X-Git-Url: http://git.efficios.com/?a=blobdiff_plain;f=liblttng-ust%2Flttng-context-veuid.c;fp=liblttng-ust%2Flttng-context-veuid.c;h=b627a974db045fa77a4fc5a9e53729058e8604f6;hb=fca2f1916cd9f22f410d8f22b9a0720c978c2025;hp=0000000000000000000000000000000000000000;hpb=735bef4705cc42f25d26f25be09ba98f1efb8511;p=lttng-ust.git

diff --git a/liblttng-ust/lttng-context-veuid.c b/liblttng-ust/lttng-context-veuid.c
new file mode 100644
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+++ b/liblttng-ust/lttng-context-veuid.c
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+/*
+ * lttng-context-veuid.c
+ *
+ * LTTng UST namespaced effective user ID context.
+ *
+ * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *               2019 Michael Jeanson <mjeanson@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#define _LGPL_SOURCE
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <lttng/ust-events.h>
+#include <lttng/ust-tracer.h>
+#include <lttng/ringbuffer-config.h>
+#include "creds.h"
+
+
+/*
+ * At the kernel level, user IDs and group IDs are a per-thread attribute.
+ * However, POSIX requires that all threads in a process share the same
+ * credentials. The NPTL threading implementation handles the POSIX
+ * requirements by providing wrapper functions for the various system calls
+ * that change process UIDs and GIDs. These wrapper functions (including those
+ * for setreuid() and setregid()) employ a signal-based technique to ensure
+ * that when one thread changes credentials, all of the other threads in the
+ * process also change their credentials.
+ */
+
+/*
+ * We cache the result to ensure we don't trigger a system call for
+ * each event. User / group IDs are global to the process.
+ */
+static uid_t cached_veuid = INVALID_UID;
+
+static
+uid_t get_veuid(void)
+{
+	uid_t veuid;
+
+	veuid = CMM_LOAD_SHARED(cached_veuid);
+
+	if (caa_unlikely(veuid == INVALID_UID)) {
+		veuid = geteuid();
+		CMM_STORE_SHARED(cached_veuid, veuid);
+	}
+
+	return veuid;
+}
+
+/*
+ * The veuid can change on setuid, setreuid, setresuid and seteuid.
+ */
+void lttng_context_veuid_reset(void)
+{
+	CMM_STORE_SHARED(cached_veuid, INVALID_UID);
+}
+
+static
+size_t veuid_get_size(struct lttng_ctx_field *field, size_t offset)
+{
+	size_t size = 0;
+
+	size += lib_ring_buffer_align(offset, lttng_alignof(uid_t));
+	size += sizeof(uid_t);
+	return size;
+}
+
+static
+void veuid_record(struct lttng_ctx_field *field,
+		 struct lttng_ust_lib_ring_buffer_ctx *ctx,
+		 struct lttng_channel *chan)
+{
+	uid_t veuid;
+
+	veuid = get_veuid();
+	lib_ring_buffer_align_ctx(ctx, lttng_alignof(veuid));
+	chan->ops->event_write(ctx, &veuid, sizeof(veuid));
+}
+
+static
+void veuid_get_value(struct lttng_ctx_field *field,
+		struct lttng_ctx_value *value)
+{
+	value->u.s64 = get_veuid();
+}
+
+int lttng_add_veuid_to_ctx(struct lttng_ctx **ctx)
+{
+	struct lttng_ctx_field *field;
+
+	field = lttng_append_context(ctx);
+	if (!field)
+		return -ENOMEM;
+	if (lttng_find_context(*ctx, "veuid")) {
+		lttng_remove_context_field(ctx, field);
+		return -EEXIST;
+	}
+	field->event_field.name = "veuid";
+	field->event_field.type.atype = atype_integer;
+	field->event_field.type.u.basic.integer.size = sizeof(uid_t) * CHAR_BIT;
+	field->event_field.type.u.basic.integer.alignment = lttng_alignof(uid_t) * CHAR_BIT;
+	field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(uid_t);
+	field->event_field.type.u.basic.integer.reverse_byte_order = 0;
+	field->event_field.type.u.basic.integer.base = 10;
+	field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
+	field->get_size = veuid_get_size;
+	field->record = veuid_record;
+	field->get_value = veuid_get_value;
+	lttng_context_update(*ctx);
+	return 0;
+}