| 1 | /* |
| 2 | * SPDX-License-Identifier: LGPL-2.1-only |
| 3 | * |
| 4 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 5 | * Copyright (C) 2020 Michael Jeanson <mjeanson@efficios.com> |
| 6 | * |
| 7 | * LTTng UST time namespace context. |
| 8 | */ |
| 9 | |
| 10 | #define _LGPL_SOURCE |
| 11 | #include <stddef.h> |
| 12 | #include <sys/types.h> |
| 13 | #include <sys/stat.h> |
| 14 | #include <unistd.h> |
| 15 | #include <lttng/ust-events.h> |
| 16 | #include <lttng/ust-tracer.h> |
| 17 | #include <lttng/ringbuffer-context.h> |
| 18 | #include <ust-tid.h> |
| 19 | #include <urcu/tls-compat.h> |
| 20 | #include "lttng-tracer-core.h" |
| 21 | #include "ns.h" |
| 22 | #include "context-internal.h" |
| 23 | |
| 24 | |
| 25 | /* |
| 26 | * We cache the result to ensure we don't stat(2) the proc filesystem on |
| 27 | * each event. |
| 28 | */ |
| 29 | static DEFINE_URCU_TLS_INIT(ino_t, cached_time_ns, NS_INO_UNINITIALIZED); |
| 30 | |
| 31 | static |
| 32 | ino_t get_time_ns(void) |
| 33 | { |
| 34 | struct stat sb; |
| 35 | ino_t time_ns; |
| 36 | |
| 37 | time_ns = CMM_LOAD_SHARED(URCU_TLS(cached_time_ns)); |
| 38 | |
| 39 | /* |
| 40 | * If the cache is populated, do nothing and return the |
| 41 | * cached inode number. |
| 42 | */ |
| 43 | if (caa_likely(time_ns != NS_INO_UNINITIALIZED)) |
| 44 | return time_ns; |
| 45 | |
| 46 | /* |
| 47 | * At this point we have to populate the cache, set the initial |
| 48 | * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode |
| 49 | * number from the proc filesystem, this is the value we will |
| 50 | * cache. |
| 51 | */ |
| 52 | time_ns = NS_INO_UNAVAILABLE; |
| 53 | |
| 54 | /* |
| 55 | * /proc/thread-self was introduced in kernel v3.17 |
| 56 | */ |
| 57 | if (stat("/proc/thread-self/ns/time", &sb) == 0) { |
| 58 | time_ns = sb.st_ino; |
| 59 | } else { |
| 60 | char proc_ns_path[LTTNG_PROC_NS_PATH_MAX]; |
| 61 | |
| 62 | if (snprintf(proc_ns_path, LTTNG_PROC_NS_PATH_MAX, |
| 63 | "/proc/self/task/%d/ns/time", |
| 64 | lttng_gettid()) >= 0) { |
| 65 | |
| 66 | if (stat(proc_ns_path, &sb) == 0) { |
| 67 | time_ns = sb.st_ino; |
| 68 | } |
| 69 | } |
| 70 | } |
| 71 | |
| 72 | /* |
| 73 | * And finally, store the inode number in the cache. |
| 74 | */ |
| 75 | CMM_STORE_SHARED(URCU_TLS(cached_time_ns), time_ns); |
| 76 | |
| 77 | return time_ns; |
| 78 | } |
| 79 | |
| 80 | /* |
| 81 | * The time namespace can change for 2 reasons |
| 82 | * * setns(2) called with the fd of a different time ns |
| 83 | * * clone(2) / fork(2) after a call to unshare(2) with the CLONE_NEWTIME flag |
| 84 | */ |
| 85 | void lttng_context_time_ns_reset(void) |
| 86 | { |
| 87 | CMM_STORE_SHARED(URCU_TLS(cached_time_ns), NS_INO_UNINITIALIZED); |
| 88 | } |
| 89 | |
| 90 | static |
| 91 | size_t time_ns_get_size(struct lttng_ust_ctx_field *field, size_t offset) |
| 92 | { |
| 93 | size_t size = 0; |
| 94 | |
| 95 | size += lib_ring_buffer_align(offset, lttng_alignof(ino_t)); |
| 96 | size += sizeof(ino_t); |
| 97 | return size; |
| 98 | } |
| 99 | |
| 100 | static |
| 101 | void time_ns_record(struct lttng_ust_ctx_field *field, |
| 102 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
| 103 | struct lttng_channel *chan) |
| 104 | { |
| 105 | ino_t time_ns; |
| 106 | |
| 107 | time_ns = get_time_ns(); |
| 108 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(time_ns)); |
| 109 | chan->ops->event_write(ctx, &time_ns, sizeof(time_ns)); |
| 110 | } |
| 111 | |
| 112 | static |
| 113 | void time_ns_get_value(struct lttng_ust_ctx_field *field, |
| 114 | struct lttng_ust_ctx_value *value) |
| 115 | { |
| 116 | value->u.s64 = get_time_ns(); |
| 117 | } |
| 118 | |
| 119 | int lttng_add_time_ns_to_ctx(struct lttng_ust_ctx **ctx) |
| 120 | { |
| 121 | struct lttng_ust_ctx_field *field; |
| 122 | struct lttng_ust_type_common *type; |
| 123 | int ret; |
| 124 | |
| 125 | type = lttng_ust_create_type_integer(sizeof(ino_t) * CHAR_BIT, |
| 126 | lttng_alignof(ino_t) * CHAR_BIT, |
| 127 | lttng_is_signed_type(ino_t), |
| 128 | BYTE_ORDER, 10); |
| 129 | if (!type) |
| 130 | return -ENOMEM; |
| 131 | field = lttng_append_context(ctx); |
| 132 | if (!field) { |
| 133 | ret = -ENOMEM; |
| 134 | goto error_context; |
| 135 | } |
| 136 | if (lttng_find_context(*ctx, "time_ns")) { |
| 137 | ret = -EEXIST; |
| 138 | goto error_find_context; |
| 139 | } |
| 140 | field->event_field->name = strdup("time_ns"); |
| 141 | if (!field->event_field->name) { |
| 142 | ret = -ENOMEM; |
| 143 | goto error_name; |
| 144 | } |
| 145 | field->event_field->type = type; |
| 146 | field->get_size = time_ns_get_size; |
| 147 | field->record = time_ns_record; |
| 148 | field->get_value = time_ns_get_value; |
| 149 | lttng_context_update(*ctx); |
| 150 | return 0; |
| 151 | |
| 152 | error_name: |
| 153 | error_find_context: |
| 154 | lttng_remove_context_field(ctx, field); |
| 155 | error_context: |
| 156 | lttng_ust_destroy_type(type); |
| 157 | return ret; |
| 158 | } |
| 159 | |
| 160 | /* |
| 161 | * * Force a read (imply TLS fixup for dlopen) of TLS variables. |
| 162 | * */ |
| 163 | void lttng_fixup_time_ns_tls(void) |
| 164 | { |
| 165 | asm volatile ("" : : "m" (URCU_TLS(cached_time_ns))); |
| 166 | } |