESS(cs)->str[0];
49 }
50
comm_str__get(struct comm_str * cs)51 static struct comm_str *comm_str__get(struct comm_str *cs)
52 {
53 struct comm_str *result;
54
55 if (RC_CHK_GET(result, cs))
56 refcount_inc_not_zero(comm_str__refcnt(cs));
57
58 return result;
59 }
60
comm_str__put(struct comm_str * cs)61 static void comm_str__put(struct comm_str *cs)
62 {
63 if (!cs)
64 return;
65
66 if (refcount_dec_and_test(comm_str__refcnt(cs))) {
67 RC_CHK_FREE(cs);
68 } else {
69 if (refcount_read(comm_str__refcnt(cs)) == 1)
70 comm_strs__remove_if_last(cs);
71
72 RC_CHK_PUT(cs);
73 }
74 }
75
comm_str__new(const char * str)76 static struct comm_str *comm_str__new(const char *str)
77 {
78 struct comm_str *result = NULL;
79 RC_STRUCT(comm_str) *cs;
80
81 cs = malloc(sizeof(*cs) + strlen(str) + 1);
82 if (ADD_RC_CHK(result, cs)) {
83 refcount_set(comm_str__refcnt(result), 1);
84 strcpy(&cs->str[0], str);
85 }
86 return result;
87 }
88
comm_str__search(const void * _key,const void * _member)89 static int comm_str__search(const void *_key, const void *_member)
90 {
91 const char *key = _key;
92 const struct comm_str *member = *(const struct comm_str * const *)_member;
93
94 return strcmp(key, comm_str__str(member));
95 }
96
comm_strs__remove_if_last(struct comm_str * cs)97 static void comm_strs__remove_if_last(struct comm_str *cs)
98 {
99 struct comm_strs *comm_strs = comm_strs__get();
100
101 down_write(&comm_strs->lock);
102 /*
103 * Are there only references from the array, if so remove the array
104 * reference under the write lock so that we don't race with findnew.
105 */
106 if (refcount_read(comm_str__refcnt(cs)) == 1) {
107 struct comm_str **entry;
108
109 entry = bsearch(comm_str__str(cs), comm_strs->strs, comm_strs->num_strs,
110 sizeof(struct comm_str *), comm_str__search);
111 comm_str__put(*entry);
112 for (int i = entry - comm_strs->strs; i < comm_strs->num_strs - 1; i++)
113 comm_strs->strs[i] = comm_strs->strs[i + 1];
114 comm_strs->num_strs--;
115 }
116 up_write(&comm_strs->lock);
117 }
118
__comm_strs__find(struct comm_strs * comm_strs,const char * str)119 static struct comm_str *__comm_strs__find(struct comm_strs *comm_strs, const char *str)
120 {
121 struct comm_str **result;
122
123 result = bsearch(str, comm_strs->strs, comm_strs->num_strs, sizeof(struct comm_str *),
124 comm_str__search);
125
126 if (!result)
127 return NULL;
128
129 return comm_str__get(*result);
130 }
131
comm_strs__findnew(const char * str)132 static struct comm_str *comm_strs__findnew(const char *str)
133 {
134 struct comm_strs *comm_strs = comm_strs__get();
135 struct comm_str *result;
136
137 if (!comm_strs)
138 return NULL;
139
140 down_read(&comm_strs->lock);
141 result = __comm_strs__find(comm_strs, str);
142 up_read(&comm_strs->lock);
143 if (result)
144 return result;
145
146 down_write(&comm_strs->lock);
147 result = __comm_strs__find(comm_strs, str);
148 if (!result) {
149 if (comm_strs->num_strs == comm_strs->capacity) {
150 struct comm_str **tmp;
151
152 tmp = reallocarray(comm_strs->strs,
153 comm_strs->capacity + 16,
154 sizeof(*comm_strs->strs));
155 if (!tmp) {
156 up_write(&comm_strs->lock);
157 return NULL;
158 }
159 comm_strs->strs = tmp;
160 comm_strs->capacity += 16;
161 }
162 result = comm_str__new(str);
163 if (result) {
164 int low = 0, high = comm_strs->num_strs - 1;
165 int insert = comm_strs->num_strs; /* Default to inserting at the end. */
166
167 while (low <= high) {
168 int mid = low + (high - low) / 2;
169 int cmp = strcmp(comm_str__str(comm_strs->strs[mid]), str);
170
171 if (cmp < 0) {
172 low = mid + 1;
173 } else {
174 high = mid - 1;
175 insert = mid;
176 }
177 }
178 memmove(&comm_strs->strs[insert + 1], &comm_strs->strs[insert],
179 (comm_strs->num_strs - insert) * sizeof(struct comm_str *));
180 comm_strs->num_strs++;
181 comm_strs->strs[insert] = result;
182 }
183 }
184 up_write(&comm_strs->lock);
185 return comm_str__get(result);
186 }
187
comm__new(const char * str,u64 timestamp,bool exec)188 struct comm *comm__new(const char *str, u64 timestamp, bool exec)
189 {
190 struct comm *comm = zalloc(sizeof(*comm));
191
192 if (!comm)
193 return NULL;
194
195 comm->start = timestamp;
196 comm->exec = exec;
197
198 comm->comm_str = comm_strs__findnew(str);
199 if (!comm->comm_str) {
200 free(comm);
201 return NULL;
202 }
203
204 return comm;
205 }
206
comm__override(struct comm * comm,const char * str,u64 timestamp,bool exec)207 int comm__override(struct comm *comm, const char *str, u64 timestamp, bool exec)
208 {
209 struct comm_str *new, *old = comm->comm_str;
210
211 new = comm_strs__findnew(str);
212 if (!new)
213 return -ENOMEM;
214
215 comm_str__put(old);
216 comm->comm_str = new;
217 comm->start = timestamp;
218 if (exec)
219 comm->exec = true;
220
221 return 0;
222 }
223
comm__free(struct comm * comm)224 void comm__free(struct comm *comm)
225 {
226 comm_str__put(comm->comm_str);
227 free(comm);
228 }
229
comm__str(const struct comm * comm)230 const char *comm__str(const struct comm *comm)
231 {
232 return comm_str__str(comm->comm_str);
233 }
234