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97572c04 MD |
1 | /* |
2 | * SPDX-License-Identifier: MIT | |
3 | * | |
4 | * Copyright (C) 2024-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
5 | */ | |
6 | ||
7 | #define _LGPL_SOURCE | |
8 | #include "common/getenv.h" | |
9 | #include "common/logging.h" | |
10 | #include "common/populate.h" | |
11 | ||
12 | enum populate_policy { | |
13 | POPULATE_UNSET, | |
14 | ||
15 | POPULATE_NONE, | |
16 | POPULATE_CPU_POSSIBLE, | |
17 | ||
18 | POPULATE_UNKNOWN, | |
19 | }; | |
20 | ||
21 | static enum populate_policy map_populate_policy = POPULATE_UNSET; | |
22 | ||
23 | static void init_map_populate_policy(void) | |
24 | { | |
25 | const char *populate_env_str; | |
26 | ||
27 | if (map_populate_policy != POPULATE_UNSET) | |
28 | return; | |
29 | ||
30 | populate_env_str = lttng_ust_getenv("LTTNG_UST_MAP_POPULATE_POLICY"); | |
31 | if (!populate_env_str) { | |
32 | map_populate_policy = POPULATE_NONE; | |
33 | return; | |
34 | } | |
35 | if (!strcmp(populate_env_str, "none")) { | |
36 | map_populate_policy = POPULATE_NONE; | |
37 | } else if (!strcmp(populate_env_str, "cpu_possible")) { | |
38 | map_populate_policy = POPULATE_CPU_POSSIBLE; | |
39 | } else { | |
40 | /* | |
41 | * populate_env_str is an untrusted environment variable | |
42 | * input (can be provided to setuid/setgid binaries), so | |
43 | * don't even try to print it. | |
44 | */ | |
45 | WARN("Unknown policy for LTTNG_UST_MAP_POPULATE_POLICY environment variable."); | |
46 | map_populate_policy = POPULATE_UNKNOWN; | |
47 | } | |
48 | } | |
49 | ||
50 | /* | |
51 | * Return the shared page populate policy for global pages. Returns true | |
52 | * if shared memory pages should be pre-populated, false otherwise. | |
53 | */ | |
54 | bool lttng_ust_map_populate_is_enabled(void) | |
55 | { | |
56 | init_map_populate_policy(); | |
57 | ||
58 | switch (map_populate_policy) { | |
59 | case POPULATE_UNKNOWN: /* Fall-through */ | |
60 | case POPULATE_NONE: | |
61 | return false; | |
62 | case POPULATE_CPU_POSSIBLE: | |
63 | return true; | |
64 | default: | |
65 | abort(); | |
66 | } | |
67 | return false; | |
68 | } | |
69 | ||
70 | /* | |
71 | * Return the shared page populate policy based on the @cpu number | |
72 | * provided as input. Returns true if shared memory pages should be | |
73 | * pre-populated, false otherwise. | |
74 | * | |
75 | * The @cpu argument is currently unused except for negative value | |
76 | * validation. It is present to eventually match cpu affinity or cpu | |
77 | * online masks if those features are added in the future. | |
78 | */ | |
79 | bool lttng_ust_map_populate_cpu_is_enabled(int cpu) | |
80 | { | |
81 | /* Reject invalid cpu number. */ | |
82 | if (cpu < 0) | |
83 | return false; | |
84 | ||
85 | return lttng_ust_map_populate_is_enabled(); | |
86 | } |