Add the first Landlock tracepoints, for ruleset lifecycle:
landlock_create_ruleset fires from the landlock_create_ruleset() syscall
handler, and landlock_free_ruleset fires in free_ruleset() before the
ruleset is freed.

These tracepoints, and the ones added by the following commits, share a
common design.  Rather than one polymorphic event distinguished by a
status field (as audit uses a shared record type with a "status="
field), each lifecycle transition and denial type gets its own event
with a type-safe TP_PROTO, giving precise ftrace filtering by event name
and type-safe eBPF access.  TP_PROTO passes the object pointer and the
fields are read from it in TP_fast_assign, so an eBPF program reads the
full object state (rules, access masks, hierarchy) via BTF from a single
pointer rather than from the flattened TP_STRUCT__entry fields.  The
whole cost is paid only when a tracer is attached; the static branch is
not taken otherwise.  Trace fields carry the bare access-right and scope
names (read_file), reusing the audit name tables; audit prepends the
category (fs.read_file), which the trace event name already conveys.
The trace header's DOC comment documents the consistency and locking
guarantees these events share.

create_ruleset needs no lock because the ruleset is not yet shared (its
file descriptor is not yet installed).  The deallocation events use the
"free_" prefix, not "drop_", because they fire when the object is
actually freed.

Add trace.c, built for CONFIG_TRACEPOINTS, which defines
CREATE_TRACE_POINTS, and extend CONFIG_SECURITY_LANDLOCK_LOG to also be
selected by CONFIG_TRACEPOINTS so the common log framework is available
to a tracepoints-only build.

Add an id field to struct landlock_ruleset, gated on CONFIG_TRACEPOINTS
and assigned from landlock_get_id_range() at creation.  Only the
tracepoints consume it (audit identifies domains, not rulesets), so it
does not exist in an audit-only build.  The Landlock ID is a stable u64
that names the ruleset across the trace stream and uses the same scheme
as audit, so a ruleset can be correlated between trace and audit
records.

Cc: Günther Noack <gnoack@google.com>
Cc: Justin Suess <utilityemal77@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tingmao Wang <m@maowtm.org>
Link: https://patch.msgid.link/20260811094338.288094-8-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Audit formats denial records with per-right name strings.  A following
commit adds trace events that print the same access and scope masks with
__print_flags() and need the same names, but a trace event header cannot
include Landlock-internal headers, so the names cannot be shared from
the logging unit.

Define the filesystem, network, and scope names once, as the
_LANDLOCK_ACCESS_FS_NAMES, _LANDLOCK_ACCESS_NET_NAMES, and
_LANDLOCK_SCOPE_NAMES lists in the public Landlock header.  Each entry
is a _LANDLOCK_NAME_ENTRY() the consumer expands: audit maps it to a
"[bit] = name" array slot for an O(1) lookup, the trace events map it to
a __print_flags() { mask, name } pair.  The bit value comes only from
the LANDLOCK_* UAPI constant each entry references, so every bit-to-name
mapping has a single source and does not depend on entry order.

The shared names are unprefixed; blocker_prefix() prepends the
fs./net./scope. category for audit records, so the scope names move from
inline literals to the shared table too.  Audit records are unchanged.

No functional change.

Cc: Günther Noack <gnoack@google.com>
Cc: Tingmao Wang <m@maowtm.org>
Link: https://patch.msgid.link/20260811094338.288094-7-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>