| 1 | /* |
| 2 | * lttng-context-cgroup-ns.c |
| 3 | * |
| 4 | * LTTng UST cgroup namespace context. |
| 5 | * |
| 6 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 7 | * 2019 Michael Jeanson <mjeanson@efficios.com> |
| 8 | * |
| 9 | * This library is free software; you can redistribute it and/or |
| 10 | * modify it under the terms of the GNU Lesser General Public |
| 11 | * License as published by the Free Software Foundation; only |
| 12 | * version 2.1 of the License. |
| 13 | * |
| 14 | * This library is distributed in the hope that it will be useful, |
| 15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 17 | * Lesser General Public License for more details. |
| 18 | * |
| 19 | * You should have received a copy of the GNU Lesser General Public |
| 20 | * License along with this library; if not, write to the Free Software |
| 21 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 22 | */ |
| 23 | |
| 24 | #define _LGPL_SOURCE |
| 25 | #include <stddef.h> |
| 26 | #include <sys/types.h> |
| 27 | #include <sys/stat.h> |
| 28 | #include <unistd.h> |
| 29 | #include <lttng/ust-events.h> |
| 30 | #include <lttng/ust-tracer.h> |
| 31 | #include <lttng/ringbuffer-config.h> |
| 32 | #include <lttng/ust-tid.h> |
| 33 | #include <urcu/tls-compat.h> |
| 34 | #include "lttng-tracer-core.h" |
| 35 | #include "ns.h" |
| 36 | |
| 37 | |
| 38 | /* |
| 39 | * We cache the result to ensure we don't stat(2) the proc filesystem on |
| 40 | * each event. |
| 41 | */ |
| 42 | static DEFINE_URCU_TLS_INIT(ino_t, cached_cgroup_ns, NS_INO_UNINITIALIZED); |
| 43 | |
| 44 | static |
| 45 | ino_t get_cgroup_ns(void) |
| 46 | { |
| 47 | struct stat sb; |
| 48 | ino_t cgroup_ns; |
| 49 | |
| 50 | cgroup_ns = CMM_LOAD_SHARED(URCU_TLS(cached_cgroup_ns)); |
| 51 | |
| 52 | /* |
| 53 | * If the cache is populated, do nothing and return the |
| 54 | * cached inode number. |
| 55 | */ |
| 56 | if (caa_likely(cgroup_ns != NS_INO_UNINITIALIZED)) |
| 57 | return cgroup_ns; |
| 58 | |
| 59 | /* |
| 60 | * At this point we have to populate the cache, set the initial |
| 61 | * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode |
| 62 | * number from the proc filesystem, this is the value we will |
| 63 | * cache. |
| 64 | */ |
| 65 | cgroup_ns = NS_INO_UNAVAILABLE; |
| 66 | |
| 67 | /* |
| 68 | * /proc/thread-self was introduced in kernel v3.17 |
| 69 | */ |
| 70 | if (stat("/proc/thread-self/ns/cgroup", &sb) == 0) { |
| 71 | cgroup_ns = sb.st_ino; |
| 72 | } else { |
| 73 | char proc_ns_path[LTTNG_PROC_NS_PATH_MAX]; |
| 74 | |
| 75 | if (snprintf(proc_ns_path, LTTNG_PROC_NS_PATH_MAX, |
| 76 | "/proc/self/task/%d/ns/cgroup", |
| 77 | lttng_gettid()) >= 0) { |
| 78 | |
| 79 | if (stat(proc_ns_path, &sb) == 0) { |
| 80 | cgroup_ns = sb.st_ino; |
| 81 | } |
| 82 | } |
| 83 | } |
| 84 | |
| 85 | /* |
| 86 | * And finally, store the inode number in the cache. |
| 87 | */ |
| 88 | CMM_STORE_SHARED(URCU_TLS(cached_cgroup_ns), cgroup_ns); |
| 89 | |
| 90 | return cgroup_ns; |
| 91 | } |
| 92 | |
| 93 | /* |
| 94 | * The cgroup namespace can change for 3 reasons |
| 95 | * * clone(2) called with CLONE_NEWCGROUP |
| 96 | * * setns(2) called with the fd of a different cgroup ns |
| 97 | * * unshare(2) called with CLONE_NEWCGROUP |
| 98 | */ |
| 99 | void lttng_context_cgroup_ns_reset(void) |
| 100 | { |
| 101 | CMM_STORE_SHARED(URCU_TLS(cached_cgroup_ns), NS_INO_UNINITIALIZED); |
| 102 | } |
| 103 | |
| 104 | static |
| 105 | size_t cgroup_ns_get_size(struct lttng_ctx_field *field, size_t offset) |
| 106 | { |
| 107 | size_t size = 0; |
| 108 | |
| 109 | size += lib_ring_buffer_align(offset, lttng_alignof(ino_t)); |
| 110 | size += sizeof(ino_t); |
| 111 | return size; |
| 112 | } |
| 113 | |
| 114 | static |
| 115 | void cgroup_ns_record(struct lttng_ctx_field *field, |
| 116 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
| 117 | struct lttng_channel *chan) |
| 118 | { |
| 119 | ino_t cgroup_ns; |
| 120 | |
| 121 | cgroup_ns = get_cgroup_ns(); |
| 122 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(cgroup_ns)); |
| 123 | chan->ops->event_write(ctx, &cgroup_ns, sizeof(cgroup_ns)); |
| 124 | } |
| 125 | |
| 126 | static |
| 127 | void cgroup_ns_get_value(struct lttng_ctx_field *field, |
| 128 | struct lttng_ctx_value *value) |
| 129 | { |
| 130 | value->u.s64 = get_cgroup_ns(); |
| 131 | } |
| 132 | |
| 133 | int lttng_add_cgroup_ns_to_ctx(struct lttng_ctx **ctx) |
| 134 | { |
| 135 | struct lttng_ctx_field *field; |
| 136 | |
| 137 | field = lttng_append_context(ctx); |
| 138 | if (!field) |
| 139 | return -ENOMEM; |
| 140 | if (lttng_find_context(*ctx, "cgroup_ns")) { |
| 141 | lttng_remove_context_field(ctx, field); |
| 142 | return -EEXIST; |
| 143 | } |
| 144 | field->event_field.name = "cgroup_ns"; |
| 145 | field->event_field.type.atype = atype_integer; |
| 146 | field->event_field.type.u.integer.size = sizeof(ino_t) * CHAR_BIT; |
| 147 | field->event_field.type.u.integer.alignment = lttng_alignof(ino_t) * CHAR_BIT; |
| 148 | field->event_field.type.u.integer.signedness = lttng_is_signed_type(ino_t); |
| 149 | field->event_field.type.u.integer.reverse_byte_order = 0; |
| 150 | field->event_field.type.u.integer.base = 10; |
| 151 | field->event_field.type.u.integer.encoding = lttng_encode_none; |
| 152 | field->get_size = cgroup_ns_get_size; |
| 153 | field->record = cgroup_ns_record; |
| 154 | field->get_value = cgroup_ns_get_value; |
| 155 | lttng_context_update(*ctx); |
| 156 | return 0; |
| 157 | } |
| 158 | |
| 159 | /* |
| 160 | * * Force a read (imply TLS fixup for dlopen) of TLS variables. |
| 161 | * */ |
| 162 | void lttng_fixup_cgroup_ns_tls(void) |
| 163 | { |
| 164 | asm volatile ("" : : "m" (URCU_TLS(cached_cgroup_ns))); |
| 165 | } |