| 1 | /* |
| 2 | * SPDX-License-Identifier: LGPL-2.1-only |
| 3 | * |
| 4 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 5 | * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com> |
| 6 | * |
| 7 | * LTTng UST pid 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 | |
| 19 | #include "context-internal.h" |
| 20 | #include "ns.h" |
| 21 | |
| 22 | /* |
| 23 | * We cache the result to ensure we don't stat(2) the proc filesystem on |
| 24 | * each event. The PID namespace is global to the process. |
| 25 | */ |
| 26 | static ino_t cached_pid_ns = NS_INO_UNINITIALIZED; |
| 27 | |
| 28 | static |
| 29 | ino_t get_pid_ns(void) |
| 30 | { |
| 31 | struct stat sb; |
| 32 | ino_t pid_ns; |
| 33 | |
| 34 | pid_ns = CMM_LOAD_SHARED(cached_pid_ns); |
| 35 | |
| 36 | /* |
| 37 | * If the cache is populated, do nothing and return the |
| 38 | * cached inode number. |
| 39 | */ |
| 40 | if (caa_likely(pid_ns != NS_INO_UNINITIALIZED)) |
| 41 | return pid_ns; |
| 42 | |
| 43 | /* |
| 44 | * At this point we have to populate the cache, set the initial |
| 45 | * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode |
| 46 | * number from the proc filesystem, this is the value we will |
| 47 | * cache. |
| 48 | */ |
| 49 | pid_ns = NS_INO_UNAVAILABLE; |
| 50 | |
| 51 | if (stat("/proc/self/ns/pid", &sb) == 0) { |
| 52 | pid_ns = sb.st_ino; |
| 53 | } |
| 54 | |
| 55 | /* |
| 56 | * And finally, store the inode number in the cache. |
| 57 | */ |
| 58 | CMM_STORE_SHARED(cached_pid_ns, pid_ns); |
| 59 | |
| 60 | return pid_ns; |
| 61 | } |
| 62 | |
| 63 | /* |
| 64 | * A process's PID namespace membership is determined when the process is |
| 65 | * created and cannot be changed thereafter. |
| 66 | * |
| 67 | * The pid namespace can change only on clone(2) / fork(2) : |
| 68 | * - clone(2) with the CLONE_NEWPID flag |
| 69 | * - clone(2) / fork(2) after a call to unshare(2) with the CLONE_NEWPID flag |
| 70 | * - clone(2) / fork(2) after a call to setns(2) with a PID namespace fd |
| 71 | */ |
| 72 | void lttng_context_pid_ns_reset(void) |
| 73 | { |
| 74 | CMM_STORE_SHARED(cached_pid_ns, NS_INO_UNINITIALIZED); |
| 75 | } |
| 76 | |
| 77 | static |
| 78 | size_t pid_ns_get_size(struct lttng_ust_ctx_field *field, size_t offset) |
| 79 | { |
| 80 | size_t size = 0; |
| 81 | |
| 82 | size += lib_ring_buffer_align(offset, lttng_alignof(ino_t)); |
| 83 | size += sizeof(ino_t); |
| 84 | return size; |
| 85 | } |
| 86 | |
| 87 | static |
| 88 | void pid_ns_record(struct lttng_ust_ctx_field *field, |
| 89 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
| 90 | struct lttng_ust_channel_buffer *chan) |
| 91 | { |
| 92 | ino_t pid_ns; |
| 93 | |
| 94 | pid_ns = get_pid_ns(); |
| 95 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(pid_ns)); |
| 96 | chan->ops->event_write(ctx, &pid_ns, sizeof(pid_ns)); |
| 97 | } |
| 98 | |
| 99 | static |
| 100 | void pid_ns_get_value(struct lttng_ust_ctx_field *field, |
| 101 | struct lttng_ust_ctx_value *value) |
| 102 | { |
| 103 | value->u.s64 = get_pid_ns(); |
| 104 | } |
| 105 | |
| 106 | int lttng_add_pid_ns_to_ctx(struct lttng_ust_ctx **ctx) |
| 107 | { |
| 108 | struct lttng_ust_ctx_field *field; |
| 109 | struct lttng_ust_type_common *type; |
| 110 | int ret; |
| 111 | |
| 112 | type = lttng_ust_create_type_integer(sizeof(ino_t) * CHAR_BIT, |
| 113 | lttng_alignof(ino_t) * CHAR_BIT, |
| 114 | lttng_is_signed_type(ino_t), |
| 115 | BYTE_ORDER, 10); |
| 116 | if (!type) |
| 117 | return -ENOMEM; |
| 118 | field = lttng_append_context(ctx); |
| 119 | if (!field) { |
| 120 | ret = -ENOMEM; |
| 121 | goto error_context; |
| 122 | } |
| 123 | if (lttng_find_context(*ctx, "pid_ns")) { |
| 124 | ret = -EEXIST; |
| 125 | goto error_find_context; |
| 126 | } |
| 127 | field->event_field->name = strdup("pid_ns"); |
| 128 | if (!field->event_field->name) { |
| 129 | ret = -ENOMEM; |
| 130 | goto error_name; |
| 131 | } |
| 132 | field->event_field->type = type; |
| 133 | field->get_size = pid_ns_get_size; |
| 134 | field->record = pid_ns_record; |
| 135 | field->get_value = pid_ns_get_value; |
| 136 | lttng_context_update(*ctx); |
| 137 | return 0; |
| 138 | |
| 139 | error_name: |
| 140 | error_find_context: |
| 141 | lttng_remove_context_field(ctx, field); |
| 142 | error_context: |
| 143 | lttng_ust_destroy_type(type); |
| 144 | return ret; |
| 145 | } |